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

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  1 /*
  2  * descriptor table internals; you almost certainly want file.h instead.
  3  */
  4 
  5 #ifndef __LINUX_FDTABLE_H
  6 #define __LINUX_FDTABLE_H
  7 
  8 #include <linux/posix_types.h>
  9 #include <linux/compiler.h>
 10 #include <linux/spinlock.h>
 11 #include <linux/rcupdate.h>
 12 #include <linux/types.h>
 13 #include <linux/init.h>
 14 #include <linux/fs.h>
 15 
 16 #include <asm/atomic.h>
 17 
 18 /*
 19  * The default fd array needs to be at least BITS_PER_LONG,
 20  * as this is the granularity returned by copy_fdset().
 21  */
 22 #define NR_OPEN_DEFAULT BITS_PER_LONG
 23 
 24 /*
 25  * The embedded_fd_set is a small fd_set,
 26  * suitable for most tasks (which open <= BITS_PER_LONG files)
 27  */
 28 struct embedded_fd_set {
 29         unsigned long fds_bits[1];
 30 };
 31 
 32 struct fdtable {
 33         unsigned int max_fds;
 34         struct file __rcu **fd;      /* current fd array */
 35         fd_set *close_on_exec;
 36         fd_set *open_fds;
 37         struct rcu_head rcu;
 38         struct fdtable *next;
 39 };
 40 
 41 /*
 42  * Open file table structure
 43  */
 44 struct files_struct {
 45   /*
 46    * read mostly part
 47    */
 48         atomic_t count;
 49         struct fdtable __rcu *fdt;
 50         struct fdtable fdtab;
 51   /*
 52    * written part on a separate cache line in SMP
 53    */
 54         spinlock_t file_lock ____cacheline_aligned_in_smp;
 55         int next_fd;
 56         struct embedded_fd_set close_on_exec_init;
 57         struct embedded_fd_set open_fds_init;
 58         struct file __rcu * fd_array[NR_OPEN_DEFAULT];
 59 };
 60 
 61 #define rcu_dereference_check_fdtable(files, fdtfd) \
 62         (rcu_dereference_check((fdtfd), \
 63                                rcu_read_lock_held() || \
 64                                lockdep_is_held(&(files)->file_lock) || \
 65                                atomic_read(&(files)->count) == 1 || \
 66                                rcu_my_thread_group_empty()))
 67 
 68 #define files_fdtable(files) \
 69                 (rcu_dereference_check_fdtable((files), (files)->fdt))
 70 
 71 struct file_operations;
 72 struct vfsmount;
 73 struct dentry;
 74 
 75 extern int expand_files(struct files_struct *, int nr);
 76 extern void free_fdtable_rcu(struct rcu_head *rcu);
 77 extern void __init files_defer_init(void);
 78 
 79 static inline void free_fdtable(struct fdtable *fdt)
 80 {
 81         call_rcu(&fdt->rcu, free_fdtable_rcu);
 82 }
 83 
 84 static inline struct file * fcheck_files(struct files_struct *files, unsigned int fd)
 85 {
 86         struct file * file = NULL;
 87         struct fdtable *fdt = files_fdtable(files);
 88 
 89         if (fd < fdt->max_fds)
 90                 file = rcu_dereference_check_fdtable(files, fdt->fd[fd]);
 91         return file;
 92 }
 93 
 94 /*
 95  * Check whether the specified fd has an open file.
 96  */
 97 #define fcheck(fd)      fcheck_files(current->files, fd)
 98 
 99 struct task_struct;
100 
101 struct files_struct *get_files_struct(struct task_struct *);
102 void put_files_struct(struct files_struct *fs);
103 void reset_files_struct(struct files_struct *);
104 int unshare_files(struct files_struct **);
105 struct files_struct *dup_fd(struct files_struct *, int *);
106 
107 extern struct kmem_cache *files_cachep;
108 
109 #endif /* __LINUX_FDTABLE_H */
110 

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