linux-kernel - [PATCH] xfs: allow ro mounts if rtdev or logdev are read-only

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Message-ID: <20250425085217.9189-1-hans.holmberg@wdc.com>
Date: Fri, 25 Apr 2025 08:52:53 +0000
From: Hans Holmberg <Hans.Holmberg@....com>
To: Carlos Maiolino <cem@...nel.org>
CC: Dave Chinner <david@...morbit.com>, "Darrick J . Wong"
	<djwong@...nel.org>, hch <hch@....de>, "linux-xfs@...r.kernel.org"
	<linux-xfs@...r.kernel.org>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>, Hans Holmberg <Hans.Holmberg@....com>
Subject: [PATCH] xfs: allow ro mounts if rtdev or logdev are read-only

Allow read-only mounts on rtdevs and logdevs that are marked as
read-only and make sure those mounts can't be remounted read-write.

Signed-off-by: Hans Holmberg <hans.holmberg@....com>
---

I will post a couple of xfstests to add coverage for these cases.

 fs/xfs/xfs_super.c | 24 +++++++++++++++++++++---
 1 file changed, 21 insertions(+), 3 deletions(-)

diff --git a/fs/xfs/xfs_super.c b/fs/xfs/xfs_super.c
index b2dd0c0bf509..d7ac1654bc80 100644
--- a/fs/xfs/xfs_super.c
+++ b/fs/xfs/xfs_super.c
@@ -380,10 +380,14 @@ xfs_blkdev_get(
 	struct file		**bdev_filep)
 {
 	int			error = 0;
+	blk_mode_t		mode;
 
-	*bdev_filep = bdev_file_open_by_path(name,
-		BLK_OPEN_READ | BLK_OPEN_WRITE | BLK_OPEN_RESTRICT_WRITES,
-		mp->m_super, &fs_holder_ops);
+	mode = BLK_OPEN_READ | BLK_OPEN_RESTRICT_WRITES;
+	if (!xfs_is_readonly(mp))
+		mode |= BLK_OPEN_WRITE;
+
+	*bdev_filep = bdev_file_open_by_path(name, mode,
+			mp->m_super, &fs_holder_ops);
 	if (IS_ERR(*bdev_filep)) {
 		error = PTR_ERR(*bdev_filep);
 		*bdev_filep = NULL;
@@ -1969,6 +1973,20 @@ xfs_remount_rw(
 	struct xfs_sb		*sbp = &mp->m_sb;
 	int error;
 
+	if (mp->m_logdev_targp && mp->m_logdev_targp != mp->m_ddev_targp &&
+	    bdev_read_only(mp->m_logdev_targp->bt_bdev)) {
+		xfs_warn(mp,
+			"ro->rw transition prohibited by read-only logdev");
+		return -EACCES;
+	}
+
+	if (mp->m_rtdev_targp &&
+	    bdev_read_only(mp->m_rtdev_targp->bt_bdev)) {
+		xfs_warn(mp,
+			"ro->rw transition prohibited by read-only rtdev");
+		return -EACCES;
+	}
+
 	if (xfs_has_norecovery(mp)) {
 		xfs_warn(mp,
 			"ro->rw transition prohibited on norecovery mount");
-- 
2.34.1