dm mpath: delay retry of bypassed pg

If I/O needs retrying and only bypassed priority groups are available,
set the pg_init_delay_retry flag to wait before retrying.

If, for example, the reason for the bypass is that the controller is
getting reset or there is a firmware upgrade happening, retrying right
away would cause a flood of log messages and retries for what could be a
few seconds or even several minutes.

Signed-off-by: Mike Christie <michaelc@cs.wisc.edu>
Acked-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

1 files changed, 6 insertions, 2 deletions

diff --git a/drivers/md/dm-mpath.c b/drivers/md/dm-mpath.c
index c35160786cf4..2469ba68dc2b 100644
--- a/drivers/md/dm-mpath.c
+++ b/drivers/md/dm-mpath.c
@@ -329,14 +329,18 @@ static void __choose_pgpath(struct multipath *m, size_t nr_bytes)
         /*
          * Loop through priority groups until we find a valid path.
          * First time we skip PGs marked 'bypassed'.
-         * Second time we only try the ones we skipped.
+         * Second time we only try the ones we skipped, but set
+         * pg_init_delay_retry so we do not hammer controllers.
          */
         do {
                 list_for_each_entry(pg, &m->priority_groups, list) {
                         if (pg->bypassed == bypassed)
                                 continue;
-                        if (!__choose_path_in_pg(m, pg, nr_bytes))
+                        if (!__choose_path_in_pg(m, pg, nr_bytes)) {
+                                if (!bypassed)
+                                        m->pg_init_delay_retry = 1;
                                 return;
+                        }
                 }
         } while (bypassed--);