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Howlett" , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , Steven Rostedt , Masami Hiramatsu , "Mathieu Desnoyers" , Zach O'Keefe , , , , Shivank Garg , Branden Moore Subject: [PATCH V2 1/2] mm/khugepaged: do synchronous writeback for MADV_COLLAPSE Date: Thu, 20 Nov 2025 06:50:48 +0000 Message-ID: <20251120065043.41738-8-shivankg@amd.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20251120065043.41738-6-shivankg@amd.com> References: <20251120065043.41738-6-shivankg@amd.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-ClientProxiedBy: satlexmb07.amd.com (10.181.42.216) To satlexmb07.amd.com (10.181.42.216) X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: BL6PEPF0001AB78:EE_|SJ0PR12MB7476:EE_ X-MS-Office365-Filtering-Correlation-Id: 4ec15ce0-123d-4380-640a-08de2801a9f4 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|82310400026|1800799024|36860700013|376014|7416014; X-Microsoft-Antispam-Message-Info: =?us-ascii?Q?sWsJ7xdP/mxdabdrnFW316HL+pieKXLvV6Nxt8oclYB7uN3spTkKMtMRFa+N?= =?us-ascii?Q?24god4mmu0Dkhw+WdwTFJS7PeJ/PnNKxS4VtP1M3MNB0tgqF8oyWjE/2Mt+w?= =?us-ascii?Q?9I63ok4Zs5G2RQOpbBSFkJP1PNRME6y7P14tGgCW6g6X/HlRXtsXpueCZN4S?= =?us-ascii?Q?BdSAQjYfXppfLNdkVCDF7bwJfHcOEGNVUVWDPWVSJnFow5sGiNjVdBDwdsH3?= =?us-ascii?Q?wOycHtFKYEs0dbaUY5Y4rDNJQJhAcMmuq5/tbuu7tJJxTLumfbe3qpXjbfgl?= =?us-ascii?Q?8/O0ofAEl09lRDehXDCfXe1O3P9a1dL1tEEW0VFUQ+bahe/UBeNuxQY46zVg?= =?us-ascii?Q?mSly3nPsN85Vwk2GrJAwh/hWkZkyFV8O34WEzLBA30y/wJ0MN8lTNgpr7fll?= =?us-ascii?Q?SM2a5hCcEfVOpkS4xK6LVLO/k/JO/7dfnrta9ilnVQL9tm+e++td6R+pk++g?= =?us-ascii?Q?klQ2EbdJIdPTULo4L7eIoYWA5nQETfDx5TCG/42F0P9akDDcgEG1Vto5xr7y?= =?us-ascii?Q?wcf0b194jACN1GtGq3r9u2aV0xrehMbsiJw3Qv0exwaxJV7EC7jpmXpLdoDZ?= =?us-ascii?Q?H3aDOJDFySN9AjTEeAnKm1ZIgeyPb8Y31h6/KK4+UgjqWHCGI1DmXup4AKhp?= =?us-ascii?Q?xbYXsIUduyWcVSX9rkXgflxOSPkvkHJkzu5Xh0E1rhLsPlWpq+uw/HbLfsE0?= =?us-ascii?Q?uuWnuyuZpUZdWrCu+poQTQV6zVJ9cvNUtGEIBvE42vxnGYIJuGfcy0eqDJKm?= =?us-ascii?Q?WgR1vZJ3FKVO21lL4L+wJGIE8PiHm9mEMq5J/96KQnwW9z4qP4i+vcsGHVzO?= =?us-ascii?Q?bxia0Y6tAyc8W5XqFek44PSA4n9zUgtxc3bK1IWlps38+mJ2BjHIlle4HQn1?= =?us-ascii?Q?eyI2zpzmqLv4dkv0uD9D7FuB5IUQnxlBpyAUKRWJqYpmAr+TkCCYx6Dhgeng?= =?us-ascii?Q?xsR/qg0AIwVelKHw3U33DroFSrytlR/DufaW9yG247SfljlbrOHPa6DP1C0M?= =?us-ascii?Q?V3A3E4yitjRnZkRGJPETUY6i5701d6uDKy5nSUjJ9+3Jxm+HRGEs0ua747x0?= =?us-ascii?Q?v/K9DiGeprsqEWHqbcXZLa5OgESgdV1TTXkkJK5JKPqmjQkVOiRJp9F+9bjk?= =?us-ascii?Q?dLUOr1diVAYtnvXQ5UcTPLLkmGB7fx7fX2XSfNIW0pT6R0xt6+8PDiLnCYU6?= =?us-ascii?Q?VXG8VdcIr7iH0R58UHrwUc7Fw++b+ynn/NZn2rrBjvfkPgbvfOUSldR8Tp9L?