mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
synced 2024-09-12 13:55:32 +00:00
![Tejun Heo](/assets/img/avatar_default.png)
Now that all io_cq related data structures are in block core layer, io_cq lookup can be moved from cfq-iosched.c to blk-ioc.c. Lookup logic from cfq_cic_lookup() is moved to ioc_lookup_icq() with parameter return type changes (cfqd -> request_queue, cfq_io_cq -> io_cq) and cfq_cic_lookup() becomes thin wrapper around cfq_cic_lookup(). Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
356 lines
9.4 KiB
C
356 lines
9.4 KiB
C
/*
|
|
* 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/bootmem.h> /* for max_pfn/max_low_pfn */
|
|
#include <linux/slab.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);
|
|
}
|
|
EXPORT_SYMBOL(get_io_context);
|
|
|
|
/*
|
|
* Releasing ioc may nest into another put_io_context() leading to nested
|
|
* fast path release. As the ioc's can't be the same, this is okay but
|
|
* makes lockdep whine. Keep track of nesting and use it as subclass.
|
|
*/
|
|
#ifdef CONFIG_LOCKDEP
|
|
#define ioc_release_depth(q) ((q) ? (q)->ioc_release_depth : 0)
|
|
#define ioc_release_depth_inc(q) (q)->ioc_release_depth++
|
|
#define ioc_release_depth_dec(q) (q)->ioc_release_depth--
|
|
#else
|
|
#define ioc_release_depth(q) 0
|
|
#define ioc_release_depth_inc(q) do { } while (0)
|
|
#define ioc_release_depth_dec(q) do { } while (0)
|
|
#endif
|
|
|
|
/*
|
|
* 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);
|
|
struct request_queue *last_q = NULL;
|
|
|
|
spin_lock_irq(&ioc->lock);
|
|
|
|
while (!hlist_empty(&ioc->icq_list)) {
|
|
struct io_cq *icq = hlist_entry(ioc->icq_list.first,
|
|
struct io_cq, ioc_node);
|
|
struct request_queue *this_q = icq->q;
|
|
|
|
if (this_q != last_q) {
|
|
/*
|
|
* Need to switch to @this_q. Once we release
|
|
* @ioc->lock, it can go away along with @cic.
|
|
* Hold on to it.
|
|
*/
|
|
__blk_get_queue(this_q);
|
|
|
|
/*
|
|
* blk_put_queue() might sleep thanks to kobject
|
|
* idiocy. Always release both locks, put and
|
|
* restart.
|
|
*/
|
|
if (last_q) {
|
|
spin_unlock(last_q->queue_lock);
|
|
spin_unlock_irq(&ioc->lock);
|
|
blk_put_queue(last_q);
|
|
} else {
|
|
spin_unlock_irq(&ioc->lock);
|
|
}
|
|
|
|
last_q = this_q;
|
|
spin_lock_irq(this_q->queue_lock);
|
|
spin_lock(&ioc->lock);
|
|
continue;
|
|
}
|
|
ioc_release_depth_inc(this_q);
|
|
icq->exit(icq);
|
|
icq->release(icq);
|
|
ioc_release_depth_dec(this_q);
|
|
}
|
|
|
|
if (last_q) {
|
|
spin_unlock(last_q->queue_lock);
|
|
spin_unlock_irq(&ioc->lock);
|
|
blk_put_queue(last_q);
|
|
} else {
|
|
spin_unlock_irq(&ioc->lock);
|
|
}
|
|
|
|
kmem_cache_free(iocontext_cachep, ioc);
|
|
}
|
|
|
|
/**
|
|
* put_io_context - put a reference of io_context
|
|
* @ioc: io_context to put
|
|
* @locked_q: request_queue the caller is holding queue_lock of (hint)
|
|
*
|
|
* Decrement reference count of @ioc and release it if the count reaches
|
|
* zero. If the caller is holding queue_lock of a queue, it can indicate
|
|
* that with @locked_q. This is an optimization hint and the caller is
|
|
* allowed to pass in %NULL even when it's holding a queue_lock.
|
|
*/
|
|
void put_io_context(struct io_context *ioc, struct request_queue *locked_q)
|
|
{
|
|
struct request_queue *last_q = locked_q;
|
|
unsigned long flags;
|
|
|
|
if (ioc == NULL)
|
|
return;
|
|
|
|
BUG_ON(atomic_long_read(&ioc->refcount) <= 0);
|
|
if (locked_q)
|
|
lockdep_assert_held(locked_q->queue_lock);
|
|
|
|
if (!atomic_long_dec_and_test(&ioc->refcount))
|
|
return;
|
|
|
|
/*
|
|
* Destroy @ioc. This is a bit messy because icq's are chained
|
|
* from both ioc and queue, and ioc->lock nests inside queue_lock.
|
|
* The inner ioc->lock should be held to walk our icq_list and then
|
|
* for each icq the outer matching queue_lock should be grabbed.
|
|
* ie. We need to do reverse-order double lock dancing.
|
|
*
|
|
* Another twist is that we are often called with one of the
|
|
* matching queue_locks held as indicated by @locked_q, which
|
|
* prevents performing double-lock dance for other queues.
|
|
*
|
|
* So, we do it in two stages. The fast path uses the queue_lock
|
|
* the caller is holding and, if other queues need to be accessed,
|
|
* uses trylock to avoid introducing locking dependency. This can
|
|
* handle most cases, especially if @ioc was performing IO on only
|
|
* single device.
|
|
*
|
|
* If trylock doesn't cut it, we defer to @ioc->release_work which
|
|
* can do all the double-locking dancing.
