From 31abdab9c11bb1694ecd1476a7edbe8e964d94ac Mon Sep 17 00:00:00 2001
From: Al Viro <viro@zeniv.linux.org.uk>
Date: Sat, 18 May 2013 02:38:52 -0400
Subject: [PATCH] hpfs: deadlock and race in directory lseek()

For one thing, there's an ABBA deadlock on hpfs fs-wide lock and i_mutex
in hpfs_dir_lseek() - there's a lot of methods that grab the former with
the caller already holding the latter, so it must take i_mutex first.

For another, locking the damn thing, carefully validating the offset,
then dropping locks and assigning the offset is obviously racy.

Moreover, we _must_ do hpfs_add_pos(), or the machinery in dnode.c
won't modify the sucker on B-tree surgeries.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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