cregit-Linux how code gets into the kernel

Release 4.14 block/blk-ioc.c

Directory: block
// SPDX-License-Identifier: GPL-2.0
/*
 * Functions related to io context handling
 */
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/bio.h>
#include <linux/blkdev.h>
#include <linux/slab.h>
#include <linux/sched/task.h>

#include "blk.h"

/*
 * For io context allocations
 */

static struct kmem_cache *iocontext_cachep;

/**
 * get_io_context - increment reference count to io_context
 * @ioc: io_context to get
 *
 * Increment reference count to @ioc.
 */

void get_io_context(struct io_context *ioc) { BUG_ON(atomic_long_read(&ioc->refcount) <= 0); atomic_long_inc(&ioc->refcount); }

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EXPORT_SYMBOL(get_io_context);
static void icq_free_icq_rcu(struct rcu_head *head) { struct io_cq *icq = container_of(head, struct io_cq, __rcu_head); kmem_cache_free(icq->__rcu_icq_cache, icq); }

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/* * Exit an icq. Called with ioc locked for blk-mq, and with both ioc * and queue locked for legacy. */
static void ioc_exit_icq(struct io_cq *icq) { struct elevator_type *et = icq->q->elevator->type; if (icq->flags & ICQ_EXITED) return; if (et->uses_mq && et->ops.mq.exit_icq) et->ops.mq.exit_icq(icq); else if (!et->uses_mq && et->ops.sq.elevator_exit_icq_fn) et->ops.sq.elevator_exit_icq_fn(icq); icq->flags |= ICQ_EXITED; }

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Tejun Heo5661.54%250.00%
Jens Axboe3538.46%250.00%
Total91100.00%4100.00%

/* * Release an icq. Called with ioc locked for blk-mq, and with both ioc * and queue locked for legacy. */
static void ioc_destroy_icq(struct io_cq *icq) { struct io_context *ioc = icq->ioc; struct request_queue *q = icq->q; struct elevator_type *et = q->elevator->type; lockdep_assert_held(&ioc->lock); radix_tree_delete(&ioc->icq_tree, icq->q->id); hlist_del_init(&icq->ioc_node); list_del_init(&icq->q_node); /* * Both setting lookup hint to and clearing it from @icq are done * under queue_lock. If it's not pointing to @icq now, it never * will. Hint assignment itself can race safely. */ if (rcu_access_pointer(ioc->icq_hint) == icq) rcu_assign_pointer(ioc->icq_hint, NULL); ioc_exit_icq(icq); /* * @icq->q might have gone away by the time RCU callback runs * making it impossible to determine icq_cache. Record it in @icq. */ icq->__rcu_icq_cache = et->icq_cache; call_rcu(&icq->__rcu_head, icq_free_icq_rcu); }

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Tejun Heo12299.19%266.67%
Paul E. McKenney10.81%133.33%
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/* * Slow path for ioc release in put_io_context(). Performs double-lock * dancing to unlink all icq's and then frees ioc. */
static void ioc_release_fn(struct work_struct *work) { struct io_context *ioc = container_of(work, struct io_context, release_work); unsigned long flags; /* * Exiting icq may call into put_io_context() through elevator * which will trigger lockdep warning. The ioc's are guaranteed to * be different, use a different locking subclass here. Use * irqsave variant as there's no spin_lock_irq_nested(). */ spin_lock_irqsave_nested(&ioc->lock, flags, 1); while (!hlist_empty(&ioc->icq_list)) { struct io_cq *icq = hlist_entry(ioc->icq_list.first, struct io_cq, ioc_node); struct request_queue *q = icq->q; if (spin_trylock(q->queue_lock)) { ioc_destroy_icq(icq); spin_unlock(q->queue_lock); } else { spin_unlock_irqrestore(&ioc->lock, flags); cpu_relax(); spin_lock_irqsave_nested(&ioc->lock, flags, 1); } } spin_unlock_irqrestore(&ioc->lock, flags); kmem_cache_free(iocontext_cachep, ioc); }

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Tejun Heo12179.61%562.50%
Jens Axboe3019.74%225.00%
Paul Bolle10.66%112.50%
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/** * put_io_context - put a reference of io_context * @ioc: io_context to put * * Decrement reference count of @ioc and release it if the count reaches * zero. */
void put_io_context(struct io_context *ioc) { unsigned long flags; bool free_ioc = false; if (ioc == NULL) return; BUG_ON(atomic_long_read(&ioc->refcount) <= 0); /* * Releasing ioc requires reverse order double locking and we may * already be holding a queue_lock. Do it asynchronously from wq. */ if (atomic_long_dec_and_test(&ioc->refcount)) { spin_lock_irqsave(&ioc->lock, flags); if (!hlist_empty(&ioc->icq_list)) queue_work(system_power_efficient_wq, &ioc->release_work); else free_ioc = true; spin_unlock_irqrestore(&ioc->lock, flags); } if (free_ioc) kmem_cache_free(iocontext_cachep, ioc); }

