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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id D2866C76196 for ; Tue, 11 Apr 2023 14:05:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229916AbjDKOF1 (ORCPT ); Tue, 11 Apr 2023 10:05:27 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35022 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229654AbjDKOFY (ORCPT ); Tue, 11 Apr 2023 10:05:24 -0400 Received: from szxga02-in.huawei.com (szxga02-in.huawei.com [45.249.212.188]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A287EE5B; Tue, 11 Apr 2023 07:05:21 -0700 (PDT) Received: from dggpeml500021.china.huawei.com (unknown [172.30.72.56]) by szxga02-in.huawei.com (SkyGuard) with ESMTP id 4PwnYq54W2zSrTf; Tue, 11 Apr 2023 22:01:03 +0800 (CST) Received: from [10.174.177.174] (10.174.177.174) by dggpeml500021.china.huawei.com (7.185.36.21) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2507.23; Tue, 11 Apr 2023 22:04:58 +0800 Message-ID: <6df9fd42-1b1b-746a-10aa-7bd64ec2ce76@huawei.com> Date: Tue, 11 Apr 2023 22:04:58 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:102.0) Gecko/20100101 Thunderbird/102.1.2 Subject: Re: [PATCH v2 2/2] ext4: use __GFP_NOFAIL if allocating extents_status cannot fail Content-Language: en-US To: Jan Kara CC: , , , , , , , , Baokun Li References: <20230406132834.1669710-1-libaokun1@huawei.com> <20230406132834.1669710-3-libaokun1@huawei.com> <20230411091957.wuwa7wii7pj35ua7@quack3> From: Baokun Li In-Reply-To: <20230411091957.wuwa7wii7pj35ua7@quack3> Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 7bit X-Originating-IP: [10.174.177.174] X-ClientProxiedBy: dggems703-chm.china.huawei.com (10.3.19.180) To dggpeml500021.china.huawei.com (7.185.36.21) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2023/4/11 17:19, Jan Kara wrote: > On Thu 06-04-23 21:28:34, Baokun Li wrote: >> If extent status tree update fails, we have inconsistency between what is >> stored in the extent status tree and what is stored on disk. And that can >> cause even data corruption issues in some cases. >> >> In the extent status tree, we have extents which we can just drop without >> issues and extents we must not drop - this depends on the extent's status >> - currently ext4_es_is_delayed() extents must stay, others may be dropped. >> >> For extents that cannot be dropped we use __GFP_NOFAIL to allocate memory. >> A helper function is also added to help determine if the current extent can >> be dropped, although only ext4_es_is_delayed() extents cannot be dropped >> currently. In addition, with the above logic, the undo operation in >> __es_remove_extent that may cause inconsistency if the split extent fails >> is unnecessary, so we remove it as well. >> >> Suggested-by: Jan Kara >> Signed-off-by: Baokun Li >> --- >> V1->V2: >> Add the patch 2 as suggested by Jan Kara. >> >> fs/ext4/extents_status.c | 36 +++++++++++++++++++++++++++++------- >> 1 file changed, 29 insertions(+), 7 deletions(-) >> >> diff --git a/fs/ext4/extents_status.c b/fs/ext4/extents_status.c >> index 7bc221038c6c..8eed17f35b11 100644 >> --- a/fs/ext4/extents_status.c >> +++ b/fs/ext4/extents_status.c >> @@ -448,12 +448,29 @@ static void ext4_es_list_del(struct inode *inode) >> spin_unlock(&sbi->s_es_lock); >> } >> >> +/* >> + * Helper function to help determine if memory allocation for this >> + * extent_status is allowed to fail. >> + */ >> +static inline bool ext4_es_alloc_should_nofail(struct extent_status *es) > I'd call this function ext4_es_must_keep() and also use it in > es_do_reclaim_extents() instead of ext4_es_is_delayed(). Do this as a > preparatory patch please. Totally agree! ext4_es_must_keep() is short and clear. It does make more sense to replace ext4_es_is_delayed() in es_do_reclaim_extents() with the new helper, I'll try to find out if there are any ext4_es_is_delayed() that need to be replaced as well. >> @@ -792,9 +809,16 @@ static int __es_insert_extent(struct inode *inode, struct extent_status *newes) >> } >> >> es = ext4_es_alloc_extent(inode, newes->es_lblk, newes->es_len, >> - newes->es_pblk); >> - if (!es) >> - return -ENOMEM; >> + newes->es_pblk, 0); > I would just call this like: > > es = ext4_es_alloc_extent(inode, newes->es_lblk, newes->es_len, > newes->es_pblk, ext4_es_must_keep(newes)); > > to save the ifs below. Yes! It does get a little long-winded here. > >> + if (!es) { >> + /* Use GFP_NOFAIL if the allocation cannot fail. */ >> + if (ext4_es_alloc_should_nofail(newes)) >> + es = ext4_es_alloc_extent(inode, newes->es_lblk, >> + newes->es_len, newes->es_pblk, 1); >> + else >> + return -ENOMEM; >> + } >> + >> rb_link_node(&es->rb_node, parent, p); >> rb_insert_color(&es->rb_node, &tree->root); >> >> @@ -1349,8 +1373,6 @@ static int __es_remove_extent(struct inode *inode, ext4_lblk_t lblk, >> ext4_es_status(&orig_es)); >> err = __es_insert_extent(inode, &newes); >> if (err) { >> - es->es_lblk = orig_es.es_lblk; >> - es->es_len = orig_es.es_len; >> if ((err == -ENOMEM) && >> __es_shrink(EXT4_SB(inode->i_sb), >> 128, EXT4_I(inode))) > Also now __es_remove_extent() cannot fail (it will always remove what it > should, maybe more) so please just make it void function (as a separate > cleanup patch afterwards). Thanks! > > Honza Yes! Thank you very much for the review! I will send a patch V3 with the changes suggested by you. -- With Best Regards, Baokun Li .