Commit 0e94ed33 authored by Nilay Shroff's avatar Nilay Shroff Committed by Jens Axboe
Browse files

block: protect debugfs attribute method hctx_busy_show 



The hctx_busy_show method in debugfs is currently unprotected. This
method iterates over all started requests in a tagset and prints them.
However, the tags can be updated concurrently via the sysfs attributes
'nr_requests' or 'scheduler' (elevator switch), leading to potential
race conditions.

Since sysfs attributes 'nr_requests' and 'scheduler' are already
protected using q->elevator_lock, extend this protection to the debugfs
'busy' attribute as well to ensure consistency.

Signed-off-by: default avatarNilay Shroff <nilay@linux.ibm.com>
Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20250313115235.3707600-4-nilay@linux.ibm.com


Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 78800f59

block/blk-mq-debugfs.c

+5 −0
Original line number Diff line number Diff line
@@ -347,9 +347,14 @@ static int hctx_busy_show(void *data, struct seq_file *m) 
{

	struct blk_mq_hw_ctx *hctx = data;

	struct show_busy_params params = { .m = m, .hctx = hctx };

	int res;



	res = mutex_lock_interruptible(&hctx->queue->elevator_lock);

	if (res)

		return res;

	blk_mq_tagset_busy_iter(hctx->queue->tag_set, hctx_show_busy_rq,

				&params);

	mutex_unlock(&hctx->queue->elevator_lock);



	return 0;

}