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authorMikulas Patocka <mpatocka@redhat.com>2012-07-20 14:25:05 +0100
committerAlasdair G Kergon <agk@redhat.com>2012-07-20 14:25:05 +0100
commit650d2a06b4fe1cc1d218c20e256650f68bf0ca31 (patch)
tree586e7da8f7bd3e895b52514bb4bd1ff1f1400181
parent751f188dd5ab95b3f2b5f2f467c38aae5a2877eb (diff)
downloadlinux-stericsson-650d2a06b4fe1cc1d218c20e256650f68bf0ca31.tar.gz
dm thin: do not send discards to shared blocks
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 <mpatocka@redhat.com> Cc: stable@kernel.org Signed-off-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com>
-rw-r--r--drivers/md/dm-thin.c6
1 files changed, 5 insertions, 1 deletions
diff --git a/drivers/md/dm-thin.c b/drivers/md/dm-thin.c
index ce59824fb414..68694da0d21d 100644
--- a/drivers/md/dm-thin.c
+++ b/drivers/md/dm-thin.c
@@ -1245,7 +1245,10 @@ 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;
@@ -2628,6 +2631,7 @@ 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);