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authorZhiqiang Liu <liuzhiqiang26@huawei.com>2020-06-15 00:53:30 +0800
committerJens Axboe <axboe@kernel.dk>2020-06-14 16:47:56 -0600
commitbe23e837333a914df3f24bf0b32e87b0331ab8d1 (patch)
treec3964da73c7ecb68dbeb1a77267f925ec6e196cf /drivers/md
parentb3a9e3b9622ae10064826dccb4f7a52bd88c7407 (diff)
bcache: fix potential deadlock problem in btree_gc_coalesce
coccicheck reports: drivers/md//bcache/btree.c:1538:1-7: preceding lock on line 1417 In btree_gc_coalesce func, if the coalescing process fails, we will goto to out_nocoalesce tag directly without releasing new_nodes[i]->write_lock. Then, it will cause a deadlock when trying to acquire new_nodes[i]-> write_lock for freeing new_nodes[i] before return. btree_gc_coalesce func details as follows: if alloc new_nodes[i] fails: goto out_nocoalesce; // obtain new_nodes[i]->write_lock mutex_lock(&new_nodes[i]->write_lock) // main coalescing process for (i = nodes - 1; i > 0; --i) [snipped] if coalescing process fails: // Here, directly goto out_nocoalesce // tag will cause a deadlock goto out_nocoalesce; [snipped] // release new_nodes[i]->write_lock mutex_unlock(&new_nodes[i]->write_lock) // coalesing succ, return return; out_nocoalesce: btree_node_free(new_nodes[i]) // free new_nodes[i] // obtain new_nodes[i]->write_lock mutex_lock(&new_nodes[i]->write_lock); // set flag for reuse clear_bit(BTREE_NODE_dirty, &ew_nodes[i]->flags); // release new_nodes[i]->write_lock mutex_unlock(&new_nodes[i]->write_lock); To fix the problem, we add a new tag 'out_unlock_nocoalesce' for releasing new_nodes[i]->write_lock before out_nocoalesce tag. If coalescing process fails, we will go to out_unlock_nocoalesce tag for releasing new_nodes[i]->write_lock before free new_nodes[i] in out_nocoalesce tag. (Coly Li helps to clean up commit log format.) Fixes: 2a285686c109816 ("bcache: btree locking rework") Signed-off-by: Zhiqiang Liu <liuzhiqiang26@huawei.com> Signed-off-by: Coly Li <colyli@suse.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'drivers/md')
-rw-r--r--drivers/md/bcache/btree.c8
1 files changed, 6 insertions, 2 deletions
diff --git a/drivers/md/bcache/btree.c b/drivers/md/bcache/btree.c
index 39de94edd73a..6548a601edf0 100644
--- a/drivers/md/bcache/btree.c
+++ b/drivers/md/bcache/btree.c
@@ -1389,7 +1389,7 @@ static int btree_gc_coalesce(struct btree *b, struct btree_op *op,
if (__set_blocks(n1, n1->keys + n2->keys,
block_bytes(b->c)) >
btree_blocks(new_nodes[i]))
- goto out_nocoalesce;
+ goto out_unlock_nocoalesce;
keys = n2->keys;
/* Take the key of the node we're getting rid of */
@@ -1418,7 +1418,7 @@ static int btree_gc_coalesce(struct btree *b, struct btree_op *op,
if (__bch_keylist_realloc(&keylist,
bkey_u64s(&new_nodes[i]->key)))
- goto out_nocoalesce;
+ goto out_unlock_nocoalesce;
bch_btree_node_write(new_nodes[i], &cl);
bch_keylist_add(&keylist, &new_nodes[i]->key);
@@ -1464,6 +1464,10 @@ static int btree_gc_coalesce(struct btree *b, struct btree_op *op,
/* Invalidated our iterator */
return -EINTR;
+out_unlock_nocoalesce:
+ for (i = 0; i < nodes; i++)
+ mutex_unlock(&new_nodes[i]->write_lock);
+
out_nocoalesce:
closure_sync(&cl);