From: Dmitry Monakhov <dmonakhov@openvz.org>
Date: Wed, 10 Oct 2012 05:04:58 +0000 (-0400)
Subject: ext4: race-condition protection for ext4_convert_unwritten_extents_endio
X-Git-Tag: v3.2.33~70
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=814a7833df19e1de7447f870ae890adb12561627;p=pandora-kernel.git

ext4: race-condition protection for ext4_convert_unwritten_extents_endio

commit dee1f973ca341c266229faa5a1a5bb268bed3531 upstream.

We assumed that at the time we call ext4_convert_unwritten_extents_endio()
extent in question is fully inside [map.m_lblk, map->m_len] because
it was already split during submission.  But this may not be true due to
a race between writeback vs fallocate.

If extent in question is larger than requested we will split it again.
Special precautions should being done if zeroout required because
[map.m_lblk, map->m_len] already contains valid data.

Signed-off-by: Dmitry Monakhov <dmonakhov@openvz.org>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---

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