diff options
Diffstat (limited to 'mm/memory.c')
| -rw-r--r-- | mm/memory.c | 43 |
1 files changed, 12 insertions, 31 deletions
diff --git a/mm/memory.c b/mm/memory.c index a8430ff..532a55b 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -1174,41 +1174,22 @@ no_page: pte_unmap_unlock(ptep, ptl); if (!pte_none(pte)) return page; - /* Fall through to ZERO_PAGE handling */ + no_page_table: /* * When core dumping an enormous anonymous area that nobody - * has touched so far, we don't want to allocate page tables. + * has touched so far, we don't want to allocate unnecessary pages or + * page tables. Return error instead of NULL to skip handle_mm_fault, + * then get_dump_page() will return NULL to leave a hole in the dump. + * But we can only make this optimization where a hole would surely + * be zero-filled if handle_mm_fault() actually did handle it. */ - if (flags & FOLL_ANON) { - page = ZERO_PAGE(0); - if (flags & FOLL_GET) - get_page(page); - BUG_ON(flags & FOLL_WRITE); - } + if ((flags & FOLL_DUMP) && + (!vma->vm_ops || !vma->vm_ops->fault)) + return ERR_PTR(-EFAULT); return page; } -/* Can we do the FOLL_ANON optimization? */ -static inline int use_zero_page(struct vm_area_struct *vma) -{ - /* - * We don't want to optimize FOLL_ANON for make_pages_present() - * when it tries to page in a VM_LOCKED region. As to VM_SHARED, - * we want to get the page from the page tables to make sure - * that we serialize and update with any other user of that - * mapping. - */ - if (vma->vm_flags & (VM_LOCKED | VM_SHARED)) - return 0; - /* - * And if we have a fault routine, it's not an anonymous region. - */ - return !vma->vm_ops || !vma->vm_ops->fault; -} - - - int __get_user_pages(struct task_struct *tsk, struct mm_struct *mm, unsigned long start, int nr_pages, int flags, struct page **pages, struct vm_area_struct **vmas) @@ -1288,8 +1269,8 @@ int __get_user_pages(struct task_struct *tsk, struct mm_struct *mm, foll_flags = FOLL_TOUCH; if (pages) foll_flags |= FOLL_GET; - if (!write && use_zero_page(vma)) - foll_flags |= FOLL_ANON; + if (flags & GUP_FLAGS_DUMP) + foll_flags |= FOLL_DUMP; do { struct page *page; @@ -1446,7 +1427,7 @@ struct page *get_dump_page(unsigned long addr) struct page *page; if (__get_user_pages(current, current->mm, addr, 1, - GUP_FLAGS_FORCE, &page, &vma) < 1) + GUP_FLAGS_FORCE | GUP_FLAGS_DUMP, &page, &vma) < 1) return NULL; if (page == ZERO_PAGE(0)) { page_cache_release(page); |