From 8ff232c1a819c2e98d85974a3bff0b7b8e2970ed Mon Sep 17 00:00:00 2001 From: Hannes Reinecke Date: Wed, 15 Jul 2015 13:23:24 +0200 Subject: [PATCH] dm mpath: always return reservation conflict without failing over If dm-mpath encounters an reservation conflict it should not fail the path (as communication with the target is not affected) but should rather retry on another path. However, in doing so we might be inducing a ping-pong between paths, with no guarantee of any forward progress. And arguably a reservation conflict is an unexpected error, so we should be passing it upwards to allow the application to take appropriate steps. This change resolves a show-stopper problem seen with the pNFS SCSI layout because it is trivial to hit reservation conflict based failover loops without it. Doubts were raised about the implications of this change relative to products like IBM's SVC. But there is little point withholding a fix for Linux because a proprietary product may or may not have some issues in its implementation of how it interfaces with Linux. In the future, if there is glaring evidence that this change is certainly problematic we can revisit it. Signed-off-by: Hannes Reinecke Acked-by: Christoph Hellwig Tested-by: Christoph Hellwig Signed-off-by: Mike Snitzer # tweaked header --- drivers/md/dm-mpath.c | 14 ++++++++------ 1 file changed, 8 insertions(+), 6 deletions(-) diff --git a/drivers/md/dm-mpath.c b/drivers/md/dm-mpath.c index f31fa1364abc..e477af8596e2 100644 --- a/drivers/md/dm-mpath.c +++ b/drivers/md/dm-mpath.c @@ -1530,6 +1530,14 @@ static void activate_path(struct work_struct *work) static int noretry_error(int error) { switch (error) { + case -EBADE: + /* + * EBADE signals an reservation conflict. + * We shouldn't fail the path here as we can communicate with + * the target. We should failover to the next path, but in + * doing so we might be causing a ping-pong between paths. + * So just return the reservation conflict error. + */ case -EOPNOTSUPP: case -EREMOTEIO: case -EILSEQ: @@ -1574,9 +1582,6 @@ static int do_end_io(struct multipath *m, struct request *clone, if (!test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags)) { if (!must_push_back_rq(m)) r = -EIO; - } else { - if (error == -EBADE) - r = error; } } @@ -1625,9 +1630,6 @@ static int do_end_io_bio(struct multipath *m, struct bio *clone, if (!must_push_back_bio(m)) return -EIO; return DM_ENDIO_REQUEUE; - } else { - if (error == -EBADE) - return error; } } -- GitLab