From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3059EC32771 for ; Wed, 17 Aug 2022 00:01:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237880AbiHQABA (ORCPT ); Tue, 16 Aug 2022 20:01:00 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51312 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237491AbiHQAA6 (ORCPT ); Tue, 16 Aug 2022 20:00:58 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5578B92F54; Tue, 16 Aug 2022 17:00:57 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 02C69B81B6E; Wed, 17 Aug 2022 00:00:56 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8DDDAC433C1; Wed, 17 Aug 2022 00:00:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1660694454; bh=FbfOYpIdukfWy/0NOEuz/PqKaeNCFxaBDEefJJvAzSI=; h=Date:To:From:Subject:From; b=YOlFWTXGWxHbANf/1L6EiZQjAfgYNdxgciU3E0LK/ZRGlamauXwoDMEmgDNgWjsKk U+YXnOSYoyOM2THpqZ2F3wDuY/m/Bmk9ddgd/5af9tKLQFWALZf8mdFzAux14XXP4h voxtwOHIauQiHOlGNOGGS5Tym3RRE5sk4R/qRhJI= Date: Tue, 16 Aug 2022 17:00:53 -0700 To: mm-commits@vger.kernel.org, ying.huang@intel.com, willy@infradead.org, stable@vger.kernel.org, rcampbell@nvidia.com, peterx@redhat.com, paulus@ozlabs.org, lyude@redhat.com, logang@deltatee.com, kherbst@redhat.com, jhubbard@nvidia.com, jgg@nvidia.com, felix.kuehling@amd.com, david@redhat.com, bskeggs@redhat.com, alex.sierra@amd.com, apopple@nvidia.com, akpm@linux-foundation.org From: Andrew Morton Subject: + mm-migrate_devicec-copy-pte-dirty-bit-to-page.patch added to mm-hotfixes-unstable branch Message-Id: <20220817000054.8DDDAC433C1@smtp.kernel.org> Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org The patch titled Subject: mm/migrate_device.c: copy pte dirty bit to page has been added to the -mm mm-hotfixes-unstable branch. Its filename is mm-migrate_devicec-copy-pte-dirty-bit-to-page.patch This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-migrate_devicec-copy-pte-dirty-bit-to-page.patch This patch will later appear in the mm-hotfixes-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next via the mm-everything branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm and is updated there every 2-3 working days ------------------------------------------------------ From: Alistair Popple Subject: mm/migrate_device.c: copy pte dirty bit to page Date: Tue, 16 Aug 2022 17:39:24 +1000 migrate_vma_setup() has a fast path in migrate_vma_collect_pmd() that installs migration entries directly if it can lock the migrating page. When removing a dirty pte the dirty bit is supposed to be carried over to the underlying page to prevent it being lost. Currently migrate_vma_*() can only be used for private anonymous mappings. That means loss of the dirty bit usually doesn't result in data loss because these pages are typically not file-backed. However pages may be backed by swap storage which can result in data loss if an attempt is made to migrate a dirty page that doesn't yet have the PageDirty flag set. In this case migration will fail due to unexpected references but the dirty pte bit will be lost. If the page is subsequently reclaimed data won't be written back to swap storage as it is considered uptodate, resulting in data loss if the page is subsequently accessed. Prevent this by copying the dirty bit to the page when removing the pte to match what try_to_migrate_one() does. Link: https://lkml.kernel.org/r/6e77914685ede036c419fa65b6adc27f25a6c3e9.1660635033.git-series.apopple@nvidia.com Fixes: 8c3328f1f36a ("mm/migrate: migrate_vma() unmap page from vma while collecting pages") Signed-off-by: Alistair Popple Acked-by: Peter Xu Reported-by: Huang Ying Reviewed-by: Huang Ying Cc: Alex Sierra Cc: Ben Skeggs Cc: David Hildenbrand Cc: Felix Kuehling Cc: Jason Gunthorpe Cc: John Hubbard Cc: Karol Herbst Cc: Logan Gunthorpe Cc: Lyude Paul Cc: Matthew Wilcox (Oracle) Cc: Paul Mackerras Cc: Ralph Campbell Cc: Signed-off-by: Andrew Morton --- mm/migrate_device.c | 21 ++++++++------------- 1 file changed, 8 insertions(+), 13 deletions(-) --- a/mm/migrate_device.c~mm-migrate_devicec-copy-pte-dirty-bit-to-page +++ a/mm/migrate_device.c @@ -7,6 +7,7 @@ #include #include #include +#include #include #include #include @@ -61,7 +62,7 @@ static int migrate_vma_collect_pmd(pmd_t struct migrate_vma *migrate = walk->private; struct vm_area_struct *vma = walk->vma; struct mm_struct *mm = vma->vm_mm; - unsigned long addr = start, unmapped = 0; + unsigned long addr = start; spinlock_t *ptl; pte_t *ptep; @@ -193,11 +194,10 @@ again: bool anon_exclusive; pte_t swp_pte; + flush_cache_page(vma, addr, pte_pfn(*ptep)); + pte = ptep_clear_flush(vma, addr, ptep); anon_exclusive = PageAnon(page) && PageAnonExclusive(page); if (anon_exclusive) { - flush_cache_page(vma, addr, pte_pfn(*ptep)); - ptep_clear_flush(vma, addr, ptep); - if (page_try_share_anon_rmap(page)) { set_pte_at(mm, addr, ptep, pte); unlock_page(page); @@ -205,12 +205,14 @@ again: mpfn = 0; goto next; } - } else { - ptep_get_and_clear(mm, addr, ptep); } migrate->cpages++; + /* Set the dirty flag on the folio now the pte is gone. */ + if (pte_dirty(pte)) + folio_mark_dirty(page_folio(page)); + /* Setup special migration page table entry */ if (mpfn & MIGRATE_PFN_WRITE) entry = make_writable_migration_entry( @@ -242,9 +244,6 @@ again: */ page_remove_rmap(page, vma, false); put_page(page); - - if (pte_present(pte)) - unmapped++; } else { put_page(page); mpfn = 0; @@ -257,10 +256,6 @@ next: arch_leave_lazy_mmu_mode(); pte_unmap_unlock(ptep - 1, ptl); - /* Only flush the TLB if we actually modified any entries */ - if (unmapped) - flush_tlb_range(walk->vma, start, end); - return 0; } _ Patches currently in -mm which might be from apopple@nvidia.com are mm-migrate_devicec-copy-pte-dirty-bit-to-page.patch mm-gupc-simplify-and-fix-check_and_migrate_movable_pages-return-codes.patch