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bcache: fix potential deadlock problem in btree_gc_coalesce
[ Upstream commitbe23e83733
] 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:2a285686c1
("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> Signed-off-by: Sasha Levin <sashal@kernel.org>
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b0873334bc
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1 changed files with 6 additions and 2 deletions
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@ -1432,7 +1432,7 @@ static int btree_gc_coalesce(struct btree *b, struct btree_op *op,
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if (__set_blocks(n1, n1->keys + n2->keys,
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if (__set_blocks(n1, n1->keys + n2->keys,
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block_bytes(b->c)) >
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block_bytes(b->c)) >
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btree_blocks(new_nodes[i]))
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btree_blocks(new_nodes[i]))
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goto out_nocoalesce;
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goto out_unlock_nocoalesce;
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keys = n2->keys;
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keys = n2->keys;
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/* Take the key of the node we're getting rid of */
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/* Take the key of the node we're getting rid of */
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@ -1461,7 +1461,7 @@ static int btree_gc_coalesce(struct btree *b, struct btree_op *op,
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if (__bch_keylist_realloc(&keylist,
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if (__bch_keylist_realloc(&keylist,
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bkey_u64s(&new_nodes[i]->key)))
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bkey_u64s(&new_nodes[i]->key)))
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goto out_nocoalesce;
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goto out_unlock_nocoalesce;
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bch_btree_node_write(new_nodes[i], &cl);
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bch_btree_node_write(new_nodes[i], &cl);
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bch_keylist_add(&keylist, &new_nodes[i]->key);
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bch_keylist_add(&keylist, &new_nodes[i]->key);
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@ -1507,6 +1507,10 @@ static int btree_gc_coalesce(struct btree *b, struct btree_op *op,
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/* Invalidated our iterator */
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/* Invalidated our iterator */
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return -EINTR;
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return -EINTR;
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out_unlock_nocoalesce:
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for (i = 0; i < nodes; i++)
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mutex_unlock(&new_nodes[i]->write_lock);
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out_nocoalesce:
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out_nocoalesce:
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closure_sync(&cl);
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closure_sync(&cl);
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bch_keylist_free(&keylist);
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bch_keylist_free(&keylist);
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