= =?us-ascii?Q?DMUKD8TGdi4Ex43au8j9xib8Gyj/zDJrEltqCIa90MQm0SUD2SYKLNmEUA21?= =?us-ascii?Q?568al0RBi/ap/xJtpXRr03ZNQ9UIKynIQciK0qrq1xus0SJuzfio5KgIY5DT?= =?us-ascii?Q?k5m03j0aUdOb+BYcRBjkZ3785aWb5lT43PRKWnZjTdx855Ol8lKSl3GKkHti?= =?us-ascii?Q?4QazqB3LbUE23lQ7qCLGj1UyKMCbU7f0SVmizlGqW4GU/MS1Pxan7PYaoW+s?= =?us-ascii?Q?nz/dmUHlb4IeRxFjalpuHVAv0+eio+YxZ5tt1gf6Oa4QgEQpyIIBlzaszG6c?= =?us-ascii?Q?IqHqYOoKSlW4eop8SK+XXsI1TQwGD1pnwaTu31ez?= X-Forefront-Antispam-Report: CIP:165.204.84.17;CTRY:US;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:satlexmb07.amd.com;PTR:InfoDomainNonexistent;CAT:NONE;SFS:(13230040)(82310400026)(1800799024)(36860700013)(376014)(7416014);DIR:OUT;SFP:1101; X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 20 Nov 2025 06:54:34.4205 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 4ec15ce0-123d-4380-640a-08de2801a9f4 X-MS-Exchange-CrossTenant-Id: 3dd8961f-e488-4e60-8e11-a82d994e183d X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=3dd8961f-e488-4e60-8e11-a82d994e183d;Ip=[165.204.84.17];Helo=[satlexmb07.amd.com] X-MS-Exchange-CrossTenant-AuthSource: BL6PEPF0001AB78.namprd02.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: SJ0PR12MB7476 Content-Type: text/plain; charset="utf-8" When MADV_COLLAPSE is called on file-backed mappings (e.g., executable text sections), the pages may still be dirty from recent writes and cause collapse to fail with -EINVAL. This is particularly problematic for freshly copied executables on filesystems, where page cache folios remain dirty until background writeback completes. The current code in collapse_file() triggers async writeback via filemap_flush() and expects khugepaged to revisit the page later. However, MADV_COLLAPSE is a synchronous operation where userspace expects immediate results. Perform synchronous writeback in madvise_collapse() before attempting collapse to avoid failing on first attempt. Reported-by: Branden Moore Closes: https://lore.kernel.org/all/4e26fe5e-7374-467c-a333-9dd48f85d7cc@am= d.com Fixes: 34488399fa08 ("mm/madvise: add file and shmem support to MADV_COLLAP= SE") Suggested-by: David Hildenbrand Signed-off-by: Shivank Garg --- mm/khugepaged.c | 26 ++++++++++++++++++++++++++ 1 file changed, 26 insertions(+) diff --git a/mm/khugepaged.c b/mm/khugepaged.c index 97d1b2824386..066a332c76ad 100644 --- a/mm/khugepaged.c +++ b/mm/khugepaged.c @@ -22,6 +22,7 @@ #include #include #include +#include =20 #include #include "internal.h" @@ -2784,6 +2785,31 @@ int madvise_collapse(struct vm_area_struct *vma, uns= igned long start, hstart =3D (start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK; hend =3D end & HPAGE_PMD_MASK; =20 + /* + * For file-backed VMAs, perform synchronous writeback to ensure + * dirty folios are flushed before attempting collapse. This avoids + * failing on the first attempt when freshly-written executable text + * is still dirty in the page cache. + */ + if (!vma_is_anonymous(vma) && vma->vm_file) { + struct address_space *mapping =3D vma->vm_file->f_mapping; + + if (mapping_can_writeback(mapping)) { + pgoff_t pgoff_start =3D linear_page_index(vma, hstart); + pgoff_t pgoff_end =3D linear_page_index(vma, hend); + loff_t lstart =3D (loff_t)pgoff_start << PAGE_SHIFT; + loff_t lend =3D ((loff_t)pgoff_end << PAGE_SHIFT) - 1; + + mmap_read_unlock(mm); + mmap_locked =3D false; + + if (filemap_write_and_wait_range(mapping, lstart, lend)) { + last_fail =3D SCAN_FAIL; + goto out_maybelock; + } + } + } + for (addr =3D hstart; addr < hend; addr +=3D HPAGE_PMD_SIZE) { int result =3D SCAN_FAIL; =20 --=20 2.43.0 From nobody Tue Dec 2 02:19:46 2025 Received: from MW6PR02CU001.outbound.protection.outlook.com (mail-westus2azon11012064.outbound.protection.outlook.com [52.101.48.64]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id C49B92FD691; 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Wed, 19 Nov 2025 22:55:15 -0800 From: Shivank Garg To: Andrew Morton , David Hildenbrand , Lorenzo Stoakes CC: Zi Yan , Baolin Wang , "Liam R . Howlett" , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , Steven Rostedt , Masami Hiramatsu , "Mathieu Desnoyers" , Zach O'Keefe , , , , Shivank Garg Subject: [PATCH V2 2/2] mm/khugepaged: map dirty/writeback pages failures to EAGAIN Date: Thu, 20 Nov 2025 06:50:50 +0000 Message-ID: <20251120065043.41738-10-shivankg@amd.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20251120065043.41738-6-shivankg@amd.com> References: <20251120065043.41738-6-shivankg@amd.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-ClientProxiedBy: satlexmb07.amd.com (10.181.42.216) To satlexmb07.amd.com (10.181.42.216) X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: BL6PEPF0001AB74:EE_|IA1PR12MB8192:EE_ X-MS-Office365-Filtering-Correlation-Id: c1bffacd-d233-4b20-6f35-08de2801c5e1 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|82310400026|376014|7416014|36860700013|1800799024; X-Microsoft-Antispam-Message-Info: =?us-ascii?Q?6xc3kw69oKGIlYjKBUY+vJ0S1h8c6GUdZofsfUMTDyYtY62MQzmjAvQ8LHyw?= =?us-ascii?Q?mBVqrSFNOLQS51ObIePLTOZQfXPYZOXnhZ6sd9IiGopz16/bFsmxD1jHT+j6?= =?us-ascii?Q?kgmJXT4VXGVrrGwFcc6xrr1VYWt9RYZps4nh5n3uo8tnE1/7ryN0V2YkSUGk?