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X-OriginatorOrg: arm.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 26 Jun 2025 05:00:00.3510 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: af68ed44-dbd6-44f2-c292-08ddb46e4dfd X-MS-Exchange-CrossTenant-Id: f34e5979-57d9-4aaa-ad4d-b122a662184d X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=f34e5979-57d9-4aaa-ad4d-b122a662184d;Ip=[4.158.2.129];Helo=[outbound-uk1.az.dlp.m.darktrace.com] X-MS-Exchange-CrossTenant-AuthSource: AMS0EPF000001A3.eurprd05.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: PAVPR08MB9553 On 26/06/25 10:27 am, Lorenzo Stoakes wrote: > On Thu, Jun 26, 2025 at 09:22:28AM +0530, Dev Jain wrote: >> On 25/06/25 6:58 pm, Lorenzo Stoakes wrote: >>> On Wed, Jun 25, 2025 at 11:28:06AM +0530, Dev Jain wrote: >>>> Suppose a folio is under migration, and khugepaged is also trying to >>>> collapse it. collapse_pte_mapped_thp() will retrieve the folio from the >>>> page cache via filemap_lock_folio(), thus taking a reference on the folio >>>> and sleeping on the folio lock, since the lock is held by the migration >>>> path. Migration will then fail in >>>> __folio_migrate_mapping -> folio_ref_freeze. Reduce the probability of >>>> such a race happening (leading to migration failure) by bailing out >>>> if we detect a PMD is marked with a migration entry. >>>> >>>> This fixes the migration-shared-anon-thp testcase failure on Apple M3. >>> Hm is this related to the series at all? Seems somewhat unrelated? >> Not related. >> >>> Is there a Fixes, Closes, etc.? Do we need something in stable? >> We don't need anything. This is an "expected race" in the sense that >> both migration and khugepaged collapse are best effort algorithms. >> I am just seeing a test failure on my system because my system hits >> the race more often. So this patch reduces the window for the race. > Does it rely on previous patches? If not probably best to send this one > separately :) To prevent rebasing headaches for others (if any) I thought to send all together. I'll send it separately if still that is the preference.