From: Eryu Guan <guaneryu@gmail.com>
Date: Fri, 22 Feb 2013 20:27:47 +0000 (-0500)
Subject: ext4: no need to remove extent if len is 0 in ext4_es_remove_extent()
X-Git-Tag: v3.9-rc1~64^2~1
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=d43814721111041e26671a153e300e2054fb36fa;p=pandora-kernel.git

ext4: no need to remove extent if len is 0 in ext4_es_remove_extent()

len is 0 means no extent needs to be removed, so return immediately.
Otherwise it could trigger the following BUG_ON() in
ext4_es_remove_extent()

	end = lblk + len - 1;
	BUG_ON(end < lblk);

This could be reproduced by a simple truncate(1) command by an
unprivileged user

	truncate -s $(($((2**32 - 1)) * 4096)) /mnt/ext4/testfile

The same is true for __es_insert_extent().

Patched kernel passed xfstests regression test.

Signed-off-by: Eryu Guan <guaneryu@gmail.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Reviewed-by: Zheng Liu <wenqing.lz@taobao.com>
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