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