~ [ source navigation ] ~ [ diff markup ] ~ [ identifier search ] ~

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

Version: ~ [ linux-5.1-rc5 ] ~ [ linux-5.0.7 ] ~ [ linux-4.20.17 ] ~ [ linux-4.19.34 ] ~ [ linux-4.18.20 ] ~ [ linux-4.17.19 ] ~ [ linux-4.16.18 ] ~ [ linux-4.15.18 ] ~ [ linux-4.14.111 ] ~ [ linux-4.13.16 ] ~ [ linux-4.12.14 ] ~ [ linux-4.11.12 ] ~ [ linux-4.10.17 ] ~ [ linux-4.9.168 ] ~ [ linux-4.8.17 ] ~ [ linux-4.7.10 ] ~ [ linux-4.6.7 ] ~ [ linux-4.5.7 ] ~ [ linux-4.4.178 ] ~ [ linux-4.3.6 ] ~ [ linux-4.2.8 ] ~ [ linux-4.1.52 ] ~ [ linux-4.0.9 ] ~ [ linux-3.19.8 ] ~ [ linux-3.18.138 ] ~ [ linux-3.17.8 ] ~ [ linux-3.16.65 ] ~ [ linux-3.15.10 ] ~ [ linux-3.14.79 ] ~ [ linux-3.13.11 ] ~ [ linux-3.12.74 ] ~ [ linux-3.11.10 ] ~ [ linux-3.10.108 ] ~ [ linux-3.9.11 ] ~ [ linux-3.8.13 ] ~ [ linux-3.7.10 ] ~ [ linux-3.6.11 ] ~ [ linux-3.5.7 ] ~ [ linux-3.4.113 ] ~ [ linux-3.3.8 ] ~ [ linux-3.2.102 ] ~ [ linux-3.1.10 ] ~ [ linux-3.0.101 ] ~ [ linux-2.6.39.4 ] ~ [ linux-2.6.38.8 ] ~ [ linux-2.6.37.6 ] ~ [ linux-2.6.36.4 ] ~ [ linux-2.6.35.14 ] ~ [ linux-2.6.34.15 ] ~ [ linux-2.6.33.20 ] ~ [ linux-2.6.32.71 ] ~ [ linux-2.6.0 ] ~ [ linux-2.4.37.11 ] ~ [ unix-v6-master ] ~ [ ccs-tools-1.8.5 ] ~ [ policy-sample ] ~
Architecture: ~ [ i386 ] ~ [ alpha ] ~ [ m68k ] ~ [ mips ] ~ [ ppc ] ~ [ sparc ] ~ [ sparc64 ] ~

