The bdi->ra_pages could be updated under q->limits_lock while applying
bdi limits (please refer blk_apply_bdi_limits()). So protect accessing
sysfs attribute read_ahead_kb using q->limits_lock instead of q->sysfs_
lock.
Signed-off-by: Nilay Shroff <nilay@xxxxxxxxxxxxx>
---
block/blk-sysfs.c | 19 +++++++++++++------
1 file changed, 13 insertions(+), 6 deletions(-)
diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
index 876376bfdac3..a8116d3d9127 100644
--- a/block/blk-sysfs.c
+++ b/block/blk-sysfs.c
@@ -105,9 +105,9 @@ static ssize_t queue_ra_show(struct gendisk *disk, char *page)
{
int 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;
}
@@ -119,17 +119,24 @@ queue_ra_store(struct gendisk *disk, const char *page, size_t count)
ssize_t ret;
unsigned int memflags;
struct request_queue *q = disk->queue;
-
- mutex_lock(&q->sysfs_lock);
+ /*
+ * We don't use atomic update helper queue_limits_start_update() and
+ * queue_limits_commit_update() here for updaing ra_pages bacause
+ * blk_apply_bdi_limits() which is invoked from queue_limits_commit_
+ * update() can overwrite the ra_pages value which user actaully wants
+ * to store here. The blk_apply_bdi_limits() sets value of ra_pages
+ * based on the optimal I/O size(io_opt).
+ */
+ mutex_lock(&q->limits_lock);
memflags = blk_mq_freeze_queue(q);
-
ret = queue_var_store(&ra_kb, page, count);
if (ret < 0)
goto out;
disk->bdi->ra_pages = ra_kb >> (PAGE_SHIFT - 10);
out:
+ mutex_unlock(&q->limits_lock);
blk_mq_unfreeze_queue(q, memflags);
- mutex_unlock(&q->sysfs_lock);
+
return ret;
}
--
2.47.1
