Commit 5e40f445 authored by Nilay Shroff's avatar Nilay Shroff Committed by Jens Axboe
Browse files

block: protect read_ahead_kb using q->limits_lock 



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: default avatarChristoph Hellwig <hch@lst.de>
Reviewed-by: default avatarHannes Reinecke <hare@suse.de>
Reviewed-by: default avatarMing Lei <ming.lei@redhat.com>
Signed-off-by: default avatarNilay Shroff <nilay@linux.ibm.com>
Link: https://lore.kernel.org/r/20250304102551.2533767-8-nilay@linux.ibm.com


Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 245618f8

block/blk-sysfs.c

+10 −6
Original line number Diff line number Diff line
@@ -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,

include/linux/blkdev.h

+3 −0
Original line number Diff line number Diff line
@@ -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;



	/*