[patch resend] vfs: fix vfs_rename_dir for FS_RENAME_DOES_D_MOVE filesystems

[Miklos Szeredi]

From: Miklos Szeredi <mszeredi@xxxxxxx>

vfs_rename_dir() doesn't properly account for filesystems with
FS_RENAME_DOES_D_MOVE.  If new_dentry has a target inode attached, it
unhashes the new_dentry prior to the rename() iop and rehashes it
after, but doesn't account for the possibility that rename() may have
swapped {old,new}_dentry.  For FS_RENAME_DOES_D_MOVE filesystems, it
rehashes new_dentry (now the old renamed-from name, which d_move()
expected to go away), such that a subsequent lookup will find it.

This was caught by the recently posted POSIX fstest suite, rename/10.t 
test 62 (and others) on ceph.

The bug was introduced by: commit 349457ccf2592c14bdf13b6706170ae2e94931b1
"[PATCH] Allow file systems to manually d_move() inside of ->rename()"

Fix by not rehashing the new dentry.  Rehashing used to be needed by
d_move() but isn't anymore.

Reported-by: Sage Weil <sage@xxxxxxxxxxxx>
CC: Zach Brown <zach.brown@xxxxxxxxxx>
Signed-off-by: Miklos Szeredi <mszeredi@xxxxxxx>
---
 fs/namei.c |    2 --
 1 file changed, 2 deletions(-)

Index: linux-2.6/fs/namei.c
===================================================================
--- linux-2.6.orig/fs/namei.c	2008-07-29 21:28:55.000000000 +0200
+++ linux-2.6/fs/namei.c	2008-07-29 21:36:50.000000000 +0200
@@ -2542,8 +2542,6 @@ static int vfs_rename_dir(struct inode *
 		if (!error)
 			target->i_flags |= S_DEAD;
 		mutex_unlock(&target->i_mutex);
-		if (d_unhashed(new_dentry))
-			d_rehash(new_dentry);
 		dput(new_dentry);
 	}
 	if (!error)
--
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