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: Hannes Reinecke <hare@xxxxxxx>
Signed-off-by: Nilay Shroff <nilay@xxxxxxxxxxxxx>
---
block/blk-sysfs.c | 16 ++++++++++------
include/linux/blkdev.h | 3 +++
2 files changed, 13 insertions(+), 6 deletions(-)
diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
index 46033d640e30..67c5c4cee6b4 100644
--- a/block/blk-sysfs.c
+++ b/block/blk-sysfs.c
@@ -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,
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 0ee3b5c9388e..3bee1b4858b6 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -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;
/*
--
2.47.1
