From: Darrick J. Wong <djwong@kernel.org>
Date: Sun, 22 Feb 2026 22:41:16 +0000 (-0800)
Subject: xfs_healer: use getmntent to find moved filesystems
X-Git-Tag: v7.0.0~39
X-Git-Url: http://git-server-git.apps.pok.os.sepia.ceph.com/?a=commitdiff_plain;h=54c0ba68b007b3fa992835dbe8822ee3056759f2;p=xfsprogs-dev.git

xfs_healer: use getmntent to find moved filesystems

It's possible that a mounted filesystem can move mountpoints between the
time of the initial mount (at which point xfs_healer starts) and when
it actually wants to start a repair.  When this happens,
weakhandle::mountpoint becomes obsolete and opening it will either fail
with ENOENT or the handle revalidation will return ESTALE.

However, we do still have a means to find the mounted filesystem -- the
fsname parameter (aka the path to the data device at mount time).  This
is record in /proc/mounts, which means that we can iterate getmntent to
see if we can find the mount elsewhere.

As documented a few patches ago, this would be easier if we had
revocable fds that didn't pin mounts, but that's a very huge ask.

This getmntent code enables xfs_healer to find a filesystem that has
been bind mounted in a new place and the original mountpoint detached:

# mount /dev/sda /mnt
# xfs_healer /mnt &
# mount /mnt /opt --bind
# umount /mnt

The key here is that each bind mount gets a separate struct mount
object.

Signed-off-by: "Darrick J. Wong" <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
---

diff --git a/healer/weakhandle.c b/healer/weakhandle.c
index 849aa288..5df52075 100644
--- a/healer/weakhandle.c
+++ b/healer/weakhandle.c
@@ -65,10 +65,14 @@ out_wh:
 	return -1;
 }
 
-/* Reopen a file handle obtained via weak reference. */
-int
-weakhandle_reopen(
+/*
+ * Reopen a file handle obtained via weak reference, using the given path to a
+ * mount point.
+ */
+static int
+weakhandle_reopen_from(
 	struct weakhandle	*wh,
+	const char		*path,
 	int			*fd)
 {
 	void			*hanp;
@@ -78,7 +82,7 @@ weakhandle_reopen(
 
 	*fd = -1;
 
-	mnt_fd = open(wh->mntpoint, O_RDONLY);
+	mnt_fd = open(path, O_RDONLY);
 	if (mnt_fd < 0)
 		return -1;
 
@@ -102,6 +106,49 @@ out_mntfd:
 	return -1;
 }
 
+/* Reopen a file handle obtained via weak reference. */
+int
+weakhandle_reopen(
+	struct weakhandle	*wh,
+	int			*fd)
+{
+	FILE			*mtab;
+	struct mntent		*mnt;
+	int			ret;
+
+	/* First try reopening using the original mountpoint */
+	ret = weakhandle_reopen_from(wh, wh->mntpoint, fd);
+	if (!ret)
+		return 0;
+
+	/*
+	 * That didn't work, so now walk /proc/mounts to find a mount with the
+	 * same fsname (aka xfs data device path) as when we started.
+	 */
+	mtab = setmntent(_PATH_PROC_MOUNTS, "r");
+	if (!mtab)
+		return -1;
+
+	while ((mnt = getmntent(mtab)) != NULL) {
+		if (strcmp(mnt->mnt_type, "xfs"))
+			continue;
+		if (strcmp(mnt->mnt_fsname, wh->fsname))
+			continue;
+
+		ret = weakhandle_reopen_from(wh, mnt->mnt_dir, fd);
+		if (!ret)
+			break;
+	}
+
+	if (*fd < 0) {
+		errno = ESTALE;
+		ret = -1;
+	}
+
+	endmntent(mtab);
+	return ret;
+}
+
 /* Tear down a weak handle */
 void
 weakhandle_free(