From 5b8bbc39d5678179f2fd4ee2e09005d8f277834c Mon Sep 17 00:00:00 2001 From: Mikulas Patocka Date: Fri, 20 Jul 2012 14:25:05 +0100 Subject: [PATCH] dm thin: do not send discards to shared blocks commit 650d2a06b4fe1cc1d218c20e256650f68bf0ca31 upstream. When process_discard receives a partial discard that doesn't cover a full block, it sends this discard down to that block. Unfortunately, the block can be shared and the discard would corrupt the other snapshots sharing this block. This patch detects block sharing and ends the discard with success when sending it to the shared block. The above change means that if the device supports discard it can't be guaranteed that a discard request zeroes data. Therefore, we set ti->discard_zeroes_data_unsupported. Thin target discard support with this bug arrived in commit 104655fd4dcebd50068ef30253a001da72e3a081 (dm thin: support discards). Signed-off-by: Mikulas Patocka Signed-off-by: Mike Snitzer Signed-off-by: Alasdair G Kergon Signed-off-by: Greg Kroah-Hartman --- drivers/md/dm-thin.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/drivers/md/dm-thin.c b/drivers/md/dm-thin.c index eb3d138ff55a..e0a0ebe64c09 100644 --- a/drivers/md/dm-thin.c +++ b/drivers/md/dm-thin.c @@ -1240,7 +1240,10 @@ static void process_discard(struct thin_c *tc, struct bio *bio) cell_release_singleton(cell, bio); cell_release_singleton(cell2, bio); - remap_and_issue(tc, bio, lookup_result.block); + if ((!lookup_result.shared) && pool->pf.discard_passdown) + remap_and_issue(tc, bio, lookup_result.block); + else + bio_endio(bio, 0); } break; @@ -2575,6 +2578,7 @@ static int thin_ctr(struct dm_target *ti, unsigned argc, char **argv) if (tc->pool->pf.discard_enabled) { ti->discards_supported = 1; ti->num_discard_requests = 1; + ti->discard_zeroes_data_unsupported = 1; } dm_put(pool_md); -- 2.39.5