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b2441318 | 1 | /* SPDX-License-Identifier: GPL-2.0 */ |
fd0928df JA |
2 | #ifndef IOCONTEXT_H |
3 | #define IOCONTEXT_H | |
4 | ||
4ac845a2 | 5 | #include <linux/radix-tree.h> |
34e6bbf2 | 6 | #include <linux/rcupdate.h> |
b2efa052 | 7 | #include <linux/workqueue.h> |
4ac845a2 | 8 | |
dc86900e | 9 | enum { |
621032ad | 10 | ICQ_EXITED = 1 << 2, |
30a2da7b | 11 | ICQ_DESTROYED = 1 << 3, |
dc86900e TH |
12 | }; |
13 | ||
f1f8cc94 TH |
14 | /* |
15 | * An io_cq (icq) is association between an io_context (ioc) and a | |
16 | * request_queue (q). This is used by elevators which need to track | |
17 | * information per ioc - q pair. | |
18 | * | |
19 | * Elevator can request use of icq by setting elevator_type->icq_size and | |
20 | * ->icq_align. Both size and align must be larger than that of struct | |
21 | * io_cq and elevator can use the tail area for private information. The | |
22 | * recommended way to do this is defining a struct which contains io_cq as | |
23 | * the first member followed by private members and using its size and | |
24 | * align. For example, | |
25 | * | |
26 | * struct snail_io_cq { | |
27 | * struct io_cq icq; | |
28 | * int poke_snail; | |
29 | * int feed_snail; | |
30 | * }; | |
31 | * | |
32 | * struct elevator_type snail_elv_type { | |
33 | * .ops = { ... }, | |
34 | * .icq_size = sizeof(struct snail_io_cq), | |
35 | * .icq_align = __alignof__(struct snail_io_cq), | |
36 | * ... | |
37 | * }; | |
38 | * | |
39 | * If icq_size is set, block core will manage icq's. All requests will | |
40 | * have its ->elv.icq field set before elevator_ops->elevator_set_req_fn() | |
41 | * is called and be holding a reference to the associated io_context. | |
42 | * | |
43 | * Whenever a new icq is created, elevator_ops->elevator_init_icq_fn() is | |
44 | * called and, on destruction, ->elevator_exit_icq_fn(). Both functions | |
45 | * are called with both the associated io_context and queue locks held. | |
46 | * | |
47 | * Elevator is allowed to lookup icq using ioc_lookup_icq() while holding | |
48 | * queue lock but the returned icq is valid only until the queue lock is | |
49 | * released. Elevators can not and should not try to create or destroy | |
50 | * icq's. | |
51 | * | |
52 | * As icq's are linked from both ioc and q, the locking rules are a bit | |
53 | * complex. | |
54 | * | |
55 | * - ioc lock nests inside q lock. | |
56 | * | |
57 | * - ioc->icq_list and icq->ioc_node are protected by ioc lock. | |
58 | * q->icq_list and icq->q_node by q lock. | |
59 | * | |
60 | * - ioc->icq_tree and ioc->icq_hint are protected by ioc lock, while icq | |
61 | * itself is protected by q lock. However, both the indexes and icq | |
62 | * itself are also RCU managed and lookup can be performed holding only | |
63 | * the q lock. | |
64 | * | |
65 | * - icq's are not reference counted. They are destroyed when either the | |
66 | * ioc or q goes away. Each request with icq set holds an extra | |
67 | * reference to ioc to ensure it stays until the request is completed. | |
68 | * | |
69 | * - Linking and unlinking icq's are performed while holding both ioc and q | |
70 | * locks. Due to the lock ordering, q exit is simple but ioc exit | |
71 | * requires reverse-order double lock dance. | |
72 | */ | |
c5869807 TH |
73 | struct io_cq { |
74 | struct request_queue *q; | |
75 | struct io_context *ioc; | |
fd0928df | 76 | |
7e5a8794 TH |
77 | /* |
78 | * q_node and ioc_node link io_cq through icq_list of q and ioc | |
79 | * respectively. Both fields are unused once ioc_exit_icq() is | |
80 | * called and shared with __rcu_icq_cache and __rcu_head which are | |
81 | * used for RCU free of io_cq. | |
82 | */ | |
83 | union { | |
84 | struct list_head q_node; | |
85 | struct kmem_cache *__rcu_icq_cache; | |
86 | }; | |
87 | union { | |
88 | struct hlist_node ioc_node; | |
89 | struct rcu_head __rcu_head; | |
90 | }; | |
dc86900e | 91 | |
d705ae6b | 92 | unsigned int flags; |
fd0928df JA |
93 | }; |
94 | ||
95 | /* | |
d38ecf93 JA |
96 | * I/O subsystem state of the associated processes. It is refcounted |
97 | * and kmalloc'ed. These could be shared between processes. | |
fd0928df JA |
98 | */ |
99 | struct io_context { | |
d9c7d394 | 100 | atomic_long_t refcount; |
f6e8d01b | 101 | atomic_t active_ref; |
d38ecf93 | 102 | |
5ef16305 CH |
103 | unsigned short ioprio; |
104 | ||
105 | #ifdef CONFIG_BLK_ICQ | |
d38ecf93 JA |
106 | /* all the fields below are protected by this lock */ |
107 | spinlock_t lock; | |
fd0928df | 108 | |
c5869807 TH |
109 | struct radix_tree_root icq_tree; |
110 | struct io_cq __rcu *icq_hint; | |
111 | struct hlist_head icq_list; | |
b2efa052 TH |
112 | |
113 | struct work_struct release_work; | |
5ef16305 | 114 | #endif /* CONFIG_BLK_ICQ */ |
fd0928df JA |
115 | }; |
116 | ||
b69f2292 | 117 | struct task_struct; |
da9cbc87 | 118 | #ifdef CONFIG_BLOCK |
11a3122f | 119 | void put_io_context(struct io_context *ioc); |
b69f2292 | 120 | void exit_io_context(struct task_struct *task); |
88c9a2ce CH |
121 | int __copy_io(unsigned long clone_flags, struct task_struct *tsk); |
122 | static inline int copy_io(unsigned long clone_flags, struct task_struct *tsk) | |
123 | { | |
124 | if (!current->io_context) | |
125 | return 0; | |
126 | return __copy_io(clone_flags, tsk); | |
127 | } | |
da9cbc87 | 128 | #else |
da9cbc87 | 129 | struct io_context; |
11a3122f | 130 | static inline void put_io_context(struct io_context *ioc) { } |
42ec57a8 | 131 | static inline void exit_io_context(struct task_struct *task) { } |
88c9a2ce CH |
132 | static inline int copy_io(unsigned long clone_flags, struct task_struct *tsk) |
133 | { | |
134 | return 0; | |
135 | } | |
136 | #endif /* CONFIG_BLOCK */ | |
da9cbc87 | 137 | |
88c9a2ce | 138 | #endif /* IOCONTEXT_H */ |