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Tue, 22 Feb 2022 08:04:23 +0000 Received: from DB9PR04MB9426.eurprd04.prod.outlook.com ([fe80::fde1:fffd:bbe0:492]) by DB9PR04MB9426.eurprd04.prod.outlook.com ([fe80::fde1:fffd:bbe0:492%4]) with mapi id 15.20.4995.027; Tue, 22 Feb 2022 08:04:23 +0000 Message-ID: Date: Tue, 22 Feb 2022 16:04:10 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.6.1 Content-Language: en-US To: Souptick Joarder , Qu Wenruo Cc: Chris Mason , Josef Bacik , dsterba@suse.com, nathan@kernel.org, Nick Desaulniers , linux-btrfs@vger.kernel.org, linux-kernel@vger.kernel.org, llvm@lists.linux.dev, kernel test robot References: <20220220144606.5695-1-jrdr.linux@gmail.com> <0a2e57ad-2973-ea01-ceda-3262cde1f5aa@gmx.com> From: Qu Wenruo Subject: Re: [PATCH] btrfs: Initialize ret to 0 in scrub_simple_mirror() In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-ClientProxiedBy: SJ0PR13CA0208.namprd13.prod.outlook.com (2603:10b6:a03:2c3::33) To DB9PR04MB9426.eurprd04.prod.outlook.com (2603:10a6:10:36a::14) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-Correlation-Id: 5464afe4-d629-4593-da6f-08d9f5d9efa9 X-MS-TrafficTypeDiagnostic: DB3PR0402MB3865:EE_ X-LD-Processed: f7a17af6-1c5c-4a36-aa8b-f5be247aa4ba,ExtFwd X-Microsoft-Antispam-PRVS: X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; 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Thus adding LLVM list here is correct. To me, the root problem is that, we lack the hint to allow clang to know that, @logical_length passed in would not cause u64 overflow. Unfortunately the sanity check to prevent overflow is hidden far away inside tree-checker.c. Maybe some ASSERT() for overflow check would help LLVM to know that? Thanks, Qu >> >> Firstly, the while loop will always get at least one run. >> >> Secondly, in that loop, we either set ret to some error value and break, >> or after at least one find_first_extent_item() and scrub_extent() call, >> we increase cur_logical and reached the limit of the while loop and exit. >> >> So there is no possible routine to leave @ret uninitialized and returned >> to caller. >> >> Thanks, >> Qu >> >>> --- >>> fs/btrfs/scrub.c | 2 +- >>> 1 file changed, 1 insertion(+), 1 deletion(-) >>> >>> diff --git a/fs/btrfs/scrub.c b/fs/btrfs/scrub.c >>> index 4baa8e43d585..5ca7e5ffbc96 100644 >>> --- a/fs/btrfs/scrub.c >>> +++ b/fs/btrfs/scrub.c >>> @@ -3325,7 +3325,7 @@ static int scrub_simple_mirror(struct scrub_ctx *sctx, >>> const u32 max_length = SZ_64K; >>> struct btrfs_path path = {}; >>> u64 cur_logical = logical_start; >>> - int ret; >>> + int ret = 0; >>> >>> /* The range must be inside the bg */ >>> ASSERT(logical_start >= bg->start && >