From 49e99fc717f624aa75ca755d6e7bc029efd3f0e9 Mon Sep 17 00:00:00 2001 From: Joe Thornber Date: Wed, 9 Dec 2015 16:23:24 +0000 Subject: [PATCH] dm thin metadata: fix bug when taking a metadata snapshot When you take a metadata snapshot the btree roots for the mapping and details tree need to have their reference counts incremented so they persist for the lifetime of the metadata snap. The roots being incremented were those currently written in the superblock, which could possibly be out of date if concurrent IO is triggering new mappings, breaking of sharing, etc. Fix this by performing a commit with the metadata lock held while taking a metadata snapshot. Signed-off-by: Joe Thornber Signed-off-by: Mike Snitzer Cc: stable@vger.kernel.org --- drivers/md/dm-thin-metadata.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/drivers/md/dm-thin-metadata.c b/drivers/md/dm-thin-metadata.c index 67871e74c82b..c219a053c7f6 100644 --- a/drivers/md/dm-thin-metadata.c +++ b/drivers/md/dm-thin-metadata.c @@ -1206,6 +1206,12 @@ static int __reserve_metadata_snap(struct dm_pool_metadata *pmd) struct dm_block *copy, *sblock; dm_block_t held_root; + /* + * We commit to ensure the btree roots which we increment in a + * moment are up to date. + */ + __commit_transaction(pmd); + /* * Copy the superblock. */ -- 2.20.1