mm: add FOLL_MLOCK follow_page flag. (110d74a9) · Commits · 戴 / test

include/linux/mm.h

+1 −0

Original line number	Diff line number	Diff line
		@@ -1415,6 +1415,7 @@ struct page follow_page(struct vm_area_struct , unsigned long address,
		#define FOLL_GET 0x04 /* do get_page on page */
		#define FOLL_DUMP 0x08 /* give error on hole if it would be zero */
		#define FOLL_FORCE 0x10 /* get_user_pages read/write w/o permission */
		#define FOLL_MLOCK 0x40 /* mark page as mlocked */

		typedef int (pte_fn_t)(pte_t pte, pgtable_t token, unsigned long addr,
		void *data);

mm/memory.c

+22 −0

Original line number	Diff line number	Diff line
		@@ -1310,6 +1310,28 @@ struct page follow_page(struct vm_area_struct vma, unsigned long address,
		*/
		mark_page_accessed(page);
		}
		if (flags & FOLL_MLOCK) {
		/*
		* The preliminary mapping check is mainly to avoid the
		* pointless overhead of lock_page on the ZERO_PAGE
		* which might bounce very badly if there is contention.
		*
		* If the page is already locked, we don't need to
		* handle it now - vmscan will handle it later if and
		* when it attempts to reclaim the page.
		*/
		if (page->mapping && trylock_page(page)) {
		lru_add_drain(); /* push cached pages to LRU */
		/*
		* Because we lock page here and migration is
		* blocked by the pte's page reference, we need
		* only check for file-cache page truncation.
		*/
		if (page->mapping)
		mlock_vma_page(page);
		unlock_page(page);
		}
		}
		unlock:
		pte_unmap_unlock(ptep, ptl);
		out:

mm/mlock.c

+5 −60

Original line number	Diff line number	Diff line
		@@ -159,10 +159,9 @@ static long __mlock_vma_pages_range(struct vm_area_struct *vma,
		{
		struct mm_struct *mm = vma->vm_mm;
		unsigned long addr = start;
		struct page pages[16]; / 16 gives a reasonable batch */
		int nr_pages = (end - start) / PAGE_SIZE;
		int ret = 0;
		int gup_flags;
		int ret;

		VM_BUG_ON(start & ~PAGE_MASK);
		VM_BUG_ON(end & ~PAGE_MASK);
		@@ -170,7 +169,7 @@ static long __mlock_vma_pages_range(struct vm_area_struct *vma,
		VM_BUG_ON(end > vma->vm_end);
		VM_BUG_ON(!rwsem_is_locked(&mm->mmap_sem));

		gup_flags = FOLL_TOUCH \| FOLL_GET;
		gup_flags = FOLL_TOUCH \| FOLL_MLOCK;
		/*
		* We want to touch writable mappings with a write fault in order
		* to break COW, except for shared mappings because these don't COW
		@@ -185,63 +184,9 @@ static long __mlock_vma_pages_range(struct vm_area_struct *vma,
		nr_pages--;
		}

		while (nr_pages > 0) {
		int i;

		cond_resched();

		/*
		* get_user_pages makes pages present if we are
		* setting mlock. and this extra reference count will
		* disable migration of this page. However, page may
		* still be truncated out from under us.
		*/
		ret = __get_user_pages(current, mm, addr,
		min_t(int, nr_pages, ARRAY_SIZE(pages)),
		gup_flags, pages, NULL);
		/*
		* This can happen for, e.g., VM_NONLINEAR regions before
		* a page has been allocated and mapped at a given offset,
		* or for addresses that map beyond end of a file.
		* We'll mlock the pages if/when they get faulted in.
		*/
		if (ret < 0)
		break;

		lru_add_drain(); /* push cached pages to LRU */

		for (i = 0; i < ret; i++) {
		struct page *page = pages[i];

		if (page->mapping) {
		/*
		* That preliminary check is mainly to avoid
		* the pointless overhead of lock_page on the
		* ZERO_PAGE: which might bounce very badly if
		* there is contention. However, we're still
		* dirtying its cacheline with get/put_page:
		* we'll add another __get_user_pages flag to
		* avoid it if that case turns out to matter.
		*/
		lock_page(page);
		/*
		* Because we lock page here and migration is
		* blocked by the elevated reference, we need
		* only check for file-cache page truncation.
		*/
		if (page->mapping)
		mlock_vma_page(page);
		unlock_page(page);
		}
		put_page(page); /* ref from get_user_pages() */
		}

		addr += ret * PAGE_SIZE;
		nr_pages -= ret;
		ret = 0;
		}

		return ret; /* 0 or negative error code */
		ret = __get_user_pages(current, mm, addr, nr_pages, gup_flags,
		NULL, NULL);
		return max(ret, 0); /* 0 or negative error code */
		}

		/*

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