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1 : : /* SPDX-License-Identifier: GPL-2.0 */ 2 : : #ifndef IOCONTEXT_H 3 : : #define IOCONTEXT_H 4 : : 5 : : #include <linux/radix-tree.h> 6 : : #include <linux/rcupdate.h> 7 : : #include <linux/workqueue.h> 8 : : 9 : : enum { 10 : : ICQ_EXITED = 1 << 2, 11 : : }; 12 : : 13 : : /* 14 : : * An io_cq (icq) is association between an io_context (ioc) and a 15 : : * request_queue (q). This is used by elevators which need to track 16 : : * information per ioc - q pair. 17 : : * 18 : : * Elevator can request use of icq by setting elevator_type->icq_size and 19 : : * ->icq_align. Both size and align must be larger than that of struct 20 : : * io_cq and elevator can use the tail area for private information. The 21 : : * recommended way to do this is defining a struct which contains io_cq as 22 : : * the first member followed by private members and using its size and 23 : : * align. For example, 24 : : * 25 : : * struct snail_io_cq { 26 : : * struct io_cq icq; 27 : : * int poke_snail; 28 : : * int feed_snail; 29 : : * }; 30 : : * 31 : : * struct elevator_type snail_elv_type { 32 : : * .ops = { ... }, 33 : : * .icq_size = sizeof(struct snail_io_cq), 34 : : * .icq_align = __alignof__(struct snail_io_cq), 35 : : * ... 36 : : * }; 37 : : * 38 : : * If icq_size is set, block core will manage icq's. All requests will 39 : : * have its ->elv.icq field set before elevator_ops->elevator_set_req_fn() 40 : : * is called and be holding a reference to the associated io_context. 41 : : * 42 : : * Whenever a new icq is created, elevator_ops->elevator_init_icq_fn() is 43 : : * called and, on destruction, ->elevator_exit_icq_fn(). Both functions 44 : : * are called with both the associated io_context and queue locks held. 45 : : * 46 : : * Elevator is allowed to lookup icq using ioc_lookup_icq() while holding 47 : : * queue lock but the returned icq is valid only until the queue lock is 48 : : * released. Elevators can not and should not try to create or destroy 49 : : * icq's. 50 : : * 51 : : * As icq's are linked from both ioc and q, the locking rules are a bit 52 : : * complex. 53 : : * 54 : : * - ioc lock nests inside q lock. 55 : : * 56 : : * - ioc->icq_list and icq->ioc_node are protected by ioc lock. 57 : : * q->icq_list and icq->q_node by q lock. 58 : : * 59 : : * - ioc->icq_tree and ioc->icq_hint are protected by ioc lock, while icq 60 : : * itself is protected by q lock. However, both the indexes and icq 61 : : * itself are also RCU managed and lookup can be performed holding only 62 : : * the q lock. 63 : : * 64 : : * - icq's are not reference counted. They are destroyed when either the 65 : : * ioc or q goes away. Each request with icq set holds an extra 66 : : * reference to ioc to ensure it stays until the request is completed. 67 : : * 68 : : * - Linking and unlinking icq's are performed while holding both ioc and q 69 : : * locks. Due to the lock ordering, q exit is simple but ioc exit 70 : : * requires reverse-order double lock dance. 71 : : */ 72 : : struct io_cq { 73 : : struct request_queue *q; 74 : : struct io_context *ioc; 75 : : 76 : : /* 77 : : * q_node and ioc_node link io_cq through icq_list of q and ioc 78 : : * respectively. Both fields are unused once ioc_exit_icq() is 79 : : * called and shared with __rcu_icq_cache and __rcu_head which are 80 : : * used for RCU free of io_cq. 81 : : */ 82 : : union { 83 : : struct list_head q_node; 84 : : struct kmem_cache *__rcu_icq_cache; 85 : : }; 86 : : union { 87 : : struct hlist_node ioc_node; 88 : : struct rcu_head __rcu_head; 89 : : }; 90 : : 91 : : unsigned int flags; 92 : : }; 93 : : 94 : : /* 95 : : * I/O subsystem state of the associated processes. It is refcounted 96 : : * and kmalloc'ed. These could be shared between processes. 97 : : */ 98 : : struct io_context { 99 : : atomic_long_t refcount; 100 : : atomic_t active_ref; 101 : : atomic_t nr_tasks; 102 : : 103 : : /* all the fields below are protected by this lock */ 104 : : spinlock_t lock; 105 : : 106 : : unsigned short ioprio; 107 : : 108 : : /* 109 : : * For request batching 110 : : */ 111 : : int nr_batch_requests; /* Number of requests left in the batch */ 112 : : unsigned long last_waited; /* Time last woken after wait for request */ 113 : : 114 : : struct radix_tree_root icq_tree; 115 : : struct io_cq __rcu *icq_hint; 116 : : struct hlist_head icq_list; 117 : : 118 : : struct work_struct release_work; 119 : : }; 120 : : 121 : : /** 122 : : * get_io_context_active - get active reference on ioc 123 : : * @ioc: ioc of interest 124 : : * 125 : : * Only iocs with active reference can issue new IOs. This function 126 : : * acquires an active reference on @ioc. The caller must already have an 127 : : * active reference on @ioc. 128 : : */ 129 : 0 : static inline void get_io_context_active(struct io_context *ioc) 130 : : { 131 [ # # ]: 0 : WARN_ON_ONCE(atomic_long_read(&ioc->refcount) <= 0); 132 [ # # ]: 0 : WARN_ON_ONCE(atomic_read(&ioc->active_ref) <= 0); 133 : 0 : atomic_long_inc(&ioc->refcount); 134 : 0 : atomic_inc(&ioc->active_ref); 135 : 0 : } 136 : : 137 : 0 : static inline void ioc_task_link(struct io_context *ioc) 138 : : { 139 : 0 : get_io_context_active(ioc); 140 : : 141 [ # # ]: 0 : WARN_ON_ONCE(atomic_read(&ioc->nr_tasks) <= 0); 142 : 0 : atomic_inc(&ioc->nr_tasks); 143 : 0 : } 144 : : 145 : : struct task_struct; 146 : : #ifdef CONFIG_BLOCK 147 : : void put_io_context(struct io_context *ioc); 148 : : void put_io_context_active(struct io_context *ioc); 149 : : void exit_io_context(struct task_struct *task); 150 : : struct io_context *get_task_io_context(struct task_struct *task, 151 : : gfp_t gfp_flags, int node); 152 : : #else 153 : : struct io_context; 154 : : static inline void put_io_context(struct io_context *ioc) { } 155 : : static inline void exit_io_context(struct task_struct *task) { } 156 : : #endif 157 : : 158 : : #endif