[PATCH 07/10] libxfs: fix buftarg initialization for the RT device

[Christoph Hellwig <hch@lst.de>]

libxfs_buftarg_init currently sets the rtdev targp to the ddev one when
no explicit RT device is provided, which allows tools like repair to
proceed without a specified RT device when they should not, and
potentially can cause data corruption.

Fix this by delaying the RT buftarg initialization to libxfs_mount,
where we can check if the superblock indicates an internal RT device.
This works because all external callers of libxfs_buftarg_init never
need the RT device as they just examine the sb and/or log,

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 libxfs/init.c | 11 +++++------
 1 file changed, 5 insertions(+), 6 deletions(-)

diff --git a/libxfs/init.c b/libxfs/init.c
index 842a2e1e09a9..97c5286c00a9 100644
--- a/libxfs/init.c
+++ b/libxfs/init.c
@@ -554,8 +554,7 @@ libxfs_buftarg_reinit(
 	}
 
 	if (mp->m_rtdev_targp && mp->m_rtdev_targp != mp->m_ddev_targp) {
-		if ((xi->rt.dev && xi->rt.dev == xi->data.dev) ||
-		    mp->m_rtdev_targp->bt_bdev != xi->rt.dev ||
+		if (mp->m_rtdev_targp->bt_bdev != xi->rt.dev ||
 		    mp->m_rtdev_targp->bt_mount != mp) {
 			fprintf(stderr,
 				_("%s: bad buftarg reinit, rtdev\n"),
@@ -587,10 +586,6 @@ libxfs_buftarg_init(
 		mp->m_logdev_targp = mp->m_ddev_targp;
 	else
 		mp->m_logdev_targp = libxfs_buftarg_alloc(mp, xi, &xi->log);
-	if (!xi->rt.dev || xi->rt.dev == xi->data.dev)
-		mp->m_rtdev_targp = mp->m_ddev_targp;
-	else
-		mp->m_rtdev_targp = libxfs_buftarg_alloc(mp, xi, &xi->rt);
 }
 
 /* Compute maximum possible height for per-AG btree types for this fs. */
@@ -739,6 +734,10 @@ libxfs_mount(
 	if (flags & LIBXFS_MOUNT_REPORT_CORRUPTION)
 		xfs_set_reporting_corruption(mp);
 	libxfs_buftarg_init(mp, xi);
+	if (sb->sb_rtstart)
+		mp->m_rtdev_targp = mp->m_ddev_targp;
+	else if (xi->rt.dev)
+		mp->m_rtdev_targp = libxfs_buftarg_alloc(mp, xi, &xi->rt);
 	libxfs_setup_write_error_injection(mp);
 
 	if (xi->data.name)
-- 
2.53.0