From mboxrd@z Thu Jan 1 00:00:00 1970 From: Zhiqiang Liu Subject: [PATCH V2] bcache: fix potential deadlock problem in btree_gc_coalesce Date: Sun, 26 Apr 2020 16:06:27 +0800 Message-ID: <8a6f5fe3-33f9-48e2-e347-05781c3295fd@huawei.com> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 8bit Return-path: Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org To: Coly Li , kmo@daterainc.com, linux-bcache@vger.kernel.org, "linux-kernel@vger.kernel.org" Cc: "wubo (T)" , Mingfangsen , Yanxiaodan , linfeilong , renxudong List-Id: linux-bcache@vger.kernel.org From: Zhiqiang Liu coccicheck reports: drivers/md//bcache/btree.c:1538:1-7: preceding lock on line 1417 btree_gc_coalesce func is designed to coalesce two adjacent nodes in new_nodes[GC_MERGE_NODES] and finally release one node. All nodes`write_lock, new_nodes[i]->write_lock, are holded before coalescing adjacent nodes, and them will be released after coalescing successfully. However, if the coalescing process fails, such as no enough space of new_nodes[1] to fit all of the remaining keys in new_nodes[0] and realloc keylist failed, we will goto to out_nocoalesce tag directly without releasing new_nodes[i]->write_lock. Then, a deadlock will occur after calling btree_node_free to free new_nodes[i], which also try to acquire new_nodes[i]->write_lock. Here, we add a new tag 'out_unlock_nocoalesce' before out_nocoalesce tag to release new_nodes[i]->write_lock when coalescing process fails. -- V1->V2: rewrite commit log (suggested by Coly Li) and rename the patch Fixes: 2a285686c1 ("bcache: btree locking rework") Signed-off-by: Zhiqiang Liu --- 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 fa872df4e770..cad8b0b97e33 100644 --- a/drivers/md/bcache/btree.c +++ b/drivers/md/bcache/btree.c @@ -1447,7 +1447,7 @@ 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 */ @@ -1476,7 +1476,7 @@ 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); @@ -1522,6 +1522,10 @@ 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); -- 2.19.1 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=-11.5 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=unavailable 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 1D27CC55191 for ; Sun, 26 Apr 2020 08:06:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 039BF20700 for ; Sun, 26 Apr 2020 08:06:56 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726117AbgDZIGj (ORCPT ); Sun, 26 Apr 2020 04:06:39 -0400 Received: from szxga07-in.huawei.com ([45.249.212.35]:37890 "EHLO huawei.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726112AbgDZIGi (ORCPT ); Sun, 26 Apr 2020 04:06:38 -0400 Received: from DGGEMS405-HUB.china.huawei.com (unknown [172.30.72.60]) by Forcepoint Email with ESMTP id A4842D6E4359EE11E246; Sun, 26 Apr 2020 16:06:35 +0800 (CST) Received: from [127.0.0.1] (10.166.215.235) by DGGEMS405-HUB.china.huawei.com (10.3.19.205) with Microsoft SMTP Server id 14.3.487.0; Sun, 26 Apr 2020 16:06:29 +0800 To: Coly Li , , , "linux-kernel@vger.kernel.org" CC: "wubo (T)" , Mingfangsen , Yanxiaodan , linfeilong , renxudong From: Zhiqiang Liu Subject: [PATCH V2] bcache: fix potential deadlock problem in btree_gc_coalesce Message-ID: <8a6f5fe3-33f9-48e2-e347-05781c3295fd@huawei.com> Date: Sun, 26 Apr 2020 16:06:27 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.2.2 MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 8bit X-Originating-IP: [10.166.215.235] X-CFilter-Loop: Reflected Sender: linux-bcache-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-bcache@vger.kernel.org Message-ID: <20200426080627.9lZnkaAcp2_mnghiuAQj3qcfxG8tdGDAYp5B5Atvl-U@z> From: Zhiqiang Liu coccicheck reports: drivers/md//bcache/btree.c:1538:1-7: preceding lock on line 1417 btree_gc_coalesce func is designed to coalesce two adjacent nodes in new_nodes[GC_MERGE_NODES] and finally release one node. All nodes`write_lock, new_nodes[i]->write_lock, are holded before coalescing adjacent nodes, and them will be released after coalescing successfully. However, if the coalescing process fails, such as no enough space of new_nodes[1] to fit all of the remaining keys in new_nodes[0] and realloc keylist failed, we will goto to out_nocoalesce tag directly without releasing new_nodes[i]->write_lock. Then, a deadlock will occur after calling btree_node_free to free new_nodes[i], which also try to acquire new_nodes[i]->write_lock. Here, we add a new tag 'out_unlock_nocoalesce' before out_nocoalesce tag to release new_nodes[i]->write_lock when coalescing process fails. -- V1->V2: rewrite commit log (suggested by Coly Li) and rename the patch Fixes: 2a285686c1 ("bcache: btree locking rework") Signed-off-by: Zhiqiang Liu --- 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 fa872df4e770..cad8b0b97e33 100644 --- a/drivers/md/bcache/btree.c +++ b/drivers/md/bcache/btree.c @@ -1447,7 +1447,7 @@ 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 */ @@ -1476,7 +1476,7 @@ 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); @@ -1522,6 +1522,10 @@ 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); -- 2.19.1