= =?us-ascii?Q?y+VfOHBZLoivsP1CN3xe0FX17ji5P6iFw8oiQ2pIIyOpEnmOgAnTRXZZPuZP?= =?us-ascii?Q?L9afT6u2X9eMACxI9dn1k1C6BJZJFG9c7/GhgiyDqMaHynUMQBpT1Q358vH9?= =?us-ascii?Q?5eUUutD75wmGkfoxdMUDE7P9azk68Vi3WWBEXQj28Kuw+KnGKbV6M6nzdYCt?= =?us-ascii?Q?QM2EwyOideiwPOvh03PtiohDc6UGyFk5OGECKcA0vwNwhPJyDt8BpNJ0tJzd?= =?us-ascii?Q?6JB1Kjp4bpJ/wEKAcFH3mGRSnuPwTb0J1ejruAhAsSTwiE7M5s8Q0OeBBlY2?= =?us-ascii?Q?b78ZtfXGBni7qUU8m7NHauwGhpRnfwjf9tgYw3irV9B6G1oUXpBkZpshSsjE?= =?us-ascii?Q?q6xLjjnm+BDgv7MiO0GOZHu9OqLKM6El6HCGTZqU2nwHxljdGao86vGu+CxM?= =?us-ascii?Q?O89ZPJUlW/mVMgHY9o9yI6i8Xw7fc4hSvqBR+3zJlIjmXFkpUcdHKIfDYz9X?= =?us-ascii?Q?IzRZPG8JH/JcY1wKetAtC9Gygxecn5LckLkMZiSK2afbCfGL36f0WPW+vNNN?= =?us-ascii?Q?EDVrGoV0hET/f4L24S1CHZgmqipEGe3q74b/+Li/mE38j68Q9yPJIirImKUf?= =?us-ascii?Q?H0L+c0BMukUm3ApbtfQ387sSc2WyFGwg6i+thj48OI571VPFIjYov8s3vQRJ?= =?us-ascii?Q?BNYZ62jMtvrkoLrrXck8Kf3a6ngnX3VCWg4lvKIlqUhvqL39jxIU8Q8aooW2?= =?us-ascii?Q?vVqacTDphbdEP1ahs5cvbI+2go8h2P70t34jMjCZDd2WxB8n8V9jkxeflLkp?= =?us-ascii?Q?6xxKq8V4xyerWUIqjGmsNNVBD3fnzZ2xXEj2rQjhOoOjRQsLkEKZoPvpBzN8?= =?us-ascii?Q?c2LR64Nu9ee9VkZs5ZBy3MV5L/+AbJrTT1KALD4rdtlqFrmR9tiivi0355Ve?= =?us-ascii?Q?EYYwpDxMIAFSv1KkYv0FlG4b1Lb/nsdUL5jPMXI6RWgeo3N5ffs1yJOo7359?= =?us-ascii?Q?zIDVnemxEXTHss0y16/Je+WJG94maKRPIKZQdnHfZLkXsRJxxkuGnlzxg4O8?= =?us-ascii?Q?uvtblaKeHtOjQBs0Z4ZQWX6XUz7D98rS1ZikLWQSZXAq05/cpsEAlGvSElAZ?= =?us-ascii?Q?i18An5agp9qY0FZ4kKw+bS78ko/VLynneZW3Fgfx62zsUmBpvNDMgjWpHOqD?= =?us-ascii?Q?Nx7Q83YIgxeASs+8CiTi/N4Y7uLGP+if/MiC5FFGDTR+PNF4celfNrgU+YVX?= =?us-ascii?Q?SzIcPBNNBeiNxrTLXo8Ul40Ek/DjujYbDARn5RE2gNbGZqSNXAtgKT9NxkaI?= =?us-ascii?Q?Rezsha1PDMTJ1KD2omTEVv/3by0jme/AOqPXDNNjQZXTPeoj95vkwhMubR1z?= =?us-ascii?Q?3GhkvpT51Gfcu2WY9DAZtSmeMGAN5GgwTm6kt1hKSy/gzg6K+9ctuNf3H2r1?= =?us-ascii?Q?m7fuFEHoYh7560CDjNw=3D?= X-Forefront-Antispam-Report: CIP:165.204.84.17;CTRY:US;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:satlexmb07.amd.com;PTR:InfoDomainNonexistent;CAT:NONE;SFS:(13230040)(82310400026)(376014)(7416014)(36860700013)(1800799024);DIR:OUT;SFP:1101; X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 20 Nov 2025 06:55:21.2717 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: c1bffacd-d233-4b20-6f35-08de2801c5e1 X-MS-Exchange-CrossTenant-Id: 3dd8961f-e488-4e60-8e11-a82d994e183d X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=3dd8961f-e488-4e60-8e11-a82d994e183d;Ip=[165.204.84.17];Helo=[satlexmb07.amd.com] X-MS-Exchange-CrossTenant-AuthSource: BL6PEPF0001AB74.namprd02.