From: Ted Ts'o Subject: Re: [PATCH 1/2] e2fsprogs: fix data lost with mke2fs -S Date: Thu, 16 Feb 2012 23:20:38 -0500 Message-ID: <20120217042038.GA9319@thunk.org> References: <4EF2EA9E.9080500@rs.jp.nec.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: ext4 development To: Akira Fujita Return-path: Received: from li9-11.members.linode.com ([67.18.176.11]:57025 "EHLO test.thunk.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751229Ab2BQEUl (ORCPT ); Thu, 16 Feb 2012 23:20:41 -0500 Content-Disposition: inline In-Reply-To: <4EF2EA9E.9080500@rs.jp.nec.com> Sender: linux-ext4-owner@vger.kernel.org List-ID: On Thu, Dec 22, 2011 at 05:30:22PM +0900, Akira Fujita wrote: > If we run the mke2fs with the -S option and the uninit_bg feature > simultaneously, the mke2fs marks blockgroups as uninitialized. > The e2fsck which run immediately after the mke2fs > removes all of the files. > > To avoid this, the patch prohibits user from > setting the -S option and the uninit_bg feature simultaneously. This is not the best fix. The best fix is to clear the itable_unused fields in the block group descriptors if mke2fs -S is set. See below for what I have in my tree. - Ted commit 9b6a158524fe82202bef6d0d8a101b47e6c02b64 Author: Theodore Ts'o Date: Thu Feb 16 23:16:34 2012 -0500 mke2fs: allow file systems w/ uninit_bg to be recovered with mke2fs -S The command mke2fs -S is used as a last ditch recovery command to write new superblock and block group descriptors, but _not_ to destroy the inode table in hopes of recovering from a badly corrupted file system. If the uninit_bg feature is enabled, we need to make sure to clear the unused inodes count field in the block group descriptors or else e2fsck -fy will leave the file system completely empty. Thanks to Akira Fujita for reporting this problem. Signed-off-by: "Theodore Ts'o" diff --git a/misc/mke2fs.c b/misc/mke2fs.c index 08789c4..c70c1b4 100644 --- a/misc/mke2fs.c +++ b/misc/mke2fs.c @@ -2434,6 +2434,17 @@ int main (int argc, char *argv[]) if (super_only) { fs->super->s_state |= EXT2_ERROR_FS; fs->flags &= ~(EXT2_FLAG_IB_DIRTY|EXT2_FLAG_BB_DIRTY); + /* + * The command "mke2fs -S" is used to recover + * corrupted file systems, so do not mark any of the + * inodes as unused; we want e2fsck to consider all + * inodes as potentially containing recoverable data. + */ + if (fs->super->s_feature_ro_compat & + EXT4_FEATURE_RO_COMPAT_GDT_CSUM) { + for (i = 1; i < fs->group_desc_count; i++) + ext2fs_bg_itable_unused_set(fs, i, 0); + } } else { /* rsv must be a power of two (64kB is MD RAID sb alignment) */ blk64_t rsv = 65536 / fs->blocksize;