[PATCH] ovl: fix lookup of indexed hardlinks with metacopy

[Amir Goldstein <amir73il@gmail.com>]

We recently moved setting inode flag OVL_UPPERDATA to ovl_lookup().

When looking up an overlay dentry, upperdentry may be found by index
and not by name.  In that case, we fail to read the metacopy xattr
and falsly set the OVL_UPPERDATA on the overlay inode.

This caused a regression in xfstest overlay/033 when run with
OVERLAY_MOUNT_OPTIONS="-o metacopy=on".

Fixes: 28166ab3c875 ("ovl: initialize OVL_UPPERDATA in ovl_lookup()")
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
---

Miklos,

I just ran xfstests -g overlay/quick tests with metacopy enabled
and one test failed.

Vivek,

Do you by any chance run this sort of test regularly?

You have asked about running unionmount tests with metacopy before.
I just pushed a commit to my xfstests 'unionmount' branch:
  7859f22b ovl: test unionmount tests with metacopy

It allows you to run xfstests -g overlay/union with
OVERLAY_MOUNT_OPTIONS="-o metacopy=on", to excercise all the unionmount
test configurations I created with metacopy enabled.

Maybe not so surprising that the sub-group overlay/union.nested tests
fail with metacopy enabled. This is just a test setup bug and I pushed
a fix commit to unionmount overlayfs-devel branch to fix it.

Thanks,
Amir.

 fs/overlayfs/namei.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/fs/overlayfs/namei.c b/fs/overlayfs/namei.c
index 3566282a9199..0c5a624600c1 100644
--- a/fs/overlayfs/namei.c
+++ b/fs/overlayfs/namei.c
@@ -1073,6 +1073,10 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
 			upperredirect = NULL;
 			goto out_free_oe;
 		}
+		err = ovl_check_metacopy_xattr(upperdentry);
+		if (err < 0)
+			goto out_free_oe;
+		uppermetacopy = err;
 	}
 
 	if (upperdentry || ctr) {
-- 
2.17.1