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

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Message-Id: <20230406064400.2917-1-wuchi.zero@gmail.com>
Date:   Thu,  6 Apr 2023 14:44:00 +0800
From:   wuchi <wuchi.zero@...il.com>
To:     tytso@....edu, adilger.kernel@...ger.ca, ojaswin@...ux.ibm.com,
        ritesh.list@...il.com, David.Laight@...lab.com
Cc:     linux-ext4@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH v2] ext4: simplify 32bit calculation of lblk

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@...lab.com>
Signed-off-by: wuchi <wuchi.zero@...il.com>
---
 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