vfs: fix vfs_rename_dir for FS_RENAME_DOES_D_MOVE filesystems

From: Miklos Szeredi <[email protected]>

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.

---

 fs/namei.c |    2 --
 1 file changed, 2 deletions(-)

diff -puN fs/namei.c~vfs-fix-vfs_rename_dir-for-fs_rename_does_d_move-filesystems fs/namei.c
@@ -2583,8 +2583,6 @@ 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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