v9fs: don't use primary fid when removing file

v9fs_insert uses v9fs_fid_lookup (which also locks the fid) to get the
primary fid associated with the dentry and destroys the v9fs_fid struct
after removing the file.  If another process called v9fs_fid_lookup on the
same dentry, it may wait undefinitely for the fid's lock (as the struct is
freed).

This patch changes v9fs_remove to use a cloned fid, so the primary fid is
not locked and freed.

Signed-off-by: Latchesar Ionkov <lucho@ionkov.net>
Cc: Eric Van Hensbergen <ericvh@hera.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/9p/vfs_inode.c

@@ -415,7 +415,7 @@ static int v9fs_remove(struct inode *dir, struct dentry *file, int rmdir)
 	file_inode = file->d_inode;
 	sb = file_inode->i_sb;
 	v9ses = v9fs_inode2v9ses(file_inode);
-	v9fid = v9fs_fid_lookup(file);
+	v9fid = v9fs_fid_clone(file);
 	if(IS_ERR(v9fid))
 		return PTR_ERR(v9fid);