From: Dmitry Monakhov <dmonakhov@openvz.org>
Date: Mon, 4 Mar 2013 05:36:06 +0000 (-0500)
Subject: ext4: disable merging of uninitialized extents
X-Git-Tag: v3.9-rc4~16^2~19
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=ec22ba8edb507395c95fbc617eea26a6b2d98797;p=pandora-kernel.git

ext4: disable merging of uninitialized extents

Derived from Jan's patch:http://permalink.gmane.org/gmane.comp.file-systems.ext4/36470

Merging of uninitialized extents creates all sorts of interesting race
possibilities when writeback / DIO races with fallocate. Thus
ext4_convert_unwritten_extents_endio() has to deal with a case where
extent to be converted needs to be split out first. That isn't nice
for two reasons:

1) It may need allocation of extent tree block so ENOSPC is possible.
2) It complicates end_io handling code

So we disable merging of uninitialized extents which allows us to simplify
the code. Extents will get merged after they are converted to initialized
ones.

Signed-off-by: Dmitry Monakhov <dmonakhov@openvz.org>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Reviewed-by: Jan Kara <jack@suse.cz>
---

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