| /* SPDX-License-Identifier: GPL-2.0 */ |
| #ifndef IOCONTEXT_H |
| #define IOCONTEXT_H |
| |
| #include <linux/radix-tree.h> |
| #include <linux/rcupdate.h> |
| #include <linux/workqueue.h> |
| |
| enum { |
| ICQ_EXITED = 1 << 2, |
| ICQ_DESTROYED = 1 << 3, |
| }; |
| |
| /* |
| * An io_cq (icq) is association between an io_context (ioc) and a |
| * request_queue (q). This is used by elevators which need to track |
| * information per ioc - q pair. |
| * |
| * Elevator can request use of icq by setting elevator_type->icq_size and |
| * ->icq_align. Both size and align must be larger than that of struct |
| * io_cq and elevator can use the tail area for private information. The |
| * recommended way to do this is defining a struct which contains io_cq as |
| * the first member followed by private members and using its size and |
| * align. For example, |
| * |
| * struct snail_io_cq { |
| * struct io_cq icq; |
| * int poke_snail; |
| * int feed_snail; |
| * }; |
| * |
| * struct elevator_type snail_elv_type { |
| * .ops = { ... }, |
| * .icq_size = sizeof(struct snail_io_cq), |
| * .icq_align = __alignof__(struct snail_io_cq), |
| * ... |
| * }; |
| * |
| * If icq_size is set, block core will manage icq's. All requests will |
| * have its ->elv.icq field set before elevator_ops->elevator_set_req_fn() |
| * is called and be holding a reference to the associated io_context. |
| * |
| * Whenever a new icq is created, elevator_ops->elevator_init_icq_fn() is |
| * called and, on destruction, ->elevator_exit_icq_fn(). Both functions |
| * are called with both the associated io_context and queue locks held. |
| * |
| * Elevator is allowed to lookup icq using ioc_lookup_icq() while holding |
| * queue lock but the returned icq is valid only until the queue lock is |
| * released. Elevators can not and should not try to create or destroy |
| * icq's. |
| * |
| * As icq's are linked from both ioc and q, the locking rules are a bit |
| * complex. |
| * |
| * - ioc lock nests inside q lock. |
| * |
| * - ioc->icq_list and icq->ioc_node are protected by ioc lock. |
| * q->icq_list and icq->q_node by q lock. |
| * |
| * - ioc->icq_tree and ioc->icq_hint are protected by ioc lock, while icq |
| * itself is protected by q lock. However, both the indexes and icq |
| * itself are also RCU managed and lookup can be performed holding only |
| * the q lock. |
| * |
| * - icq's are not reference counted. They are destroyed when either the |
| * ioc or q goes away. Each request with icq set holds an extra |
| * reference to ioc to ensure it stays until the request is completed. |
| * |
| * - Linking and unlinking icq's are performed while holding both ioc and q |
| * locks. Due to the lock ordering, q exit is simple but ioc exit |
| * requires reverse-order double lock dance. |
| */ |
| struct io_cq { |
| struct request_queue *q; |
| struct io_context *ioc; |
| |
| /* |
| * q_node and ioc_node link io_cq through icq_list of q and ioc |
| * respectively. Both fields are unused once ioc_exit_icq() is |
| * called and shared with __rcu_icq_cache and __rcu_head which are |
| * used for RCU free of io_cq. |
| */ |
| union { |
| struct list_head q_node; |
| struct kmem_cache *__rcu_icq_cache; |
| }; |
| union { |
| struct hlist_node ioc_node; |
| struct rcu_head __rcu_head; |
| }; |
| |
| unsigned int flags; |
| }; |
| |
| /* |
| * I/O subsystem state of the associated processes. It is refcounted |
| * and kmalloc'ed. These could be shared between processes. |
| */ |
| struct io_context { |
| atomic_long_t refcount; |
| atomic_t active_ref; |
| atomic_t nr_tasks; |
| |
| /* all the fields below are protected by this lock */ |
| spinlock_t lock; |
| |
| unsigned short ioprio; |
| |
| struct radix_tree_root icq_tree; |
| struct io_cq __rcu *icq_hint; |
| struct hlist_head icq_list; |
| |
| struct work_struct release_work; |
| }; |
| |
| /** |
| * get_io_context_active - get active reference on ioc |
| * @ioc: ioc of interest |
| * |
| * Only iocs with active reference can issue new IOs. This function |
| * acquires an active reference on @ioc. The caller must already have an |
| * active reference on @ioc. |
| */ |
| static inline void get_io_context_active(struct io_context *ioc) |
| { |
| WARN_ON_ONCE(atomic_long_read(&ioc->refcount) <= 0); |
| WARN_ON_ONCE(atomic_read(&ioc->active_ref) <= 0); |
| atomic_long_inc(&ioc->refcount); |
| atomic_inc(&ioc->active_ref); |
| } |
| |
| static inline void ioc_task_link(struct io_context *ioc) |
| { |
| get_io_context_active(ioc); |
| |
| WARN_ON_ONCE(atomic_read(&ioc->nr_tasks) <= 0); |
| atomic_inc(&ioc->nr_tasks); |
| } |
| |
| struct task_struct; |
| #ifdef CONFIG_BLOCK |
| void put_io_context(struct io_context *ioc); |
| void put_io_context_active(struct io_context *ioc); |
| void exit_io_context(struct task_struct *task); |
| struct io_context *get_task_io_context(struct task_struct *task, |
| gfp_t gfp_flags, int node); |
| #else |
| struct io_context; |
| static inline void put_io_context(struct io_context *ioc) { } |
| static inline void exit_io_context(struct task_struct *task) { } |
| #endif |
| |
| #endif |