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.

Use the sb_open_mode helper to make sure that we don't try to open
devices with write access enabled for read-only mounts.

Signed-off-by: Hans Holmberg <hans.holmberg@wdc.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Carlos Maiolino <cmaiolino@redhat.com>
Signed-off-by: Carlos Maiolino <cem@kernel.org>

diff --git a/fs/xfs/xfs_super.c b/fs/xfs/xfs_super.c
index b2dd0c0bf5097992d1665e5e6ef984fd6929fc66..5e456a6073caaddc4bb6afdff9d8e4e45b152cf8 100644 (file)
--- a/fs/xfs/xfs_super.c
+++ b/fs/xfs/xfs_super.c
@@ -380,10 +380,11 @@ 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 = sb_open_mode(mp->m_super->s_flags);
+       *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 +1970,20 @@ 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");