[PATCH v2] ext4: simplify 32bit calculation of lblk

From: wuchi
Date: Thu Apr 06 2023 - 02:44:12 EST


commit <ad4fb9cafe100a> (ext4: fix 32bit overflow in ext4_ext_find_goal())
uses value compare to fix 32bit overflow. The resion is that
(block - ext_block) will overflow and cast u32 to u64.
eg: -1(u32) cast to 0xffffffff(u64) which wasn't correct here.
Remove the brackets will solve it simply.

Suggested-by: David Laight <David.Laight@xxxxxxxxxx>
Signed-off-by: wuchi <wuchi.zero@xxxxxxxxx>
---
fs/ext4/extents.c | 5 +----
1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index 3559ea6b0781..254d380ff46e 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -237,10 +237,7 @@ static ext4_fsblk_t ext4_ext_find_goal(struct inode *inode,
ext4_fsblk_t ext_pblk = ext4_ext_pblock(ex);
ext4_lblk_t ext_block = le32_to_cpu(ex->ee_block);

- if (block > ext_block)
- return ext_pblk + (block - ext_block);
- else
- return ext_pblk - (ext_block - block);
+ return ext_pblk + block - ext_block;
}

/* it looks like index is empty;
--
2.20.1