TOMOYO Linux Cross Reference
Linux/include/linux/fs.h

   #ifndef _LINUX_FS_H
   #define _LINUX_FS_H
   
   #include <linux/linkage.h>
   #include <linux/wait_bit.h>
   #include <linux/kdev_t.h>
   #include <linux/dcache.h>
   #include <linux/path.h>
   #include <linux/stat.h>
  #include <linux/cache.h>
  #include <linux/list.h>
  #include <linux/list_lru.h>
  #include <linux/llist.h>
  #include <linux/radix-tree.h>
  #include <linux/rbtree.h>
  #include <linux/init.h>
  #include <linux/pid.h>
  #include <linux/bug.h>
  #include <linux/mutex.h>
  #include <linux/rwsem.h>
  #include <linux/mm_types.h>
  #include <linux/capability.h>
  #include <linux/semaphore.h>
  #include <linux/fcntl.h>
  #include <linux/fiemap.h>
  #include <linux/rculist_bl.h>
  #include <linux/atomic.h>
  #include <linux/shrinker.h>
  #include <linux/migrate_mode.h>
  #include <linux/uidgid.h>
  #include <linux/lockdep.h>
  #include <linux/percpu-rwsem.h>
  #include <linux/workqueue.h>
  #include <linux/delayed_call.h>
  #include <linux/uuid.h>
  #include <linux/errseq.h>
  
  #include <asm/byteorder.h>
  #include <uapi/linux/fs.h>
  
  struct backing_dev_info;
  struct bdi_writeback;
  struct bio;
  struct export_operations;
  struct hd_geometry;
  struct iovec;
  struct kiocb;
  struct kobject;
  struct pipe_inode_info;
  struct poll_table_struct;
  struct kstatfs;
  struct vm_area_struct;
  struct vfsmount;
  struct cred;
  struct swap_info_struct;
  struct seq_file;
  struct workqueue_struct;
  struct iov_iter;
  struct fscrypt_info;
  struct fscrypt_operations;
  
  extern void __init inode_init(void);
  extern void __init inode_init_early(void);
  extern void __init files_init(void);
  extern void __init files_maxfiles_init(void);
  
  extern struct files_stat_struct files_stat;
  extern unsigned long get_max_files(void);
  extern unsigned int sysctl_nr_open;
  extern struct inodes_stat_t inodes_stat;
  extern int leases_enable, lease_break_time;
  extern int sysctl_protected_symlinks;
  extern int sysctl_protected_hardlinks;
  
  struct buffer_head;
  typedef int (get_block_t)(struct inode *inode, sector_t iblock,
                          struct buffer_head *bh_result, int create);
  typedef int (dio_iodone_t)(struct kiocb *iocb, loff_t offset,
                          ssize_t bytes, void *private);
  
  #define MAY_EXEC                0x00000001
  #define MAY_WRITE               0x00000002
  #define MAY_READ                0x00000004
  #define MAY_APPEND              0x00000008
  #define MAY_ACCESS              0x00000010
  #define MAY_OPEN                0x00000020
  #define MAY_CHDIR               0x00000040
  /* called from RCU mode, don't block */
  #define MAY_NOT_BLOCK           0x00000080
  
  /*
   * flags in file.f_mode.  Note that FMODE_READ and FMODE_WRITE must correspond
   * to O_WRONLY and O_RDWR via the strange trick in __dentry_open()
   */
  
  /* file is open for reading */
  #define FMODE_READ              ((__force fmode_t)0x1)
  /* file is open for writing */
  #define FMODE_WRITE             ((__force fmode_t)0x2)
 /* file is seekable */
 #define FMODE_LSEEK             ((__force fmode_t)0x4)
 /* file can be accessed using pread */
 #define FMODE_PREAD             ((__force fmode_t)0x8)
 /* file can be accessed using pwrite */
 #define FMODE_PWRITE            ((__force fmode_t)0x10)
 /* File is opened for execution with sys_execve / sys_uselib */
 #define FMODE_EXEC              ((__force fmode_t)0x20)
 /* File is opened with O_NDELAY (only set for block devices) */
 #define FMODE_NDELAY            ((__force fmode_t)0x40)
 /* File is opened with O_EXCL (only set for block devices) */
 #define FMODE_EXCL              ((__force fmode_t)0x80)
 /* File is opened using open(.., 3, ..) and is writeable only for ioctls
    (specialy hack for floppy.c) */
 #define FMODE_WRITE_IOCTL       ((__force fmode_t)0x100)
 /* 32bit hashes as llseek() offset (for directories) */
 #define FMODE_32BITHASH         ((__force fmode_t)0x200)
 /* 64bit hashes as llseek() offset (for directories) */
 #define FMODE_64BITHASH         ((__force fmode_t)0x400)
 
 /*
  * Don't update ctime and mtime.
  *
  * Currently a special hack for the XFS open_by_handle ioctl, but we'll
  * hopefully graduate it to a proper O_CMTIME flag supported by open(2) soon.
  */
 #define FMODE_NOCMTIME          ((__force fmode_t)0x800)
 
 /* Expect random access pattern */
 #define FMODE_RANDOM            ((__force fmode_t)0x1000)
 
 /* File is huge (eg. /dev/kmem): treat loff_t as unsigned */
 #define FMODE_UNSIGNED_OFFSET   ((__force fmode_t)0x2000)
 
 /* File is opened with O_PATH; almost nothing can be done with it */
 #define FMODE_PATH              ((__force fmode_t)0x4000)
 
 /* File needs atomic accesses to f_pos */
 #define FMODE_ATOMIC_POS        ((__force fmode_t)0x8000)
 /* Write access to underlying fs */
 #define FMODE_WRITER            ((__force fmode_t)0x10000)
 /* Has read method(s) */
 #define FMODE_CAN_READ          ((__force fmode_t)0x20000)
 /* Has write method(s) */
 #define FMODE_CAN_WRITE         ((__force fmode_t)0x40000)
 
 /* File was opened by fanotify and shouldn't generate fanotify events */
 #define FMODE_NONOTIFY          ((__force fmode_t)0x4000000)
 
 /* File is capable of returning -EAGAIN if AIO will block */
 #define FMODE_AIO_NOWAIT        ((__force fmode_t)0x8000000)
 
 /*
  * Flag for rw_copy_check_uvector and compat_rw_copy_check_uvector
  * that indicates that they should check the contents of the iovec are
  * valid, but not check the memory that the iovec elements
  * points too.
  */
 #define CHECK_IOVEC_ONLY -1
 
 /*
  * Attribute flags.  These should be or-ed together to figure out what
  * has been changed!
  */
 #define ATTR_MODE       (1 << 0)
 #define ATTR_UID        (1 << 1)
 #define ATTR_GID        (1 << 2)
 #define ATTR_SIZE       (1 << 3)
 #define ATTR_ATIME      (1 << 4)
 #define ATTR_MTIME      (1 << 5)
 #define ATTR_CTIME      (1 << 6)
 #define ATTR_ATIME_SET  (1 << 7)
 #define ATTR_MTIME_SET  (1 << 8)
 #define ATTR_FORCE      (1 << 9) /* Not a change, but a change it */
 #define ATTR_ATTR_FLAG  (1 << 10)
 #define ATTR_KILL_SUID  (1 << 11)
 #define ATTR_KILL_SGID  (1 << 12)
 #define ATTR_FILE       (1 << 13)
 #define ATTR_KILL_PRIV  (1 << 14)
 #define ATTR_OPEN       (1 << 15) /* Truncating from open(O_TRUNC) */
 #define ATTR_TIMES_SET  (1 << 16)
 #define ATTR_TOUCH      (1 << 17)
 
 /*
  * Whiteout is represented by a char device.  The following constants define the
  * mode and device number to use.
  */
 #define WHITEOUT_MODE 0
 #define WHITEOUT_DEV 0
 
 /*
  * This is the Inode Attributes structure, used for notify_change().  It
  * uses the above definitions as flags, to know which values have changed.
  * Also, in this manner, a Filesystem can look at only the values it cares
  * about.  Basically, these are the attributes that the VFS layer can
  * request to change from the FS layer.
  *
  * Derek Atkins <warlord@MIT.EDU> 94-10-20
  */
 struct iattr {
         unsigned int    ia_valid;
         umode_t         ia_mode;
         kuid_t          ia_uid;
         kgid_t          ia_gid;
         loff_t          ia_size;
         struct timespec ia_atime;
         struct timespec ia_mtime;
         struct timespec ia_ctime;
 
         /*
          * Not an attribute, but an auxiliary info for filesystems wanting to
          * implement an ftruncate() like method.  NOTE: filesystem should
          * check for (ia_valid & ATTR_FILE), and not for (ia_file != NULL).
          */
         struct file     *ia_file;
 };
 
 /*
  * Includes for diskquotas.
  */
 #include <linux/quota.h>
 
 /*
  * Maximum number of layers of fs stack.  Needs to be limited to
  * prevent kernel stack overflow
  */
 #define FILESYSTEM_MAX_STACK_DEPTH 2
 
 /** 
  * enum positive_aop_returns - aop return codes with specific semantics
  *
  * @AOP_WRITEPAGE_ACTIVATE: Informs the caller that page writeback has
  *                          completed, that the page is still locked, and
  *                          should be considered active.  The VM uses this hint
  *                          to return the page to the active list -- it won't
  *                          be a candidate for writeback again in the near
  *                          future.  Other callers must be careful to unlock
  *                          the page if they get this return.  Returned by
  *                          writepage(); 
  *
  * @AOP_TRUNCATED_PAGE: The AOP method that was handed a locked page has
  *                      unlocked it and the page might have been truncated.
  *                      The caller should back up to acquiring a new page and
  *                      trying again.  The aop will be taking reasonable
  *                      precautions not to livelock.  If the caller held a page
  *                      reference, it should drop it before retrying.  Returned
  *                      by readpage().
  *
  * address_space_operation functions return these large constants to indicate
  * special semantics to the caller.  These are much larger than the bytes in a
  * page to allow for functions that return the number of bytes operated on in a
  * given page.
  */
 
 enum positive_aop_returns {
         AOP_WRITEPAGE_ACTIVATE  = 0x80000,
         AOP_TRUNCATED_PAGE      = 0x80001,
 };
 
 #define AOP_FLAG_CONT_EXPAND            0x0001 /* called from cont_expand */
 #define AOP_FLAG_NOFS                   0x0002 /* used by filesystem to direct
                                                 * helper code (eg buffer layer)
                                                 * to clear GFP_FS from alloc */
 
 /*
  * oh the beauties of C type declarations.
  */
 struct page;
 struct address_space;
 struct writeback_control;
 
 /*
  * Write life time hint values.
  */
 enum rw_hint {
         WRITE_LIFE_NOT_SET      = 0,
         WRITE_LIFE_NONE         = RWH_WRITE_LIFE_NONE,
         WRITE_LIFE_SHORT        = RWH_WRITE_LIFE_SHORT,
         WRITE_LIFE_MEDIUM       = RWH_WRITE_LIFE_MEDIUM,
         WRITE_LIFE_LONG         = RWH_WRITE_LIFE_LONG,
         WRITE_LIFE_EXTREME      = RWH_WRITE_LIFE_EXTREME,
 };
 
 #define IOCB_EVENTFD            (1 << 0)
 #define IOCB_APPEND             (1 << 1)
 #define IOCB_DIRECT             (1 << 2)
 #define IOCB_HIPRI              (1 << 3)
 #define IOCB_DSYNC              (1 << 4)
 #define IOCB_SYNC               (1 << 5)
 #define IOCB_WRITE              (1 << 6)
 #define IOCB_NOWAIT             (1 << 7)
 
 struct kiocb {
         struct file             *ki_filp;
         loff_t                  ki_pos;
         void (*ki_complete)(struct kiocb *iocb, long ret, long ret2);
         void                    *private;
         int                     ki_flags;
         enum rw_hint            ki_hint;
 } __randomize_layout;
 
 static inline bool is_sync_kiocb(struct kiocb *kiocb)
 {
         return kiocb->ki_complete == NULL;
 }
 
 /*
  * "descriptor" for what we're up to with a read.
  * This allows us to use the same read code yet
  * have multiple different users of the data that
  * we read from a file.
  *
  * The simplest case just copies the data to user
  * mode.
  */
 typedef struct {
         size_t written;
         size_t count;
         union {
                 char __user *buf;
                 void *data;
         } arg;
         int error;
 } read_descriptor_t;
 
 typedef int (*read_actor_t)(read_descriptor_t *, struct page *,
                 unsigned long, unsigned long);
 
 struct address_space_operations {
         int (*writepage)(struct page *page, struct writeback_control *wbc);
         int (*readpage)(struct file *, struct page *);
 
         /* Write back some dirty pages from this mapping. */
         int (*writepages)(struct address_space *, struct writeback_control *);
 
         /* Set a page dirty.  Return true if this dirtied it */
         int (*set_page_dirty)(struct page *page);
 
         int (*readpages)(struct file *filp, struct address_space *mapping,
                         struct list_head *pages, unsigned nr_pages);
 
         int (*write_begin)(struct file *, struct address_space *mapping,
                                 loff_t pos, unsigned len, unsigned flags,
                                 struct page **pagep, void **fsdata);
         int (*write_end)(struct file *, struct address_space *mapping,
                                 loff_t pos, unsigned len, unsigned copied,
                                 struct page *page, void *fsdata);
 
         /* Unfortunately this kludge is needed for FIBMAP. Don't use it */
         sector_t (*bmap)(struct address_space *, sector_t);
         void (*invalidatepage) (struct page *, unsigned int, unsigned int);
         int (*releasepage) (struct page *, gfp_t);
         void (*freepage)(struct page *);
         ssize_t (*direct_IO)(struct kiocb *, struct iov_iter *iter);
         /*
          * migrate the contents of a page to the specified target. If
          * migrate_mode is MIGRATE_ASYNC, it must not block.
          */
         int (*migratepage) (struct address_space *,
                         struct page *, struct page *, enum migrate_mode);
         bool (*isolate_page)(struct page *, isolate_mode_t);
         void (*putback_page)(struct page *);
         int (*launder_page) (struct page *);
         int (*is_partially_uptodate) (struct page *, unsigned long,
                                         unsigned long);
         void (*is_dirty_writeback) (struct page *, bool *, bool *);
         int (*error_remove_page)(struct address_space *, struct page *);
 
         /* swapfile support */
         int (*swap_activate)(struct swap_info_struct *sis, struct file *file,
                                 sector_t *span);
         void (*swap_deactivate)(struct file *file);
 };
 
 extern const struct address_space_operations empty_aops;
 
 /*
  * pagecache_write_begin/pagecache_write_end must be used by general code
  * to write into the pagecache.
  */
 int pagecache_write_begin(struct file *, struct address_space *mapping,
                                 loff_t pos, unsigned len, unsigned flags,
                                 struct page **pagep, void **fsdata);
 
 int pagecache_write_end(struct file *, struct address_space *mapping,
                                 loff_t pos, unsigned len, unsigned copied,
                                 struct page *page, void *fsdata);
 
 struct address_space {
         struct inode            *host;          /* owner: inode, block_device */
         struct radix_tree_root  page_tree;      /* radix tree of all pages */
         spinlock_t              tree_lock;      /* and lock protecting it */
         atomic_t                i_mmap_writable;/* count VM_SHARED mappings */
         struct rb_root          i_mmap;         /* tree of private and shared mappings */
         struct rw_semaphore     i_mmap_rwsem;   /* protect tree, count, list */
         /* Protected by tree_lock together with the radix tree */
         unsigned long           nrpages;        /* number of total pages */
         /* number of shadow or DAX exceptional entries */
         unsigned long           nrexceptional;
         pgoff_t                 writeback_index;/* writeback starts here */
         const struct address_space_operations *a_ops;   /* methods */
         unsigned long           flags;          /* error bits */
         spinlock_t              private_lock;   /* for use by the address_space */
         gfp_t                   gfp_mask;       /* implicit gfp mask for allocations */
         struct list_head        private_list;   /* ditto */
         void                    *private_data;  /* ditto */
         errseq_t                wb_err;
 } __attribute__((aligned(sizeof(long)))) __randomize_layout;
         /*
          * On most architectures that alignment is already the case; but
          * must be enforced here for CRIS, to let the least significant bit
          * of struct page's "mapping" pointer be used for PAGE_MAPPING_ANON.
          */
 struct request_queue;
 
 struct block_device {
         dev_t                   bd_dev;  /* not a kdev_t - it's a search key */
         int                     bd_openers;
         struct inode *          bd_inode;       /* will die */
         struct super_block *    bd_super;
         struct mutex            bd_mutex;       /* open/close mutex */
         void *                  bd_claiming;
         void *                  bd_holder;
         int                     bd_holders;
         bool                    bd_write_holder;
 #ifdef CONFIG_SYSFS
         struct list_head        bd_holder_disks;
 #endif
         struct block_device *   bd_contains;
         unsigned                bd_block_size;
         struct hd_struct *      bd_part;
         /* number of times partitions within this device have been opened. */
         unsigned                bd_part_count;
         int                     bd_invalidated;
         struct gendisk *        bd_disk;
         struct request_queue *  bd_queue;
         struct backing_dev_info *bd_bdi;
         struct list_head        bd_list;
         /*
          * Private data.  You must have bd_claim'ed the block_device
          * to use this.  NOTE:  bd_claim allows an owner to claim
          * the same device multiple times, the owner must take special
          * care to not mess up bd_private for that case.
          */
         unsigned long           bd_private;
 
