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v5.14.15
  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
  9enum {
 10	ICQ_EXITED		= 1 << 2,
 11	ICQ_DESTROYED		= 1 << 3,
 12};
 13
 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 */
 73struct io_cq {
 74	struct request_queue	*q;
 75	struct io_context	*ioc;
 76
 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	};
 91
 92	unsigned int		flags;
 93};
 94
 95/*
 96 * I/O subsystem state of the associated processes.  It is refcounted
 97 * and kmalloc'ed. These could be shared between processes.
 98 */
 99struct io_context {
100	atomic_long_t refcount;
101	atomic_t active_ref;
102	atomic_t nr_tasks;
103
 
 
 
104	/* all the fields below are protected by this lock */
105	spinlock_t lock;
106
107	unsigned short ioprio;
108
109	struct radix_tree_root	icq_tree;
110	struct io_cq __rcu	*icq_hint;
111	struct hlist_head	icq_list;
112
113	struct work_struct release_work;
 
114};
115
116/**
117 * get_io_context_active - get active reference on ioc
118 * @ioc: ioc of interest
119 *
120 * Only iocs with active reference can issue new IOs.  This function
121 * acquires an active reference on @ioc.  The caller must already have an
122 * active reference on @ioc.
123 */
124static inline void get_io_context_active(struct io_context *ioc)
125{
126	WARN_ON_ONCE(atomic_long_read(&ioc->refcount) <= 0);
127	WARN_ON_ONCE(atomic_read(&ioc->active_ref) <= 0);
128	atomic_long_inc(&ioc->refcount);
129	atomic_inc(&ioc->active_ref);
130}
131
132static inline void ioc_task_link(struct io_context *ioc)
133{
134	get_io_context_active(ioc);
135
136	WARN_ON_ONCE(atomic_read(&ioc->nr_tasks) <= 0);
137	atomic_inc(&ioc->nr_tasks);
138}
139
140struct task_struct;
141#ifdef CONFIG_BLOCK
142void put_io_context(struct io_context *ioc);
143void put_io_context_active(struct io_context *ioc);
144void exit_io_context(struct task_struct *task);
145struct io_context *get_task_io_context(struct task_struct *task,
146				       gfp_t gfp_flags, int node);
 
 
 
 
 
147#else
148struct io_context;
149static inline void put_io_context(struct io_context *ioc) { }
150static inline void exit_io_context(struct task_struct *task) { }
151#endif
 
 
 
 
152
153#endif
v6.9.4
  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
  9enum {
 10	ICQ_EXITED		= 1 << 2,
 11	ICQ_DESTROYED		= 1 << 3,
 12};
 13
 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 */
 73struct io_cq {
 74	struct request_queue	*q;
 75	struct io_context	*ioc;
 76
 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	};
 91
 92	unsigned int		flags;
 93};
 94
 95/*
 96 * I/O subsystem state of the associated processes.  It is refcounted
 97 * and kmalloc'ed. These could be shared between processes.
 98 */
 99struct io_context {
100	atomic_long_t refcount;
101	atomic_t active_ref;
 
102
103	unsigned short ioprio;
104
105#ifdef CONFIG_BLK_ICQ
106	/* all the fields below are protected by this lock */
107	spinlock_t lock;
108
 
 
109	struct radix_tree_root	icq_tree;
110	struct io_cq __rcu	*icq_hint;
111	struct hlist_head	icq_list;
112
113	struct work_struct release_work;
114#endif /* CONFIG_BLK_ICQ */
115};
116
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
117struct task_struct;
118#ifdef CONFIG_BLOCK
119void put_io_context(struct io_context *ioc);
 
120void exit_io_context(struct task_struct *task);
121int __copy_io(unsigned long clone_flags, struct task_struct *tsk);
122static 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}
128#else
129struct io_context;
130static inline void put_io_context(struct io_context *ioc) { }
131static inline void exit_io_context(struct task_struct *task) { }
132static inline int copy_io(unsigned long clone_flags, struct task_struct *tsk)
133{
134	return 0;
135}
136#endif /* CONFIG_BLOCK */
137
138#endif /* IOCONTEXT_H */