From: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Date: Wed, 13 May 2009 22:36:58 +0000 (-0400)
Subject: ext4: Fix sub-block zeroing for writes into preallocated extents
X-Git-Tag: linux-omap-v2.6.30-rc6~6^2~3
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=9c1ee184a30394e54165fa4c15923cabd952c106;p=pandora-kernel.git

ext4: Fix sub-block zeroing for writes into preallocated extents

We need to mark the buffer_head mapping preallocated space as new
during write_begin. Otherwise we don't zero out the page cache content
properly for a partial write. This will cause file corruption with
preallocation.

Now that we mark the buffer_head new we also need to have a valid
buffer_head blocknr so that unmap_underlying_metadata() unmaps the
correct block.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
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