From: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Date: Tue, 2 Jun 2009 12:09:33 +0000 (-0400)
Subject: ext4: Fix sub-block zeroing for writes into preallocated extents
X-Git-Tag: v2.6.27.25~4
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=9c7354d9e36b9581930a89a0c60226da5a2e7dbf;p=pandora-kernel.git

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

(cherry picked from commit 9c1ee184a30394e54165fa4c15923cabd952c106)

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
---

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