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=-9.6 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,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 81CE1C2D0DA for ; Thu, 26 Dec 2019 07:10:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 44838206CB for ; Thu, 26 Dec 2019 07:10:18 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="QlPiDmDp" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725978AbfLZHKR (ORCPT ); Thu, 26 Dec 2019 02:10:17 -0500 Received: from mail-pj1-f66.google.com ([209.85.216.66]:54742 "EHLO mail-pj1-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725268AbfLZHKR (ORCPT ); Thu, 26 Dec 2019 02:10:17 -0500 Received: by mail-pj1-f66.google.com with SMTP id kx11so2990895pjb.4 for ; Wed, 25 Dec 2019 23:10:17 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:to:cc:subject:date:message-id; bh=yV1bFCcYZRZ224Wb+sO6H6NHtG+4un9eeTRCHa7JoYY=; b=QlPiDmDpftmpJsvYzApK1rnPQf3xIQCVhozllfaTVqpPnjxYHAdP9NSUEFpTbXAolP OWFVmWicszXu4AtpmcgIPIu8MhzSnRLtoNV1FlyHKGPkzPbvPAi5laHTz2e+2nTHaZQt gS+XnMOMTOGrxvHloj9J8qNRhmyA3NkDuuD1KsO7pDQmx9bT2auhvlmwqo9MQ9mzlcX5 98Agu0LWChcN8EDvo2qpIOg4LXfpbymJUdzXBIIGBlpY9PpCi5v/wSd2ou10Z/kksJ2k 2IwKX/ncfCScqmrpO+I5Y0OksmL15T1Oa8fiVB1tKXD0uhLbzWTVYsiwq4P/dCccv2Zg S2jQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id; bh=yV1bFCcYZRZ224Wb+sO6H6NHtG+4un9eeTRCHa7JoYY=; b=qVfuPoPwsx3nnNOjWyuAu07VUuagDYTpe3NZAMNeBme4iNfZqxjW7jx5PLE3gXK6e9 /HqX6Io6unPASBMief/fc5jbrjInPJfmN47/btTiTqClzXORuFsCAMqfHy+Eyi6dZP8h uja81V1fOnk7qj0ZdBkDaN7OiQFBZZBAtSANc1d0AS9Tj6jJkpbEetz3G6gIrBy8X9EI lRBkfknWm8JhaxoA/q/Eoz9JVIEciJtNMecUcxbLMqZFzjseBOZKLhcGpqgbHVvcZlNO OnzZhbHCpz3RSTsFlLhqrDQH3m6BoAVmqxMSIfkM4rX8jusYADRAfqAl6BzMRcEtJ7BC Y+KA== X-Gm-Message-State: APjAAAUtOO0WyVXkNZa07f+jB6VY0ame4ESRdWoiGo/1AwZsmFyBlWHo O56qBWaW2On9elRfm3eArnk= X-Google-Smtp-Source: APXvYqx3Y7QtmFsQhYQybK3xpDAmtuPPda+8ERr05AVn0c4OajNHLOb4CSb89xw1xZ4fU/WAlBs9kw== X-Received: by 2002:a17:90a:8584:: with SMTP id m4mr17579508pjn.123.1577344217080; Wed, 25 Dec 2019 23:10:17 -0800 (PST) Received: from hpz4g4.kern.oss.ntt.co.jp ([222.151.198.97]) by smtp.gmail.com with ESMTPSA id i11sm9473439pjg.0.2019.12.25.23.10.15 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 25 Dec 2019 23:10:16 -0800 (PST) From: Naoto Kobayashi To: tytso@mit.edu, adilger.kernel@dilger.ca Cc: Naoto Kobayashi , linux-ext4@vger.kernel.org Subject: [PATCH] ext4: Prevent ext4_kvmalloc re-entring the filesystem and deadlocking Date: Thu, 26 Dec 2019 16:10:08 +0900 Message-Id: <20191226071008.7812-1-naoto.kobayashi4c@gmail.com> X-Mailer: git-send-email 2.16.6 Sender: linux-ext4-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-ext4@vger.kernel.org Although __vmalloc() doesn't support GFP_NOFS[1], ext4_kvmalloc/kvzalloc caller may be under GFP_NOFS context (e.g. fs/ext4/resize.c::add_new_gdb). In such cases, the memory reclaim can re-entr the filesystem and potentially deadlock. To prevent the memory relcaim re-entring the filesystem, use memalloc_nofs_save/restore that gets __vmalloc() to drop __GFP_FS flag. [1] linux-tree/Documentation/core-api/gfp-mask-fs-io.rst Signed-off-by: Naoto Kobayashi --- fs/ext4/super.c | 24 ++++++++++++++++++++++-- 1 file changed, 22 insertions(+), 2 deletions(-) diff --git a/fs/ext4/super.c b/fs/ext4/super.c index 46b6d5b150ac..4a3c9ee63a34 100644 --- a/fs/ext4/super.c +++ b/fs/ext4/super.c @@ -43,6 +43,7 @@ #include #include #include +#include #include #include @@ -204,13 +205,32 @@ void ext4_superblock_csum_set(struct super_block *sb) es->s_checksum = ext4_superblock_csum(sb, es); } +static inline void *ext4_vmalloc(size_t size, gfp_t flags, pgprot_t prot) +{ + unsigned int nofs_flag = 0; + void *ret; + + /** + * Although __vmalloc() doesn't support GFP_NOFS, we may be under + * GFP_NOFS context here. Hence we need to use memalloc_nofs_save() + * to prevent memory reclaim re-entring the filesystem here and + * potentially deadlocking. + */ + if (!(flags & __GFP_FS)) + nofs_flag = memalloc_nofs_save(); + ret = __vmalloc(size, flags, prot); + if (!(flags & __GFP_FS)) + memalloc_nofs_restore(nofs_flag); + return ret; +} + void *ext4_kvmalloc(size_t size, gfp_t flags) { void *ret; ret = kmalloc(size, flags | __GFP_NOWARN); if (!ret) - ret = __vmalloc(size, flags, PAGE_KERNEL); + ret = ext4_vmalloc(size, flags, PAGE_KERNEL); return ret; } @@ -220,7 +240,7 @@ void *ext4_kvzalloc(size_t size, gfp_t flags) ret = kzalloc(size, flags | __GFP_NOWARN); if (!ret) - ret = __vmalloc(size, flags | __GFP_ZERO, PAGE_KERNEL); + ret = ext4_vmalloc(size, flags | __GFP_ZERO, PAGE_KERNEL); return ret; } -- 2.16.5