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 static inline void get_io_context_active(struct io_context *ioc) 130 { 131 WARN_ON_ONCE(atomic_long_read(&ioc->refcount) <= 0); 132 WARN_ON_ONCE(atomic_read(&ioc->active_ref) <= 0); 133 atomic_long_inc(&ioc->refcount); 134 atomic_inc(&ioc->active_ref); 135 } 136 137 static inline void ioc_task_link(struct io_context *ioc) 138 { 139 get_io_context_active(ioc); 140 141 WARN_ON_ONCE(atomic_read(&ioc->nr_tasks) <= 0); 142 atomic_inc(&ioc->nr_tasks); 143 } 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 159