3.13.11-ckt33 -stable review patch. If anyone has any objections, please let me know.
---8<------------------------------------------------------------ From: Joe Thornber <[email protected]> commit 49e99fc717f624aa75ca755d6e7bc029efd3f0e9 upstream. 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 The roots being incremented were those currently written in the superblock, which could possibly be out of date if concurrent IO is triggering new mappings, breaking of sharing, etc.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 <[email protected]> Signed-off-by: Mike Snitzer <[email protected]> Signed-off-by: Kamal Mostafa <[email protected]> --- 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 7e3da70..f74821c 100644 --- a/drivers/md/dm-thin-metadata.c +++ b/drivers/md/dm-thin-metadata.c @@ -1205,6 +1205,12 @@ static int __reserve_metadata_snap(struct dm_pool_metadata *pmd) 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. */ dm_sm_inc_block(pmd->metadata_sm, THIN_SUPERBLOCK_LOCATION); -- 1.9.1
