[PATCH 2/2] block: avoid acquiring q->sysfs_lock while accessing sysfs attributes

[Nilay Shroff <nilay@linux.ibm.com>]

The sysfs attributes are already protected with sysfs/kernfs internal
locking. So acquiring q->sysfs_lock is not needed while accessing sysfs
attribute files. So this change helps avoid holding q->sysfs_lock while
accessing sysfs attribute files.

Signed-off-by: Nilay Shroff <nilay@linux.ibm.com>
---
 block/blk-mq-sysfs.c |  6 +-----
 block/blk-sysfs.c    | 10 +++-------
 2 files changed, 4 insertions(+), 12 deletions(-)

diff --git a/block/blk-mq-sysfs.c b/block/blk-mq-sysfs.c
index 3feeeccf8a99..da53397d99fa 100644
--- a/block/blk-mq-sysfs.c
+++ b/block/blk-mq-sysfs.c
@@ -52,7 +52,6 @@ static ssize_t blk_mq_hw_sysfs_show(struct kobject *kobj,
 	struct blk_mq_hw_ctx_sysfs_entry *entry;
 	struct blk_mq_hw_ctx *hctx;
 	struct request_queue *q;
-	ssize_t res;
 
 	entry = container_of(attr, struct blk_mq_hw_ctx_sysfs_entry, attr);
 	hctx = container_of(kobj, struct blk_mq_hw_ctx, kobj);
@@ -61,10 +60,7 @@ static ssize_t blk_mq_hw_sysfs_show(struct kobject *kobj,
 	if (!entry->show)
 		return -EIO;
 
-	mutex_lock(&q->sysfs_lock);
-	res = entry->show(hctx, page);
-	mutex_unlock(&q->sysfs_lock);
-	return res;
+	return entry->show(hctx, page);
 }
 
 static ssize_t blk_mq_hw_sysfs_nr_tags_show(struct blk_mq_hw_ctx *hctx,
diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
index 6f548a4376aa..2b8e7b311c61 100644
--- a/block/blk-sysfs.c
+++ b/block/blk-sysfs.c
@@ -664,14 +664,11 @@ queue_attr_show(struct kobject *kobj, struct attribute *attr, char *page)
 {
 	struct queue_sysfs_entry *entry = to_queue(attr);
 	struct gendisk *disk = container_of(kobj, struct gendisk, queue_kobj);
-	ssize_t res;
 
 	if (!entry->show)
 		return -EIO;
-	mutex_lock(&disk->queue->sysfs_lock);
-	res = entry->show(disk, page);
-	mutex_unlock(&disk->queue->sysfs_lock);
-	return res;
+
+	return entry->show(disk, page);
 }
 
 static ssize_t
@@ -710,11 +707,10 @@ queue_attr_store(struct kobject *kobj, struct attribute *attr,
 		return length;
 	}
 
-	mutex_lock(&q->sysfs_lock);
 	memflags = blk_mq_freeze_queue(q);
 	res = entry->store(disk, page, length);
 	blk_mq_unfreeze_queue(q, memflags);
-	mutex_unlock(&q->sysfs_lock);
+
 	return res;
 }
 
-- 
2.47.1