diff options
Diffstat (limited to 'arch/x86/mm/gup.c')
| -rw-r--r-- | arch/x86/mm/gup.c | 32 |
1 files changed, 30 insertions, 2 deletions
diff --git a/arch/x86/mm/gup.c b/arch/x86/mm/gup.c index 1680768d392c..d7db45bdfb3b 100644 --- a/arch/x86/mm/gup.c +++ b/arch/x86/mm/gup.c @@ -98,6 +98,20 @@ static inline int pte_allows_gup(unsigned long pteval, int write) } /* + * Return the compund head page with ref appropriately incremented, + * or NULL if that failed. + */ +static inline struct page *try_get_compound_head(struct page *page, int refs) +{ + struct page *head = compound_head(page); + if (WARN_ON_ONCE(page_ref_count(head) < 0)) + return NULL; + if (unlikely(!page_cache_add_speculative(head, refs))) + return NULL; + return head; +} + +/* * The performance critical leaf functions are made noinline otherwise gcc * inlines everything into a single function which results in too much * register pressure. @@ -112,7 +126,7 @@ static noinline int gup_pte_range(pmd_t pmd, unsigned long addr, ptep = pte_offset_map(&pmd, addr); do { pte_t pte = gup_get_pte(ptep); - struct page *page; + struct page *head, *page; /* Similar to the PMD case, NUMA hinting must take slow path */ if (pte_protnone(pte)) { @@ -138,7 +152,21 @@ static noinline int gup_pte_range(pmd_t pmd, unsigned long addr, } VM_BUG_ON(!pfn_valid(pte_pfn(pte))); page = pte_page(pte); - get_page(page); + + head = try_get_compound_head(page, 1); + if (!head) { + put_dev_pagemap(pgmap); + pte_unmap(ptep); + return 0; + } + + if (unlikely(pte_val(pte) != pte_val(*ptep))) { + put_page(head); + put_dev_pagemap(pgmap); + pte_unmap(ptep); + return 0; + } + put_dev_pagemap(pgmap); SetPageReferenced(page); pages[*nr] = page; |