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authorMikulas Patocka <mpatocka@redhat.com>2019-10-16 09:21:50 -0400
committerMike Snitzer <snitzer@redhat.com>2019-10-17 11:13:50 -0400
commit13bd677a472d534bf100bab2713efc3f9e3f5978 (patch)
tree21007a0c276b0c01ac45d7bda7dad7c51a19ad94
parentb21555786f18cd77f2311ad89074533109ae3ffa (diff)
downloadlinux-13bd677a472d534bf100bab2713efc3f9e3f5978.tar.bz2
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>
-rw-r--r--drivers/md/dm-cache-target.c28
1 files changed, 2 insertions, 26 deletions
diff --git a/drivers/md/dm-cache-target.c b/drivers/md/dm-cache-target.c
index d249cf8ac277..8346e6d1816c 100644
--- a/drivers/md/dm-cache-target.c
+++ b/drivers/md/dm-cache-target.c
@@ -542,7 +542,7 @@ static void wake_migration_worker(struct cache *cache)
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)
@@ -554,9 +554,7 @@ static struct dm_cache_migration *alloc_migration(struct cache *cache)
{
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));
@@ -664,10 +662,6 @@ static bool bio_detain_shared(struct cache *cache, dm_oblock_t oblock, struct bi
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);
@@ -1493,11 +1487,6 @@ static int mg_lock_writes(struct dm_cache_migration *mg)
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.
@@ -1535,11 +1524,6 @@ static int mg_start(struct cache *cache, struct policy_work *op, struct bio *bio
}
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;
@@ -1628,10 +1612,6 @@ static int invalidate_lock(struct dm_cache_migration *mg)
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,
@@ -1669,10 +1649,6 @@ static int invalidate_start(struct cache *cache, dm_cblock_t cblock,
return -EPERM;
mg = alloc_migration(cache);
- if (!mg) {
- background_work_end(cache);
- return -ENOMEM;
- }
mg->overwrite_bio = bio;
mg->invalidate_cblock = cblock;