         /* The counter of freeze processes */
         int                     bd_fsfreeze_count;
         /* Mutex for freeze */
         struct mutex            bd_fsfreeze_mutex;
 } __randomize_layout;
 
 /*
  * Radix-tree tags, for tagging dirty and writeback pages within the pagecache
  * radix trees
  */
 #define PAGECACHE_TAG_DIRTY     0
 #define PAGECACHE_TAG_WRITEBACK 1
 #define PAGECACHE_TAG_TOWRITE   2
 
 int mapping_tagged(struct address_space *mapping, int tag);
 
 static inline void i_mmap_lock_write(struct address_space *mapping)
 {
         down_write(&mapping->i_mmap_rwsem);
 }
 
 static inline void i_mmap_unlock_write(struct address_space *mapping)
 {
         up_write(&mapping->i_mmap_rwsem);
 }
 
 static inline void i_mmap_lock_read(struct address_space *mapping)
 {
         down_read(&mapping->i_mmap_rwsem);
 }
 
 static inline void i_mmap_unlock_read(struct address_space *mapping)
 {
         up_read(&mapping->i_mmap_rwsem);
 }
 
 /*
  * Might pages of this file be mapped into userspace?
  */
 static inline int mapping_mapped(struct address_space *mapping)
 {
         return  !RB_EMPTY_ROOT(&mapping->i_mmap);
 }
 
 /*
  * Might pages of this file have been modified in userspace?
  * Note that i_mmap_writable counts all VM_SHARED vmas: do_mmap_pgoff
  * marks vma as VM_SHARED if it is shared, and the file was opened for
  * writing i.e. vma may be mprotected writable even if now readonly.
  *
  * If i_mmap_writable is negative, no new writable mappings are allowed. You
  * can only deny writable mappings, if none exists right now.
  */
 static inline int mapping_writably_mapped(struct address_space *mapping)
 {
         return atomic_read(&mapping->i_mmap_writable) > 0;
 }
 
 static inline int mapping_map_writable(struct address_space *mapping)
 {
         return atomic_inc_unless_negative(&mapping->i_mmap_writable) ?
                 0 : -EPERM;
 }
 
 static inline void mapping_unmap_writable(struct address_space *mapping)
 {
         atomic_dec(&mapping->i_mmap_writable);
 }
 
 static inline int mapping_deny_writable(struct address_space *mapping)
 {
         return atomic_dec_unless_positive(&mapping->i_mmap_writable) ?
                 0 : -EBUSY;
 }
 
 static inline void mapping_allow_writable(struct address_space *mapping)
 {
         atomic_inc(&mapping->i_mmap_writable);
 }
 
 /*
  * Use sequence counter to get consistent i_size on 32-bit processors.
  */
 #if BITS_PER_LONG==32 && defined(CONFIG_SMP)
 #include <linux/seqlock.h>
 #define __NEED_I_SIZE_ORDERED
 #define i_size_ordered_init(inode) seqcount_init(&inode->i_size_seqcount)
 #else
 #define i_size_ordered_init(inode) do { } while (0)
 #endif
 
 struct posix_acl;
 #define ACL_NOT_CACHED ((void *)(-1))
 #define ACL_DONT_CACHE ((void *)(-3))
 
 static inline struct posix_acl *
 uncached_acl_sentinel(struct task_struct *task)
 {
         return (void *)task + 1;
 }
 
 static inline bool
 is_uncached_acl(struct posix_acl *acl)
 {
         return (long)acl & 1;
 }
 
 #define IOP_FASTPERM    0x0001
 #define IOP_LOOKUP      0x0002
 #define IOP_NOFOLLOW    0x0004
 #define IOP_XATTR       0x0008
 #define IOP_DEFAULT_READLINK    0x0010
 
 struct fsnotify_mark_connector;
 
 /*
  * Keep mostly read-only and often accessed (especially for
  * the RCU path lookup and 'stat' data) fields at the beginning
  * of the 'struct inode'
  */
 struct inode {
         umode_t                 i_mode;
         unsigned short          i_opflags;
         kuid_t                  i_uid;
         kgid_t                  i_gid;
         unsigned int            i_flags;
 
 #ifdef CONFIG_FS_POSIX_ACL
         struct posix_acl        *i_acl;
         struct posix_acl        *i_default_acl;
 #endif
 
         const struct inode_operations   *i_op;
         struct super_block      *i_sb;
         struct address_space    *i_mapping;
 
 #ifdef CONFIG_SECURITY
         void                    *i_security;
 #endif
 
         /* Stat data, not accessed from path walking */
         unsigned long           i_ino;
         /*
          * Filesystems may only read i_nlink directly.  They shall use the
          * following functions for modification:
          *
          *    (set|clear|inc|drop)_nlink
          *    inode_(inc|dec)_link_count
          */
         union {
                 const unsigned int i_nlink;
                 unsigned int __i_nlink;
         };
         dev_t                   i_rdev;
         loff_t                  i_size;
         struct timespec         i_atime;
         struct timespec         i_mtime;
         struct timespec         i_ctime;
         spinlock_t              i_lock; /* i_blocks, i_bytes, maybe i_size */
         unsigned short          i_bytes;
         unsigned int            i_blkbits;
         enum rw_hint            i_write_hint;
         blkcnt_t                i_blocks;
 
 #ifdef __NEED_I_SIZE_ORDERED
         seqcount_t              i_size_seqcount;
 #endif
 
         /* Misc */
         unsigned long           i_state;
         struct rw_semaphore     i_rwsem;
 
         unsigned long           dirtied_when;   /* jiffies of first dirtying */
         unsigned long           dirtied_time_when;
 
         struct hlist_node       i_hash;
         struct list_head        i_io_list;      /* backing dev IO list */
 #ifdef CONFIG_CGROUP_WRITEBACK
         struct bdi_writeback    *i_wb;          /* the associated cgroup wb */
 
         /* foreign inode detection, see wbc_detach_inode() */
         int                     i_wb_frn_winner;
         u16                     i_wb_frn_avg_time;
         u16                     i_wb_frn_history;
 #endif
         struct list_head        i_lru;          /* inode LRU list */
         struct list_head        i_sb_list;
         struct list_head        i_wb_list;      /* backing dev writeback list */
         union {
                 struct hlist_head       i_dentry;
                 struct rcu_head         i_rcu;
         };
         u64                     i_version;
         atomic_t                i_count;
         atomic_t                i_dio_count;
         atomic_t                i_writecount;
 #ifdef CONFIG_IMA
         atomic_t                i_readcount; /* struct files open RO */
 #endif
         const struct file_operations    *i_fop; /* former ->i_op->default_file_ops */
         struct file_lock_context        *i_flctx;
         struct address_space    i_data;
         struct list_head        i_devices;
         union {
                 struct pipe_inode_info  *i_pipe;
                 struct block_device     *i_bdev;
                 struct cdev             *i_cdev;
                 char                    *i_link;
                 unsigned                i_dir_seq;
         };
 
         __u32                   i_generation;
 
 #ifdef CONFIG_FSNOTIFY
         __u32                   i_fsnotify_mask; /* all events this inode cares about */
         struct fsnotify_mark_connector __rcu    *i_fsnotify_marks;
 #endif
 
 #if IS_ENABLED(CONFIG_FS_ENCRYPTION)
         struct fscrypt_info     *i_crypt_info;
 #endif
 
         void                    *i_private; /* fs or device private pointer */
 } __randomize_layout;
 
 static inline unsigned int i_blocksize(const struct inode *node)
 {
         return (1 << node->i_blkbits);
 }
 
 static inline int inode_unhashed(struct inode *inode)
 {
         return hlist_unhashed(&inode->i_hash);
 }
 
 /*
  * inode->i_mutex nesting subclasses for the lock validator:
  *
  * 0: the object of the current VFS operation
  * 1: parent
  * 2: child/target
  * 3: xattr
  * 4: second non-directory
  * 5: second parent (when locking independent directories in rename)
  *
  * I_MUTEX_NONDIR2 is for certain operations (such as rename) which lock two
  * non-directories at once.
  *
  * The locking order between these classes is
  * parent[2] -> child -> grandchild -> normal -> xattr -> second non-directory
  */
 enum inode_i_mutex_lock_class
 {
         I_MUTEX_NORMAL,
         I_MUTEX_PARENT,
         I_MUTEX_CHILD,
         I_MUTEX_XATTR,
         I_MUTEX_NONDIR2,
         I_MUTEX_PARENT2,
 };
 
 static inline void inode_lock(struct inode *inode)
 {
         down_write(&inode->i_rwsem);
 }
 
 static inline void inode_unlock(struct inode *inode)
 {
         up_write(&inode->i_rwsem);
 }
 
 static inline void inode_lock_shared(struct inode *inode)
 {
         down_read(&inode->i_rwsem);
 }
 
 static inline void inode_unlock_shared(struct inode *inode)
 {
         up_read(&inode->i_rwsem);
 }
 
 static inline int inode_trylock(struct inode *inode)
 {
         return down_write_trylock(&inode->i_rwsem);
 }
 
 static inline int inode_trylock_shared(struct inode *inode)
 {
         return down_read_trylock(&inode->i_rwsem);
 }
 
 static inline int inode_is_locked(struct inode *inode)
 {
         return rwsem_is_locked(&inode->i_rwsem);
 }
 
 static inline void inode_lock_nested(struct inode *inode, unsigned subclass)
 {
         down_write_nested(&inode->i_rwsem, subclass);
 }
 
 void lock_two_nondirectories(struct inode *, struct inode*);
 void unlock_two_nondirectories(struct inode *, struct inode*);
 
 /*
  * NOTE: in a 32bit arch with a preemptable kernel and
  * an UP compile the i_size_read/write must be atomic
  * with respect to the local cpu (unlike with preempt disabled),
  * but they don't need to be atomic with respect to other cpus like in
  * true SMP (so they need either to either locally disable irq around
  * the read or for example on x86 they can be still implemented as a
  * cmpxchg8b without the need of the lock prefix). For SMP compiles
  * and 64bit archs it makes no difference if preempt is enabled or not.
  */
 static inline loff_t i_size_read(const struct inode *inode)
 {
 #if BITS_PER_LONG==32 && defined(CONFIG_SMP)
         loff_t i_size;
         unsigned int seq;
 
         do {
                 seq = read_seqcount_begin(&inode->i_size_seqcount);
                 i_size = inode->i_size;
         } while (read_seqcount_retry(&inode->i_size_seqcount, seq));
         return i_size;
 #elif BITS_PER_LONG==32 && defined(CONFIG_PREEMPT)
         loff_t i_size;
 
         preempt_disable();
         i_size = inode->i_size;
         preempt_enable();
         return i_size;
 #else
         return inode->i_size;
 #endif
 }
 
 /*
  * NOTE: unlike i_size_read(), i_size_write() does need locking around it
  * (normally i_mutex), otherwise on 32bit/SMP an update of i_size_seqcount
  * can be lost, resulting in subsequent i_size_read() calls spinning forever.
  */
 static inline void i_size_write(struct inode *inode, loff_t i_size)
 {
 #if BITS_PER_LONG==32 && defined(CONFIG_SMP)
         preempt_disable();
         write_seqcount_begin(&inode->i_size_seqcount);
         inode->i_size = i_size;
         write_seqcount_end(&inode->i_size_seqcount);
         preempt_enable();
 #elif BITS_PER_LONG==32 && defined(CONFIG_PREEMPT)
         preempt_disable();
         inode->i_size = i_size;
         preempt_enable();
 #else
         inode->i_size = i_size;
 #endif
 }
 
 static inline unsigned iminor(const struct inode *inode)
 {
         return MINOR(inode->i_rdev);
 }
 
 static inline unsigned imajor(const struct inode *inode)
 {
         return MAJOR(inode->i_rdev);
 }
 
 extern struct block_device *I_BDEV(struct inode *inode);
 
 struct fown_struct {
         rwlock_t lock;          /* protects pid, uid, euid fields */
         struct pid *pid;        /* pid or -pgrp where SIGIO should be sent */
         enum pid_type pid_type; /* Kind of process group SIGIO should be sent to */
         kuid_t uid, euid;       /* uid/euid of process setting the owner */
         int signum;             /* posix.1b rt signal to be delivered on IO */
 };
 
 /*
  * Track a single file's readahead state
  */
 struct file_ra_state {
         pgoff_t start;                  /* where readahead started */
         unsigned int size;              /* # of readahead pages */
         unsigned int async_size;        /* do asynchronous readahead when
                                            there are only # of pages ahead */
 
         unsigned int ra_pages;          /* Maximum readahead window */
         unsigned int mmap_miss;         /* Cache miss stat for mmap accesses */
         loff_t prev_pos;                /* Cache last read() position */
 };
 
 /*
  * Check if @index falls in the readahead windows.
  */
 static inline int ra_has_index(struct file_ra_state *ra, pgoff_t index)
 {
         return (index >= ra->start &&
                 index <  ra->start + ra->size);
 }
 
 struct file {
         union {
                 struct llist_node       fu_llist;
                 struct rcu_head         fu_rcuhead;
         } f_u;
         struct path             f_path;
         struct inode            *f_inode;       /* cached value */
         const struct file_operations    *f_op;
 
         /*
          * Protects f_ep_links, f_flags.
          * Must not be taken from IRQ context.
          */
         spinlock_t              f_lock;
         enum rw_hint            f_write_hint;
         atomic_long_t           f_count;
         unsigned int            f_flags;
         fmode_t                 f_mode;
         struct mutex            f_pos_lock;
         loff_t                  f_pos;
         struct fown_struct      f_owner;
         const struct cred       *f_cred;
         struct file_ra_state    f_ra;
 
         u64                     f_version;
 #ifdef CONFIG_SECURITY
         void                    *f_security;
 #endif
         /* needed for tty driver, and maybe others */
         void                    *private_data;
 
 #ifdef CONFIG_EPOLL
         /* Used by fs/eventpoll.c to link all the hooks to this file */
         struct list_head        f_ep_links;
         struct list_head        f_tfile_llink;
 #endif /* #ifdef CONFIG_EPOLL */
         struct address_space    *f_mapping;
         errseq_t                f_wb_err;
 } __randomize_layout
   __attribute__((aligned(4)));  /* lest something weird decides that 2 is OK */
 
 struct file_handle {
         __u32 handle_bytes;
         int handle_type;
         /* file identifier */
         unsigned char f_handle[0];
 };
 
 static inline struct file *get_file(struct file *f)
 {
         atomic_long_inc(&f->f_count);
         return f;
 }
 #define get_file_rcu(x) atomic_long_inc_not_zero(&(x)->f_count)
 #define fput_atomic(x)  atomic_long_add_unless(&(x)->f_count, -1, 1)
 #define file_count(x)   atomic_long_read(&(x)->f_count)
 
 #define MAX_NON_LFS     ((1UL<<31) - 1)
 