|
|
*/
|
|
spin_lock_irqsave_nested(&ioc->lock, flags,
|
|
ioc_release_depth(locked_q));
|
|
|
|
while (!hlist_empty(&ioc->icq_list)) {
|
|
struct io_cq *icq = hlist_entry(ioc->icq_list.first,
|
|
struct io_cq, ioc_node);
|
|
struct request_queue *this_q = icq->q;
|
|
|
|
if (this_q != last_q) {
|
|
if (last_q && last_q != locked_q)
|
|
spin_unlock(last_q->queue_lock);
|
|
last_q = NULL;
|
|
|
|
if (!spin_trylock(this_q->queue_lock))
|
|
break;
|
|
last_q = this_q;
|
|
continue;
|
|
}
|
|
ioc_release_depth_inc(this_q);
|
|
icq->exit(icq);
|
|
icq->release(icq);
|
|
ioc_release_depth_dec(this_q);
|
|
}
|
|
|
|
if (last_q && last_q != locked_q)
|
|
spin_unlock(last_q->queue_lock);
|
|
|
|
spin_unlock_irqrestore(&ioc->lock, flags);
|
|
|
|
/* if no icq is left, we're done; otherwise, kick release_work */
|
|
if (hlist_empty(&ioc->icq_list))
|
|
kmem_cache_free(iocontext_cachep, ioc);
|
|
else
|
|
schedule_work(&ioc->release_work);
|
|
}
|
|
EXPORT_SYMBOL(put_io_context);
|
|
|
|
/* Called by the exiting task */
|
|
void exit_io_context(struct task_struct *task)
|
|
{
|
|
struct io_context *ioc;
|
|
|
|
/* PF_EXITING prevents new io_context from being attached to @task */
|
|
WARN_ON_ONCE(!(current->flags & PF_EXITING));
|
|
|
|
task_lock(task);
|
|
ioc = task->io_context;
|
|
task->io_context = NULL;
|
|
task_unlock(task);
|
|
|
|
atomic_dec(&ioc->nr_tasks);
|
|
put_io_context(ioc, NULL);
|
|
}
|
|
|
|
void create_io_context_slowpath(struct task_struct *task, gfp_t gfp_flags,
|
|
int node)
|
|
{
|
|
struct io_context *ioc;
|
|
|
|
ioc = kmem_cache_alloc_node(iocontext_cachep, gfp_flags | __GFP_ZERO,
|
|
node);
|
|
if (unlikely(!ioc))
|
|
return;
|
|
|
|
/* initialize */
|
|
atomic_long_set(&ioc->refcount, 1);
|
|
atomic_set(&ioc->nr_tasks, 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, somebody might already have beaten us to it */
|
|
task_lock(task);
|
|
if (!task->io_context && !(task->flags & PF_EXITING))
|
|
task->io_context = ioc;
|
|
else
|
|
kmem_cache_free(iocontext_cachep, ioc);
|
|
task_unlock(task);
|
|
}
|
|
EXPORT_SYMBOL(create_io_context_slowpath);
|
|
|
|
/**
|
|
* 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(gfp_flags & __GFP_WAIT);
|
|
|
|
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_io_context(task, gfp_flags, node));
|
|
|
|
return NULL;
|
|
}
|
|
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;
|
|
}
|
|
EXPORT_SYMBOL(ioc_lookup_icq);
|
|
|
|
void ioc_set_changed(struct io_context *ioc, int which)
|
|
{
|
|
struct io_cq *icq;
|
|
struct hlist_node *n;
|
|
|
|
hlist_for_each_entry(icq, n, &ioc->icq_list, ioc_node)
|
|
set_bit(which, &icq->changed);
|
|
}
|
|
|
|
/**
|
|
* ioc_ioprio_changed - notify ioprio change
|
|
* @ioc: io_context of interest
|
|
* @ioprio: new ioprio
|
|
*
|
|
* @ioc's ioprio has changed to @ioprio. Set %ICQ_IOPRIO_CHANGED for all
|
|
* icq's. iosched is responsible for checking the bit and applying it on
|
|
* request issue path.
|
|
*/
|
|
void ioc_ioprio_changed(struct io_context *ioc, int ioprio)
|
|
{
|
|
unsigned long flags;
|
|
|
|
spin_lock_irqsave(&ioc->lock, flags);
|
|
ioc->ioprio = ioprio;
|
|
ioc_set_changed(ioc, ICQ_IOPRIO_CHANGED);
|
|
spin_unlock_irqrestore(&ioc->lock, flags);
|
|
}
|
|
|
|
/**
|
|
* ioc_cgroup_changed - notify cgroup change
|
|
* @ioc: io_context of interest
|
|
*
|
|
* @ioc's cgroup has changed. Set %ICQ_CGROUP_CHANGED for all icq's.
|
|
* iosched is responsible for checking the bit and applying it on request
|
|
* issue path.
|
|
*/
|
|
void ioc_cgroup_changed(struct io_context *ioc)
|
|
{
|
|
unsigned long flags;
|
|
|
|
spin_lock_irqsave(&ioc->lock, flags);
|
|
ioc_set_changed(ioc, ICQ_CGROUP_CHANGED);
|
|
spin_unlock_irqrestore(&ioc->lock, flags);
|
|
}
|
|
|
|
static int __init blk_ioc_init(void)
|
|
{
|
|
iocontext_cachep = kmem_cache_create("blkdev_ioc",
|
|
sizeof(struct io_context), 0, SLAB_PANIC, NULL);
|
|
return 0;
|
|
}
|
|
subsys_initcall(blk_ioc_init);
|