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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>
This commit is contained in:
Eryu Guan 2013-02-22 15:27:47 -05:00 committed by Theodore Ts'o
parent 1231b3a1eb
commit d438147211
1 changed files with 6 additions and 0 deletions
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6
fs/ext4/extents_status.c
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@ -456,6 +456,9 @@ int ext4_es_insert_extent(struct inode *inode, ext4_lblk_t lblk,
es_debug("add [%u/%u) %llu %llx to extent status tree of inode %lu\n",
lblk, len, pblk, status, inode->i_ino);
if (!len)
return 0;
BUG_ON(end < lblk);
newes.es_lblk = lblk;
@ -649,6 +652,9 @@ int ext4_es_remove_extent(struct inode *inode, ext4_lblk_t lblk,
es_debug("remove [%u/%u) from extent status tree of inode %lu\n",
lblk, len, inode->i_ino);
if (!len)
return err;
end = lblk + len - 1;
BUG_ON(end < lblk);