From 503670ee6d0670e114a66b8cf2bcd3f71f53c2f7 Mon Sep 17 00:00:00 2001 From: "Vishal Moola (Oracle)" Date: Tue, 13 Jun 2023 19:13:11 -0700 Subject: [PATCH] mm/gup.c: reorganize try_get_folio() try_get_folio() takes in a page, then chooses to do some folio operations based on the flags (either FOLL_GET or FOLL_PIN). We can rewrite this function to be more purpose oriented. After calling try_get_folio(), if neither FOLL_GET nor FOLL_PIN are set, warn and fail. If FOLL_GET is set we can return the result. If FOLL_GET is not set then FOLL_PIN is set, so we pin the folio. This change assists with folio conversions, and makes the function more readable. Link: https://lkml.kernel.org/r/20230614021312.34085-5-vishal.moola@gmail.com Signed-off-by: Vishal Moola (Oracle) Cc: Matthew Wilcox (Oracle) Signed-off-by: Andrew Morton --- mm/gup.c | 86 ++++++++++++++++++++++++++++++++-------------------------------- 1 file changed, 43 insertions(+), 43 deletions(-) diff --git a/mm/gup.c b/mm/gup.c index 38986e5..ce14d4d 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -124,58 +124,58 @@ retry: */ struct folio *try_grab_folio(struct page *page, int refs, unsigned int flags) { + struct folio *folio; + + if (WARN_ON_ONCE((flags & (FOLL_GET | FOLL_PIN)) == 0)) + return NULL; + if (unlikely(!(flags & FOLL_PCI_P2PDMA) && is_pci_p2pdma_page(page))) return NULL; - if (flags & FOLL_GET) - return try_get_folio(page, refs); - else if (flags & FOLL_PIN) { - struct folio *folio; + folio = try_get_folio(page, refs); - /* - * Can't do FOLL_LONGTERM + FOLL_PIN gup fast path if not in a - * right zone, so fail and let the caller fall back to the slow - * path. - */ - if (unlikely((flags & FOLL_LONGTERM) && - !is_longterm_pinnable_page(page))) - return NULL; + if (flags & FOLL_GET) + return folio; - /* - * CAUTION: Don't use compound_head() on the page before this - * point, the result won't be stable. - */ - folio = try_get_folio(page, refs); - if (!folio) - return NULL; + /* FOLL_PIN is set */ + if (!folio) + return NULL; - /* - * When pinning a large folio, use an exact count to track it. - * - * However, be sure to *also* increment the normal folio - * refcount field at least once, so that the folio really - * is pinned. That's why the refcount from the earlier - * try_get_folio() is left intact. - */ - if (folio_test_large(folio)) - atomic_add(refs, &folio->_pincount); - else - folio_ref_add(folio, - refs * (GUP_PIN_COUNTING_BIAS - 1)); - /* - * Adjust the pincount before re-checking the PTE for changes. - * This is essentially a smp_mb() and is paired with a memory - * barrier in page_try_share_anon_rmap(). - */ - smp_mb__after_atomic(); + /* + * Can't do FOLL_LONGTERM + FOLL_PIN gup fast path if not in a + * right zone, so fail and let the caller fall back to the slow + * path. + */ + if (unlikely((flags & FOLL_LONGTERM) && + !folio_is_longterm_pinnable(folio))) { + if (!put_devmap_managed_page_refs(&folio->page, refs)) + folio_put_refs(folio, refs); + return NULL; + } - node_stat_mod_folio(folio, NR_FOLL_PIN_ACQUIRED, refs); + /* + * When pinning a large folio, use an exact count to track it. + * + * However, be sure to *also* increment the normal folio + * refcount field at least once, so that the folio really + * is pinned. That's why the refcount from the earlier + * try_get_folio() is left intact. + */ + if (folio_test_large(folio)) + atomic_add(refs, &folio->_pincount); + else + folio_ref_add(folio, + refs * (GUP_PIN_COUNTING_BIAS - 1)); + /* + * Adjust the pincount before re-checking the PTE for changes. + * This is essentially a smp_mb() and is paired with a memory + * barrier in page_try_share_anon_rmap(). + */ + smp_mb__after_atomic(); - return folio; - } + node_stat_mod_folio(folio, NR_FOLL_PIN_ACQUIRED, refs); - WARN_ON_ONCE(1); - return NULL; + return folio; } static void gup_put_folio(struct folio *folio, int refs, unsigned int flags) -- 2.7.4