 /* Page cache limit. The filesystems should put that into their s_maxbytes 
    limits, otherwise bad things can happen in VM. */ 
 #if BITS_PER_LONG==32
 #define MAX_LFS_FILESIZE        ((loff_t)ULONG_MAX << PAGE_SHIFT)
 #elif BITS_PER_LONG==64
 #define MAX_LFS_FILESIZE        ((loff_t)LLONG_MAX)
 #endif
 
 #define FL_POSIX        1
 #define FL_FLOCK        2
 #define FL_DELEG        4       /* NFSv4 delegation */
 #define FL_ACCESS       8       /* not trying to lock, just looking */
 #define FL_EXISTS       16      /* when unlocking, test for existence */
 #define FL_LEASE        32      /* lease held on this file */
 #define FL_CLOSE        64      /* unlock on close */
 #define FL_SLEEP        128     /* A blocking lock */
 #define FL_DOWNGRADE_PENDING    256 /* Lease is being downgraded */
 #define FL_UNLOCK_PENDING       512 /* Lease is being broken */
 #define FL_OFDLCK       1024    /* lock is "owned" by struct file */
 #define FL_LAYOUT       2048    /* outstanding pNFS layout */
 
 #define FL_CLOSE_POSIX (FL_POSIX | FL_CLOSE)
 
 /*
  * Special return value from posix_lock_file() and vfs_lock_file() for
  * asynchronous locking.
  */
 #define FILE_LOCK_DEFERRED 1
 
 /* legacy typedef, should eventually be removed */
 typedef void *fl_owner_t;
 
 struct file_lock;
 
 struct file_lock_operations {
         void (*fl_copy_lock)(struct file_lock *, struct file_lock *);
         void (*fl_release_private)(struct file_lock *);
 };
 
 struct lock_manager_operations {
         int (*lm_compare_owner)(struct file_lock *, struct file_lock *);
         unsigned long (*lm_owner_key)(struct file_lock *);
         fl_owner_t (*lm_get_owner)(fl_owner_t);
         void (*lm_put_owner)(fl_owner_t);
         void (*lm_notify)(struct file_lock *);  /* unblock callback */
         int (*lm_grant)(struct file_lock *, int);
         bool (*lm_break)(struct file_lock *);
         int (*lm_change)(struct file_lock *, int, struct list_head *);
         void (*lm_setup)(struct file_lock *, void **);
 };
 
 struct lock_manager {
         struct list_head list;
         /*
          * NFSv4 and up also want opens blocked during the grace period;
          * NLM doesn't care:
          */
         bool block_opens;
 };
 
 struct net;
 void locks_start_grace(struct net *, struct lock_manager *);
 void locks_end_grace(struct lock_manager *);
 int locks_in_grace(struct net *);
 int opens_in_grace(struct net *);
 
 /* that will die - we need it for nfs_lock_info */
 #include <linux/nfs_fs_i.h>
 
 /*
  * struct file_lock represents a generic "file lock". It's used to represent
  * POSIX byte range locks, BSD (flock) locks, and leases. It's important to
  * note that the same struct is used to represent both a request for a lock and
  * the lock itself, but the same object is never used for both.
  *
  * FIXME: should we create a separate "struct lock_request" to help distinguish
  * these two uses?
  *
  * The varous i_flctx lists are ordered by:
  *
  * 1) lock owner
  * 2) lock range start
  * 3) lock range end
  *
  * Obviously, the last two criteria only matter for POSIX locks.
  */
 struct file_lock {
         struct file_lock *fl_next;      /* singly linked list for this inode  */
         struct list_head fl_list;       /* link into file_lock_context */
         struct hlist_node fl_link;      /* node in global lists */
         struct list_head fl_block;      /* circular list of blocked processes */
         fl_owner_t fl_owner;
         unsigned int fl_flags;
         unsigned char fl_type;
         unsigned int fl_pid;
         int fl_link_cpu;                /* what cpu's list is this on? */
         struct pid *fl_nspid;
         wait_queue_head_t fl_wait;
         struct file *fl_file;
         loff_t fl_start;
         loff_t fl_end;
 
         struct fasync_struct *  fl_fasync; /* for lease break notifications */
         /* for lease breaks: */
         unsigned long fl_break_time;
         unsigned long fl_downgrade_time;
 
         const struct file_lock_operations *fl_ops;      /* Callbacks for filesystems */
         const struct lock_manager_operations *fl_lmops; /* Callbacks for lockmanagers */
         union {
                 struct nfs_lock_info    nfs_fl;
                 struct nfs4_lock_info   nfs4_fl;
                 struct {
                         struct list_head link;  /* link in AFS vnode's pending_locks list */
                         int state;              /* state of grant or error if -ve */
                 } afs;
         } fl_u;
 } __randomize_layout;
 
 struct file_lock_context {
         spinlock_t              flc_lock;
         struct list_head        flc_flock;
         struct list_head        flc_posix;
         struct list_head        flc_lease;
 };
 
 /* The following constant reflects the upper bound of the file/locking space */
 #ifndef OFFSET_MAX
 #define INT_LIMIT(x)    (~((x)1 << (sizeof(x)*8 - 1)))
 #define OFFSET_MAX      INT_LIMIT(loff_t)
 #define OFFT_OFFSET_MAX INT_LIMIT(off_t)
 #endif
 
 extern void send_sigio(struct fown_struct *fown, int fd, int band);
 
 /*
  * Return the inode to use for locking
  *
  * For overlayfs this should be the overlay inode, not the real inode returned
  * by file_inode().  For any other fs file_inode(filp) and locks_inode(filp) are
  * equal.
  */
 static inline struct inode *locks_inode(const struct file *f)
 {
         return f->f_path.dentry->d_inode;
 }
 
 #ifdef CONFIG_FILE_LOCKING
 extern int fcntl_getlk(struct file *, unsigned int, struct flock *);
 extern int fcntl_setlk(unsigned int, struct file *, unsigned int,
                         struct flock *);
 
 #if BITS_PER_LONG == 32
 extern int fcntl_getlk64(struct file *, unsigned int, struct flock64 *);
 extern int fcntl_setlk64(unsigned int, struct file *, unsigned int,
                         struct flock64 *);
 #endif
 
 extern int fcntl_setlease(unsigned int fd, struct file *filp, long arg);
 extern int fcntl_getlease(struct file *filp);
 
 /* fs/locks.c */
 void locks_free_lock_context(struct inode *inode);
 void locks_free_lock(struct file_lock *fl);
 extern void locks_init_lock(struct file_lock *);
 extern struct file_lock * locks_alloc_lock(void);
 extern void locks_copy_lock(struct file_lock *, struct file_lock *);
 extern void locks_copy_conflock(struct file_lock *, struct file_lock *);
 extern void locks_remove_posix(struct file *, fl_owner_t);
 extern void locks_remove_file(struct file *);
 extern void locks_release_private(struct file_lock *);
 extern void posix_test_lock(struct file *, struct file_lock *);
 extern int posix_lock_file(struct file *, struct file_lock *, struct file_lock *);
 extern int posix_unblock_lock(struct file_lock *);
 extern int vfs_test_lock(struct file *, struct file_lock *);
 extern int vfs_lock_file(struct file *, unsigned int, struct file_lock *, struct file_lock *);
 extern int vfs_cancel_lock(struct file *filp, struct file_lock *fl);
 extern int locks_lock_inode_wait(struct inode *inode, struct file_lock *fl);
 extern int __break_lease(struct inode *inode, unsigned int flags, unsigned int type);
 extern void lease_get_mtime(struct inode *, struct timespec *time);
 extern int generic_setlease(struct file *, long, struct file_lock **, void **priv);
 extern int vfs_setlease(struct file *, long, struct file_lock **, void **);
 extern int lease_modify(struct file_lock *, int, struct list_head *);
 struct files_struct;
 extern void show_fd_locks(struct seq_file *f,
                          struct file *filp, struct files_struct *files);
 #else /* !CONFIG_FILE_LOCKING */
 static inline int fcntl_getlk(struct file *file, unsigned int cmd,
                               struct flock __user *user)
 {
         return -EINVAL;
 }
 
 static inline int fcntl_setlk(unsigned int fd, struct file *file,
                               unsigned int cmd, struct flock __user *user)
 {
         return -EACCES;
 }
 
 #if BITS_PER_LONG == 32
 static inline int fcntl_getlk64(struct file *file, unsigned int cmd,
                                 struct flock64 __user *user)
 {
         return -EINVAL;
 }
 
 static inline int fcntl_setlk64(unsigned int fd, struct file *file,
                                 unsigned int cmd, struct flock64 __user *user)
 {
         return -EACCES;
 }
 #endif
 static inline int fcntl_setlease(unsigned int fd, struct file *filp, long arg)
 {
         return -EINVAL;
 }
 
 static inline int fcntl_getlease(struct file *filp)
 {
         return F_UNLCK;
 }
 
 static inline void
 locks_free_lock_context(struct inode *inode)
 {
 }
 
 static inline void locks_init_lock(struct file_lock *fl)
 {
         return;
 }
 
 static inline void locks_copy_conflock(struct file_lock *new, struct file_lock *fl)
 {
         return;
 }
 
 static inline void locks_copy_lock(struct file_lock *new, struct file_lock *fl)
 {
         return;
 }
 
 static inline void locks_remove_posix(struct file *filp, fl_owner_t owner)
 {
         return;
 }
 
 static inline void locks_remove_file(struct file *filp)
 {
         return;
 }
 
 static inline void posix_test_lock(struct file *filp, struct file_lock *fl)
 {
         return;
 }
 
 static inline int posix_lock_file(struct file *filp, struct file_lock *fl,
                                   struct file_lock *conflock)
 {
         return -ENOLCK;
 }
 
 static inline int posix_unblock_lock(struct file_lock *waiter)
 {
         return -ENOENT;
 }
 
 static inline int vfs_test_lock(struct file *filp, struct file_lock *fl)
 {
         return 0;
 }
 
 static inline int vfs_lock_file(struct file *filp, unsigned int cmd,
                                 struct file_lock *fl, struct file_lock *conf)
 {
         return -ENOLCK;
 }
 
 static inline int vfs_cancel_lock(struct file *filp, struct file_lock *fl)
 {
         return 0;
 }
 
 static inline int locks_lock_inode_wait(struct inode *inode, struct file_lock *fl)
 {
         return -ENOLCK;
 }
 
 static inline int __break_lease(struct inode *inode, unsigned int mode, unsigned int type)
 {
         return 0;
 }
 
 static inline void lease_get_mtime(struct inode *inode, struct timespec *time)
 {
         return;
 }
 
 static inline int generic_setlease(struct file *filp, long arg,
                                     struct file_lock **flp, void **priv)
 {
         return -EINVAL;
 }
 
 static inline int vfs_setlease(struct file *filp, long arg,
                                struct file_lock **lease, void **priv)
 {
         return -EINVAL;
 }
 
 static inline int lease_modify(struct file_lock *fl, int arg,
                                struct list_head *dispose)
 {
         return -EINVAL;
 }
 
 struct files_struct;
 static inline void show_fd_locks(struct seq_file *f,
                         struct file *filp, struct files_struct *files) {}
 #endif /* !CONFIG_FILE_LOCKING */
 
 static inline struct inode *file_inode(const struct file *f)
 {
         return f->f_inode;
 }
 
 static inline struct dentry *file_dentry(const struct file *file)
 {
         return d_real(file->f_path.dentry, file_inode(file), 0);
 }
 
 static inline int locks_lock_file_wait(struct file *filp, struct file_lock *fl)
 {
         return locks_lock_inode_wait(locks_inode(filp), fl);
 }
 
 struct fasync_struct {
         spinlock_t              fa_lock;
         int                     magic;
         int                     fa_fd;
         struct fasync_struct    *fa_next; /* singly linked list */
         struct file             *fa_file;
         struct rcu_head         fa_rcu;
 };
 
 #define FASYNC_MAGIC 0x4601
 
 /* SMP safe fasync helpers: */
 extern int fasync_helper(int, struct file *, int, struct fasync_struct **);
 extern struct fasync_struct *fasync_insert_entry(int, struct file *, struct fasync_struct **, struct fasync_struct *);
 extern int fasync_remove_entry(struct file *, struct fasync_struct **);
 extern struct fasync_struct *fasync_alloc(void);
 extern void fasync_free(struct fasync_struct *);
 
 /* can be called from interrupts */
 extern void kill_fasync(struct fasync_struct **, int, int);
 
 extern void __f_setown(struct file *filp, struct pid *, enum pid_type, int force);
 extern int f_setown(struct file *filp, unsigned long arg, int force);
 extern void f_delown(struct file *filp);
 extern pid_t f_getown(struct file *filp);
 extern int send_sigurg(struct fown_struct *fown);
 
 struct mm_struct;
 
 /*
  *      Umount options
  */
 
 #define MNT_FORCE       0x00000001      /* Attempt to forcibily umount */
 #define MNT_DETACH      0x00000002      /* Just detach from the tree */
 #define MNT_EXPIRE      0x00000004      /* Mark for expiry */
 #define UMOUNT_NOFOLLOW 0x00000008      /* Don't follow symlink on umount */
 #define UMOUNT_UNUSED   0x80000000      /* Flag guaranteed to be unused */
 
 /* sb->s_iflags */
 #define SB_I_CGROUPWB   0x00000001      /* cgroup-aware writeback enabled */
 #define SB_I_NOEXEC     0x00000002      /* Ignore executables on this fs */
 #define SB_I_NODEV      0x00000004      /* Ignore devices on this fs */
 
 /* sb->s_iflags to limit user namespace mounts */
 #define SB_I_USERNS_VISIBLE             0x00000010 /* fstype already mounted */
 
 /* Possible states of 'frozen' field */
 enum {
         SB_UNFROZEN = 0,                /* FS is unfrozen */
         SB_FREEZE_WRITE = 1,            /* Writes, dir ops, ioctls frozen */
         SB_FREEZE_PAGEFAULT = 2,        /* Page faults stopped as well */
         SB_FREEZE_FS = 3,               /* For internal FS use (e.g. to stop
                                          * internal threads if needed) */
         SB_FREEZE_COMPLETE = 4,         /* ->freeze_fs finished successfully */
 };
 
 #define SB_FREEZE_LEVELS (SB_FREEZE_COMPLETE - 1)
 
 struct sb_writers {
         int                             frozen;         /* Is sb frozen? */
         wait_queue_head_t               wait_unfrozen;  /* for get_super_thawed() */
         struct percpu_rw_semaphore      rw_sem[SB_FREEZE_LEVELS];
 };
 
 struct super_block {
         struct list_head        s_list;         /* Keep this first */
         dev_t                   s_dev;          /* search index; _not_ kdev_t */
         unsigned char           s_blocksize_bits;
         unsigned long           s_blocksize;
         loff_t                  s_maxbytes;     /* Max file size */
         struct file_system_type *s_type;
         const struct super_operations   *s_op;
         const struct dquot_operations   *dq_op;
         const struct quotactl_ops       *s_qcop;
         const struct export_operations *s_export_op;
         unsigned long           s_flags;
         unsigned long           s_iflags;       /* internal SB_I_* flags */
         unsigned long           s_magic;
         struct dentry           *s_root;
         struct rw_semaphore     s_umount;
         int                     s_count;
         atomic_t                s_active;
 #ifdef CONFIG_SECURITY
         void                    *s_security;
 #endif
         const struct xattr_handler **s_xattr;
 
         const struct fscrypt_operations *s_cop;
 
         struct hlist_bl_head    s_anon;         /* anonymous dentries for (nfs) exporting */
         struct list_head        s_mounts;       /* list of mounts; _not_ for fs use */
         struct block_device     *s_bdev;
         struct backing_dev_info *s_bdi;
         struct mtd_info         *s_mtd;
         struct hlist_node       s_instances;
         unsigned int            s_quota_types;  /* Bitmask of supported quota types */
         struct quota_info       s_dquot;        /* Diskquota specific options */
 
         struct sb_writers       s_writers;
 
         char                    s_id[32];       /* Informational name */
         uuid_t                  s_uuid;         /* UUID */
 
         void                    *s_fs_info;     /* Filesystem private info */
         unsigned int            s_max_links;
         fmode_t                 s_mode;
 
         /* Granularity of c/m/atime in ns.
            Cannot be worse than a second */
         u32                s_time_gran;
 
         /*
          * The next field is for VFS *only*. No filesystems have any business
          * even looking at it. You had been warned.
          */
         struct mutex s_vfs_rename_mutex;        /* Kludge */
 
