[PATCH 4.2.y-ckt 041/305] dm thin: restore requested 'error_if_no_space' setting on OODS to WRITE transition

From: Kamal Mostafa
Date: Fri Jan 15 2016 - 20:30:16 EST

4.2.8-ckt2 -stable review patch. If anyone has any objections, please let me know.


From: Mike Snitzer <snitzer@xxxxxxxxxx>

commit 172c238612ebf81cabccc86b788c9209af591f61 upstream.

A thin-pool that is in out-of-data-space (OODS) mode may transition back
to write mode -- without the admin adding more space to the thin-pool --
if/when blocks are released (either by deleting thin devices or
discarding provisioned blocks).

But as part of the thin-pool's earlier transition to out-of-data-space
mode the thin-pool may have set the 'error_if_no_space' flag to true if
the no_space_timeout expires without more space having been made
available. That implementation detail, of changing the pool's
error_if_no_space setting, needs to be reset back to the default that
the user specified when the thin-pool's table was loaded.

Otherwise we'll drop the user requested behaviour on the floor when this
out-of-data-space to write mode transition occurs.

Reported-by: Vivek Goyal <vgoyal@xxxxxxxxxx>
Signed-off-by: Mike Snitzer <snitzer@xxxxxxxxxx>
Acked-by: Joe Thornber <ejt@xxxxxxxxxx>
Fixes: 2c43fd26e4 ("dm thin: fix missing out-of-data-space to write mode transition if blocks are released")
Signed-off-by: Kamal Mostafa <kamal@xxxxxxxxxxxxx>
drivers/md/dm-thin.c | 1 +
1 file changed, 1 insertion(+)

diff --git a/drivers/md/dm-thin.c b/drivers/md/dm-thin.c
index 493c38e..4190e3b 100644
--- a/drivers/md/dm-thin.c
+++ b/drivers/md/dm-thin.c
@@ -2487,6 +2487,7 @@ static void set_pool_mode(struct pool *pool, enum pool_mode new_mode)
case PM_WRITE:
if (old_mode != new_mode)
notify_of_pool_mode_change(pool, "write");
+ pool->pf.error_if_no_space = pt->requested_pf.error_if_no_space;
pool->process_bio = process_bio;
pool->process_discard = process_discard_bio;