dummy/linux-stable-mirror
1
0
Fork 1
mirror of https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ synced 2025-04-19 20:58:31 +09:00
Code Issues Packages Projects Releases Wiki Activity

block: protect nr_requests update using q->elevator_lock

Browse Source 
The sysfs attribute nr_requests could be simultaneously updated from
elevator switch/update or nr_hw_queue update code path. The update to
nr_requests for each of those code paths runs holding q->elevator_lock.
So we should protect access to sysfs attribute nr_requests using q->
elevator_lock instead of q->sysfs_lock.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Nilay Shroff <nilay@linux.ibm.com>
Link: https://lore.kernel.org/r/20250304102551.2533767-6-nilay@linux.ibm.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Nilay Shroff 2025-03-04 15:52:34 +05:30 committed by Jens Axboe
parent 1bf70d08cc
commit 3efe7571c3
2 changed files with 11 additions and 9 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

10
block/blk-sysfs.c
View File

@ -55,9 +55,9 @@ static ssize_t queue_requests_show(struct gendisk *disk, char *page)
{
ssize_t ret;
mutex_lock(&disk->queue->sysfs_lock);
mutex_lock(&disk->queue->elevator_lock);
ret = queue_var_show(disk->queue->nr_requests, page);
mutex_unlock(&disk->queue->sysfs_lock);
mutex_unlock(&disk->queue->elevator_lock);
return ret;
}
@ -76,16 +76,16 @@ queue_requests_store(struct gendisk *disk, const char *page, size_t count)
if (ret < 0)
return ret;
mutex_lock(&q->sysfs_lock);
memflags = blk_mq_freeze_queue(q);
mutex_lock(&q->elevator_lock);
if (nr < BLKDEV_MIN_RQ)
nr = BLKDEV_MIN_RQ;
err = blk_mq_update_nr_requests(disk->queue, nr);
if (err)
ret = err;
mutex_unlock(&q->elevator_lock);
blk_mq_unfreeze_queue(q, memflags);
mutex_unlock(&q->sysfs_lock);
return ret;
}
@ -692,7 +692,6 @@ static struct attribute *blk_mq_queue_attrs[] = {
/*
* Attributes which are protected with q->sysfs_lock.
*/
&queue_requests_entry.attr,
#ifdef CONFIG_BLK_WBT
&queue_wb_lat_entry.attr,
#endif
@ -701,6 +700,7 @@ static struct attribute *blk_mq_queue_attrs[] = {
* q->sysfs_lock.
*/
&elv_iosched_entry.attr,
&queue_requests_entry.attr,
/*
* Attributes which don't require locking.

10
include/linux/blkdev.h
View File

@ -561,10 +561,12 @@ struct request_queue {
struct list_head flush_list;
/*
* Protects against I/O scheduler switching, specifically when
* updating q->elevator. To ensure proper locking order during
* an elevator update, first freeze the queue, then acquire
* ->elevator_lock.
* Protects against I/O scheduler switching, particularly when
* updating q->elevator. Since the elevator update code path may
* also modify q->nr_requests, this lock also protects the sysfs
* attribute nr_requests.
* To ensure proper locking order during an elevator update, first
* freeze the queue, then acquire ->elevator_lock.
*/
struct mutex elevator_lock;