ovl: explain error values when removing acl from workdir

Suggested-by: Linus Torvalds <torvalds@linux-foundation.org> 
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

1 files changed, 13 insertions, 0 deletions

diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index 8ccebaf64c5b..eff0f909cd78 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -832,6 +832,19 @@ retry:
                 if (err)
                         goto out_dput;
 
+                /*
+                 * Try to remove POSIX ACL xattrs from workdir.  We are good if:
+                 *
+                 * a) success (there was a POSIX ACL xattr and was removed)
+                 * b) -ENODATA (there was no POSIX ACL xattr)
+                 * c) -EOPNOTSUPP (POSIX ACL xattrs are not supported)
+                 *
+                 * There are various other error values that could effectively
+                 * mean that the xattr doesn't exist (e.g. -ERANGE is returned
+                 * if the xattr name is too long), but the set of filesystems
+                 * allowed as upper are limited to "normal" ones, where checking
+                 * for the above two errors is sufficient.
+                 */
                 err = vfs_removexattr(work, XATTR_NAME_POSIX_ACL_DEFAULT);
                 if (err && err != -ENODATA && err != -EOPNOTSUPP)
                         goto out_dput;