block: protect debugfs attrs using elevator_lock instead of sysfs_lock

Currently, the block debugfs attributes (tags, tags_bitmap, sched_tags,
and sched_tags_bitmap) are protected using q->sysfs_lock. However, these
attributes are updated in multiple scenarios:
- During driver probe method
- During an elevator switch/update
- During an nr_hw_queues update
- When writing to the sysfs attribute nr_requests

All these update paths (except driver probe method, which doesn't
require any protection) are already protected using q->elevator_lock. To
ensure consistency and proper synchronization, replace q->sysfs_lock
with q->elevator_lock for protecting these debugfs attributes.

Signed-off-by: Nilay Shroff <nilay@linux.ibm.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20250313115235.3707600-2-nilay@linux.ibm.com
[axboe: some commit message rewording/fixes]
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/block/blk-mq-debugfs.c b/block/blk-mq-debugfs.c
index adf5f0697b6b04bb82d6ff2528f098a9300de1b5..62775b132d4c685fd22ee812a19bbe9d965d54c9 100644 (file)
--- a/block/blk-mq-debugfs.c
+++ b/block/blk-mq-debugfs.c
@@ -400,12 +400,12 @@ static int hctx_tags_show(void *data, struct seq_file *m)
        struct request_queue *q = hctx->queue;
        int res;
 
-       res = mutex_lock_interruptible(&q->sysfs_lock);
+       res = mutex_lock_interruptible(&q->elevator_lock);
        if (res)
                goto out;
        if (hctx->tags)
                blk_mq_debugfs_tags_show(m, hctx->tags);
-       mutex_unlock(&q->sysfs_lock);
+       mutex_unlock(&q->elevator_lock);
 
 out:
        return res;
@@ -417,12 +417,12 @@ static int hctx_tags_bitmap_show(void *data, struct seq_file *m)
        struct request_queue *q = hctx->queue;
        int res;
 
-       res = mutex_lock_interruptible(&q->sysfs_lock);
+       res = mutex_lock_interruptible(&q->elevator_lock);
        if (res)
                goto out;
        if (hctx->tags)
                sbitmap_bitmap_show(&hctx->tags->bitmap_tags.sb, m);
-       mutex_unlock(&q->sysfs_lock);
+       mutex_unlock(&q->elevator_lock);
 
 out:
        return res;
@@ -434,12 +434,12 @@ static int hctx_sched_tags_show(void *data, struct seq_file *m)
        struct request_queue *q = hctx->queue;
        int res;
 
-       res = mutex_lock_interruptible(&q->sysfs_lock);
+       res = mutex_lock_interruptible(&q->elevator_lock);
        if (res)
                goto out;
        if (hctx->sched_tags)
                blk_mq_debugfs_tags_show(m, hctx->sched_tags);
-       mutex_unlock(&q->sysfs_lock);
+       mutex_unlock(&q->elevator_lock);
 
 out:
        return res;
@@ -451,12 +451,12 @@ static int hctx_sched_tags_bitmap_show(void *data, struct seq_file *m)
        struct request_queue *q = hctx->queue;
        int res;
 
-       res = mutex_lock_interruptible(&q->sysfs_lock);
+       res = mutex_lock_interruptible(&q->elevator_lock);
        if (res)
                goto out;
        if (hctx->sched_tags)
                sbitmap_bitmap_show(&hctx->sched_tags->bitmap_tags.sb, m);
-       mutex_unlock(&q->sysfs_lock);
+       mutex_unlock(&q->elevator_lock);
 
 out:
        return res;

diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index dcf8fce15e23dd1ffeefe74426bceb2c59d255b1..8d072042790e95b87d222e4d8a989913eca5ae0a 100644 (file)
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -566,9 +566,9 @@ struct request_queue {
         * nr_requests and wbt latency, this lock also protects the sysfs attrs
         * nr_requests and wbt_lat_usec. Additionally the nr_hw_queues update
         * may modify hctx tags, reserved-tags and cpumask, so this lock also
-        * helps protect the hctx attrs. To ensure proper locking order during
-        * an elevator or nr_hw_queue update, first freeze the queue, then
-        * acquire ->elevator_lock.
+        * helps protect the hctx sysfs/debugfs attrs. To ensure proper locking
+        * order during an elevator or nr_hw_queue update, first freeze the
+        * queue, then acquire ->elevator_lock.
         */
        struct mutex            elevator_lock;