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mm/migrate: set swap entry values of THP tail pages properly.
The tail pages in a THP can have swap entry information stored in their private field. When migrating to a new page, all tail pages of the new page need to update ->private to avoid future data corruption. This fix is stable-only, since after commit07e09c483c
("mm/huge_memory: work on folio->swap instead of page->private when splitting folio"), subpages of a swapcached THP no longer requires the maintenance. Adding THPs to the swapcache was introduced in commit38d8b4e6bd
("mm, THP, swap: delay splitting THP during swap out"), where each subpage of a THP added to the swapcache had its own swapcache entry and required the ->private field to point to the correct swapcache entry. Later, when THP migration functionality was implemented in commit616b837153
("mm: thp: enable thp migration in generic path"), it initially did not handle the subpages of swapcached THPs, failing to update their ->private fields or replace the subpage pointers in the swapcache. Subsequently, commite71769ae52
("mm: enable thp migration for shmem thp") addressed the swapcache update aspect. This patch fixes the update of subpage ->private fields. Closes: https://lore.kernel.org/linux-mm/1707814102-22682-1-git-send-email-quic_charante@quicinc.com/ Fixes:616b837153
("mm: thp: enable thp migration in generic path") Signed-off-by: Zi Yan <ziy@nvidia.com> Acked-by: David Hildenbrand <david@redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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1 changed files with 5 additions and 1 deletions
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@ -424,8 +424,12 @@ int migrate_page_move_mapping(struct address_space *mapping,
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if (PageSwapBacked(page)) {
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if (PageSwapBacked(page)) {
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__SetPageSwapBacked(newpage);
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__SetPageSwapBacked(newpage);
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if (PageSwapCache(page)) {
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if (PageSwapCache(page)) {
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int i;
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SetPageSwapCache(newpage);
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SetPageSwapCache(newpage);
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set_page_private(newpage, page_private(page));
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for (i = 0; i < (1 << compound_order(page)); i++)
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set_page_private(newpage + i,
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page_private(page + i));
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}
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}
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} else {
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} else {
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VM_BUG_ON_PAGE(PageSwapCache(page), page);
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VM_BUG_ON_PAGE(PageSwapCache(page), page);
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