dm mpath: avoid that path removal can trigger an infinite loop (7083abbb) · Commits · 戴 / test

If blk_get_request() fails, check whether the failure is due to a path being removed. If that is the case, fail the path by triggering a call to fail_path(). This avoids that the following scenario can be encountered while removing paths: * CPU usage of a kworker thread jumps to 100%. * Removing the DM device becomes impossible. Delay requeueing if blk_get_request() returns -EBUSY or -EWOULDBLOCK, and the queue is not dying, because in these cases immediate requeuing is inappropriate. Signed-off-by:

Bart Van Assche <bart.vanassche@sandisk.com> Cc: Hannes Reinecke <hare@suse.com> Cc: Christoph Hellwig <hch@lst.de> Cc: <stable@vger.kernel.org> Signed-off-by:

Mike Snitzer <snitzer@redhat.com>

drivers/md/dm-mpath.c

+11 −4

Original line number	Diff line number	Diff line
		@@ -489,6 +489,7 @@ static int multipath_clone_and_map(struct dm_target ti, struct request rq,
		struct pgpath *pgpath;
		struct block_device *bdev;
		struct dm_mpath_io *mpio = get_mpio(map_context);
		struct request_queue *q;
		struct request *clone;

		/* Do we need to select a new pgpath? */
		@@ -511,12 +512,18 @@ static int multipath_clone_and_map(struct dm_target ti, struct request rq,
		mpio->nr_bytes = nr_bytes;

		bdev = pgpath->path.dev->bdev;

		clone = blk_get_request(bdev_get_queue(bdev),
		rq->cmd_flags \| REQ_NOMERGE,
		GFP_ATOMIC);
		q = bdev_get_queue(bdev);
		clone = blk_get_request(q, rq->cmd_flags \| REQ_NOMERGE, GFP_ATOMIC);
		if (IS_ERR(clone)) {
		/* EBUSY, ENODEV or EWOULDBLOCK: requeue */
		bool queue_dying = blk_queue_dying(q);
		DMERR_LIMIT("blk_get_request() returned %ld%s - requeuing",
		PTR_ERR(clone), queue_dying ? " (path offline)" : "");
		if (queue_dying) {
		atomic_inc(&m->pg_init_in_progress);
		activate_or_offline_path(pgpath);
		return DM_MAPIO_REQUEUE;
		}
		return DM_MAPIO_DELAY_REQUEUE;
		}
		clone->bio = clone->biotail = NULL;

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