[PATCH v2 1/3] xfs: allow renames of project-less inodes

[Andrey Albershteyn <aalbersh@redhat.com>]

From: Andrey Albershteyn <aalbersh@redhat.com>

Special file inodes cannot 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.

In commit e23d7e82b707 ("xfs: allow cross-linking special files
without project quota"), we relaxed the project id checks to
allow hardlinking special files with differing project ids since the
projid cannot be changed. Apply the same workaround for renaming
operations.

Signed-off-by: Andrey Albershteyn <aalbersh@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
---
 fs/xfs/xfs_inode.c | 64 +++++++++++++++++++++++++++++-------------------------
 1 file changed, 34 insertions(+), 30 deletions(-)

diff --git a/fs/xfs/xfs_inode.c b/fs/xfs/xfs_inode.c
index 9c39251961a3..0ddb9ce0f5e3 100644
--- a/fs/xfs/xfs_inode.c
+++ b/fs/xfs/xfs_inode.c
@@ -877,6 +877,35 @@ xfs_create_tmpfile(
 	return error;
 }
 
+static inline int
+xfs_projid_differ(
+	struct xfs_inode	*tdp,
+	struct xfs_inode	*sip)
+{
+	/*
+	 * If we are using project inheritance, we only allow hard link/renames
+	 * creation in our tree when the project IDs are the same; else
+	 * the tree quota mechanism could be circumvented.
+	 */
+	if (unlikely((tdp->i_diflags & XFS_DIFLAG_PROJINHERIT) &&
+		     tdp->i_projid != sip->i_projid)) {
+		/*
+		 * Project quota setup skips special files which can
+		 * leave inodes in a PROJINHERIT directory without a
+		 * project ID set. We need to allow links 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(sip)->i_mode) ||
+		    sip->i_projid != 0) {
+			return -EXDEV;
+		}
+	}
+
+	return 0;
+}
+
 int
 xfs_link(
 	struct xfs_inode	*tdp,
@@ -930,27 +959,9 @@ xfs_link(
 		goto error_return;
 	}
 
-	/*
-	 * If we are using project inheritance, we only allow hard link
-	 * creation in our tree when the project IDs are the same; else
-	 * the tree quota mechanism could be circumvented.
-	 */
-	if (unlikely((tdp->i_diflags & XFS_DIFLAG_PROJINHERIT) &&
-		     tdp->i_projid != sip->i_projid)) {
-		/*
-		 * Project quota setup skips special files which can
-		 * leave inodes in a PROJINHERIT directory without a
-		 * project ID set. We need to allow links 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(sip)->i_mode) ||
-		    sip->i_projid != 0) {
-			error = -EXDEV;
-			goto error_return;
-		}
-	}
+	error = xfs_projid_differ(tdp, sip);
+	if (error)
+		goto error_return;
 
 	error = xfs_dir_add_child(tp, resblks, &du);
 	if (error)
@@ -2227,16 +2238,9 @@ xfs_rename(
 	if (du_wip.ip)
 		xfs_trans_ijoin(tp, du_wip.ip, 0);
 
-	/*
-	 * If we are using project inheritance, we only allow renames
-	 * into our tree when the project IDs are the same; else the
-	 * tree quota mechanism would be circumvented.
-	 */
-	if (unlikely((target_dp->i_diflags & XFS_DIFLAG_PROJINHERIT) &&
-		     target_dp->i_projid != src_ip->i_projid)) {
-		error = -EXDEV;
+	error = xfs_projid_differ(target_dp, src_ip);
+	if (error)
 		goto out_trans_cancel;
-	}
 
 	/* RENAME_EXCHANGE is unique from here on. */
 	if (flags & RENAME_EXCHANGE) {

-- 
2.50.0