linux-kernel - [PATCH mips-next 3/3] MIPS: checksum: fix sparse flooding on asm/checksum.h

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Message-ID: <WDTCGAs6T_1WrYWzhajhKbTIXfzTBLg0bGDdJpUkGxVMdTG4pu3AzSorhGtletaoPhEf43qQ_F6kO0dndfIfhZsc2MGwcU9indtM80T4cI0=@pm.me>
Date:   Sat, 20 Jun 2020 09:35:00 +0000
From:   Alexander Lobakin <alobakin@...me>
To:     Thomas Bogendoerfer <tsbogend@...ha.franken.de>
Cc:     Alexandre Belloni <alexandre.belloni@...tlin.com>,
        Paul Burton <paulburton@...nel.org>,
        Alexander Lobakin <alobakin@...me>, linux-mips@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH mips-next 3/3] MIPS: checksum: fix sparse flooding on asm/checksum.h

csum_fold() in MIPS' asm/checksum.h is another source of sparse flooding
when building different networking source code.
The thing is that only half of __wsum <--> u32 casts inside the funtion
is forced, which is insufficient.
Add all necessary forced typecasting to stop floods and simplify actual
bug hunting.

Signed-off-by: Alexander Lobakin <alobakin@...me>
---
 arch/mips/include/asm/checksum.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/mips/include/asm/checksum.h b/arch/mips/include/asm/checksum.h
index dcebaaf8c862..181f7d14efb9 100644
--- a/arch/mips/include/asm/checksum.h
+++ b/arch/mips/include/asm/checksum.h
@@ -113,9 +113,9 @@ static inline __sum16 csum_fold(__wsum csum)
 	u32 sum = (__force u32)csum;
 
 	sum += (sum << 16);
-	csum = (sum < csum);
+	csum = (__force __wsum)(sum < (__force u32)csum);
 	sum >>= 16;
-	sum += csum;
+	sum += (__force u32)csum;
 
 	return (__force __sum16)~sum;
 }
-- 
2.27.0