From 307615a26e95406c42c95916a66ba50434567e0f Mon Sep 17 00:00:00 2001 From: Mike Snitzer Date: Wed, 26 Sep 2012 23:45:39 +0100 Subject: [PATCH] dm thin: do not set discard_zeroes_data The dm thin pool target claims to support the zeroing of discarded data areas. This turns out to be incorrect when processing discards that do not exactly cover a complete number of blocks, so the target must always set discard_zeroes_data_unsupported. The thin pool target will zero blocks when they are allocated if the skip_block_zeroing feature is not specified. The block layer may send a discard that only partly covers a block. If a thin pool block is partially discarded then there is no guarantee that the discarded data will get zeroed before it is accessed again. Due to this, thin devices cannot claim discards will always zero data. Signed-off-by: Mike Snitzer Signed-off-by: Joe Thornber Cc: stable@vger.kernel.org # 3.4+ Signed-off-by: Alasdair G Kergon --- drivers/md/dm-thin.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/md/dm-thin.c b/drivers/md/dm-thin.c index af1fc3b2c2a..d4209231069 100644 --- a/drivers/md/dm-thin.c +++ b/drivers/md/dm-thin.c @@ -2274,6 +2274,7 @@ static int pool_ctr(struct dm_target *ti, unsigned argc, char **argv) * thin devices' discard limits consistent). */ ti->discards_supported = true; + ti->discard_zeroes_data_unsupported = true; } ti->private = pt; @@ -2745,7 +2746,6 @@ static void set_discard_limits(struct pool *pool, struct queue_limits *limits) * boundary is not sent to this target. */ limits->discard_granularity = pool->sectors_per_block << SECTOR_SHIFT; - limits->discard_zeroes_data = pool->pf.zero_new_blocks; } static void pool_io_hints(struct dm_target *ti, struct queue_limits *limits) -- 2.20.1