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X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 13 Dec 2021 11:31:15.9184 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 17b926af-cbba-4e5f-c0c7-08d9be2c1361 X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=43083d15-7273-40c1-b7db-39efd9ccc17a;Ip=[203.18.50.13];Helo=[mail.nvidia.com] X-MS-Exchange-CrossTenant-AuthSource: CO1NAM11FT016.eop-nam11.prod.protection.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: MW2PR12MB2490 Precedence: bulk Reply-To: linux-kernel@vger.kernel.org List-ID: X-Mailing-List: mm-commits@vger.kernel.org On Saturday, 11 December 2021 3:34:36 PM AEDT Matthew Wilcox wrote: > On Thu, Nov 18, 2021 at 01:54:27PM -0800, akpm@linux-foundation.org wrote: > > +++ a/mm/migrate.c > > @@ -305,15 +305,7 @@ void __migration_entry_wait(struct mm_st > > page = pfn_swap_entry_to_page(entry); > > page = compound_head(page); > > > > - /* > > - * Once page cache replacement of page migration started, page_count > > - * is zero; but we must not call put_and_wait_on_page_locked() without > > - * a ref. Use get_page_unless_zero(), and just fault again if it fails. > > - */ > > - if (!get_page_unless_zero(page)) > > - goto out; > > - pte_unmap_unlock(ptep, ptl); > > - put_and_wait_on_page_locked(page, TASK_UNINTERRUPTIBLE); > > + migration_entry_wait_on_locked(page_folio(page), ptep, ptl); > > This is clearly bogus. The 'page = compound_head(page)' line should > be deleted. > > But I think we should go further and turn this into: > > migration_entry_wait_on_locked(entry, ptep, ptl); > > Neither caller has anything useful to do with the page any more. Thanks for spotting that, I have posted a new version which does that.