commit 9358c6d4c0264b1572554c49c4b92673ea9a5c72
author Sage Weil <sage@newdream.net> Tue Mar 30 13:54:41 2010 -0700
committer Sage Weil <sage@newdream.net> Tue Mar 30 13:55:22 2010 -0700
tree 3d11a5021487dccf61b8d53c66c32df6b84223eb
parent 2eaa9cfdf33b8d7fb7aff27792192e0019ae8fc6

ceph: fix dentry rehashing on virtual .snap dir

If a lookup fails on the magic .snap directory, we bind it to a magic
snap directory inode in ceph_lookup_finish().  That code assumes the dentry
is unhashed, but a recent server-side change started returning NULL leases
on lookup failure, causing the .snap dentry to be hashed and NULL by
ceph_fill_trace().

This causes dentry hash chain corruption, or a dies when d_rehash()
includes
	BUG_ON(!d_unhashed(entry));

So, avoid processing the NULL dentry lease if it the dentry matches the
snapdir name in ceph_fill_trace().  That allows the lookup completion to
properly bind it to the snapdir inode.  BUG there if dentry is hashed to
be sure.

Signed-off-by: Sage Weil <sage@newdream.net>