From a3996d11f3ab743e6cc4e3529ce9459c2cd27139 Mon Sep 17 00:00:00 2001 From: Nilay Shroff Date: Thu, 13 Mar 2025 17:21:50 +0530 Subject: [PATCH] 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 Reviewed-by: Christoph Hellwig Link: https://lore.kernel.org/r/20250313115235.3707600-2-nilay@linux.ibm.com [axboe: some commit message rewording/fixes] Signed-off-by: Jens Axboe --- block/blk-mq-debugfs.c | 16 ++++++++-------- include/linux/blkdev.h | 6 +++--- 2 files changed, 11 insertions(+), 11 deletions(-) diff --git a/block/blk-mq-debugfs.c b/block/blk-mq-debugfs.c index adf5f0697b6b0..62775b132d4c6 100644 --- 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 dcf8fce15e23d..8d072042790e9 100644 --- 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;