From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-10.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8A147C433DF for ; Mon, 29 Jun 2020 19:03:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 68C7A2053B for ; Mon, 29 Jun 2020 19:03:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1593457387; bh=lxxQnrSMlr+97kH0qKxyqvhMkplbf2d/pEWokw3G1Go=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=xNNdpgkWn1nT1aib6cfyu3qKsHnZu38jMOh+gft+t7bKLVuCQgy9PdpmY+pQf5Xda ae1rnULCUhtc/Vf0XSAUsYleTPTlj5EAdKOcQ+HfiC9c6DxOL9blb24TwT4AT/TLod +LoubKfevOzHCztnT3eDc2pVVPh9iUzz5uPGjZBg= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730549AbgF2TCs (ORCPT ); Mon, 29 Jun 2020 15:02:48 -0400 Received: from mail.kernel.org ([198.145.29.99]:45480 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730344AbgF2TAU (ORCPT ); Mon, 29 Jun 2020 15:00:20 -0400 Received: from sasha-vm.mshome.net (c-73-47-72-35.hsd1.nh.comcast.net [73.47.72.35]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id B8DD7254FE; Mon, 29 Jun 2020 15:54:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1593446058; bh=lxxQnrSMlr+97kH0qKxyqvhMkplbf2d/pEWokw3G1Go=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=kw+a2qTqpdNQe+5kwqc63kVw9Fa8K5O2dlzMHlMEiQZQ2UlZTg/zVKQ3sZrnnI6hi i29vc0wer8zfW1LTDuJgjl+z2vIlvlnq5W6GZ16A9RDYpY9l56bZ4f4warR5WCpip3 s3DZ6Qeidh4fwUxPaL15hQakH3INa67zMXIme2lE= From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Zhiqiang Liu , Coly Li , Jens Axboe , Sasha Levin Subject: [PATCH 4.4 058/135] bcache: fix potential deadlock problem in btree_gc_coalesce Date: Mon, 29 Jun 2020 11:51:52 -0400 Message-Id: <20200629155309.2495516-59-sashal@kernel.org> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20200629155309.2495516-1-sashal@kernel.org> References: <20200629155309.2495516-1-sashal@kernel.org> MIME-Version: 1.0 X-KernelTest-Patch: http://kernel.org/pub/linux/kernel/v4.x/stable-review/patch-4.4.229-rc1.gz X-KernelTest-Tree: git://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable-rc.git X-KernelTest-Branch: linux-4.4.y X-KernelTest-Patches: git://git.kernel.org/pub/scm/linux/kernel/git/stable/stable-queue.git X-KernelTest-Version: 4.4.229-rc1 X-KernelTest-Deadline: 2020-07-01T15:53+00:00 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Zhiqiang Liu [ Upstream commit be23e837333a914df3f24bf0b32e87b0331ab8d1 ] 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 Signed-off-by: Coly Li Signed-off-by: Jens Axboe Signed-off-by: Sasha Levin --- drivers/md/bcache/btree.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/drivers/md/bcache/btree.c b/drivers/md/bcache/btree.c index 5c93582c71cc6..634e9284b7bee 100644 --- a/drivers/md/bcache/btree.c +++ b/drivers/md/bcache/btree.c @@ -1375,7 +1375,7 @@ 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 */ @@ -1404,7 +1404,7 @@ 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); @@ -1450,6 +1450,10 @@ 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); bch_keylist_free(&keylist); -- 2.25.1