Commit f57e88a8 authored by Hugh Dickins's avatar Hugh Dickins Committed by Linus Torvalds
Browse files

[PATCH] unpaged: ZERO_PAGE in VM_UNPAGED 



It's strange enough to be looking out for anonymous pages in VM_UNPAGED areas,
let's not insert the ZERO_PAGE there - though whether it would matter will
depend on what we decide about ZERO_PAGE refcounting.

But whereas do_anonymous_page may (exceptionally) be called on a VM_UNPAGED
area, do_no_page should never be: just BUG_ON.

Signed-off-by: default avatarHugh Dickins <hugh@veritas.com>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent ee498ed7

drivers/char/mem.c

+1 −1
Original line number Diff line number Diff line
@@ -591,7 +591,7 @@ static inline size_t read_zero_pagealigned(char __user * buf, size_t size) 


		if (vma->vm_start > addr || (vma->vm_flags & VM_WRITE) == 0)

			goto out_up;

		if (vma->vm_flags & (VM_SHARED | VM_HUGETLB))

		if (vma->vm_flags & (VM_SHARED | VM_HUGETLB | VM_UNPAGED))

			break;

		count = vma->vm_end - addr;

		if (count > size)

mm/memory.c

+12 −2
Original line number Diff line number Diff line
@@ -1812,7 +1812,16 @@ static int do_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma, 
	spinlock_t *ptl;

	pte_t entry;



	if (write_access) {

	/*

	 * A VM_UNPAGED vma will normally be filled with present ptes

	 * by remap_pfn_range, and never arrive here; but it might have

	 * holes, or if !VM_DONTEXPAND, mremap might have expanded it.

	 * It's weird enough handling anon pages in unpaged vmas, we do

	 * not want to worry about ZERO_PAGEs too (it may or may not

	 * matter if their counts wrap): just give them anon pages.

	 */



	if (write_access || (vma->vm_flags & VM_UNPAGED)) {

		/* Allocate our own private page. */

		pte_unmap(page_table);
@@ -1887,6 +1896,7 @@ static int do_no_page(struct mm_struct *mm, struct vm_area_struct *vma, 
	int anon = 0;



	pte_unmap(page_table);

	BUG_ON(vma->vm_flags & VM_UNPAGED);



	if (vma->vm_file) {

		mapping = vma->vm_file->f_mapping;
@@ -1962,7 +1972,7 @@ retry: 
			inc_mm_counter(mm, anon_rss);

			lru_cache_add_active(new_page);

			page_add_anon_rmap(new_page, vma, address);

		} else if (!(vma->vm_flags & VM_UNPAGED)) {

		} else {

			inc_mm_counter(mm, file_rss);

			page_add_file_rmap(new_page);

		}

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