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Subject[PATCH 4.18 113/168] dm raid: fix stripe adding reshape deadlock
Date
4.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Heinz Mauelshagen <heinzm@redhat.com>

[ Upstream commit 644e2537fdc77baeeefc829524937bca64329f82 ]

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>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/md/dm-raid.c | 11 +++--------
1 file changed, 3 insertions(+), 8 deletions(-)

--- a/drivers/md/dm-raid.c
+++ b/drivers/md/dm-raid.c
@@ -3869,14 +3869,13 @@ static int rs_start_reshape(struct raid_
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_
}
}

- /* 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

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