From 19fa1a6756ed9e92daa9537c03b47d6b55cc2316 Mon Sep 17 00:00:00 2001 From: Joe Thornber Date: Tue, 17 Dec 2013 12:09:40 -0500 Subject: dm thin: fix discard support to a previously shared block If a snapshot is created and later deleted the origin dm_thin_device's snapshotted_time will have been updated to reflect the snapshot's creation time. The 'shared' flag in the dm_thin_lookup_result struct returned from dm_thin_find_block() is an approximation based on snapshotted_time -- this is done to avoid 0(n), or worse, time complexity. In this case, the shared flag would be true. But because the 'shared' flag reflects an approximation a block can be incorrectly assumed to be shared (e.g. false positive for 'shared' because the snapshot no longer exists). This could result in discards issued to a thin device not being passed down to the pool's underlying data device. To fix this we double check that a thin block is really still in-use after a mapping is removed using dm_pool_block_is_used(). If the reference count for a block is now zero the discard is allowed to be passed down. Also add a 'definitely_not_shared' member to the dm_thin_new_mapping structure -- reflects that the 'shared' flag in the response from dm_thin_find_block() can only be held as definitive if false is returned. Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1043527 Signed-off-by: Joe Thornber Signed-off-by: Mike Snitzer Cc: stable@vger.kernel.org --- drivers/md/dm-thin-metadata.h | 2 ++ 1 file changed, 2 insertions(+) (limited to 'drivers/md/dm-thin-metadata.h') diff --git a/drivers/md/dm-thin-metadata.h b/drivers/md/dm-thin-metadata.h index 7bcc0e1..2edf5db 100644 --- a/drivers/md/dm-thin-metadata.h +++ b/drivers/md/dm-thin-metadata.h @@ -181,6 +181,8 @@ int dm_pool_get_data_block_size(struct dm_pool_metadata *pmd, sector_t *result); int dm_pool_get_data_dev_size(struct dm_pool_metadata *pmd, dm_block_t *result); +int dm_pool_block_is_used(struct dm_pool_metadata *pmd, dm_block_t b, bool *result); + /* * Returns -ENOSPC if the new size is too small and already allocated * blocks would be lost. -- cgit v1.1