         /*
          * Filesystem subtype.  If non-empty the filesystem type field
          * in /proc/mounts will be "type.subtype"
          */
         char *s_subtype;
 
         const struct dentry_operations *s_d_op; /* default d_op for dentries */
 
         /*
          * Saved pool identifier for cleancache (-1 means none)
          */
         int cleancache_poolid;
 
         struct shrinker s_shrink;       /* per-sb shrinker handle */
 
         /* Number of inodes with nlink == 0 but still referenced */
         atomic_long_t s_remove_count;
 
         /* Being remounted read-only */
         int s_readonly_remount;
 
         /* AIO completions deferred from interrupt context */
         struct workqueue_struct *s_dio_done_wq;
         struct hlist_head s_pins;
 
         /*
          * Owning user namespace and default context in which to
          * interpret filesystem uids, gids, quotas, device nodes,
          * xattrs and security labels.
          */
         struct user_namespace *s_user_ns;
 
         /*
          * Keep the lru lists last in the structure so they always sit on their
          * own individual cachelines.
          */
         struct list_lru         s_dentry_lru ____cacheline_aligned_in_smp;
         struct list_lru         s_inode_lru ____cacheline_aligned_in_smp;
         struct rcu_head         rcu;
         struct work_struct      destroy_work;
 
         struct mutex            s_sync_lock;    /* sync serialisation lock */
 
         /*
          * Indicates how deep in a filesystem stack this SB is
          */
         int s_stack_depth;
 
         /* s_inode_list_lock protects s_inodes */
         spinlock_t              s_inode_list_lock ____cacheline_aligned_in_smp;
         struct list_head        s_inodes;       /* all inodes */
 
         spinlock_t              s_inode_wblist_lock;
         struct list_head        s_inodes_wb;    /* writeback inodes */
 } __randomize_layout;
 
 /* Helper functions so that in most cases filesystems will
  * not need to deal directly with kuid_t and kgid_t and can
  * instead deal with the raw numeric values that are stored
  * in the filesystem.
  */
 static inline uid_t i_uid_read(const struct inode *inode)
 {
         return from_kuid(inode->i_sb->s_user_ns, inode->i_uid);
 }
 
 static inline gid_t i_gid_read(const struct inode *inode)
 {
         return from_kgid(inode->i_sb->s_user_ns, inode->i_gid);
 }
 
 static inline void i_uid_write(struct inode *inode, uid_t uid)
 {
         inode->i_uid = make_kuid(inode->i_sb->s_user_ns, uid);
 }
 
 static inline void i_gid_write(struct inode *inode, gid_t gid)
 {
         inode->i_gid = make_kgid(inode->i_sb->s_user_ns, gid);
 }
 
 extern struct timespec current_time(struct inode *inode);
 
 /*
  * Snapshotting support.
  */
 
 void __sb_end_write(struct super_block *sb, int level);
 int __sb_start_write(struct super_block *sb, int level, bool wait);
 
 #define __sb_writers_acquired(sb, lev)  \
         percpu_rwsem_acquire(&(sb)->s_writers.rw_sem[(lev)-1], 1, _THIS_IP_)
 #define __sb_writers_release(sb, lev)   \
         percpu_rwsem_release(&(sb)->s_writers.rw_sem[(lev)-1], 1, _THIS_IP_)
 
 /**
  * sb_end_write - drop write access to a superblock
  * @sb: the super we wrote to
  *
  * Decrement number of writers to the filesystem. Wake up possible waiters
  * wanting to freeze the filesystem.
  */
 static inline void sb_end_write(struct super_block *sb)
 {
         __sb_end_write(sb, SB_FREEZE_WRITE);
 }
 
 /**
  * sb_end_pagefault - drop write access to a superblock from a page fault
  * @sb: the super we wrote to
  *
  * Decrement number of processes handling write page fault to the filesystem.
  * Wake up possible waiters wanting to freeze the filesystem.
  */
 static inline void sb_end_pagefault(struct super_block *sb)
 {
         __sb_end_write(sb, SB_FREEZE_PAGEFAULT);
 }
 
 /**
  * sb_end_intwrite - drop write access to a superblock for internal fs purposes
  * @sb: the super we wrote to
  *
  * Decrement fs-internal number of writers to the filesystem.  Wake up possible
  * waiters wanting to freeze the filesystem.
  */
 static inline void sb_end_intwrite(struct super_block *sb)
 {
         __sb_end_write(sb, SB_FREEZE_FS);
 }
 
 /**
  * sb_start_write - get write access to a superblock
  * @sb: the super we write to
  *
  * When a process wants to write data or metadata to a file system (i.e. dirty
  * a page or an inode), it should embed the operation in a sb_start_write() -
  * sb_end_write() pair to get exclusion against file system freezing. This
  * function increments number of writers preventing freezing. If the file
  * system is already frozen, the function waits until the file system is
  * thawed.
  *
  * Since freeze protection behaves as a lock, users have to preserve
  * ordering of freeze protection and other filesystem locks. Generally,
  * freeze protection should be the outermost lock. In particular, we have:
  *
  * sb_start_write
  *   -> i_mutex                 (write path, truncate, directory ops, ...)
  *   -> s_umount                (freeze_super, thaw_super)
  */
 static inline void sb_start_write(struct super_block *sb)
 {
         __sb_start_write(sb, SB_FREEZE_WRITE, true);
 }
 
 static inline int sb_start_write_trylock(struct super_block *sb)
 {
         return __sb_start_write(sb, SB_FREEZE_WRITE, false);
 }
 
 /**
  * sb_start_pagefault - get write access to a superblock from a page fault
  * @sb: the super we write to
  *
  * When a process starts handling write page fault, it should embed the
  * operation into sb_start_pagefault() - sb_end_pagefault() pair to get
  * exclusion against file system freezing. This is needed since the page fault
  * is going to dirty a page. This function increments number of running page
  * faults preventing freezing. If the file system is already frozen, the
  * function waits until the file system is thawed.
  *
  * Since page fault freeze protection behaves as a lock, users have to preserve
  * ordering of freeze protection and other filesystem locks. It is advised to
  * put sb_start_pagefault() close to mmap_sem in lock ordering. Page fault
  * handling code implies lock dependency:
  *
  * mmap_sem
  *   -> sb_start_pagefault
  */
 static inline void sb_start_pagefault(struct super_block *sb)
 {
         __sb_start_write(sb, SB_FREEZE_PAGEFAULT, true);
 }
 
 /*
  * sb_start_intwrite - get write access to a superblock for internal fs purposes
  * @sb: the super we write to
  *
  * This is the third level of protection against filesystem freezing. It is
  * free for use by a filesystem. The only requirement is that it must rank
  * below sb_start_pagefault.
  *
  * For example filesystem can call sb_start_intwrite() when starting a
  * transaction which somewhat eases handling of freezing for internal sources
  * of filesystem changes (internal fs threads, discarding preallocation on file
  * close, etc.).
  */
 static inline void sb_start_intwrite(struct super_block *sb)
 {
         __sb_start_write(sb, SB_FREEZE_FS, true);
 }
 
 
 extern bool inode_owner_or_capable(const struct inode *inode);
 
 /*
  * VFS helper functions..
  */
 extern int vfs_create(struct inode *, struct dentry *, umode_t, bool);
 extern int vfs_mkdir(struct inode *, struct dentry *, umode_t);
 extern int vfs_mknod(struct inode *, struct dentry *, umode_t, dev_t);
 extern int vfs_symlink(struct inode *, struct dentry *, const char *);
 extern int vfs_link(struct dentry *, struct inode *, struct dentry *, struct inode **);
 extern int vfs_rmdir(struct inode *, struct dentry *);
 extern int vfs_unlink(struct inode *, struct dentry *, struct inode **);
 extern int vfs_rename(struct inode *, struct dentry *, struct inode *, struct dentry *, struct inode **, unsigned int);
 extern int vfs_whiteout(struct inode *, struct dentry *);
 
 extern struct dentry *vfs_tmpfile(struct dentry *dentry, umode_t mode,
                                   int open_flag);
 
 /*
  * VFS file helper functions.
  */
 extern void inode_init_owner(struct inode *inode, const struct inode *dir,
                         umode_t mode);
 extern bool may_open_dev(const struct path *path);
 /*
  * VFS FS_IOC_FIEMAP helper definitions.
  */
 struct fiemap_extent_info {
         unsigned int fi_flags;          /* Flags as passed from user */
         unsigned int fi_extents_mapped; /* Number of mapped extents */
         unsigned int fi_extents_max;    /* Size of fiemap_extent array */
         struct fiemap_extent __user *fi_extents_start; /* Start of
                                                         fiemap_extent array */
 };
 int fiemap_fill_next_extent(struct fiemap_extent_info *info, u64 logical,
                             u64 phys, u64 len, u32 flags);
 int fiemap_check_flags(struct fiemap_extent_info *fieinfo, u32 fs_flags);
 
 /*
  * File types
  *
  * NOTE! These match bits 12..15 of stat.st_mode
  * (ie "(i_mode >> 12) & 15").
  */
 #define DT_UNKNOWN      0
 #define DT_FIFO         1
 #define DT_CHR          2
 #define DT_DIR          4
 #define DT_BLK          6
 #define DT_REG          8
 #define DT_LNK          10
 #define DT_SOCK         12
 #define DT_WHT          14
 
 /*
  * This is the "filldir" function type, used by readdir() to let
  * the kernel specify what kind of dirent layout it wants to have.
  * This allows the kernel to read directories into kernel space or
  * to have different dirent layouts depending on the binary type.
  */
 struct dir_context;
 typedef int (*filldir_t)(struct dir_context *, const char *, int, loff_t, u64,
                          unsigned);
 
 struct dir_context {
         const filldir_t actor;
         loff_t pos;
 };
 
 struct block_device_operations;
 
 /* These macros are for out of kernel modules to test that
  * the kernel supports the unlocked_ioctl and compat_ioctl
  * fields in struct file_operations. */
 #define HAVE_COMPAT_IOCTL 1
 #define HAVE_UNLOCKED_IOCTL 1
 
 /*
  * These flags let !MMU mmap() govern direct device mapping vs immediate
  * copying more easily for MAP_PRIVATE, especially for ROM filesystems.
  *
  * NOMMU_MAP_COPY:      Copy can be mapped (MAP_PRIVATE)
  * NOMMU_MAP_DIRECT:    Can be mapped directly (MAP_SHARED)
  * NOMMU_MAP_READ:      Can be mapped for reading
  * NOMMU_MAP_WRITE:     Can be mapped for writing
  * NOMMU_MAP_EXEC:      Can be mapped for execution
  */
 #define NOMMU_MAP_COPY          0x00000001
 #define NOMMU_MAP_DIRECT        0x00000008
 #define NOMMU_MAP_READ          VM_MAYREAD
 #define NOMMU_MAP_WRITE         VM_MAYWRITE
 #define NOMMU_MAP_EXEC          VM_MAYEXEC
 
 #define NOMMU_VMFLAGS \
         (NOMMU_MAP_READ | NOMMU_MAP_WRITE | NOMMU_MAP_EXEC)
 
 
 struct iov_iter;
 
 struct file_operations {
         struct module *owner;
         loff_t (*llseek) (struct file *, loff_t, int);
         ssize_t (*read) (struct file *, char __user *, size_t, loff_t *);
         ssize_t (*write) (struct file *, const char __user *, size_t, loff_t *);
         ssize_t (*read_iter) (struct kiocb *, struct iov_iter *);
         ssize_t (*write_iter) (struct kiocb *, struct iov_iter *);
         int (*iterate) (struct file *, struct dir_context *);
         int (*iterate_shared) (struct file *, struct dir_context *);
         unsigned int (*poll) (struct file *, struct poll_table_struct *);
         long (*unlocked_ioctl) (struct file *, unsigned int, unsigned long);
         long (*compat_ioctl) (struct file *, unsigned int, unsigned long);
         int (*mmap) (struct file *, struct vm_area_struct *);
         int (*open) (struct inode *, struct file *);
         int (*flush) (struct file *, fl_owner_t id);
         int (*release) (struct inode *, struct file *);
         int (*fsync) (struct file *, loff_t, loff_t, int datasync);
         int (*fasync) (int, struct file *, int);
         int (*lock) (struct file *, int, struct file_lock *);
         ssize_t (*sendpage) (struct file *, struct page *, int, size_t, loff_t *, int);
         unsigned long (*get_unmapped_area)(struct file *, unsigned long, unsigned long, unsigned long, unsigned long);
         int (*check_flags)(int);
         int (*flock) (struct file *, int, struct file_lock *);
         ssize_t (*splice_write)(struct pipe_inode_info *, struct file *, loff_t *, size_t, unsigned int);
         ssize_t (*splice_read)(struct file *, loff_t *, struct pipe_inode_info *, size_t, unsigned int);
         int (*setlease)(struct file *, long, struct file_lock **, void **);
         long (*fallocate)(struct file *file, int mode, loff_t offset,
                           loff_t len);
         void (*show_fdinfo)(struct seq_file *m, struct file *f);
 #ifndef CONFIG_MMU
         unsigned (*mmap_capabilities)(struct file *);
 #endif
         ssize_t (*copy_file_range)(struct file *, loff_t, struct file *,
                         loff_t, size_t, unsigned int);
         int (*clone_file_range)(struct file *, loff_t, struct file *, loff_t,
                         u64);
         ssize_t (*dedupe_file_range)(struct file *, u64, u64, struct file *,
                         u64);
 } __randomize_layout;
 
 struct inode_operations {
         struct dentry * (*lookup) (struct inode *,struct dentry *, unsigned int);
         const char * (*get_link) (struct dentry *, struct inode *, struct delayed_call *);
         int (*permission) (struct inode *, int);
         struct posix_acl * (*get_acl)(struct inode *, int);
 
         int (*readlink) (struct dentry *, char __user *,int);
 
         int (*create) (struct inode *,struct dentry *, umode_t, bool);
         int (*link) (struct dentry *,struct inode *,struct dentry *);
         int (*unlink) (struct inode *,struct dentry *);
         int (*symlink) (struct inode *,struct dentry *,const char *);
         int (*mkdir) (struct inode *,struct dentry *,umode_t);
         int (*rmdir) (struct inode *,struct dentry *);
         int (*mknod) (struct inode *,struct dentry *,umode_t,dev_t);
         int (*rename) (struct inode *, struct dentry *,
                         struct inode *, struct dentry *, unsigned int);
         int (*setattr) (struct dentry *, struct iattr *);
         int (*getattr) (const struct path *, struct kstat *, u32, unsigned int);
         ssize_t (*listxattr) (struct dentry *, char *, size_t);
         int (*fiemap)(struct inode *, struct fiemap_extent_info *, u64 start,
                       u64 len);
         int (*update_time)(struct inode *, struct timespec *, int);
         int (*atomic_open)(struct inode *, struct dentry *,
                            struct file *, unsigned open_flag,
                            umode_t create_mode, int *opened);
         int (*tmpfile) (struct inode *, struct dentry *, umode_t);
         int (*set_acl)(struct inode *, struct posix_acl *, int);
 } ____cacheline_aligned;
 
 static inline ssize_t call_read_iter(struct file *file, struct kiocb *kio,
                                      struct iov_iter *iter)
 {
         return file->f_op->read_iter(kio, iter);
 }
 
 static inline ssize_t call_write_iter(struct file *file, struct kiocb *kio,
                                       struct iov_iter *iter)
 {
         return file->f_op->write_iter(kio, iter);
 }
 
 static inline int call_mmap(struct file *file, struct vm_area_struct *vma)
 {
         return file->f_op->mmap(file, vma);
 }
 
 ssize_t rw_copy_check_uvector(int type, const struct iovec __user * uvector,
                               unsigned long nr_segs, unsigned long fast_segs,
                               struct iovec *fast_pointer,
                               struct iovec **ret_pointer);
 