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: IA1PR12MB8192 Content-Type: text/plain; charset="utf-8" When collapse_file encounters dirty or writeback pages in file-backed mappings, it currently SCAN_FAIL which maps to -EINVAL. This is misleading as EINVAL suggests invalid arguments, whereas dirty/writeback pages represent transient conditions that may resolve on retry. Introduce SCAN_PAGE_NOT_CLEAN to cover both dirty and writeback states, mapping it to -EAGAIN. For MADV_COLLAPSE, this provides userspace with a clear signal that retry may succeed after writeback completes, making -EAGAIN semantically correct. For khugepaged, this is harmless as it will naturally revisit the range during periodic scans after async writeback completes. Signed-off-by: Shivank Garg Reviewed-by: Dev Jain Reviewed-by: Lance Yang --- include/trace/events/huge_memory.h | 3 ++- mm/khugepaged.c | 8 +++++--- 2 files changed, 7 insertions(+), 4 deletions(-) diff --git a/include/trace/events/huge_memory.h b/include/trace/events/huge= _memory.h index 4cde53b45a85..1caf24b951e1 100644 --- a/include/trace/events/huge_memory.h +++ b/include/trace/events/huge_memory.h @@ -37,7 +37,8 @@ EM( SCAN_PAGE_HAS_PRIVATE, "page_has_private") \ EM( SCAN_STORE_FAILED, "store_failed") \ EM( SCAN_COPY_MC, "copy_poisoned_page") \ - EMe(SCAN_PAGE_FILLED, "page_filled") + EM( SCAN_PAGE_FILLED, "page_filled") \ + EMe(SCAN_PAGE_NOT_CLEAN, "page_not_clean") =20 #undef EM #undef EMe diff --git a/mm/khugepaged.c b/mm/khugepaged.c index 066a332c76ad..282b413d17e8 100644 --- a/mm/khugepaged.c +++ b/mm/khugepaged.c @@ -59,6 +59,7 @@ enum scan_result { SCAN_STORE_FAILED, SCAN_COPY_MC, SCAN_PAGE_FILLED, + SCAN_PAGE_NOT_CLEAN, }; =20 #define CREATE_TRACE_POINTS @@ -1968,11 +1969,11 @@ static int collapse_file(struct mm_struct *mm, unsi= gned long addr, */ xas_unlock_irq(&xas); filemap_flush(mapping); - result =3D SCAN_FAIL; + result =3D SCAN_PAGE_NOT_CLEAN; goto xa_unlocked; } else if (folio_test_writeback(folio)) { xas_unlock_irq(&xas); - result =3D SCAN_FAIL; + result =3D SCAN_PAGE_NOT_CLEAN; goto xa_unlocked; } else if (folio_trylock(folio)) { folio_get(folio); @@ -2019,7 +2020,7 @@ static int collapse_file(struct mm_struct *mm, unsign= ed long addr, * folio is dirty because it hasn't been flushed * since first write. */ - result =3D SCAN_FAIL; + result =3D SCAN_PAGE_NOT_CLEAN; goto out_unlock; } =20 @@ -2748,6 +2749,7 @@ static int madvise_collapse_errno(enum scan_result r) case SCAN_PAGE_LRU: case SCAN_DEL_PAGE_LRU: case SCAN_PAGE_FILLED: + case SCAN_PAGE_NOT_CLEAN: return -EAGAIN; /* * Other: Trying again likely not to succeed / error intrinsic to --=20 2.43.0