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Win64; x64; rv:102.0) Gecko/20100101 Thunderbird/102.6.1 Subject: Re: [PATCH] lib/scatterlist: Fix to calculate the last_pg properly Content-Language: en-US To: Jason Gunthorpe CC: Matthew Wilcox , , , , , , , , , References: <20230109144701.83021-1-yishaih@nvidia.com> From: Yishai Hadas In-Reply-To: Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 8bit X-Originating-IP: [10.126.231.37] X-ClientProxiedBy: rnnvmail201.nvidia.com (10.129.68.8) To rnnvmail201.nvidia.com (10.129.68.8) X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: BN8NAM11FT016:EE_|CH2PR12MB4118:EE_ X-MS-Office365-Filtering-Correlation-Id: ba42e1e2-98b2-43c4-2362-08daf31c1b51 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; X-Microsoft-Antispam-Message-Info: 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 X-Forefront-Antispam-Report: CIP:216.228.117.161;CTRY:US;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:mail.nvidia.com;PTR:dc6edge2.nvidia.com;CAT:NONE;SFS:(13230022)(4636009)(346002)(39860400002)(396003)(376002)(136003)(451199015)(46966006)(40470700004)(36840700001)(36860700001)(82740400003)(2906002)(53546011)(31686004)(107886003)(7636003)(356005)(2616005)(26005)(186003)(16526019)(40480700001)(478600001)(316002)(5660300002)(82310400005)(6862004)(8936002)(37006003)(36756003)(86362001)(47076005)(426003)(40460700003)(31696002)(41300700001)(16576012)(70586007)(8676002)(70206006)(4326008)(54906003)(336012)(6636002)(43740500002);DIR:OUT;SFP:1101; X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 10 Jan 2023 15:05:26.7251 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: ba42e1e2-98b2-43c4-2362-08daf31c1b51 X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=43083d15-7273-40c1-b7db-39efd9ccc17a;Ip=[216.228.117.161];Helo=[mail.nvidia.com] X-MS-Exchange-CrossTenant-AuthSource: BN8NAM11FT016.eop-nam11.prod.protection.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: CH2PR12MB4118 X-Rspamd-Queue-Id: 500D51C0022 X-Rspamd-Server: rspam09 X-Rspam-User: X-Stat-Signature: qpjdxqu76cezjihwpgu5jwggun9auh6g X-HE-Tag: 1673363129-161104 X-HE-Meta: U2FsdGVkX1/kZAftd8d1ryJvQvF4EirdMNQlmW5cckqvX2s/V6KH9L0ETIVUNs9zDSoUW5HOPyp2XphIQ/R826NsI5cMjNOFI5HdfD31WPcRhOELhuLyHAGE01SuMuki2g5yUfmTIrrZARUqmjOjj5MPR2kC2gFGvQwvIEbuh25F1SIGRouPdP0UFE0sfdycaN09jFCTn6IrUNgL2skt39iIXjtL92D3rqMx46mCznm1gWV4Z4Bc6oCPkdw6uBUZaqwyRQwXo4YH3BEM1Ifjwd2OiNYWSFuxkg4Z3cbf5nvqr/kMEhu5Xu8OvhWHDDoQdexTp/0AduWCXn4XPcvv2iUtYim+hAJaK91GqhR7uHVPD/N+l7t+JAD00J5BUvJR/Lk1+VYAUjKw1pDFTJ4FkL97Y/KXgDQpVtEFovvI7p7HVbcd7pMeoS7Myeot8P6JAQHGBl4wSmQ2s/9Ur4eY1OzagxQ4WKXPHWi8o8hqGlYOMYXoA+kBITJuzPEkU6w9cbDKM9B+6Hu3E2TKzoK38cci+USQM3H+FhJpHpxCTfFhXceZmhhhpJcBLC49OITdzFSU5udGmN1XUE5gL+fTUWjZ2nrhBZLUmrVnsm5YAg050ft9jbQjajuwhirSMO1DiH2RCx35TIAhHuf1ij/lZjBhsnNi/Lmqttne7ttgWd/y+zFAartocfyNY0CPl3/ZS4/7/ZlxX7AsW3NRq4Nz9/Ez/eTF7vS+XXhCtD+b7c0/EEj3EWLekHuq2F44vi7iCXWKW5RDN9GFMitG8dbVKWDf0Yz94AW2Iu7S1iMDxwqap3brmOInnWvfoDoE0DNeHykVB6RMEL0eAes36mqgsx8Zgc/Y/oevd3EPp/+95lMnP9vWhgDQNq5RSR50tAW6GhuNJUxvIc8IPlG0BedrsmhV2js7yhl8JZlW9XtJHVsf8XfS2ytQ7cC3a5PzZ9fRC8Kufbwupe1qXNUD/un BPFeNwG2 YX9HmVxZ2e5zCU9QnrkEhEi9Dqg== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 10/01/2023 15:53, Jason Gunthorpe wrote: > On Tue, Jan 10, 2023 at 10:01:53AM +0200, Yishai Hadas wrote: >> On 10/01/2023 7:08, Matthew Wilcox wrote: >>> On Mon, Jan 09, 2023 at 04:47:01PM +0200, Yishai Hadas wrote: >>>> if (sgt_append->prv) { >>>> + unsigned long paddr = >>>> + (page_to_pfn(sg_page(sgt_append->prv)) * PAGE_SIZE + >>> 1. page_to_pfn() * PAGE_SIZE is spelled page_to_phys() >>> >>> 2. physical addresses have type phys_addr_t. Oh, wait, paddr isn't a >>> physical address, it's a pfn because you divide by PAGE_SIZE at the end. >>> But you will get truncation on 32-bit, because page_to_pfn() has type >>> unsigned long. Anyway, this shouldn't be called paddr. Maybe last_pfn >>> or something? >>> >>>> + sgt_append->prv->offset + sgt_append->prv->length) / >>>> + PAGE_SIZE; >> In this area of the patch I just reverted to what we had in 6.1 [1] where we >> were good. >> >> I can send V1 and replace the 'paddr' to be called 'last_pfn' if it's really >> needed. > Please change it as Matthew describes so it is clearer > > Jason OK Once cleaning the code and renaming to 'last_pfn', could also see that we had to use below '- 1' instead of '- PAGE_SIZE'. The expected diff compared to V0 can be seen below. Will repeat some testing and send V1 once be ready. +++ b/lib/scatterlist.c @@ -470,18 +470,16 @@ int sg_alloc_append_table_from_pages(struct sg_append_table *sgt_append,                 return -EOPNOTSUPP;         if (sgt_append->prv) { -               unsigned long paddr = -                       (page_to_pfn(sg_page(sgt_append->prv)) * PAGE_SIZE + -                        sgt_append->prv->offset + sgt_append->prv->length) / -                       PAGE_SIZE; +               unsigned long last_pfn = (page_to_phys(sg_page(sgt_append->prv)) + +                       sgt_append->prv->offset + sgt_append->prv->length) / PAGE_SIZE;                 if (WARN_ON(offset))                         return -EINVAL;                 /* Merge contiguous pages into the last SG */                 prv_len = sgt_append->prv->length; -               if (page_to_pfn(pages[0]) == paddr) { -                       last_pg = pfn_to_page(paddr - PAGE_SIZE); +               if (page_to_pfn(pages[0]) == last_pfn) { +                       last_pg = pfn_to_page(last_pfn - 1);                         while (n_pages && pages_are_mergeable(pages[0], last_pg)) {                                 if (sgt_append->prv->length + PAGE_SIZE > max_segment)                                         break; Yishai