 extern ssize_t __vfs_read(struct file *, char __user *, size_t, loff_t *);
 extern ssize_t __vfs_write(struct file *, const char __user *, size_t, loff_t *);
 extern ssize_t vfs_read(struct file *, char __user *, size_t, loff_t *);
 extern ssize_t vfs_write(struct file *, const char __user *, size_t, loff_t *);
 extern ssize_t vfs_readv(struct file *, const struct iovec __user *,
                 unsigned long, loff_t *, int);
 extern ssize_t vfs_writev(struct file *, const struct iovec __user *,
                 unsigned long, loff_t *, int);
 extern ssize_t vfs_copy_file_range(struct file *, loff_t , struct file *,
                                    loff_t, size_t, unsigned int);
 extern int vfs_clone_file_prep_inodes(struct inode *inode_in, loff_t pos_in,
                                       struct inode *inode_out, loff_t pos_out,
                                       u64 *len, bool is_dedupe);
 extern int vfs_clone_file_range(struct file *file_in, loff_t pos_in,
                 struct file *file_out, loff_t pos_out, u64 len);
 extern int vfs_dedupe_file_range_compare(struct inode *src, loff_t srcoff,
                                          struct inode *dest, loff_t destoff,
                                          loff_t len, bool *is_same);
 extern int vfs_dedupe_file_range(struct file *file,
                                  struct file_dedupe_range *same);
 
 struct super_operations {
         struct inode *(*alloc_inode)(struct super_block *sb);
         void (*destroy_inode)(struct inode *);
 
         void (*dirty_inode) (struct inode *, int flags);
         int (*write_inode) (struct inode *, struct writeback_control *wbc);
         int (*drop_inode) (struct inode *);
         void (*evict_inode) (struct inode *);
         void (*put_super) (struct super_block *);
         int (*sync_fs)(struct super_block *sb, int wait);
         int (*freeze_super) (struct super_block *);
         int (*freeze_fs) (struct super_block *);
         int (*thaw_super) (struct super_block *);
         int (*unfreeze_fs) (struct super_block *);
         int (*statfs) (struct dentry *, struct kstatfs *);
         int (*remount_fs) (struct super_block *, int *, char *);
         void (*umount_begin) (struct super_block *);
 
         int (*show_options)(struct seq_file *, struct dentry *);
         int (*show_devname)(struct seq_file *, struct dentry *);
         int (*show_path)(struct seq_file *, struct dentry *);
         int (*show_stats)(struct seq_file *, struct dentry *);
 #ifdef CONFIG_QUOTA
         ssize_t (*quota_read)(struct super_block *, int, char *, size_t, loff_t);
         ssize_t (*quota_write)(struct super_block *, int, const char *, size_t, loff_t);
         struct dquot **(*get_dquots)(struct inode *);
 #endif
         int (*bdev_try_to_free_page)(struct super_block*, struct page*, gfp_t);
         long (*nr_cached_objects)(struct super_block *,
                                   struct shrink_control *);
         long (*free_cached_objects)(struct super_block *,
                                     struct shrink_control *);
 };
 
 /*
  * Inode flags - they have no relation to superblock flags now
  */
 #define S_SYNC          1       /* Writes are synced at once */
 #define S_NOATIME       2       /* Do not update access times */
 #define S_APPEND        4       /* Append-only file */
 #define S_IMMUTABLE     8       /* Immutable file */
 #define S_DEAD          16      /* removed, but still open directory */
 #define S_NOQUOTA       32      /* Inode is not counted to quota */
 #define S_DIRSYNC       64      /* Directory modifications are synchronous */
 #define S_NOCMTIME      128     /* Do not update file c/mtime */
 #define S_SWAPFILE      256     /* Do not truncate: swapon got its bmaps */
 #define S_PRIVATE       512     /* Inode is fs-internal */
 #define S_IMA           1024    /* Inode has an associated IMA struct */
 #define S_AUTOMOUNT     2048    /* Automount/referral quasi-directory */
 #define S_NOSEC         4096    /* no suid or xattr security attributes */
 #ifdef CONFIG_FS_DAX
 #define S_DAX           8192    /* Direct Access, avoiding the page cache */
 #else
 #define S_DAX           0       /* Make all the DAX code disappear */
 #endif
 
 /*
  * Note that nosuid etc flags are inode-specific: setting some file-system
  * flags just means all the inodes inherit those flags by default. It might be
  * possible to override it selectively if you really wanted to with some
  * ioctl() that is not currently implemented.
  *
  * Exception: MS_RDONLY is always applied to the entire file system.
  *
  * Unfortunately, it is possible to change a filesystems flags with it mounted
  * with files in use.  This means that all of the inodes will not have their
  * i_flags updated.  Hence, i_flags no longer inherit the superblock mount
  * flags, so these have to be checked separately. -- rmk@arm.uk.linux.org
  */
 #define __IS_FLG(inode, flg)    ((inode)->i_sb->s_flags & (flg))
 
 #define IS_RDONLY(inode)        ((inode)->i_sb->s_flags & MS_RDONLY)
 #define IS_SYNC(inode)          (__IS_FLG(inode, MS_SYNCHRONOUS) || \
                                         ((inode)->i_flags & S_SYNC))
 #define IS_DIRSYNC(inode)       (__IS_FLG(inode, MS_SYNCHRONOUS|MS_DIRSYNC) || \
                                         ((inode)->i_flags & (S_SYNC|S_DIRSYNC)))
 #define IS_MANDLOCK(inode)      __IS_FLG(inode, MS_MANDLOCK)
 #define IS_NOATIME(inode)       __IS_FLG(inode, MS_RDONLY|MS_NOATIME)
 #define IS_I_VERSION(inode)     __IS_FLG(inode, MS_I_VERSION)
 
 #define IS_NOQUOTA(inode)       ((inode)->i_flags & S_NOQUOTA)
 #define IS_APPEND(inode)        ((inode)->i_flags & S_APPEND)
 #define IS_IMMUTABLE(inode)     ((inode)->i_flags & S_IMMUTABLE)
 #define IS_POSIXACL(inode)      __IS_FLG(inode, MS_POSIXACL)
 
 #define IS_DEADDIR(inode)       ((inode)->i_flags & S_DEAD)
 #define IS_NOCMTIME(inode)      ((inode)->i_flags & S_NOCMTIME)
 #define IS_SWAPFILE(inode)      ((inode)->i_flags & S_SWAPFILE)
 #define IS_PRIVATE(inode)       ((inode)->i_flags & S_PRIVATE)
 #define IS_IMA(inode)           ((inode)->i_flags & S_IMA)
 #define IS_AUTOMOUNT(inode)     ((inode)->i_flags & S_AUTOMOUNT)
 #define IS_NOSEC(inode)         ((inode)->i_flags & S_NOSEC)
 #define IS_DAX(inode)           ((inode)->i_flags & S_DAX)
 
 #define IS_WHITEOUT(inode)      (S_ISCHR(inode->i_mode) && \
                                  (inode)->i_rdev == WHITEOUT_DEV)
 
 static inline bool HAS_UNMAPPED_ID(struct inode *inode)
 {
         return !uid_valid(inode->i_uid) || !gid_valid(inode->i_gid);
 }
 
 static inline enum rw_hint file_write_hint(struct file *file)
 {
         if (file->f_write_hint != WRITE_LIFE_NOT_SET)
                 return file->f_write_hint;
 
         return file_inode(file)->i_write_hint;
 }
 
 static inline int iocb_flags(struct file *file);
 
 static inline void init_sync_kiocb(struct kiocb *kiocb, struct file *filp)
 {
         *kiocb = (struct kiocb) {
                 .ki_filp = filp,
                 .ki_flags = iocb_flags(filp),
                 .ki_hint = file_write_hint(filp),
         };
 }
 
 /*
  * Inode state bits.  Protected by inode->i_lock
  *
  * Three bits determine the dirty state of the inode, I_DIRTY_SYNC,
  * I_DIRTY_DATASYNC and I_DIRTY_PAGES.
  *
  * Four bits define the lifetime of an inode.  Initially, inodes are I_NEW,
  * until that flag is cleared.  I_WILL_FREE, I_FREEING and I_CLEAR are set at
  * various stages of removing an inode.
  *
  * Two bits are used for locking and completion notification, I_NEW and I_SYNC.
  *
  * I_DIRTY_SYNC         Inode is dirty, but doesn't have to be written on
  *                      fdatasync().  i_atime is the usual cause.
  * I_DIRTY_DATASYNC     Data-related inode changes pending. We keep track of
  *                      these changes separately from I_DIRTY_SYNC so that we
  *                      don't have to write inode on fdatasync() when only
  *                      mtime has changed in it.
  * I_DIRTY_PAGES        Inode has dirty pages.  Inode itself may be clean.
  * I_NEW                Serves as both a mutex and completion notification.
  *                      New inodes set I_NEW.  If two processes both create
  *                      the same inode, one of them will release its inode and
  *                      wait for I_NEW to be released before returning.
  *                      Inodes in I_WILL_FREE, I_FREEING or I_CLEAR state can
  *                      also cause waiting on I_NEW, without I_NEW actually
  *                      being set.  find_inode() uses this to prevent returning
  *                      nearly-dead inodes.
  * I_WILL_FREE          Must be set when calling write_inode_now() if i_count
  *                      is zero.  I_FREEING must be set when I_WILL_FREE is
  *                      cleared.
  * I_FREEING            Set when inode is about to be freed but still has dirty
  *                      pages or buffers attached or the inode itself is still
  *                      dirty.
  * I_CLEAR              Added by clear_inode().  In this state the inode is
  *                      clean and can be destroyed.  Inode keeps I_FREEING.
  *
  *                      Inodes that are I_WILL_FREE, I_FREEING or I_CLEAR are
  *                      prohibited for many purposes.  iget() must wait for
  *                      the inode to be completely released, then create it
  *                      anew.  Other functions will just ignore such inodes,
  *                      if appropriate.  I_NEW is used for waiting.
  *
  * I_SYNC               Writeback of inode is running. The bit is set during
  *                      data writeback, and cleared with a wakeup on the bit
  *                      address once it is done. The bit is also used to pin
  *                      the inode in memory for flusher thread.
  *
  * I_REFERENCED         Marks the inode as recently references on the LRU list.
  *
  * I_DIO_WAKEUP         Never set.  Only used as a key for wait_on_bit().
  *
  * I_WB_SWITCH          Cgroup bdi_writeback switching in progress.  Used to
  *                      synchronize competing switching instances and to tell
  *                      wb stat updates to grab mapping->tree_lock.  See
  *                      inode_switch_wb_work_fn() for details.
  *
  * I_OVL_INUSE          Used by overlayfs to get exclusive ownership on upper
  *                      and work dirs among overlayfs mounts.
  *
  * Q: What is the difference between I_WILL_FREE and I_FREEING?
  */
 #define I_DIRTY_SYNC            (1 << 0)
 #define I_DIRTY_DATASYNC        (1 << 1)
 #define I_DIRTY_PAGES           (1 << 2)
 #define __I_NEW                 3
 #define I_NEW                   (1 << __I_NEW)
 #define I_WILL_FREE             (1 << 4)
 #define I_FREEING               (1 << 5)
 #define I_CLEAR                 (1 << 6)
 #define __I_SYNC                7
 #define I_SYNC                  (1 << __I_SYNC)
 #define I_REFERENCED            (1 << 8)
 #define __I_DIO_WAKEUP          9
 #define I_DIO_WAKEUP            (1 << __I_DIO_WAKEUP)
 #define I_LINKABLE              (1 << 10)
 #define I_DIRTY_TIME            (1 << 11)
 #define __I_DIRTY_TIME_EXPIRED  12
 #define I_DIRTY_TIME_EXPIRED    (1 << __I_DIRTY_TIME_EXPIRED)
 #define I_WB_SWITCH             (1 << 13)
 #define I_OVL_INUSE                     (1 << 14)
 
 #define I_DIRTY (I_DIRTY_SYNC | I_DIRTY_DATASYNC | I_DIRTY_PAGES)
 #define I_DIRTY_ALL (I_DIRTY | I_DIRTY_TIME)
 
 extern void __mark_inode_dirty(struct inode *, int);
 static inline void mark_inode_dirty(struct inode *inode)
 {
         __mark_inode_dirty(inode, I_DIRTY);
 }
 
 static inline void mark_inode_dirty_sync(struct inode *inode)
 {
         __mark_inode_dirty(inode, I_DIRTY_SYNC);
 }
 
 extern void inc_nlink(struct inode *inode);
 extern void drop_nlink(struct inode *inode);
 extern void clear_nlink(struct inode *inode);
 extern void set_nlink(struct inode *inode, unsigned int nlink);
 
 static inline void inode_inc_link_count(struct inode *inode)
 {
         inc_nlink(inode);
         mark_inode_dirty(inode);
 }
 
 static inline void inode_dec_link_count(struct inode *inode)
 {
         drop_nlink(inode);
         mark_inode_dirty(inode);
 }
 
 /**
  * inode_inc_iversion - increments i_version
  * @inode: inode that need to be updated
  *
  * Every time the inode is modified, the i_version field will be incremented.
  * The filesystem has to be mounted with i_version flag
  */
 
 static inline void inode_inc_iversion(struct inode *inode)
 {
        spin_lock(&inode->i_lock);
        inode->i_version++;
        spin_unlock(&inode->i_lock);
 }
 
 enum file_time_flags {
         S_ATIME = 1,
         S_MTIME = 2,
         S_CTIME = 4,
         S_VERSION = 8,
 };
 
 extern void touch_atime(const struct path *);
 static inline void file_accessed(struct file *file)
 {
         if (!(file->f_flags & O_NOATIME))
                 touch_atime(&file->f_path);
 }
 
 int sync_inode(struct inode *inode, struct writeback_control *wbc);
 int sync_inode_metadata(struct inode *inode, int wait);
 
 struct file_system_type {
         const char *name;
         int fs_flags;
 #define FS_REQUIRES_DEV         1 
 #define FS_BINARY_MOUNTDATA     2
 #define FS_HAS_SUBTYPE          4
 #define FS_USERNS_MOUNT         8       /* Can be mounted by userns root */
 #define FS_RENAME_DOES_D_MOVE   32768   /* FS will handle d_move() during rename() internally. */
         struct dentry *(*mount) (struct file_system_type *, int,
                        const char *, void *);
         void (*kill_sb) (struct super_block *);
         struct module *owner;
         struct file_system_type * next;
         struct hlist_head fs_supers;
 
         struct lock_class_key s_lock_key;
         struct lock_class_key s_umount_key;
         struct lock_class_key s_vfs_rename_key;
         struct lock_class_key s_writers_key[SB_FREEZE_LEVELS];
 
         struct lock_class_key i_lock_key;
         struct lock_class_key i_mutex_key;
         struct lock_class_key i_mutex_dir_key;
 };
 
 #define MODULE_ALIAS_FS(NAME) MODULE_ALIAS("fs-" NAME)
 
 extern struct dentry *mount_ns(struct file_system_type *fs_type,
         int flags, void *data, void *ns, struct user_namespace *user_ns,
         int (*fill_super)(struct super_block *, void *, int));
 extern struct dentry *mount_bdev(struct file_system_type *fs_type,
         int flags, const char *dev_name, void *data,
         int (*fill_super)(struct super_block *, void *, int));
 extern struct dentry *mount_single(struct file_system_type *fs_type,
         int flags, void *data,
         int (*fill_super)(struct super_block *, void *, int));
 extern struct dentry *mount_nodev(struct file_system_type *fs_type,
         int flags, void *data,
         int (*fill_super)(struct super_block *, void *, int));
 extern struct dentry *mount_subtree(struct vfsmount *mnt, const char *path);
 void generic_shutdown_super(struct super_block *sb);
 void kill_block_super(struct super_block *sb);
 void kill_anon_super(struct super_block *sb);
 void kill_litter_super(struct super_block *sb);
 void deactivate_super(struct super_block *sb);
 void deactivate_locked_super(struct super_block *sb);
 int set_anon_super(struct super_block *s, void *data);
 int get_anon_bdev(dev_t *);
 void free_anon_bdev(dev_t);
 struct super_block *sget_userns(struct file_system_type *type,
                         int (*test)(struct super_block *,void *),
                         int (*set)(struct super_block *,void *),
                         int flags, struct user_namespace *user_ns,
                         void *data);
 struct super_block *sget(struct file_system_type *type,
                         int (*test)(struct super_block *,void *),
                         int (*set)(struct super_block *,void *),
                         int flags, void *data);
 extern struct dentry *mount_pseudo_xattr(struct file_system_type *, char *,
                                          const struct super_operations *ops,
                                          const struct xattr_handler **xattr,
                                          const struct dentry_operations *dops,
                                          unsigned long);
 
 static inline struct dentry *
 mount_pseudo(struct file_system_type *fs_type, char *name,
              const struct super_operations *ops,
              const struct dentry_operations *dops, unsigned long magic)
 {
         return mount_pseudo_xattr(fs_type, name, ops, NULL, dops, magic);
 }
 
