[PATCH 2/4] xfs: allow renames of project-less inodes

[Andrey Albershteyn <aalbersh@redhat.com>]

Identical problem as worked around in commit e23d7e82b707 ("xfs:
allow cross-linking special files without project quota") exists
with renames. Renaming special file without project ID is not
possible inside PROJINHERIT directory.

Special files inodes can not have project ID set from userspace and
are skipped during initial project setup. Those inodes are left
project-less in the project directory. New inodes created after
project initialization do have an ID. Creating hard links or
renaming those project-less inodes then fails on different ID check.

Add workaround to allow renames of special files without project ID.

Signed-off-by: Andrey Albershteyn <aalbersh@redhat.com>
---
 fs/xfs/xfs_inode.c | 15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)

diff --git a/fs/xfs/xfs_inode.c b/fs/xfs/xfs_inode.c
index 58fb7a5062e1..508113515eec 100644
--- a/fs/xfs/xfs_inode.c
+++ b/fs/xfs/xfs_inode.c
@@ -3275,8 +3275,19 @@ xfs_rename(
 	 */
 	if (unlikely((target_dp->i_diflags & XFS_DIFLAG_PROJINHERIT) &&
 		     target_dp->i_projid != src_ip->i_projid)) {
-		error = -EXDEV;
-		goto out_trans_cancel;
+		/*
+		 * Project quota setup skips special files which can
+		 * leave inodes in a PROJINHERIT directory without a
+		 * project ID set. We need to allow renames to be made
+		 * to these "project-less" inodes because userspace
+		 * expects them to succeed after project ID setup,
+		 * but everything else should be rejected.
+		 */
+		if (!special_file(VFS_I(src_ip)->i_mode) ||
+		    src_ip->i_projid != 0) {
+			error = -EXDEV;
+			goto out_trans_cancel;
+		}
 	}
 
 	/* RENAME_EXCHANGE is unique from here on. */
-- 
2.42.0