blob: 5941b2f5667c9c83a7c4907de57ae1731a79a3cd [file] [log] [blame]
From 0edc6e36e4e1801dacb47af3d4701282b2ae58fe Mon Sep 17 00:00:00 2001
From: Zhiqiang Liu <>
Date: Mon, 15 Jun 2020 00:53:30 +0800
Subject: [PATCH] bcache: fix potential deadlock problem in btree_gc_coalesce
commit be23e837333a914df3f24bf0b32e87b0331ab8d1 upstream.
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
// main coalescing process
for (i = nodes - 1; i > 0; --i)
if coalescing process fails:
// Here, directly goto out_nocoalesce
// tag will cause a deadlock
goto out_nocoalesce;
// release new_nodes[i]->write_lock
// coalesing succ, return
btree_node_free(new_nodes[i]) // free new_nodes[i]
// obtain new_nodes[i]->write_lock
// set flag for reuse
clear_bit(BTREE_NODE_dirty, &ew_nodes[i]->flags);
// release 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 <>
Signed-off-by: Coly Li <>
Signed-off-by: Jens Axboe <>
Signed-off-by: Paul Gortmaker <>
diff --git a/drivers/md/bcache/btree.c b/drivers/md/bcache/btree.c
index d307c65d90fc..b6a50e5e818e 100644
--- a/drivers/md/bcache/btree.c
+++ b/drivers/md/bcache/btree.c
@@ -1438,7 +1438,7 @@ static int btree_gc_coalesce(struct btree *b, struct btree_op *op,
if (__set_blocks(n1, n1->keys + n2->keys,
block_bytes(b->c)) >
- goto out_nocoalesce;
+ goto out_unlock_nocoalesce;
keys = n2->keys;
/* Take the key of the node we're getting rid of */
@@ -1467,7 +1467,7 @@ static int btree_gc_coalesce(struct btree *b, struct btree_op *op,
if (__bch_keylist_realloc(&keylist,
- goto out_nocoalesce;
+ goto out_unlock_nocoalesce;
bch_btree_node_write(new_nodes[i], &cl);
bch_keylist_add(&keylist, &new_nodes[i]->key);
@@ -1513,6 +1513,10 @@ static int btree_gc_coalesce(struct btree *b, struct btree_op *op,
/* Invalidated our iterator */
return -EINTR;
+ for (i = 0; i < nodes; i++)
+ mutex_unlock(&new_nodes[i]->write_lock);