 /* Alas, no aliases. Too much hassle with bringing module.h everywhere */
 #define fops_get(fops) \
         (((fops) && try_module_get((fops)->owner) ? (fops) : NULL))
 #define fops_put(fops) \
         do { if (fops) module_put((fops)->owner); } while(0)
 /*
  * This one is to be used *ONLY* from ->open() instances.
  * fops must be non-NULL, pinned down *and* module dependencies
  * should be sufficient to pin the caller down as well.
  */
 #define replace_fops(f, fops) \
         do {    \
                 struct file *__file = (f); \
                 fops_put(__file->f_op); \
                 BUG_ON(!(__file->f_op = (fops))); \
         } while(0)
 
 extern int register_filesystem(struct file_system_type *);
 extern int unregister_filesystem(struct file_system_type *);
 extern struct vfsmount *kern_mount_data(struct file_system_type *, void *data);
 #define kern_mount(type) kern_mount_data(type, NULL)
 extern void kern_unmount(struct vfsmount *mnt);
 extern int may_umount_tree(struct vfsmount *);
 extern int may_umount(struct vfsmount *);
 extern long do_mount(const char *, const char __user *,
                      const char *, unsigned long, void *);
 extern struct vfsmount *collect_mounts(const struct path *);
 extern void drop_collected_mounts(struct vfsmount *);
 extern int iterate_mounts(int (*)(struct vfsmount *, void *), void *,
                           struct vfsmount *);
 extern int vfs_statfs(const struct path *, struct kstatfs *);
 extern int user_statfs(const char __user *, struct kstatfs *);
 extern int fd_statfs(int, struct kstatfs *);
 extern int vfs_ustat(dev_t, struct kstatfs *);
 extern int freeze_super(struct super_block *super);
 extern int thaw_super(struct super_block *super);
 extern bool our_mnt(struct vfsmount *mnt);
 extern __printf(2, 3)
 int super_setup_bdi_name(struct super_block *sb, char *fmt, ...);
 extern int super_setup_bdi(struct super_block *sb);
 
 extern int current_umask(void);
 
 extern void ihold(struct inode * inode);
 extern void iput(struct inode *);
 extern int generic_update_time(struct inode *, struct timespec *, int);
 
 /* /sys/fs */
 extern struct kobject *fs_kobj;
 
 #define MAX_RW_COUNT (INT_MAX & PAGE_MASK)
 
 #ifdef CONFIG_MANDATORY_FILE_LOCKING
 extern int locks_mandatory_locked(struct file *);
 extern int locks_mandatory_area(struct inode *, struct file *, loff_t, loff_t, unsigned char);
 
 /*
  * Candidates for mandatory locking have the setgid bit set
  * but no group execute bit -  an otherwise meaningless combination.
  */
 
 static inline int __mandatory_lock(struct inode *ino)
 {
         return (ino->i_mode & (S_ISGID | S_IXGRP)) == S_ISGID;
 }
 
 /*
  * ... and these candidates should be on MS_MANDLOCK mounted fs,
  * otherwise these will be advisory locks
  */
 
 static inline int mandatory_lock(struct inode *ino)
 {
         return IS_MANDLOCK(ino) && __mandatory_lock(ino);
 }
 
 static inline int locks_verify_locked(struct file *file)
 {
         if (mandatory_lock(locks_inode(file)))
                 return locks_mandatory_locked(file);
         return 0;
 }
 
 static inline int locks_verify_truncate(struct inode *inode,
                                     struct file *f,
                                     loff_t size)
 {
         if (!inode->i_flctx || !mandatory_lock(inode))
                 return 0;
 
         if (size < inode->i_size) {
                 return locks_mandatory_area(inode, f, size, inode->i_size - 1,
                                 F_WRLCK);
         } else {
                 return locks_mandatory_area(inode, f, inode->i_size, size - 1,
                                 F_WRLCK);
         }
 }
 
 #else /* !CONFIG_MANDATORY_FILE_LOCKING */
 
 static inline int locks_mandatory_locked(struct file *file)
 {
         return 0;
 }
 
 static inline int locks_mandatory_area(struct inode *inode, struct file *filp,
                                        loff_t start, loff_t end, unsigned char type)
 {
         return 0;
 }
 
 static inline int __mandatory_lock(struct inode *inode)
 {
         return 0;
 }
 
 static inline int mandatory_lock(struct inode *inode)
 {
         return 0;
 }
 
 static inline int locks_verify_locked(struct file *file)
 {
         return 0;
 }
 
 static inline int locks_verify_truncate(struct inode *inode, struct file *filp,
                                         size_t size)
 {
         return 0;
 }
 
 #endif /* CONFIG_MANDATORY_FILE_LOCKING */
 
 
 #ifdef CONFIG_FILE_LOCKING
 static inline int break_lease(struct inode *inode, unsigned int mode)
 {
         /*
          * Since this check is lockless, we must ensure that any refcounts
          * taken are done before checking i_flctx->flc_lease. Otherwise, we
          * could end up racing with tasks trying to set a new lease on this
          * file.
          */
         smp_mb();
         if (inode->i_flctx && !list_empty_careful(&inode->i_flctx->flc_lease))
                 return __break_lease(inode, mode, FL_LEASE);
         return 0;
 }
 
 static inline int break_deleg(struct inode *inode, unsigned int mode)
 {
         /*
          * Since this check is lockless, we must ensure that any refcounts
          * taken are done before checking i_flctx->flc_lease. Otherwise, we
          * could end up racing with tasks trying to set a new lease on this
          * file.
          */
         smp_mb();
         if (inode->i_flctx && !list_empty_careful(&inode->i_flctx->flc_lease))
                 return __break_lease(inode, mode, FL_DELEG);
         return 0;
 }
 
 static inline int try_break_deleg(struct inode *inode, struct inode **delegated_inode)
 {
         int ret;
 
         ret = break_deleg(inode, O_WRONLY|O_NONBLOCK);
         if (ret == -EWOULDBLOCK && delegated_inode) {
                 *delegated_inode = inode;
                 ihold(inode);
         }
         return ret;
 }
 
 static inline int break_deleg_wait(struct inode **delegated_inode)
 {
         int ret;
 
         ret = break_deleg(*delegated_inode, O_WRONLY);
         iput(*delegated_inode);
         *delegated_inode = NULL;
         return ret;
 }
 
 static inline int break_layout(struct inode *inode, bool wait)
 {
         smp_mb();
         if (inode->i_flctx && !list_empty_careful(&inode->i_flctx->flc_lease))
                 return __break_lease(inode,
                                 wait ? O_WRONLY : O_WRONLY | O_NONBLOCK,
                                 FL_LAYOUT);
         return 0;
 }
 
 #else /* !CONFIG_FILE_LOCKING */
 static inline int break_lease(struct inode *inode, unsigned int mode)
 {
         return 0;
 }
 
 static inline int break_deleg(struct inode *inode, unsigned int mode)
 {
         return 0;
 }
 
 static inline int try_break_deleg(struct inode *inode, struct inode **delegated_inode)
 {
         return 0;
 }
 
 static inline int break_deleg_wait(struct inode **delegated_inode)
 {
         BUG();
         return 0;
 }
 
 static inline int break_layout(struct inode *inode, bool wait)
 {
         return 0;
 }
 
 #endif /* CONFIG_FILE_LOCKING */
 
 /* fs/open.c */
 struct audit_names;
 struct filename {
         const char              *name;  /* pointer to actual string */
         const __user char       *uptr;  /* original userland pointer */
         struct audit_names      *aname;
         int                     refcnt;
         const char              iname[];
 };
 
 extern long vfs_truncate(const struct path *, loff_t);
 extern int do_truncate(struct dentry *, loff_t start, unsigned int time_attrs,
                        struct file *filp);
 extern int vfs_fallocate(struct file *file, int mode, loff_t offset,
                         loff_t len);
 extern long do_sys_open(int dfd, const char __user *filename, int flags,
                         umode_t mode);
 extern struct file *file_open_name(struct filename *, int, umode_t);
 extern struct file *filp_open(const char *, int, umode_t);
 extern struct file *file_open_root(struct dentry *, struct vfsmount *,
                                    const char *, int, umode_t);
 extern struct file * dentry_open(const struct path *, int, const struct cred *);
 extern int filp_close(struct file *, fl_owner_t id);
 
 extern struct filename *getname_flags(const char __user *, int, int *);
 extern struct filename *getname(const char __user *);
 extern struct filename *getname_kernel(const char *);
 extern void putname(struct filename *name);
 
 enum {
         FILE_CREATED = 1,
         FILE_OPENED = 2
 };
 extern int finish_open(struct file *file, struct dentry *dentry,
                         int (*open)(struct inode *, struct file *),
                         int *opened);
 extern int finish_no_open(struct file *file, struct dentry *dentry);
 
 /* fs/ioctl.c */
 
 extern int ioctl_preallocate(struct file *filp, void __user *argp);
 
 /* fs/dcache.c */
 extern void __init vfs_caches_init_early(void);
 extern void __init vfs_caches_init(void);
 
 extern struct kmem_cache *names_cachep;
 
 #define __getname()             kmem_cache_alloc(names_cachep, GFP_KERNEL)
 #define __putname(name)         kmem_cache_free(names_cachep, (void *)(name))
 
 #ifdef CONFIG_BLOCK
 extern int register_blkdev(unsigned int, const char *);
 extern void unregister_blkdev(unsigned int, const char *);
 extern void bdev_unhash_inode(dev_t dev);
 extern struct block_device *bdget(dev_t);
 extern struct block_device *bdgrab(struct block_device *bdev);
 extern void bd_set_size(struct block_device *, loff_t size);
 extern void bd_forget(struct inode *inode);
 extern void bdput(struct block_device *);
 extern void invalidate_bdev(struct block_device *);
 extern void iterate_bdevs(void (*)(struct block_device *, void *), void *);
 extern int sync_blockdev(struct block_device *bdev);
 extern void kill_bdev(struct block_device *);
 extern struct super_block *freeze_bdev(struct block_device *);
 extern void emergency_thaw_all(void);
 extern int thaw_bdev(struct block_device *bdev, struct super_block *sb);
 extern int fsync_bdev(struct block_device *);
 
 extern struct super_block *blockdev_superblock;
 
 static inline bool sb_is_blkdev_sb(struct super_block *sb)
 {
         return sb == blockdev_superblock;
 }
 #else
 static inline void bd_forget(struct inode *inode) {}
 static inline int sync_blockdev(struct block_device *bdev) { return 0; }
 static inline void kill_bdev(struct block_device *bdev) {}
 static inline void invalidate_bdev(struct block_device *bdev) {}
 
 static inline struct super_block *freeze_bdev(struct block_device *sb)
 {
         return NULL;
 }
 
 static inline int thaw_bdev(struct block_device *bdev, struct super_block *sb)
 {
         return 0;
 }
 
 static inline void iterate_bdevs(void (*f)(struct block_device *, void *), void *arg)
 {
 }
 
 static inline bool sb_is_blkdev_sb(struct super_block *sb)
 {
         return false;
 }
 #endif
 extern int sync_filesystem(struct super_block *);
 extern const struct file_operations def_blk_fops;
 extern const struct file_operations def_chr_fops;
 #ifdef CONFIG_BLOCK
 extern int ioctl_by_bdev(struct block_device *, unsigned, unsigned long);
 extern int blkdev_ioctl(struct block_device *, fmode_t, unsigned, unsigned long);
 extern long compat_blkdev_ioctl(struct file *, unsigned, unsigned long);
 extern int blkdev_get(struct block_device *bdev, fmode_t mode, void *holder);
 extern struct block_device *blkdev_get_by_path(const char *path, fmode_t mode,
                                                void *holder);
 extern struct block_device *blkdev_get_by_dev(dev_t dev, fmode_t mode,
                                               void *holder);
 extern void blkdev_put(struct block_device *bdev, fmode_t mode);
 extern int __blkdev_reread_part(struct block_device *bdev);
 extern int blkdev_reread_part(struct block_device *bdev);
 
 #ifdef CONFIG_SYSFS
 extern int bd_link_disk_holder(struct block_device *bdev, struct gendisk *disk);
 extern void bd_unlink_disk_holder(struct block_device *bdev,
                                   struct gendisk *disk);
 #else
 static inline int bd_link_disk_holder(struct block_device *bdev,
                                       struct gendisk *disk)
 {
         return 0;
 }
 static inline void bd_unlink_disk_holder(struct block_device *bdev,
                                          struct gendisk *disk)
 {
 }
 #endif
 #endif
 
 /* fs/char_dev.c */
 #define CHRDEV_MAJOR_HASH_SIZE  255
 /* Marks the bottom of the first segment of free char majors */
 #define CHRDEV_MAJOR_DYN_END 234
 extern int alloc_chrdev_region(dev_t *, unsigned, unsigned, const char *);
 extern int register_chrdev_region(dev_t, unsigned, const char *);
 extern int __register_chrdev(unsigned int major, unsigned int baseminor,
                              unsigned int count, const char *name,
                              const struct file_operations *fops);
 extern void __unregister_chrdev(unsigned int major, unsigned int baseminor,
                                 unsigned int count, const char *name);
 extern void unregister_chrdev_region(dev_t, unsigned);
 extern void chrdev_show(struct seq_file *,off_t);
 
 static inline int register_chrdev(unsigned int major, const char *name,
                                   const struct file_operations *fops)
 {
         return __register_chrdev(major, 0, 256, name, fops);
 }
 
 static inline void unregister_chrdev(unsigned int major, const char *name)
 {
         __unregister_chrdev(major, 0, 256, name);
 }
 
 /* fs/block_dev.c */
 #define BDEVNAME_SIZE   32      /* Largest string for a blockdev identifier */
 #define BDEVT_SIZE      10      /* Largest string for MAJ:MIN for blkdev */
 
 #ifdef CONFIG_BLOCK
 #define BLKDEV_MAJOR_HASH_SIZE  255
 extern const char *__bdevname(dev_t, char *buffer);
 extern const char *bdevname(struct block_device *bdev, char *buffer);
 extern struct block_device *lookup_bdev(const char *);
 extern void blkdev_show(struct seq_file *,off_t);
 
 #else
 #define BLKDEV_MAJOR_HASH_SIZE  0
 #endif
 
 extern void init_special_inode(struct inode *, umode_t, dev_t);
 
 /* Invalid inode operations -- fs/bad_inode.c */
 extern void make_bad_inode(struct inode *);
 extern bool is_bad_inode(struct inode *);
 
 #ifdef CONFIG_BLOCK
 extern void check_disk_size_change(struct gendisk *disk,
                                    struct block_device *bdev);
 extern int revalidate_disk(struct gendisk *);
 extern int check_disk_change(struct block_device *);
 extern int __invalidate_device(struct block_device *, bool);
 extern int invalidate_partition(struct gendisk *, int);
 #endif
 unsigned long invalidate_mapping_pages(struct address_space *mapping,
                                         pgoff_t start, pgoff_t end);
 
 static inline void invalidate_remote_inode(struct inode *inode)
 {
         if (S_ISREG(inode->i_mode) || S_ISDIR(inode->i_mode) ||
             S_ISLNK(inode->i_mode))
                 invalidate_mapping_pages(inode->i_mapping, 0, -1);
 }
 extern int invalidate_inode_pages2(struct address_space *mapping);
 extern int invalidate_inode_pages2_range(struct address_space *mapping,
                                          pgoff_t start, pgoff_t end);
 extern int write_inode_now(struct inode *, int);
 extern int filemap_fdatawrite(struct address_space *);
 extern int filemap_flush(struct address_space *);
 extern int filemap_fdatawait(struct address_space *);
 extern int filemap_fdatawait_keep_errors(struct address_space *mapping);
 extern int filemap_fdatawait_range(struct address_space *, loff_t lstart,
                                    loff_t lend);
 extern bool filemap_range_has_page(struct address_space *, loff_t lstart,
                                   loff_t lend);
 extern int filemap_write_and_wait(struct address_space *mapping);
 extern int filemap_write_and_wait_range(struct address_space *mapping,
                                         loff_t lstart, loff_t lend);
 extern int __filemap_fdatawrite_range(struct address_space *mapping,
                                 loff_t start, loff_t end, int sync_mode);
 extern int filemap_fdatawrite_range(struct address_space *mapping,
                                 loff_t start, loff_t end);
 extern int filemap_check_errors(struct address_space *mapping);
 
 extern void __filemap_set_wb_err(struct address_space *mapping, int err);
 extern int __must_check file_check_and_advance_wb_err(struct file *file);
 extern int __must_check file_write_and_wait_range(struct file *file,
                                                 loff_t start, loff_t end);
 
