[PATCH 3.16.y-ckt 058/126] dm thin: restore requested 'error_if_no_space' setting on OODS to WRITE transition

[Luis Henriques]

3.16.7-ckt22 -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")
[ luis: backported to 3.16: adjusted context ]
Signed-off-by: Luis Henriques <luis.henriques@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 6d8895422f31..e298762d29a6 100644
--- a/drivers/md/dm-thin.c
+++ b/drivers/md/dm-thin.c
@@ -1786,6 +1786,7 @@ 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;
 		dm_pool_metadata_read_write(pool->pmd);
 		pool->process_bio = process_bio;
 		pool->process_discard = process_discard;
--
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