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charset="utf-8" folio split clears PG_has_hwpoisoned, but the flag should be preserved in after-split folios containing pages with PG_hwpoisoned flag if the folio is split to >0 order folios. Scan all pages in a to-be-split folio to determine which after-split folios need the flag. An alternatives is to change PG_has_hwpoisoned to PG_maybe_hwpoisoned to avoid the scan and set it on all after-split folios, but resulting false positive has undesirable negative impact. To remove false positive, caller of folio_test_has_hwpoisoned() and folio_contain_hwpoisoned_page() needs to do the scan. That might be causing a hassle for current and future callers and more costly than doing the scan in the split code. More details are discussed in [1]. It is OK that current implementation does not do this, because memory failure code always tries to split to order-0 folios and if a folio cannot be split to order-0, memory failure code either gives warnings or the split is not performed. Link: https://lore.kernel.org/all/CAHbLzkoOZm0PXxE9qwtF4gKR=3DcpRXrSrJ9V9Pm= 2DJexs985q4g@mail.gmail.com/ [1] Signed-off-by: Zi Yan --- mm/huge_memory.c | 28 +++++++++++++++++++++++++--- 1 file changed, 25 insertions(+), 3 deletions(-) diff --git a/mm/huge_memory.c b/mm/huge_memory.c index fc65ec3393d2..f3896c1f130f 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -3455,6 +3455,17 @@ bool can_split_folio(struct folio *folio, int caller= _pins, int *pextra_pins) caller_pins; } =20 +static bool page_range_has_hwpoisoned(struct page *first_page, long nr_pag= es) +{ + long i; + + for (i =3D 0; i < nr_pages; i++) + if (PageHWPoison(first_page + i)) + return true; + + return false; +} + /* * It splits @folio into @new_order folios and copies the @folio metadata = to * all the resulting folios. @@ -3462,22 +3473,32 @@ bool can_split_folio(struct folio *folio, int calle= r_pins, int *pextra_pins) static void __split_folio_to_order(struct folio *folio, int old_order, int new_order) { + /* Scan poisoned pages when split a poisoned folio to large folios */ + bool check_poisoned_pages =3D folio_test_has_hwpoisoned(folio) && + new_order !=3D 0; long new_nr_pages =3D 1 << new_order; long nr_pages =3D 1 << old_order; long i; =20 + folio_clear_has_hwpoisoned(folio); + + /* Check first new_nr_pages since the loop below skips them */ + if (check_poisoned_pages && + page_range_has_hwpoisoned(folio_page(folio, 0), new_nr_pages)) + folio_set_has_hwpoisoned(folio); /* * Skip the first new_nr_pages, since the new folio from them have all * the flags from the original folio. */ for (i =3D new_nr_pages; i < nr_pages; i +=3D new_nr_pages) { struct page *new_head =3D &folio->page + i; - /* * Careful: new_folio is not a "real" folio before we cleared PageTail. * Don't pass it around before clear_compound_head(). */ struct folio *new_folio =3D (struct folio *)new_head; + bool poisoned_new_folio =3D check_poisoned_pages && + page_range_has_hwpoisoned(new_head, new_nr_pages); =20 VM_BUG_ON_PAGE(atomic_read(&new_folio->_mapcount) !=3D -1, new_head); =20 @@ -3514,6 +3535,9 @@ static void __split_folio_to_order(struct folio *foli= o, int old_order, (1L << PG_dirty) | LRU_GEN_MASK | LRU_REFS_MASK)); =20 + if (poisoned_new_folio) + folio_set_has_hwpoisoned(new_folio); + new_folio->mapping =3D folio->mapping; new_folio->index =3D folio->index + i; =20 @@ -3600,8 +3624,6 @@ static int __split_unmapped_folio(struct folio *folio= , int new_order, int start_order =3D uniform_split ? new_order : old_order - 1; int split_order; =20 - folio_clear_has_hwpoisoned(folio); - /* * split to new_order one order at a time. For uniform split, * folio is split to new_order directly. --=20 2.51.0