From: Vasily Averin Subject: ext2/ext3 errors behaviour fixes Date: Wed, 04 Oct 2006 11:50:00 +0400 Message-ID: <452367A8.3010405@sw.ru> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: Eric Sandeen , Kirill Korotaev Return-path: Received: from mailhub.sw.ru ([195.214.233.200]:28598 "EHLO relay.sw.ru") by vger.kernel.org with ESMTP id S1161129AbWJDHuK (ORCPT ); Wed, 4 Oct 2006 03:50:10 -0400 To: Theodore Tso , Stephen Tweedie , Andrew Morton , adilger@clusterfs.com, Linux Kernel Mailing List , linux-ext4@vger.kernel.org, devel@openvz.org, cmm@us.ibm.com Sender: linux-ext4-owner@vger.kernel.org List-Id: linux-ext4.vger.kernel.org Hello all, Current error behaviour for ext2 and ext3 filesystems does not fully correspond to the documentation and should be fixed. According to man 8 mount, ext2 and ext3 file systems allow to set one of 3 different on-errors behaviours: ---- start of quote man 8 mount ---- errors=continue / errors=remount-ro / errors=panic Define the behaviour when an error is encountered. (Either ignore errors and just mark the file system erroneous and continue, or remount the file system read-only, or panic and halt the system.) The default is set in the filesystem superblock, and can be changed using tune2fs(8). ---- end of quote ---- However EXT3_ERRORS_CONTINUE is not read from the superblock, and thus ERRORS_CONT is not saved on the sbi->s_mount_opt. It leads to the incorrect handle of errors on ext3. Then we've checked corresponding code in ext2 and discovered that it is buggy as well: - EXT2_ERRORS_CONTINUE is not read from the superblock (the same); - parse_option() does not clean the alternative values and thus something like (ERRORS_CONT|ERRORS_RO) can be set; - if options are omitted, parse_option() does not set any of these options. Therefore it is possible to set any combination of these options on the ext2: - none of them may be set: EXT2_ERRORS_CONTINUE on superblock / empty mount options; - any of them may be set using mount options; - 2 any options may be set: by using EXT2_ERRORS_RO/EXT2_ERRORS_PANIC on the superblock and other value in mount options; - and finally all three options may be set by adding third option in remount. Currently ext2 uses these values only in ext2_error() and it is not leading to any noticeable troubles. However somebody may be discouraged when he will try to workaround EXT2_ERRORS_PANIC on the superblock by using errors=continue in mount options. The following patches fix this. Thank you, Vasily Averin SWsoft Virtuozzo/OpenVZ Linux kernel team