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Jens Axboe5247.71%222.22%
Tejun Heo3128.44%444.44%
Xiaotian Feng2119.27%111.11%
Viresh Kumar32.75%111.11%
Nikanth Karthikesan21.83%111.11%
Total109100.00%9100.00%

EXPORT_SYMBOL(put_io_context); /** * put_io_context_active - put active reference on ioc * @ioc: ioc of interest * * Undo get_io_context_active(). If active reference reaches zero after * put, @ioc can never issue further IOs and ioscheds are notified. */
void put_io_context_active(struct io_context *ioc) { struct elevator_type *et; unsigned long flags; struct io_cq *icq; if (!atomic_dec_and_test(&ioc->active_ref)) { put_io_context(ioc); return; } /* * Need ioc lock to walk icq_list and q lock to exit icq. Perform * reverse double locking. Read comment in ioc_release_fn() for * explanation on the nested locking annotation. */ retry: spin_lock_irqsave_nested(&ioc->lock, flags, 1); hlist_for_each_entry(icq, &ioc->icq_list, ioc_node) { if (icq->flags & ICQ_EXITED) continue; et = icq->q->elevator->type; if (et->uses_mq) { ioc_exit_icq(icq); } else { if (spin_trylock(icq->q->queue_lock)) { ioc_exit_icq(icq); spin_unlock(icq->q->queue_lock); } else { spin_unlock_irqrestore(&ioc->lock, flags); cpu_relax(); goto retry; } } } spin_unlock_irqrestore(&ioc->lock, flags); put_io_context(ioc); }

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Louis Rilling10.61%120.00%
Total164100.00%5100.00%

/* Called by the exiting task */
void exit_io_context(struct task_struct *task) { struct io_context *ioc; task_lock(task); ioc = task->io_context; task->io_context = NULL; task_unlock(task); atomic_dec(&ioc->nr_tasks); put_io_context_active(ioc); }

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static void __ioc_clear_queue(struct list_head *icq_list) { unsigned long flags; while (!list_empty(icq_list)) { struct io_cq *icq = list_entry(icq_list->next, struct io_cq, q_node); struct io_context *ioc = icq->ioc; spin_lock_irqsave(&ioc->lock, flags); ioc_destroy_icq(icq); spin_unlock_irqrestore(&ioc->lock, flags); } }

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Tejun Heo5775.00%266.67%
Jens Axboe1925.00%133.33%
Total76100.00%3100.00%

/** * ioc_clear_queue - break any ioc association with the specified queue * @q: request_queue being cleared * * Walk @q->icq_list and exit all io_cq's. */
void ioc_clear_queue(struct request_queue *q) { LIST_HEAD(icq_list); spin_lock_irq(q->queue_lock); list_splice_init(&q->icq_list, &icq_list); if (q->mq_ops) { spin_unlock_irq(q->queue_lock); __ioc_clear_queue(&icq_list); } else { __ioc_clear_queue(&icq_list); spin_unlock_irq(q->queue_lock); } }

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Jens Axboe6694.29%150.00%
Tejun Heo45.71%150.00%
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int create_task_io_context(struct task_struct *task, gfp_t gfp_flags, int node) { struct io_context *ioc; int ret; ioc = kmem_cache_alloc_node(iocontext_cachep, gfp_flags | __GFP_ZERO, node); if (unlikely(!ioc)) return -ENOMEM; /* initialize */ atomic_long_set(&ioc->refcount, 1); atomic_set(&ioc->nr_tasks, 1); atomic_set(&ioc->active_ref, 1); spin_lock_init(&ioc->lock); INIT_RADIX_TREE(&ioc->icq_tree, GFP_ATOMIC | __GFP_HIGH); INIT_HLIST_HEAD(&ioc->icq_list); INIT_WORK(&ioc->release_work, ioc_release_fn); /* * Try to install. ioc shouldn't be installed if someone else * already did or @task, which isn't %current, is exiting. Note * that we need to allow ioc creation on exiting %current as exit * path may issue IOs from e.g. exit_files(). The exit path is * responsible for not issuing IO after exit_io_context(). */ task_lock(task); if (!task->io_context && (task == current || !(task->flags & PF_EXITING))) task->io_context = ioc; else kmem_cache_free(iocontext_cachep, ioc); ret = task->io_context ? 0 : -EBUSY; task_unlock(task); return ret; }

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Jens Axboe6536.31%215.38%
Eric Dumazet158.38%17.69%
Olof Johansson105.59%17.69%
Paul Bolle84.47%17.69%
Nikanth Karthikesan10.56%17.69%
Total179100.00%13100.00%

