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=-7.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED 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 4AD16C10F0B for ; Thu, 18 Apr 2019 07:30:30 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1F2D82083D for ; Thu, 18 Apr 2019 07:30:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730682AbfDRHa2 (ORCPT ); Thu, 18 Apr 2019 03:30:28 -0400 Received: from mx2.suse.de ([195.135.220.15]:56688 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1729446AbfDRHa2 (ORCPT ); Thu, 18 Apr 2019 03:30:28 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 8A9B0AF38; Thu, 18 Apr 2019 07:30:26 +0000 (UTC) Subject: Re: [PATCH] btrfs: extent_io: Handle memory allocation failure in __clear_extent_bit() To: Nikolay Borisov , linux-btrfs@vger.kernel.org Cc: Josef Bacik References: <20190418072114.4573-1-wqu@suse.com> From: Qu Wenruo Openpgp: preference=signencrypt Autocrypt: addr=wqu@suse.de; prefer-encrypt=mutual; keydata= mQENBFnVga8BCACyhFP3ExcTIuB73jDIBA/vSoYcTyysFQzPvez64TUSCv1SgXEByR7fju3o 8RfaWuHCnkkea5luuTZMqfgTXrun2dqNVYDNOV6RIVrc4YuG20yhC1epnV55fJCThqij0MRL 1NxPKXIlEdHvN0Kov3CtWA+R1iNN0RCeVun7rmOrrjBK573aWC5sgP7YsBOLK79H3tmUtz6b 9Imuj0ZyEsa76Xg9PX9Hn2myKj1hfWGS+5og9Va4hrwQC8ipjXik6NKR5GDV+hOZkktU81G5 gkQtGB9jOAYRs86QG/b7PtIlbd3+pppT0gaS+wvwMs8cuNG+Pu6KO1oC4jgdseFLu7NpABEB AAG0F1F1IFdlbnJ1byA8d3F1QHN1c2UuZGU+iQFUBBMBCAA+AhsDBQsJCAcCBhUICQoLAgQW AgMBAh4BAheAFiEELd9y5aWlW6idqkLhwj2R86El/qgFAlnVgp0FCQlmAm4ACgkQwj2R86El /qilmgf/cUq9kFQo577ku5gc6rFpVg68ublBwjYpwjw0b//xo+Wo1wm+RRbUGs+djSZAqw12 D4F3r0mBTI7abUCNWAbFkYZSAIFVi0DMkjypIVS7PSaEt04rM9VBTToE+YqU6WENeJ57R2p2 +hI0wZrBwxObdsdaOtxWtsp3bmhIbdqxSKrtXuRawy4KnQYcLuGzOce9okdlbAE0W3KHm1gQ oNAe6FX8nC9qo14m8LqEbThYH+qj4iCMlN8HIfbSx4F3e7nHZ+UAMW+E/lnMRkIB9Df+JyVd /NlXzIjZAggcWsqpx6D4wyAuexKWkiGQeUeArUNihAwXjmyqWPGmjVyIh+oC6LkBDQRZ1YGv AQgAqlPrYeBLMv3PAZ75YhQIwH6c4SNcB++hQ9TCT5gIQNw51+SQzkXIGgmzxMIS49cZcE4K Xk/kHw5hieQeQZa60BWVRNXwoRI4ib8okgDuMkD5Kz1WEyO149+BZ7HD4/yK0VFJGuvDJR8T 7RZwB69uVSLjkuNZZmCmDcDzS0c/SJOg5nkxt1iTtgUETb1wNKV6yR9XzRkrEW/qShChyrS9 fNN8e9c0MQsC4fsyz9Ylx1TOY/IF/c6rqYoEEfwnpdlz0uOM1nA1vK+wdKtXluCa79MdfaeD /dt76Kp/o6CAKLLcjU1Iwnkq1HSrYfY3HZWpvV9g84gPwxwxX0uXquHxLwARAQABiQE8BBgB CAAmFiEELd9y5aWlW6idqkLhwj2R86El/qgFAlnVga8CGwwFCQPCZwAACgkQwj2R86El/qgN 8Qf+M0vM2Idwm5txZZSs+/kSgcPxEwYmxUinnUJGyc0ZWYQXPl0cBetZon9El0naijGzNWvf HxIPB+ZFehk6Otgc78p1a3/xck/s1myFRLrmbbTJNoFiyL25ljcq0J8z5Zp4yuABL2RiLdaZ Pt/jfwjBHwGR+QKp6dD2qMrUWf9b7TFzYDMZXzZ2/eoIgtyjEelNBPrIgOFe24iKMjaGjd97 fJuRcBMHdhUAxvXQF1oRtd83JvYJ5OtwTd8MgkEfl+fo7HwWkuHbzc70L4fFKv2BowqFdaHy mId1ijGPGr46tuZ5a4cw/zbaPYx6fJ4sK9tSv/6V1QPNUdqml6hm6pfs6A== Message-ID: Date: Thu, 18 Apr 2019 15:30:20 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-btrfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org On 2019/4/18 下午3:24, Nikolay Borisov wrote: > > > On 18.04.19 г. 10:21 ч., Qu Wenruo wrote: >> There is a BUG_ON() in __clear_extent_bit() for memory allocation >> failure. >> >> While comment of __clear_extent_bit() says it can return error, but we >> always return 0. >> >> Some __clear_extent_bit() callers just ignore the return value, while >> some still expect error. >> >> Let's return proper error for this memory allocation anyway, to remove >> that BUG_ON() as a first step, so at least we can continue test. > > I remember Josef did some changes into this code and said that prealloc > shouldn't fail because this will cause mayhem down the road i.e. proper > error handling is missing. If anything I think it should be added first > and then remove the BUG_ONs. That's true, we could have some strange lockup due to lock_extent_bits(), as if some clear_extent_bits() failed due to ENOMEM and caller just ignore the error, we could have a lockup. I'll try to pre-allocate certain amount of extent_state as the last chance of redemption. Anyway, such BUG_ON() right after kmalloc() is really a blockage for error injection test. Thanks, Qu > >> >> Signed-off-by: Qu Wenruo >> --- >> fs/btrfs/extent_io.c | 12 ++++++++++-- >> 1 file changed, 10 insertions(+), 2 deletions(-) >> >> diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c >> index 828708f6510c..f1bfc632ef7b 100644 >> --- a/fs/btrfs/extent_io.c >> +++ b/fs/btrfs/extent_io.c >> @@ -743,7 +743,10 @@ int __clear_extent_bit(struct extent_io_tree *tree, u64 start, u64 end, >> >> if (state->start < start) { >> prealloc = alloc_extent_state_atomic(prealloc); >> - BUG_ON(!prealloc); >> + if (!prealloc) { >> + err = -ENOMEM; >> + goto out; >> + } >> err = split_state(tree, state, prealloc, start); >> if (err) >> extent_io_tree_panic(tree, err); >> @@ -766,7 +769,10 @@ int __clear_extent_bit(struct extent_io_tree *tree, u64 start, u64 end, >> */ >> if (state->start <= end && state->end > end) { >> prealloc = alloc_extent_state_atomic(prealloc); >> - BUG_ON(!prealloc); >> + if (!prealloc) { >> + err = -ENOMEM; >> + goto out; >> + } >> err = split_state(tree, state, prealloc, end + 1); >> if (err) >> extent_io_tree_panic(tree, err); >> @@ -801,6 +807,8 @@ int __clear_extent_bit(struct extent_io_tree *tree, u64 start, u64 end, >> if (prealloc) >> free_extent_state(prealloc); >> >> + if (err) >> + return err; >> return 0; >> >> } >>