4 #include <linux/radix-tree.h>
5 #include <linux/rcupdate.h>
6 #include <linux/workqueue.h>
9 ICQ_IOPRIO_CHANGED
= 1 << 0,
10 ICQ_CGROUP_CHANGED
= 1 << 1,
13 ICQ_CHANGED_MASK
= ICQ_IOPRIO_CHANGED
| ICQ_CGROUP_CHANGED
,
17 * An io_cq (icq) is association between an io_context (ioc) and a
18 * request_queue (q). This is used by elevators which need to track
19 * information per ioc - q pair.
21 * Elevator can request use of icq by setting elevator_type->icq_size and
22 * ->icq_align. Both size and align must be larger than that of struct
23 * io_cq and elevator can use the tail area for private information. The
24 * recommended way to do this is defining a struct which contains io_cq as
25 * the first member followed by private members and using its size and
28 * struct snail_io_cq {
34 * struct elevator_type snail_elv_type {
36 * .icq_size = sizeof(struct snail_io_cq),
37 * .icq_align = __alignof__(struct snail_io_cq),
41 * If icq_size is set, block core will manage icq's. All requests will
42 * have its ->elv.icq field set before elevator_ops->elevator_set_req_fn()
43 * is called and be holding a reference to the associated io_context.
45 * Whenever a new icq is created, elevator_ops->elevator_init_icq_fn() is
46 * called and, on destruction, ->elevator_exit_icq_fn(). Both functions
47 * are called with both the associated io_context and queue locks held.
49 * Elevator is allowed to lookup icq using ioc_lookup_icq() while holding
50 * queue lock but the returned icq is valid only until the queue lock is
51 * released. Elevators can not and should not try to create or destroy
54 * As icq's are linked from both ioc and q, the locking rules are a bit
57 * - ioc lock nests inside q lock.
59 * - ioc->icq_list and icq->ioc_node are protected by ioc lock.
60 * q->icq_list and icq->q_node by q lock.
62 * - ioc->icq_tree and ioc->icq_hint are protected by ioc lock, while icq
63 * itself is protected by q lock. However, both the indexes and icq
64 * itself are also RCU managed and lookup can be performed holding only
67 * - icq's are not reference counted. They are destroyed when either the
68 * ioc or q goes away. Each request with icq set holds an extra
69 * reference to ioc to ensure it stays until the request is completed.
71 * - Linking and unlinking icq's are performed while holding both ioc and q
72 * locks. Due to the lock ordering, q exit is simple but ioc exit
73 * requires reverse-order double lock dance.
76 struct request_queue
*q
;
77 struct io_context
*ioc
;
80 * q_node and ioc_node link io_cq through icq_list of q and ioc
81 * respectively. Both fields are unused once ioc_exit_icq() is
82 * called and shared with __rcu_icq_cache and __rcu_head which are
83 * used for RCU free of io_cq.
86 struct list_head q_node
;
87 struct kmem_cache
*__rcu_icq_cache
;
90 struct hlist_node ioc_node
;
91 struct rcu_head __rcu_head
;
98 * I/O subsystem state of the associated processes. It is refcounted
99 * and kmalloc'ed. These could be shared between processes.
102 atomic_long_t refcount
;
105 /* all the fields below are protected by this lock */
108 unsigned short ioprio
;
111 * For request batching
113 int nr_batch_requests
; /* Number of requests left in the batch */
114 unsigned long last_waited
; /* Time last woken after wait for request */
116 struct radix_tree_root icq_tree
;
117 struct io_cq __rcu
*icq_hint
;
118 struct hlist_head icq_list
;
120 struct work_struct release_work
;
123 static inline struct io_context
*ioc_task_link(struct io_context
*ioc
)
126 * if ref count is zero, don't allow sharing (ioc is going away, it's
129 if (ioc
&& atomic_long_inc_not_zero(&ioc
->refcount
)) {
130 atomic_inc(&ioc
->nr_tasks
);
139 void put_io_context(struct io_context
*ioc
);
140 void exit_io_context(struct task_struct
*task
);
141 struct io_context
*get_task_io_context(struct task_struct
*task
,
142 gfp_t gfp_flags
, int node
);
143 void ioc_ioprio_changed(struct io_context
*ioc
, int ioprio
);
144 void ioc_cgroup_changed(struct io_context
*ioc
);
145 unsigned int icq_get_changed(struct io_cq
*icq
);
148 static inline void put_io_context(struct io_context
*ioc
) { }
149 static inline void exit_io_context(struct task_struct
*task
) { }
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