Enable the vfs_utimes() helper to handle idmapped mounts by passing down
the mount's user namespace. If the initial user namespace is passed
nothing changes so non-idmapped mounts will see identical behavior as
before.

Link: https://lore.kernel.org/r/20210112220124.837960-26-christian.brauner@ubuntu.com (local)
Cc: Christoph Hellwig <hch@lst.de>
Cc: David Howells <dhowells@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: linux-fsdevel@vger.kernel.org
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Christian Brauner <redacted>
---
/* v2 */
unchanged

/* v3 */
unchanged

/* v4 */
- Serge Hallyn [off-list ref]:
  - Use "mnt_userns" to refer to a vfsmount's userns everywhere to make
    terminology consistent.

/* v5 */
unchanged
base-commit: 7c53f6b671f4aba70ff15e1b05148b10d58c2837

/* v6 */
base-commit: 19c329f6808995b142b3966301f217c831e7cf31

- Christoph Hellwig [off-list ref]:
  - Don't use unnecessary local variable just call mnt_user_ns()
    directly.
---
 fs/utimes.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/utimes.c b/fs/utimes.c
index 4572b91ddb91..39f356017635 100644
--- a/fs/utimes.c
+++ b/fs/utimes.c

@@ -62,7 +62,7 @@ int vfs_utimes(const struct path *path, struct timespec64 *times)
 	}
 retry_deleg:
 	inode_lock(inode);
-	error = notify_change(&init_user_ns, path->dentry, &newattrs,
+	error = notify_change(mnt_user_ns(path->mnt), path->dentry, &newattrs,
 			      &delegated_inode);
 	inode_unlock(inode);
 	if (delegated_inode) {

-- 
2.30.0