[dm-devel] [PATCH 0/2] block/scsi/dm-rq: fix leak of request private data in dm-mpath

[Ming Lei]

Hi,

When one request is dispatched to LLD via dm-rq, if the result is
BLK_STS_*RESOURCE, dm-rq will free the request. However, LLD may allocate
private stuff for this request, so this way will cause memory leak.

Add .cleanup_rq() callback and implement it in SCSI for fixing the issue.
And SCSI is the only driver which allocates private stuff in .queue_rq()
path.

Another use case of this callback is to free the request and re-submit
bios during cpu hotplug when the hctx is dead, see the following link:

https://lore.kernel.org/linux-block/f122e8f2-5ede-2d83-9ca0-bc713ce66d01@huawei.com/T/#t

Ming Lei (2):
  blk-mq: add callback of .cleanup_rq
  scsi: implement .cleanup_rq callback

 drivers/md/dm-rq.c      |  1 +
 drivers/scsi/scsi_lib.c | 15 +++++++++++++++
 include/linux/blk-mq.h  | 13 +++++++++++++
 3 files changed, 29 insertions(+)

Cc: Ewan D. Milne <emilne at redhat.com>
Cc: Bart Van Assche <bvanassche at acm.org>
Cc: Hannes Reinecke <hare at suse.com>
Cc: Christoph Hellwig <hch at lst.de>
Cc: Mike Snitzer <snitzer at redhat.com>
Cc: dm-devel at redhat.com
Cc: <stable at vger.kernel.org>
Fixes: 396eaf21ee17 ("blk-mq: improve DM's blk-mq IO merging via blk_insert_cloned_request feedback")
-- 
2.20.1