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Wed, 11 Jan 2023 02:11:24 -0800 Received: from drhqmail201.nvidia.com (10.126.190.180) by drhqmail201.nvidia.com (10.126.190.180) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.986.36; Wed, 11 Jan 2023 02:11:23 -0800 Received: from vdi.nvidia.com (10.127.8.10) by mail.nvidia.com (10.126.190.180) with Microsoft SMTP Server id 15.2.986.36 via Frontend Transport; Wed, 11 Jan 2023 02:11:20 -0800 From: Yishai Hadas To: , , , , , , , CC: , , , , Subject: [PATCH V1] lib/scatterlist: Fix to calculate the last_pg properly Date: Wed, 11 Jan 2023 12:10:54 +0200 Message-ID: <20230111101054.188136-1-yishaih@nvidia.com> X-Mailer: git-send-email 2.21.0 MIME-Version: 1.0 X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: BN8NAM11FT087:EE_|SA1PR12MB8119:EE_ X-MS-Office365-Filtering-Correlation-Id: 2f57fa33-e1ed-46ae-5b62-08daf3bc34c6 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; 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X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 11 Jan 2023 10:11:28.9287 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 2f57fa33-e1ed-46ae-5b62-08daf3bc34c6 X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=43083d15-7273-40c1-b7db-39efd9ccc17a;Ip=[216.228.118.232];Helo=[mail.nvidia.com] X-MS-Exchange-CrossTenant-AuthSource: BN8NAM11FT087.eop-nam11.prod.protection.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: SA1PR12MB8119 Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org The last_pg is wrong, it is actually the first page of the last scatterlist element. To get the last page of the last scatterlist element we have to add prv->length. So it is checking mergability against the wrong page, Further, a SG element is not guaranteed to end on a page boundary, so we have to check the sub page location also for merge eligibility. Fix the above by checking physical contiguity based on PFNs, compute the actual last page and then call pages_are_mergable(). Fixes: 1567b49d1a40 ("lib/scatterlist: add check when merging zone device pages") Reported-by: Jason Gunthorpe Signed-off-by: Yishai Hadas Reviewed-by: Chaitanya Kulkarni --- Changelog: v1: * Rename 'paddr' to 'next_pfn' as it's actually. * Move to use page_to_phys() to clarify the code. * Fix to use (next_pfn - 1) instead of (paddr - PAGE_SIZE). v0: https://lore.kernel.org/lkml/Y7zyyTxdoJulq7OD@casper.infradead.org/T/ lib/scatterlist.c | 25 +++++++++++++++---------- 1 file changed, 15 insertions(+), 10 deletions(-) diff --git a/lib/scatterlist.c b/lib/scatterlist.c index f72aa50c6654..8d7519a8f308 100644 --- a/lib/scatterlist.c +++ b/lib/scatterlist.c @@ -470,22 +470,27 @@ int sg_alloc_append_table_from_pages(struct sg_append_table *sgt_append, return -EOPNOTSUPP; if (sgt_append->prv) { + unsigned long next_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; - last_pg = sg_page(sgt_append->prv); - while (n_pages && pages_are_mergeable(pages[0], last_pg)) { - if (sgt_append->prv->length + PAGE_SIZE > max_segment) - break; - sgt_append->prv->length += PAGE_SIZE; - last_pg = pages[0]; - pages++; - n_pages--; + if (page_to_pfn(pages[0]) == next_pfn) { + last_pg = pfn_to_page(next_pfn - 1); + while (n_pages && pages_are_mergeable(pages[0], last_pg)) { + if (sgt_append->prv->length + PAGE_SIZE > max_segment) + break; + sgt_append->prv->length += PAGE_SIZE; + last_pg = pages[0]; + pages++; + n_pages--; + } + if (!n_pages) + goto out; } - if (!n_pages) - goto out; } /* compute number of contiguous chunks */