From: Mikulas Patocka mpatocka@redhat.com
commit 13bd677a472d534bf100bab2713efc3f9e3f5978 upstream.
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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- drivers/md/dm-cache-target.c | 28 ++-------------------------- 1 file changed, 2 insertions(+), 26 deletions(-)
--- a/drivers/md/dm-cache-target.c +++ b/drivers/md/dm-cache-target.c @@ -541,7 +541,7 @@ static void wake_migration_worker(struct
static struct dm_bio_prison_cell_v2 *alloc_prison_cell(struct cache *cache) { - return dm_bio_prison_alloc_cell_v2(cache->prison, GFP_NOWAIT); + return dm_bio_prison_alloc_cell_v2(cache->prison, GFP_NOIO); }
static void free_prison_cell(struct cache *cache, struct dm_bio_prison_cell_v2 *cell) @@ -553,9 +553,7 @@ static struct dm_cache_migration *alloc_ { struct dm_cache_migration *mg;
- mg = mempool_alloc(&cache->migration_pool, GFP_NOWAIT); - if (!mg) - return NULL; + mg = mempool_alloc(&cache->migration_pool, GFP_NOIO);
memset(mg, 0, sizeof(*mg));
@@ -663,10 +661,6 @@ static bool bio_detain_shared(struct cac struct dm_bio_prison_cell_v2 *cell_prealloc, *cell;
cell_prealloc = alloc_prison_cell(cache); /* FIXME: allow wait if calling from worker */ - if (!cell_prealloc) { - defer_bio(cache, bio); - return false; - }
build_key(oblock, end, &key); r = dm_cell_get_v2(cache->prison, &key, lock_level(bio), bio, cell_prealloc, &cell); @@ -1492,11 +1486,6 @@ static int mg_lock_writes(struct dm_cach struct dm_bio_prison_cell_v2 *prealloc;
prealloc = alloc_prison_cell(cache); - if (!prealloc) { - DMERR_LIMIT("%s: alloc_prison_cell failed", cache_device_name(cache)); - mg_complete(mg, false); - return -ENOMEM; - }
/* * Prevent writes to the block, but allow reads to continue. @@ -1534,11 +1523,6 @@ static int mg_start(struct cache *cache, }
mg = alloc_migration(cache); - if (!mg) { - policy_complete_background_work(cache->policy, op, false); - background_work_end(cache); - return -ENOMEM; - }
mg->op = op; mg->overwrite_bio = bio; @@ -1627,10 +1611,6 @@ static int invalidate_lock(struct dm_cac struct dm_bio_prison_cell_v2 *prealloc;
prealloc = alloc_prison_cell(cache); - if (!prealloc) { - invalidate_complete(mg, false); - return -ENOMEM; - }
build_key(mg->invalidate_oblock, oblock_succ(mg->invalidate_oblock), &key); r = dm_cell_lock_v2(cache->prison, &key, @@ -1668,10 +1648,6 @@ static int invalidate_start(struct cache return -EPERM;
mg = alloc_migration(cache); - if (!mg) { - background_work_end(cache); - return -ENOMEM; - }
mg->overwrite_bio = bio; mg->invalidate_cblock = cblock;