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block: protect debugfs attrs using elevator_lock instead of sysfs_lock

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Currently, the block debugfs attributes (tags, tags_bitmap, sched_tags,
and sched_tags_bitmap) are protected using q->sysfs_lock. However, these
attributes are updated in multiple scenarios:
- During driver probe method
- During an elevator switch/update
- During an nr_hw_queues update
- When writing to the sysfs attribute nr_requests

All these update paths (except driver probe method, which doesn't
require any protection) are already protected using q->elevator_lock. To
ensure consistency and proper synchronization, replace q->sysfs_lock
with q->elevator_lock for protecting these debugfs attributes.

Signed-off-by: Nilay Shroff <nilay@linux.ibm.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20250313115235.3707600-2-nilay@linux.ibm.com
[axboe: some commit message rewording/fixes]
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Nilay Shroff 2025-03-13 17:21:50 +05:30 committed by Jens Axboe
parent 75618ac6e9
commit a3996d11f3
2 changed files with 11 additions and 11 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

16
block/blk-mq-debugfs.c
View File

@ -400,12 +400,12 @@ static int hctx_tags_show(void *data, struct seq_file *m)
struct request_queue *q = hctx->queue;
int res;
res = mutex_lock_interruptible(&q->sysfs_lock);
res = mutex_lock_interruptible(&q->elevator_lock);
if (res)
goto out;
if (hctx->tags)
blk_mq_debugfs_tags_show(m, hctx->tags);
mutex_unlock(&q->sysfs_lock);
mutex_unlock(&q->elevator_lock);
out:
return res;
@ -417,12 +417,12 @@ static int hctx_tags_bitmap_show(void *data, struct seq_file *m)
struct request_queue *q = hctx->queue;
int res;
res = mutex_lock_interruptible(&q->sysfs_lock);
res = mutex_lock_interruptible(&q->elevator_lock);
if (res)
goto out;
if (hctx->tags)
sbitmap_bitmap_show(&hctx->tags->bitmap_tags.sb, m);
mutex_unlock(&q->sysfs_lock);
mutex_unlock(&q->elevator_lock);
out:
return res;
@ -434,12 +434,12 @@ static int hctx_sched_tags_show(void *data, struct seq_file *m)
struct request_queue *q = hctx->queue;
int res;
res = mutex_lock_interruptible(&q->sysfs_lock);
res = mutex_lock_interruptible(&q->elevator_lock);
if (res)
goto out;
if (hctx->sched_tags)
blk_mq_debugfs_tags_show(m, hctx->sched_tags);
mutex_unlock(&q->sysfs_lock);
mutex_unlock(&q->elevator_lock);
out:
return res;
@ -451,12 +451,12 @@ static int hctx_sched_tags_bitmap_show(void *data, struct seq_file *m)
struct request_queue *q = hctx->queue;
int res;
res = mutex_lock_interruptible(&q->sysfs_lock);
res = mutex_lock_interruptible(&q->elevator_lock);
if (res)
goto out;
if (hctx->sched_tags)
sbitmap_bitmap_show(&hctx->sched_tags->bitmap_tags.sb, m);
mutex_unlock(&q->sysfs_lock);
mutex_unlock(&q->elevator_lock);
out:
return res;

6
include/linux/blkdev.h
View File

@ -566,9 +566,9 @@ struct request_queue {
* nr_requests and wbt latency, this lock also protects the sysfs attrs
* nr_requests and wbt_lat_usec. Additionally the nr_hw_queues update
* may modify hctx tags, reserved-tags and cpumask, so this lock also
* helps protect the hctx attrs. To ensure proper locking order during
* an elevator or nr_hw_queue update, first freeze the queue, then
* acquire ->elevator_lock.
* helps protect the hctx sysfs/debugfs attrs. To ensure proper locking
* order during an elevator or nr_hw_queue update, first freeze the
* queue, then acquire ->elevator_lock.
*/
struct mutex elevator_lock;