 /**
  * filemap_set_wb_err - set a writeback error on an address_space
  * @mapping: mapping in which to set writeback error
  * @err: error to be set in mapping
  *
  * When writeback fails in some way, we must record that error so that
  * userspace can be informed when fsync and the like are called.  We endeavor
  * to report errors on any file that was open at the time of the error.  Some
  * internal callers also need to know when writeback errors have occurred.
  *
  * When a writeback error occurs, most filesystems will want to call
  * filemap_set_wb_err to record the error in the mapping so that it will be
  * automatically reported whenever fsync is called on the file.
  *
  * FIXME: mention FS_* flag here?
  */
 static inline void filemap_set_wb_err(struct address_space *mapping, int err)
 {
         /* Fastpath for common case of no error */
         if (unlikely(err))
                 __filemap_set_wb_err(mapping, err);
 }
 
 /**
  * filemap_check_wb_error - has an error occurred since the mark was sampled?
  * @mapping: mapping to check for writeback errors
  * @since: previously-sampled errseq_t
  *
  * Grab the errseq_t value from the mapping, and see if it has changed "since"
  * the given value was sampled.
  *
  * If it has then report the latest error set, otherwise return 0.
  */
 static inline int filemap_check_wb_err(struct address_space *mapping,
                                         errseq_t since)
 {
         return errseq_check(&mapping->wb_err, since);
 }
 
 /**
  * filemap_sample_wb_err - sample the current errseq_t to test for later errors
  * @mapping: mapping to be sampled
  *
  * Writeback errors are always reported relative to a particular sample point
  * in the past. This function provides those sample points.
  */
 static inline errseq_t filemap_sample_wb_err(struct address_space *mapping)
 {
         return errseq_sample(&mapping->wb_err);
 }
 
 extern int vfs_fsync_range(struct file *file, loff_t start, loff_t end,
                            int datasync);
 extern int vfs_fsync(struct file *file, int datasync);
 
 /*
  * Sync the bytes written if this was a synchronous write.  Expect ki_pos
  * to already be updated for the write, and will return either the amount
  * of bytes passed in, or an error if syncing the file failed.
  */
 static inline ssize_t generic_write_sync(struct kiocb *iocb, ssize_t count)
 {
         if (iocb->ki_flags & IOCB_DSYNC) {
                 int ret = vfs_fsync_range(iocb->ki_filp,
                                 iocb->ki_pos - count, iocb->ki_pos - 1,
                                 (iocb->ki_flags & IOCB_SYNC) ? 0 : 1);
                 if (ret)
                         return ret;
         }
 
         return count;
 }
 
 extern void emergency_sync(void);
 extern void emergency_remount(void);
 #ifdef CONFIG_BLOCK
 extern sector_t bmap(struct inode *, sector_t);
 #endif
 extern int notify_change(struct dentry *, struct iattr *, struct inode **);
 extern int inode_permission(struct inode *, int);
 extern int __inode_permission(struct inode *, int);
 extern int generic_permission(struct inode *, int);
 extern int __check_sticky(struct inode *dir, struct inode *inode);
 
 static inline bool execute_ok(struct inode *inode)
 {
         return (inode->i_mode & S_IXUGO) || S_ISDIR(inode->i_mode);
 }
 
 static inline void file_start_write(struct file *file)
 {
         if (!S_ISREG(file_inode(file)->i_mode))
                 return;
         __sb_start_write(file_inode(file)->i_sb, SB_FREEZE_WRITE, true);
 }
 
 static inline bool file_start_write_trylock(struct file *file)
 {
         if (!S_ISREG(file_inode(file)->i_mode))
                 return true;
         return __sb_start_write(file_inode(file)->i_sb, SB_FREEZE_WRITE, false);
 }
 
 static inline void file_end_write(struct file *file)
 {
         if (!S_ISREG(file_inode(file)->i_mode))
                 return;
         __sb_end_write(file_inode(file)->i_sb, SB_FREEZE_WRITE);
 }
 
 static inline int do_clone_file_range(struct file *file_in, loff_t pos_in,
                                       struct file *file_out, loff_t pos_out,
                                       u64 len)
 {
         int ret;
 
         file_start_write(file_out);
         ret = vfs_clone_file_range(file_in, pos_in, file_out, pos_out, len);
         file_end_write(file_out);
 
         return ret;
 }
 
 /*
  * get_write_access() gets write permission for a file.
  * put_write_access() releases this write permission.
  * This is used for regular files.
  * We cannot support write (and maybe mmap read-write shared) accesses and
  * MAP_DENYWRITE mmappings simultaneously. The i_writecount field of an inode
  * can have the following values:
  * 0: no writers, no VM_DENYWRITE mappings
  * < 0: (-i_writecount) vm_area_structs with VM_DENYWRITE set exist
  * > 0: (i_writecount) users are writing to the file.
  *
  * Normally we operate on that counter with atomic_{inc,dec} and it's safe
  * except for the cases where we don't hold i_writecount yet. Then we need to
  * use {get,deny}_write_access() - these functions check the sign and refuse
  * to do the change if sign is wrong.
  */
 static inline int get_write_access(struct inode *inode)
 {
         return atomic_inc_unless_negative(&inode->i_writecount) ? 0 : -ETXTBSY;
 }
 static inline int deny_write_access(struct file *file)
 {
         struct inode *inode = file_inode(file);
         return atomic_dec_unless_positive(&inode->i_writecount) ? 0 : -ETXTBSY;
 }
 static inline void put_write_access(struct inode * inode)
 {
         atomic_dec(&inode->i_writecount);
 }
 static inline void allow_write_access(struct file *file)
 {
         if (file)
                 atomic_inc(&file_inode(file)->i_writecount);
 }
 static inline bool inode_is_open_for_write(const struct inode *inode)
 {
         return atomic_read(&inode->i_writecount) > 0;
 }
 
 #ifdef CONFIG_IMA
 static inline void i_readcount_dec(struct inode *inode)
 {
         BUG_ON(!atomic_read(&inode->i_readcount));
         atomic_dec(&inode->i_readcount);
 }
 static inline void i_readcount_inc(struct inode *inode)
 {
         atomic_inc(&inode->i_readcount);
 }
 #else
 static inline void i_readcount_dec(struct inode *inode)
 {
         return;
 }
 static inline void i_readcount_inc(struct inode *inode)
 {
         return;
 }
 #endif
 extern int do_pipe_flags(int *, int);
 
 #define __kernel_read_file_id(id) \
         id(UNKNOWN, unknown)            \
         id(FIRMWARE, firmware)          \
         id(FIRMWARE_PREALLOC_BUFFER, firmware)  \
         id(MODULE, kernel-module)               \
         id(KEXEC_IMAGE, kexec-image)            \
         id(KEXEC_INITRAMFS, kexec-initramfs)    \
         id(POLICY, security-policy)             \
         id(MAX_ID, )
 
 #define __fid_enumify(ENUM, dummy) READING_ ## ENUM,
 #define __fid_stringify(dummy, str) #str,
 
 enum kernel_read_file_id {
         __kernel_read_file_id(__fid_enumify)
 };
 
 static const char * const kernel_read_file_str[] = {
         __kernel_read_file_id(__fid_stringify)
 };
 
 static inline const char *kernel_read_file_id_str(enum kernel_read_file_id id)
 {
         if ((unsigned)id >= READING_MAX_ID)
                 return kernel_read_file_str[READING_UNKNOWN];
 
         return kernel_read_file_str[id];
 }
 
 extern int kernel_read(struct file *, loff_t, char *, unsigned long);
 extern int kernel_read_file(struct file *, void **, loff_t *, loff_t,
                             enum kernel_read_file_id);
 extern int kernel_read_file_from_path(char *, void **, loff_t *, loff_t,
                                       enum kernel_read_file_id);
 extern int kernel_read_file_from_fd(int, void **, loff_t *, loff_t,
                                     enum kernel_read_file_id);
 extern ssize_t kernel_write(struct file *, const char *, size_t, loff_t);
 extern ssize_t __kernel_write(struct file *, const char *, size_t, loff_t *);
 extern struct file * open_exec(const char *);
  
 /* fs/dcache.c -- generic fs support functions */
 extern bool is_subdir(struct dentry *, struct dentry *);
 extern bool path_is_under(const struct path *, const struct path *);
 
 extern char *file_path(struct file *, char *, int);
 
 #include <linux/err.h>
 
 /* needed for stackable file system support */
 extern loff_t default_llseek(struct file *file, loff_t offset, int whence);
 
 extern loff_t vfs_llseek(struct file *file, loff_t offset, int whence);
 
 extern int inode_init_always(struct super_block *, struct inode *);
 extern void inode_init_once(struct inode *);
 extern void address_space_init_once(struct address_space *mapping);
 extern struct inode * igrab(struct inode *);
 extern ino_t iunique(struct super_block *, ino_t);
 extern int inode_needs_sync(struct inode *inode);
 extern int generic_delete_inode(struct inode *inode);
 static inline int generic_drop_inode(struct inode *inode)
 {
         return !inode->i_nlink || inode_unhashed(inode);
 }
 
 extern struct inode *ilookup5_nowait(struct super_block *sb,
                 unsigned long hashval, int (*test)(struct inode *, void *),
                 void *data);
 extern struct inode *ilookup5(struct super_block *sb, unsigned long hashval,
                 int (*test)(struct inode *, void *), void *data);
 extern struct inode *ilookup(struct super_block *sb, unsigned long ino);
 
 extern struct inode * iget5_locked(struct super_block *, unsigned long, int (*test)(struct inode *, void *), int (*set)(struct inode *, void *), void *);
 extern struct inode * iget_locked(struct super_block *, unsigned long);
 extern struct inode *find_inode_nowait(struct super_block *,
                                        unsigned long,
                                        int (*match)(struct inode *,
                                                     unsigned long, void *),
                                        void *data);
 extern int insert_inode_locked4(struct inode *, unsigned long, int (*test)(struct inode *, void *), void *);
 extern int insert_inode_locked(struct inode *);
 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 extern void lockdep_annotate_inode_mutex_key(struct inode *inode);
 #else
 static inline void lockdep_annotate_inode_mutex_key(struct inode *inode) { };
 #endif
 extern void unlock_new_inode(struct inode *);
 extern unsigned int get_next_ino(void);
 extern void evict_inodes(struct super_block *sb);
 
 extern void __iget(struct inode * inode);
 extern void iget_failed(struct inode *);
 extern void clear_inode(struct inode *);
 extern void __destroy_inode(struct inode *);
 extern struct inode *new_inode_pseudo(struct super_block *sb);
 extern struct inode *new_inode(struct super_block *sb);
 extern void free_inode_nonrcu(struct inode *inode);
 extern int should_remove_suid(struct dentry *);
 extern int file_remove_privs(struct file *);
 
 extern void __insert_inode_hash(struct inode *, unsigned long hashval);
 static inline void insert_inode_hash(struct inode *inode)
 {
         __insert_inode_hash(inode, inode->i_ino);
 }
 
 extern void __remove_inode_hash(struct inode *);
 static inline void remove_inode_hash(struct inode *inode)
 {
         if (!inode_unhashed(inode) && !hlist_fake(&inode->i_hash))
                 __remove_inode_hash(inode);
 }
 
 extern void inode_sb_list_add(struct inode *inode);
 
 #ifdef CONFIG_BLOCK
 extern int bdev_read_only(struct block_device *);
 #endif
 extern int set_blocksize(struct block_device *, int);
 extern int sb_set_blocksize(struct super_block *, int);
 extern int sb_min_blocksize(struct super_block *, int);
 
 extern int generic_file_mmap(struct file *, struct vm_area_struct *);
 extern int generic_file_readonly_mmap(struct file *, struct vm_area_struct *);
 extern ssize_t generic_write_checks(struct kiocb *, struct iov_iter *);
 extern ssize_t generic_file_read_iter(struct kiocb *, struct iov_iter *);
 extern ssize_t __generic_file_write_iter(struct kiocb *, struct iov_iter *);
 extern ssize_t generic_file_write_iter(struct kiocb *, struct iov_iter *);
 extern ssize_t generic_file_direct_write(struct kiocb *, struct iov_iter *);
 extern ssize_t generic_perform_write(struct file *, struct iov_iter *, loff_t);
 
 ssize_t vfs_iter_read(struct file *file, struct iov_iter *iter, loff_t *ppos,
                 int flags);
 ssize_t vfs_iter_write(struct file *file, struct iov_iter *iter, loff_t *ppos,
                 int flags);
 
 /* fs/block_dev.c */
 extern ssize_t blkdev_read_iter(struct kiocb *iocb, struct iov_iter *to);
 extern ssize_t blkdev_write_iter(struct kiocb *iocb, struct iov_iter *from);
 extern int blkdev_fsync(struct file *filp, loff_t start, loff_t end,
                         int datasync);
 extern void block_sync_page(struct page *page);
 
 /* fs/splice.c */
 extern ssize_t generic_file_splice_read(struct file *, loff_t *,
                 struct pipe_inode_info *, size_t, unsigned int);
 extern ssize_t iter_file_splice_write(struct pipe_inode_info *,
                 struct file *, loff_t *, size_t, unsigned int);
 extern ssize_t generic_splice_sendpage(struct pipe_inode_info *pipe,
                 struct file *out, loff_t *, size_t len, unsigned int flags);
 extern long do_splice_direct(struct file *in, loff_t *ppos, struct file *out,
                 loff_t *opos, size_t len, unsigned int flags);
 
 
 extern void
 file_ra_state_init(struct file_ra_state *ra, struct address_space *mapping);
 extern loff_t noop_llseek(struct file *file, loff_t offset, int whence);
 extern loff_t no_llseek(struct file *file, loff_t offset, int whence);
 extern loff_t vfs_setpos(struct file *file, loff_t offset, loff_t maxsize);
 extern loff_t generic_file_llseek(struct file *file, loff_t offset, int whence);
 extern loff_t generic_file_llseek_size(struct file *file, loff_t offset,
                 int whence, loff_t maxsize, loff_t eof);
 extern loff_t fixed_size_llseek(struct file *file, loff_t offset,
                 int whence, loff_t size);
 extern loff_t no_seek_end_llseek_size(struct file *, loff_t, int, loff_t);
 extern loff_t no_seek_end_llseek(struct file *, loff_t, int);
 extern int generic_file_open(struct inode * inode, struct file * filp);
 extern int nonseekable_open(struct inode * inode, struct file * filp);
 
 #ifdef CONFIG_BLOCK
 typedef void (dio_submit_t)(struct bio *bio, struct inode *inode,
                             loff_t file_offset);
 
 enum {
         /* need locking between buffered and direct access */
         DIO_LOCKING     = 0x01,
 
         /* filesystem does not support filling holes */
         DIO_SKIP_HOLES  = 0x02,
 
         /* filesystem can handle aio writes beyond i_size */
         DIO_ASYNC_EXTEND = 0x04,
 
         /* inode/fs/bdev does not need truncate protection */
         DIO_SKIP_DIO_COUNT = 0x08,
 };
 
 void dio_end_io(struct bio *bio);
 
 ssize_t __blockdev_direct_IO(struct kiocb *iocb, struct inode *inode,
                              struct block_device *bdev, struct iov_iter *iter,
                              get_block_t get_block,
                              dio_iodone_t end_io, dio_submit_t submit_io,
                              int flags);
 
 static inline ssize_t blockdev_direct_IO(struct kiocb *iocb,
                                          struct inode *inode,
                                          struct iov_iter *iter,
                                          get_block_t get_block)
 {
         return __blockdev_direct_IO(iocb, inode, inode->i_sb->s_bdev, iter,
                         get_block, NULL, NULL, DIO_LOCKING | DIO_SKIP_HOLES);
 }
 #endif
 
 void inode_dio_wait(struct inode *inode);
 
