diff mbox series

[6/7] xfs_repair: check plausibility of root dir pointer before trashing it

Message ID 158086363533.2079685.15692340020655871081.stgit@magnolia (mailing list archive)
State Accepted
Headers show
Series xfs_repair: do not trash valid root dirs | expand

Commit Message

Darrick J. Wong Feb. 5, 2020, 12:47 a.m. UTC 
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(+)

Comments

Christoph Hellwig Feb. 17, 2020, 1:53 p.m. UTC | #1 
On Tue, Feb 04, 2020 at 04:47:15PM -0800, Darrick J. Wong wrote:
> 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>

Looks good,

Reviewed-by: Christoph Hellwig <hch@lst.de>
diff mbox series

Patch

diff --git a/repair/xfs_repair.c b/repair/xfs_repair.c
index 111306fe..b34d41d4 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.
@@ -438,6 +469,20 @@  calc_mkfs(
 
 	rootino = libxfs_ialloc_calc_rootino(mp, mp->m_sb.sb_unit);
 
+	/*
+	 * 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 " valid but in unaligned location (expected %"PRIu64") possibly due to sunit change\n"),
+			mp->m_sb.sb_rootino, rootino);
+		rootino = mp->m_sb.sb_rootino;
+	}
+
 	validate_sb_ino(&mp->m_sb.sb_rootino, rootino,
 			_("root"));
 	validate_sb_ino(&mp->m_sb.sb_rbmino, rootino + 1,