dm raid: fix stripe adding reshape deadlock

When initiating a stripe adding reshape, a deadlock between
md_stop_writes() waiting for the sync thread to stop and the running
sync thread waiting for inactive stripes occurs (this frequently happens
on single-core but rarely on multi-core systems).

Fix this deadlock by setting MD_RECOVERY_WAIT to have the main MD
resynchronization thread worker (md_do_sync()) bail out when initiating
the reshape via constructor arguments.

Signed-off-by: Heinz Mauelshagen <heinzm@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>

diff --git a/drivers/md/dm-raid.c b/drivers/md/dm-raid.c
index d8406e0..9129c5e 100644 (file)
--- a/drivers/md/dm-raid.c
+++ b/drivers/md/dm-raid.c
@@ -3869,14 +3869,13 @@ static int rs_start_reshape(struct raid_set *rs)
        struct mddev *mddev = &rs->md;
        struct md_personality *pers = mddev->pers;
 
+       /* Don't allow the sync thread to work until the table gets reloaded. */
+       set_bit(MD_RECOVERY_WAIT, &mddev->recovery);
+
        r = rs_setup_reshape(rs);
        if (r)
                return r;
 
-       /* Need to be resumed to be able to start reshape, recovery is frozen until raid_resume() though */
-       if (test_and_clear_bit(RT_FLAG_RS_SUSPENDED, &rs->runtime_flags))
-               mddev_resume(mddev);
-
        /*
         * Check any reshape constraints enforced by the personalility
         *
@@ -3900,10 +3899,6 @@ static int rs_start_reshape(struct raid_set *rs)
                }
        }
 
-       /* Suspend because a resume will happen in raid_resume() */
-       set_bit(RT_FLAG_RS_SUSPENDED, &rs->runtime_flags);
-       mddev_suspend(mddev);
-
        /*
         * Now reshape got set up, update superblocks to
         * reflect the fact so that a table reload will