 /*
  * inode_dio_begin - signal start of a direct I/O requests
  * @inode: inode the direct I/O happens on
  *
  * This is called once we've finished processing a direct I/O request,
  * and is used to wake up callers waiting for direct I/O to be quiesced.
  */
 static inline void inode_dio_begin(struct inode *inode)
 {
         atomic_inc(&inode->i_dio_count);
 }
 
 /*
  * inode_dio_end - signal finish of a direct I/O requests
  * @inode: inode the direct I/O happens on
  *
  * This is called once we've finished processing a direct I/O request,
  * and is used to wake up callers waiting for direct I/O to be quiesced.
  */
 static inline void inode_dio_end(struct inode *inode)
 {
         if (atomic_dec_and_test(&inode->i_dio_count))
                 wake_up_bit(&inode->i_state, __I_DIO_WAKEUP);
 }
 
 extern void inode_set_flags(struct inode *inode, unsigned int flags,
                             unsigned int mask);
 
 extern const struct file_operations generic_ro_fops;
 
 #define special_file(m) (S_ISCHR(m)||S_ISBLK(m)||S_ISFIFO(m)||S_ISSOCK(m))
 
 extern int readlink_copy(char __user *, int, const char *);
 extern int page_readlink(struct dentry *, char __user *, int);
 extern const char *page_get_link(struct dentry *, struct inode *,
                                  struct delayed_call *);
 extern void page_put_link(void *);
 extern int __page_symlink(struct inode *inode, const char *symname, int len,
                 int nofs);
 extern int page_symlink(struct inode *inode, const char *symname, int len);
 extern const struct inode_operations page_symlink_inode_operations;
 extern void kfree_link(void *);
 extern void generic_fillattr(struct inode *, struct kstat *);
 extern int vfs_getattr_nosec(const struct path *, struct kstat *, u32, unsigned int);
 extern int vfs_getattr(const struct path *, struct kstat *, u32, unsigned int);
 void __inode_add_bytes(struct inode *inode, loff_t bytes);
 void inode_add_bytes(struct inode *inode, loff_t bytes);
 void __inode_sub_bytes(struct inode *inode, loff_t bytes);
 void inode_sub_bytes(struct inode *inode, loff_t bytes);
 loff_t inode_get_bytes(struct inode *inode);
 void inode_set_bytes(struct inode *inode, loff_t bytes);
 const char *simple_get_link(struct dentry *, struct inode *,
                             struct delayed_call *);
 extern const struct inode_operations simple_symlink_inode_operations;
 
 extern int iterate_dir(struct file *, struct dir_context *);
 
 extern int vfs_statx(int, const char __user *, int, struct kstat *, u32);
 extern int vfs_statx_fd(unsigned int, struct kstat *, u32, unsigned int);
 
 static inline int vfs_stat(const char __user *filename, struct kstat *stat)
 {
         return vfs_statx(AT_FDCWD, filename, AT_NO_AUTOMOUNT,
                          stat, STATX_BASIC_STATS);
 }
 static inline int vfs_lstat(const char __user *name, struct kstat *stat)
 {
         return vfs_statx(AT_FDCWD, name, AT_SYMLINK_NOFOLLOW | AT_NO_AUTOMOUNT,
                          stat, STATX_BASIC_STATS);
 }
 static inline int vfs_fstatat(int dfd, const char __user *filename,
                               struct kstat *stat, int flags)
 {
         return vfs_statx(dfd, filename, flags | AT_NO_AUTOMOUNT,
                          stat, STATX_BASIC_STATS);
 }
 static inline int vfs_fstat(int fd, struct kstat *stat)
 {
         return vfs_statx_fd(fd, stat, STATX_BASIC_STATS, 0);
 }
 
 
 extern const char *vfs_get_link(struct dentry *, struct delayed_call *);
 extern int vfs_readlink(struct dentry *, char __user *, int);
 
 extern int __generic_block_fiemap(struct inode *inode,
                                   struct fiemap_extent_info *fieinfo,
                                   loff_t start, loff_t len,
                                   get_block_t *get_block);
 extern int generic_block_fiemap(struct inode *inode,
                                 struct fiemap_extent_info *fieinfo, u64 start,
                                 u64 len, get_block_t *get_block);
 
 extern struct file_system_type *get_filesystem(struct file_system_type *fs);
 extern void put_filesystem(struct file_system_type *fs);
 extern struct file_system_type *get_fs_type(const char *name);
 extern struct super_block *get_super(struct block_device *);
 extern struct super_block *get_super_thawed(struct block_device *);
 extern struct super_block *get_super_exclusive_thawed(struct block_device *bdev);
 extern struct super_block *get_active_super(struct block_device *bdev);
 extern void drop_super(struct super_block *sb);
 extern void drop_super_exclusive(struct super_block *sb);
 extern void iterate_supers(void (*)(struct super_block *, void *), void *);
 extern void iterate_supers_type(struct file_system_type *,
                                 void (*)(struct super_block *, void *), void *);
 
 extern int dcache_dir_open(struct inode *, struct file *);
 extern int dcache_dir_close(struct inode *, struct file *);
 extern loff_t dcache_dir_lseek(struct file *, loff_t, int);
 extern int dcache_readdir(struct file *, struct dir_context *);
 extern int simple_setattr(struct dentry *, struct iattr *);
 extern int simple_getattr(const struct path *, struct kstat *, u32, unsigned int);
 extern int simple_statfs(struct dentry *, struct kstatfs *);
 extern int simple_open(struct inode *inode, struct file *file);
 extern int simple_link(struct dentry *, struct inode *, struct dentry *);
 extern int simple_unlink(struct inode *, struct dentry *);
 extern int simple_rmdir(struct inode *, struct dentry *);
 extern int simple_rename(struct inode *, struct dentry *,
                          struct inode *, struct dentry *, unsigned int);
 extern int noop_fsync(struct file *, loff_t, loff_t, int);
 extern int simple_empty(struct dentry *);
 extern int simple_readpage(struct file *file, struct page *page);
 extern int simple_write_begin(struct file *file, struct address_space *mapping,
                         loff_t pos, unsigned len, unsigned flags,
                         struct page **pagep, void **fsdata);
 extern int simple_write_end(struct file *file, struct address_space *mapping,
                         loff_t pos, unsigned len, unsigned copied,
                         struct page *page, void *fsdata);
 extern int always_delete_dentry(const struct dentry *);
 extern struct inode *alloc_anon_inode(struct super_block *);
 extern int simple_nosetlease(struct file *, long, struct file_lock **, void **);
 extern const struct dentry_operations simple_dentry_operations;
 
 extern struct dentry *simple_lookup(struct inode *, struct dentry *, unsigned int flags);
 extern ssize_t generic_read_dir(struct file *, char __user *, size_t, loff_t *);
 extern const struct file_operations simple_dir_operations;
 extern const struct inode_operations simple_dir_inode_operations;
 extern void make_empty_dir_inode(struct inode *inode);
 extern bool is_empty_dir_inode(struct inode *inode);
 struct tree_descr { const char *name; const struct file_operations *ops; int mode; };
 struct dentry *d_alloc_name(struct dentry *, const char *);
 extern int simple_fill_super(struct super_block *, unsigned long,
                              const struct tree_descr *);
 extern int simple_pin_fs(struct file_system_type *, struct vfsmount **mount, int *count);
 extern void simple_release_fs(struct vfsmount **mount, int *count);
 
 extern ssize_t simple_read_from_buffer(void __user *to, size_t count,
                         loff_t *ppos, const void *from, size_t available);
 extern ssize_t simple_write_to_buffer(void *to, size_t available, loff_t *ppos,
                 const void __user *from, size_t count);
 
 extern int __generic_file_fsync(struct file *, loff_t, loff_t, int);
 extern int generic_file_fsync(struct file *, loff_t, loff_t, int);
 
 extern int generic_check_addressable(unsigned, u64);
 
 #ifdef CONFIG_MIGRATION
 extern int buffer_migrate_page(struct address_space *,
                                 struct page *, struct page *,
                                 enum migrate_mode);
 #else
 #define buffer_migrate_page NULL
 #endif
 
 extern int setattr_prepare(struct dentry *, struct iattr *);
 extern int inode_newsize_ok(const struct inode *, loff_t offset);
 extern void setattr_copy(struct inode *inode, const struct iattr *attr);
 
 extern int file_update_time(struct file *file);
 
 static inline bool io_is_direct(struct file *filp)
 {
         return (filp->f_flags & O_DIRECT) || IS_DAX(filp->f_mapping->host);
 }
 
 static inline bool vma_is_dax(struct vm_area_struct *vma)
 {
         return vma->vm_file && IS_DAX(vma->vm_file->f_mapping->host);
 }
 
 static inline int iocb_flags(struct file *file)
 {
         int res = 0;
         if (file->f_flags & O_APPEND)
                 res |= IOCB_APPEND;
         if (io_is_direct(file))
                 res |= IOCB_DIRECT;
         if ((file->f_flags & O_DSYNC) || IS_SYNC(file->f_mapping->host))
                 res |= IOCB_DSYNC;
         if (file->f_flags & __O_SYNC)
                 res |= IOCB_SYNC;
         return res;
 }
 
 static inline int kiocb_set_rw_flags(struct kiocb *ki, int flags)
 {
         if (unlikely(flags & ~RWF_SUPPORTED))
                 return -EOPNOTSUPP;
 
         if (flags & RWF_NOWAIT) {
                 if (!(ki->ki_filp->f_mode & FMODE_AIO_NOWAIT))
                         return -EOPNOTSUPP;
                 ki->ki_flags |= IOCB_NOWAIT;
         }
         if (flags & RWF_HIPRI)
                 ki->ki_flags |= IOCB_HIPRI;
         if (flags & RWF_DSYNC)
                 ki->ki_flags |= IOCB_DSYNC;
         if (flags & RWF_SYNC)
                 ki->ki_flags |= (IOCB_DSYNC | IOCB_SYNC);
         return 0;
 }
 
 static inline ino_t parent_ino(struct dentry *dentry)
 {
         ino_t res;
 
         /*
          * Don't strictly need d_lock here? If the parent ino could change
          * then surely we'd have a deeper race in the caller?
          */
         spin_lock(&dentry->d_lock);
         res = dentry->d_parent->d_inode->i_ino;
         spin_unlock(&dentry->d_lock);
         return res;
 }
 
 /* Transaction based IO helpers */
 
 /*
  * An argresp is stored in an allocated page and holds the
  * size of the argument or response, along with its content
  */
 struct simple_transaction_argresp {
         ssize_t size;
         char data[0];
 };
 
 #define SIMPLE_TRANSACTION_LIMIT (PAGE_SIZE - sizeof(struct simple_transaction_argresp))
 
 char *simple_transaction_get(struct file *file, const char __user *buf,
                                 size_t size);
 ssize_t simple_transaction_read(struct file *file, char __user *buf,
                                 size_t size, loff_t *pos);
 int simple_transaction_release(struct inode *inode, struct file *file);
 
 void simple_transaction_set(struct file *file, size_t n);
 
 /*
  * simple attribute files
  *
  * These attributes behave similar to those in sysfs:
  *
  * Writing to an attribute immediately sets a value, an open file can be
  * written to multiple times.
  *
  * Reading from an attribute creates a buffer from the value that might get
  * read with multiple read calls. When the attribute has been read
  * completely, no further read calls are possible until the file is opened
  * again.
  *
  * All attributes contain a text representation of a numeric value
  * that are accessed with the get() and set() functions.
  */
 #define DEFINE_SIMPLE_ATTRIBUTE(__fops, __get, __set, __fmt)            \
 static int __fops ## _open(struct inode *inode, struct file *file)      \
 {                                                                       \
         __simple_attr_check_format(__fmt, 0ull);                        \
         return simple_attr_open(inode, file, __get, __set, __fmt);      \
 }                                                                       \
 static const struct file_operations __fops = {                          \
         .owner   = THIS_MODULE,                                         \
         .open    = __fops ## _open,                                     \
         .release = simple_attr_release,                                 \
         .read    = simple_attr_read,                                    \
         .write   = simple_attr_write,                                   \
         .llseek  = generic_file_llseek,                                 \
 }
 
 static inline __printf(1, 2)
 void __simple_attr_check_format(const char *fmt, ...)
 {
         /* don't do anything, just let the compiler check the arguments; */
 }
 
 int simple_attr_open(struct inode *inode, struct file *file,
                      int (*get)(void *, u64 *), int (*set)(void *, u64),
                      const char *fmt);
 int simple_attr_release(struct inode *inode, struct file *file);
 ssize_t simple_attr_read(struct file *file, char __user *buf,
                          size_t len, loff_t *ppos);
 ssize_t simple_attr_write(struct file *file, const char __user *buf,
                           size_t len, loff_t *ppos);
 
 struct ctl_table;
 int proc_nr_files(struct ctl_table *table, int write,
                   void __user *buffer, size_t *lenp, loff_t *ppos);
 int proc_nr_dentry(struct ctl_table *table, int write,
                   void __user *buffer, size_t *lenp, loff_t *ppos);
 int proc_nr_inodes(struct ctl_table *table, int write,
                    void __user *buffer, size_t *lenp, loff_t *ppos);
 int __init get_filesystem_list(char *buf);
 
 #define __FMODE_EXEC            ((__force int) FMODE_EXEC)
 #define __FMODE_NONOTIFY        ((__force int) FMODE_NONOTIFY)
 
 #define ACC_MODE(x) ("\004\002\006\006"[(x)&O_ACCMODE])
 #define OPEN_FMODE(flag) ((__force fmode_t)(((flag + 1) & O_ACCMODE) | \
                                             (flag & __FMODE_NONOTIFY)))
 
 static inline bool is_sxid(umode_t mode)
 {
         return (mode & S_ISUID) || ((mode & S_ISGID) && (mode & S_IXGRP));
 }
 
 static inline int check_sticky(struct inode *dir, struct inode *inode)
 {
         if (!(dir->i_mode & S_ISVTX))
                 return 0;
 
         return __check_sticky(dir, inode);
 }
 
 static inline void inode_has_no_xattr(struct inode *inode)
 {
         if (!is_sxid(inode->i_mode) && (inode->i_sb->s_flags & MS_NOSEC))
                 inode->i_flags |= S_NOSEC;
 }
 
 static inline bool is_root_inode(struct inode *inode)
 {
         return inode == inode->i_sb->s_root->d_inode;
 }
 
 static inline bool dir_emit(struct dir_context *ctx,
                             const char *name, int namelen,
                             u64 ino, unsigned type)
 {
         return ctx->actor(ctx, name, namelen, ctx->pos, ino, type) == 0;
 }
 static inline bool dir_emit_dot(struct file *file, struct dir_context *ctx)
 {
         return ctx->actor(ctx, ".", 1, ctx->pos,
                           file->f_path.dentry->d_inode->i_ino, DT_DIR) == 0;
 }
 static inline bool dir_emit_dotdot(struct file *file, struct dir_context *ctx)
 {
         return ctx->actor(ctx, "..", 2, ctx->pos,
                           parent_ino(file->f_path.dentry), DT_DIR) == 0;
 }
 static inline bool dir_emit_dots(struct file *file, struct dir_context *ctx)
 {
         if (ctx->pos == 0) {
                 if (!dir_emit_dot(file, ctx))
                         return false;
                 ctx->pos = 1;
         }
         if (ctx->pos == 1) {
                 if (!dir_emit_dotdot(file, ctx))
                         return false;
                 ctx->pos = 2;
         }
         return true;
 }
 static inline bool dir_relax(struct inode *inode)
 {
         inode_unlock(inode);
         inode_lock(inode);
         return !IS_DEADDIR(inode);
 }
 
 static inline bool dir_relax_shared(struct inode *inode)
 {
         inode_unlock_shared(inode);
         inode_lock_shared(inode);
         return !IS_DEADDIR(inode);
 }
 
 extern bool path_noexec(const struct path *path);
 extern void inode_nohighmem(struct inode *inode);
 
 #endif /* _LINUX_FS_H */