/** * get_task_io_context - get io_context of a task * @task: task of interest * @gfp_flags: allocation flags, used if allocation is necessary * @node: allocation node, used if allocation is necessary * * Return io_context of @task. If it doesn't exist, it is created with * @gfp_flags and @node. The returned io_context has its reference count * incremented. * * This function always goes through task_lock() and it's better to use * %current->io_context + get_io_context() for %current. */
struct io_context *get_task_io_context(struct task_struct *task, gfp_t gfp_flags, int node) { struct io_context *ioc; might_sleep_if(gfpflags_allow_blocking(gfp_flags)); do { task_lock(task); ioc = task->io_context; if (likely(ioc)) { get_io_context(ioc); task_unlock(task); return ioc; } task_unlock(task); } while (!create_task_io_context(task, gfp_flags, node)); return NULL; }

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Tejun Heo5259.09%350.00%
Jens Axboe2932.95%116.67%
Paul Bolle44.55%116.67%
Mel Gorman33.41%116.67%
Total88100.00%6100.00%

EXPORT_SYMBOL(get_task_io_context); /** * ioc_lookup_icq - lookup io_cq from ioc * @ioc: the associated io_context * @q: the associated request_queue * * Look up io_cq associated with @ioc - @q pair from @ioc. Must be called * with @q->queue_lock held. */
struct io_cq *ioc_lookup_icq(struct io_context *ioc, struct request_queue *q) { struct io_cq *icq; lockdep_assert_held(q->queue_lock); /* * icq's are indexed from @ioc using radix tree and hint pointer, * both of which are protected with RCU. All removals are done * holding both q and ioc locks, and we're holding q lock - if we * find a icq which points to us, it's guaranteed to be valid. */ rcu_read_lock(); icq = rcu_dereference(ioc->icq_hint); if (icq && icq->q == q) goto out; icq = radix_tree_lookup(&ioc->icq_tree, q->id); if (icq && icq->q == q) rcu_assign_pointer(ioc->icq_hint, icq); /* allowed to race */ else icq = NULL; out: rcu_read_unlock(); return icq; }

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EXPORT_SYMBOL(ioc_lookup_icq); /** * ioc_create_icq - create and link io_cq * @ioc: io_context of interest * @q: request_queue of interest * @gfp_mask: allocation mask * * Make sure io_cq linking @ioc and @q exists. If icq doesn't exist, they * will be created using @gfp_mask. * * The caller is responsible for ensuring @ioc won't go away and @q is * alive and will stay alive until this function returns. */
struct io_cq *ioc_create_icq(struct io_context *ioc, struct request_queue *q, gfp_t gfp_mask) { struct elevator_type *et = q->elevator->type; struct io_cq *icq; /* allocate stuff */ icq = kmem_cache_alloc_node(et->icq_cache, gfp_mask | __GFP_ZERO, q->node); if (!icq) return NULL; if (radix_tree_maybe_preload(gfp_mask) < 0) { kmem_cache_free(et->icq_cache, icq); return NULL; } icq->ioc = ioc; icq->q = q; INIT_LIST_HEAD(&icq->q_node); INIT_HLIST_NODE(&icq->ioc_node); /* lock both q and ioc and try to link @icq */ spin_lock_irq(q->queue_lock); spin_lock(&ioc->lock); if (likely(!radix_tree_insert(&ioc->icq_tree, q->id, icq))) { hlist_add_head(&icq->ioc_node, &ioc->icq_list); list_add(&icq->q_node, &q->icq_list); if (et->uses_mq && et->ops.mq.init_icq) et->ops.mq.init_icq(icq); else if (!et->uses_mq && et->ops.sq.elevator_init_icq_fn) et->ops.sq.elevator_init_icq_fn(icq); } else { kmem_cache_free(et->icq_cache, icq); icq = ioc_lookup_icq(ioc, q); if (!icq) printk(KERN_ERR "cfq: icq link failed!\n"); } spin_unlock(&ioc->lock); spin_unlock_irq(q->queue_lock); radix_tree_preload_end(); return icq; }

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Total282100.00%5100.00%


static int __init blk_ioc_init(void) { iocontext_cachep = kmem_cache_create("blkdev_ioc", sizeof(struct io_context), 0, SLAB_PANIC, NULL); return 0; }

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Adrian Bunk13.23%150.00%
Total31100.00%2100.00%

subsys_initcall(blk_ioc_init);

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Tejun Heo112968.34%1644.44%
Jens Axboe41625.18%513.89%
Omar Sandoval311.88%12.78%
Xiaotian Feng211.27%12.78%
Eric Dumazet150.91%12.78%
Paul Bolle130.79%25.56%
Olof Johansson100.61%12.78%
Viresh Kumar30.18%12.78%
Mel Gorman30.18%12.78%
Nikanth Karthikesan30.18%12.78%
Ingo Molnar30.18%12.78%
Greg Kroah-Hartman10.06%12.78%
Louis Rilling10.06%12.78%
Adrian Bunk10.06%12.78%
Paul E. McKenney10.06%12.78%
Jan Kara10.06%12.78%
Total1652100.00%36100.00%
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