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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 6/6] xfs_repair: check plausibility of root dir pointer before trashing it
Date: Wed, 04 Dec 2019 09:05:02 -0800
Message-ID: <157547910268.974712.78208912903649937.stgit@magnolia> (raw)
In-Reply-To: <157547906289.974712.8933333382010386076.stgit@magnolia>

From: Darrick J. Wong <darrick.wong@oracle.com>

If sb_rootino doesn't point to where we think mkfs should have allocated
the root directory, check to see if the alleged root directory actually
looks like a root directory.  If so, we'll let it live because someone
could have changed sunit since formatting time, and that changes the
root directory inode estimate.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
---
 repair/xfs_repair.c |   45 +++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 45 insertions(+)


diff --git a/repair/xfs_repair.c b/repair/xfs_repair.c
index abd568c9..b0407f4b 100644
--- a/repair/xfs_repair.c
+++ b/repair/xfs_repair.c
@@ -426,6 +426,37 @@ _("would reset superblock %s inode pointer to %"PRIu64"\n"),
 	*ino = expected_ino;
 }
 
+/* Does the root directory inode look like a plausible root directory? */
+static bool
+has_plausible_rootdir(
+	struct xfs_mount	*mp)
+{
+	struct xfs_inode	*ip;
+	xfs_ino_t		ino;
+	int			error;
+	bool			ret = false;
+
+	error = -libxfs_iget(mp, NULL, mp->m_sb.sb_rootino, 0, &ip,
+			&xfs_default_ifork_ops);
+	if (error)
+		goto out;
+	if (!S_ISDIR(VFS_I(ip)->i_mode))
+		goto out_rele;
+
+	error = -libxfs_dir_lookup(NULL, ip, &xfs_name_dotdot, &ino, NULL);
+	if (error)
+		goto out_rele;
+
+	/* The root directory '..' entry points to the directory. */
+	if (ino == mp->m_sb.sb_rootino)
+		ret = true;
+
+out_rele:
+	libxfs_irele(ip);
+out:
+	return ret;
+}
+
 /*
  * Make sure that the first 3 inodes in the filesystem are the root directory,
  * the realtime bitmap, and the realtime summary, in that order.
@@ -436,6 +467,20 @@ calc_mkfs(
 {
 	xfs_ino_t		rootino = libxfs_ialloc_calc_rootino(mp, -1);
 
+	/*
+	 * If the root inode isn't where we think it is, check its plausibility
+	 * as a root directory.  It's possible that somebody changed sunit
+	 * since the filesystem was created, which can change the value of the
+	 * above computation.  Don't blow up the root directory if this is the
+	 * case.
+	 */
+	if (mp->m_sb.sb_rootino != rootino && has_plausible_rootdir(mp)) {
+		do_warn(
+_("sb root inode value %" PRIu64 " inconsistent with alignment (expected %"PRIu64")\n"),
+			mp->m_sb.sb_rootino, rootino);
+		rootino = mp->m_sb.sb_rootino;
+	}
+
 	ensure_fixed_ino(&mp->m_sb.sb_rootino, rootino,
 			_("root"));
 	ensure_fixed_ino(&mp->m_sb.sb_rbmino, rootino + 1,


  parent reply index

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-12-04 17:04 [PATCH v2 0/6] xfs_repair: do not trash valid root dirs Darrick J. Wong
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 ` Darrick J. Wong [this message]
2019-12-05 14:38   ` [PATCH 6/6] xfs_repair: check plausibility of root dir pointer before trashing it Brian Foster

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