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authorAlistair Popple <apopple@nvidia.com>2022-09-02 03:35:53 +0300
committerAndrew Morton <akpm@linux-foundation.org>2022-09-12 02:22:30 +0300
commitfd35ca3d12cc9922d7d9a35f934e72132dbc4853 (patch)
tree9be7a1a7712c0ae20321e50609b78a534b9df12a /mm
parenta3589e1d5fe39c3d9fdd291b111524b93d08bc32 (diff)
downloadlinux-fd35ca3d12cc9922d7d9a35f934e72132dbc4853.tar.xz
mm/migrate_device.c: copy pte dirty bit to page
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/dd48e4882ce859c295c1a77612f66d198b0403f9.1662078528.git-series.apopple@nvidia.com Fixes: 8c3328f1f36a ("mm/migrate: migrate_vma() unmap page from vma while collecting pages") Signed-off-by: Alistair Popple <apopple@nvidia.com> Acked-by: Peter Xu <peterx@redhat.com> Reviewed-by: "Huang, Ying" <ying.huang@intel.com> Reported-by: "Huang, Ying" <ying.huang@intel.com> Acked-by: David Hildenbrand <david@redhat.com> Cc: Alex Sierra <alex.sierra@amd.com> Cc: Ben Skeggs <bskeggs@redhat.com> Cc: Felix Kuehling <Felix.Kuehling@amd.com> Cc: huang ying <huang.ying.caritas@gmail.com> Cc: Jason Gunthorpe <jgg@nvidia.com> Cc: John Hubbard <jhubbard@nvidia.com> Cc: Karol Herbst <kherbst@redhat.com> Cc: Logan Gunthorpe <logang@deltatee.com> Cc: Lyude Paul <lyude@redhat.com> Cc: Matthew Wilcox <willy@infradead.org> Cc: Nadav Amit <nadav.amit@gmail.com> Cc: Paul Mackerras <paulus@ozlabs.org> Cc: Ralph Campbell <rcampbell@nvidia.com> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'mm')
-rw-r--r--mm/migrate_device.c9
1 files changed, 7 insertions, 2 deletions
diff --git a/mm/migrate_device.c b/mm/migrate_device.c
index 4cc849c3b54c..dbf6c7a7a7c9 100644
--- a/mm/migrate_device.c
+++ b/mm/migrate_device.c
@@ -7,6 +7,7 @@
#include <linux/export.h>
#include <linux/memremap.h>
#include <linux/migrate.h>
+#include <linux/mm.h>
#include <linux/mm_inline.h>
#include <linux/mmu_notifier.h>
#include <linux/oom.h>
@@ -196,7 +197,7 @@ again:
flush_cache_page(vma, addr, pte_pfn(*ptep));
anon_exclusive = PageAnon(page) && PageAnonExclusive(page);
if (anon_exclusive) {
- ptep_clear_flush(vma, addr, ptep);
+ pte = ptep_clear_flush(vma, addr, ptep);
if (page_try_share_anon_rmap(page)) {
set_pte_at(mm, addr, ptep, pte);
@@ -206,11 +207,15 @@ again:
goto next;
}
} else {
- ptep_get_and_clear(mm, addr, ptep);
+ pte = 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(