- Fix DM snapshot deadlock that can occur due to COW throttling
preventing locks from being released.
- Fix DM cache's GFP_NOWAIT allocation failure error paths by switching
to GFP_NOIO.
- Make __hash_find() static in the DM clone target.
dm cache: fix bugs when a GFP_NOWAIT allocation fails
GFP_NOWAIT allocation can fail anytime - it doesn't wait for memory being
available and it fails if the mempool is exhausted and there is not enough
memory.
If we go down this path:
map_bio -> mg_start -> alloc_migration -> mempool_alloc(GFP_NOWAIT)
we can see that map_bio() doesn't check the return value of mg_start(),
and the bio is leaked.
If we go down this path:
map_bio -> mg_start -> mg_lock_writes -> alloc_prison_cell ->
dm_bio_prison_alloc_cell_v2 -> mempool_alloc(GFP_NOWAIT) ->
mg_lock_writes -> mg_complete
the bio is ended with an error - it is unacceptable because it could
cause filesystem corruption if the machine ran out of memory
temporarily.
Change GFP_NOWAIT to GFP_NOIO, so that the mempool code will properly
wait until memory becomes available. mempool_alloc with GFP_NOIO can't
fail, so remove the code paths that deal with allocation failure.
Cc: stable@vger.kernel.org
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
1 file changed