  1 #ifndef IOCONTEXT_H
  2 #define IOCONTEXT_H
  3 
  4 #include <linux/radix-tree.h>
  5 #include <linux/rcupdate.h>
  6 #include <linux/workqueue.h>
  7 
  8 enum {
  9         ICQ_EXITED              = 1 << 2,
 10 };
 11 
 12 /*
 13  * An io_cq (icq) is association between an io_context (ioc) and a
 14  * request_queue (q).  This is used by elevators which need to track
 15  * information per ioc - q pair.
 16  *
 17  * Elevator can request use of icq by setting elevator_type->icq_size and
 18  * ->icq_align.  Both size and align must be larger than that of struct
 19  * io_cq and elevator can use the tail area for private information.  The
 20  * recommended way to do this is defining a struct which contains io_cq as
 21  * the first member followed by private members and using its size and
 22  * align.  For example,
 23  *
 24  *      struct snail_io_cq {
 25  *              struct io_cq    icq;
 26  *              int             poke_snail;
 27  *              int             feed_snail;
 28  *      };
 29  *
 30  *      struct elevator_type snail_elv_type {
 31  *              .ops =          { ... },
 32  *              .icq_size =     sizeof(struct snail_io_cq),
 33  *              .icq_align =    __alignof__(struct snail_io_cq),
 34  *              ...
 35  *      };
 36  *
 37  * If icq_size is set, block core will manage icq's.  All requests will
 38  * have its ->elv.icq field set before elevator_ops->elevator_set_req_fn()
 39  * is called and be holding a reference to the associated io_context.
 40  *
 41  * Whenever a new icq is created, elevator_ops->elevator_init_icq_fn() is
 42  * called and, on destruction, ->elevator_exit_icq_fn().  Both functions
 43  * are called with both the associated io_context and queue locks held.
 44  *
 45  * Elevator is allowed to lookup icq using ioc_lookup_icq() while holding
 46  * queue lock but the returned icq is valid only until the queue lock is
 47  * released.  Elevators can not and should not try to create or destroy
 48  * icq's.
 49  *
 50  * As icq's are linked from both ioc and q, the locking rules are a bit
 51  * complex.
 52  *
 53  * - ioc lock nests inside q lock.
 54  *
 55  * - ioc->icq_list and icq->ioc_node are protected by ioc lock.
 56  *   q->icq_list and icq->q_node by q lock.
 57  *
 58  * - ioc->icq_tree and ioc->icq_hint are protected by ioc lock, while icq
 59  *   itself is protected by q lock.  However, both the indexes and icq
 60  *   itself are also RCU managed and lookup can be performed holding only
 61  *   the q lock.
 62  *
 63  * - icq's are not reference counted.  They are destroyed when either the
 64  *   ioc or q goes away.  Each request with icq set holds an extra
 65  *   reference to ioc to ensure it stays until the request is completed.
 66  *
 67  * - Linking and unlinking icq's are performed while holding both ioc and q
 68  *   locks.  Due to the lock ordering, q exit is simple but ioc exit
 69  *   requires reverse-order double lock dance.
 70  */
 71 struct io_cq {
 72         struct request_queue    *q;
 73         struct io_context       *ioc;
 74 
 75         /*
 76          * q_node and ioc_node link io_cq through icq_list of q and ioc
 77          * respectively.  Both fields are unused once ioc_exit_icq() is
 78          * called and shared with __rcu_icq_cache and __rcu_head which are
 79          * used for RCU free of io_cq.
 80          */
 81         union {
 82                 struct list_head        q_node;
 83                 struct kmem_cache       *__rcu_icq_cache;
 84         };
 85         union {
 86                 struct hlist_node       ioc_node;
 87                 struct rcu_head         __rcu_head;
 88         };
 89 
 90         unsigned int            flags;
 91 };
 92 
 93 /*
 94  * I/O subsystem state of the associated processes.  It is refcounted
 95  * and kmalloc'ed. These could be shared between processes.
 96  */
 97 struct io_context {
 98         atomic_long_t refcount;
 99         atomic_t active_ref;
100         atomic_t nr_tasks;
101 
102         /* all the fields below are protected by this lock */
103         spinlock_t lock;
104 
105         unsigned short ioprio;
106 
107         /*
108          * For request batching
109          */
110         int nr_batch_requests;     /* Number of requests left in the batch */
111         unsigned long last_waited; /* Time last woken after wait for request */
112 
113         struct radix_tree_root  icq_tree;
114         struct io_cq __rcu      *icq_hint;
115         struct hlist_head       icq_list;
116 
117         struct work_struct release_work;
118 };
119 
120 /**
121  * get_io_context_active - get active reference on ioc
122  * @ioc: ioc of interest
123  *
124  * Only iocs with active reference can issue new IOs.  This function
125  * acquires an active reference on @ioc.  The caller must already have an
126  * active reference on @ioc.
127  */
128 static inline void get_io_context_active(struct io_context *ioc)
129 {
130         WARN_ON_ONCE(atomic_long_read(&ioc->refcount) <= 0);
131         WARN_ON_ONCE(atomic_read(&ioc->active_ref) <= 0);
132         atomic_long_inc(&ioc->refcount);
133         atomic_inc(&ioc->active_ref);
134 }
135 
136 static inline void ioc_task_link(struct io_context *ioc)
137 {
138         get_io_context_active(ioc);
139 
140         WARN_ON_ONCE(atomic_read(&ioc->nr_tasks) <= 0);
141         atomic_inc(&ioc->nr_tasks);
142 }
143 
144 struct task_struct;
145 #ifdef CONFIG_BLOCK
146 void put_io_context(struct io_context *ioc);
147 void put_io_context_active(struct io_context *ioc);
148 void exit_io_context(struct task_struct *task);
149 struct io_context *get_task_io_context(struct task_struct *task,
150                                        gfp_t gfp_flags, int node);
151 #else
152 struct io_context;
153 static inline void put_io_context(struct io_context *ioc) { }
154 static inline void exit_io_context(struct task_struct *task) { }
155 #endif
156 
157 #endif
158 

~ [ source navigation ] ~ [ diff markup ] ~ [ identifier search ] ~

kernel.org | git.kernel.org | LWN.net | Project Home | Wiki (Japanese) | Wiki (English) | SVN repository | Mail admin

Linux® is a registered trademark of Linus Torvalds in the United States and other countries.
TOMOYO® is a registered trademark of NTT DATA CORPORATION.

osdn.jp