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block: protect read_ahead_kb using q->limits_lock

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The bdi->ra_pages could be updated under q->limits_lock because it's
usually calculated from the queue limits by queue_limits_commit_update.
So protect reading/writing the sysfs attribute read_ahead_kb using
q->limits_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/20250304102551.2533767-8-nilay@linux.ibm.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Nilay Shroff 2025-03-04 15:52:36 +05:30 committed by Jens Axboe
parent 245618f8e4
commit 5e40f4452d
2 changed files with 13 additions and 6 deletions
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16
block/blk-sysfs.c
View File

@ -93,9 +93,9 @@ static ssize_t queue_ra_show(struct gendisk *disk, char *page)
{
ssize_t ret;
mutex_lock(&disk->queue->sysfs_lock);
mutex_lock(&disk->queue->limits_lock);
ret = queue_var_show(disk->bdi->ra_pages << (PAGE_SHIFT - 10), page);
mutex_unlock(&disk->queue->sysfs_lock);
mutex_unlock(&disk->queue->limits_lock);
return ret;
}
@ -111,12 +111,15 @@ queue_ra_store(struct gendisk *disk, const char *page, size_t count)
ret = queue_var_store(&ra_kb, page, count);
if (ret < 0)
return ret;
mutex_lock(&q->sysfs_lock);
/*
* ->ra_pages is protected by ->limits_lock because it is usually
* calculated from the queue limits by queue_limits_commit_update.
*/
mutex_lock(&q->limits_lock);
memflags = blk_mq_freeze_queue(q);
disk->bdi->ra_pages = ra_kb >> (PAGE_SHIFT - 10);
mutex_unlock(&q->limits_lock);
blk_mq_unfreeze_queue(q, memflags);
mutex_unlock(&q->sysfs_lock);
return ret;
}
@ -670,7 +673,8 @@ static struct attribute *queue_attrs[] = {
&queue_dma_alignment_entry.attr,
/*
* Attributes which are protected with q->sysfs_lock.
* Attributes which require some form of locking other than
* q->sysfs_lock.
*/
&queue_ra_entry.attr,

3
include/linux/blkdev.h
View File

@ -571,6 +571,9 @@ struct request_queue {
struct mutex elevator_lock;
struct mutex sysfs_lock;
/*
* Protects queue limits and also sysfs attribute read_ahead_kb.
*/
struct mutex limits_lock;
/*