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From: "Darrick J. Wong" <darrick.wong@oracle.com>
To: sandeen@sandeen.net, darrick.wong@oracle.com
Cc: linux-xfs@vger.kernel.org, alex@zadara.com
Subject: [PATCH v2 0/6] xfs_repair: do not trash valid root dirs
Date: Wed, 04 Dec 2019 09:04:22 -0800
Message-ID: <157547906289.974712.8933333382010386076.stgit@magnolia> (raw)

Hi all,

Alex Lyakas observed that xfs_repair can accidentally trash the root
directory on a filesystem.  Specifically, if one formats a V4 filesystem
without sparse inodes but with sunit/swidth set and then mounts that
filesystem with a different sunit/swidth, the kernel will update the
values in the superblock.  This causes xfs_repair's sb_rootino
estimation to differ from the actual root directory, and it discards the
actual root directory even though there's nothing wrong with it.

Therefore, hoist the logic that computes the root inode location into
libxfs so that the kernel will avoid the sb update if the proposed
sunit/swidth changes would alter the sb_rootino estimation; and then
teach xfs_repair to retain the root directory even if the estimation
doesn't add up, as long as sb_rootino points to a directory whose '..'
entry points to itself.

This is an extraordinary way to destroy everything.  Enjoy!
Comments and questions are, as always, welcome.

--D

             reply index

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-12-04 17:04 Darrick J. Wong [this message]
2019-12-04 17:04 ` [PATCH 1/6] xfs: don't commit sunit/swidth updates to disk if that would cause repair failures Darrick J. Wong
2019-12-04 17:04 ` [PATCH 2/6] mkfs: check root inode location Darrick J. Wong
2019-12-05 14:36   ` Brian Foster
2019-12-04 17:04 ` [PATCH 3/6] xfs_repair: enforce that inode btree chunks can't point to AG headers Darrick J. Wong
2019-12-05 14:37   ` Brian Foster
2019-12-05 16:28     ` Darrick J. Wong
2019-12-06 16:00       ` Brian Foster
2019-12-04 17:04 ` [PATCH 4/6] xfs_repair: refactor fixed inode location checks Darrick J. Wong
2019-12-05 14:37   ` Brian Foster
2019-12-04 17:04 ` [PATCH 5/6] xfs_repair: use libxfs function to calculate root inode location Darrick J. Wong
2019-12-05 14:37   ` Brian Foster
2019-12-04 17:05 ` [PATCH 6/6] xfs_repair: check plausibility of root dir pointer before trashing it Darrick J. Wong
2019-12-05 14:38   ` Brian Foster

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