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Commit a0f7a756 authored by Naoya Horiguchi's avatar Naoya Horiguchi Committed by Linus Torvalds
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mm/rmap.c: fix pgoff calculation to handle hugepage correctly 



I triggered VM_BUG_ON() in vma_address() when I tried to migrate an
anonymous hugepage with mbind() in the kernel v3.16-rc3.  This is
because pgoff's calculation in rmap_walk_anon() fails to consider
compound_order() only to have an incorrect value.

This patch introduces page_to_pgoff(), which gets the page's offset in
PAGE_CACHE_SIZE.

Kirill pointed out that page cache tree should natively handle
hugepages, and in order to make hugetlbfs fit it, page->index of
hugetlbfs page should be in PAGE_CACHE_SIZE.  This is beyond this patch,
but page_to_pgoff() contains the point to be fixed in a single function.

Signed-off-by: default avatarNaoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Acked-by: default avatarKirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Hillf Danton <dhillf@gmail.com>
Cc: Naoya Horiguchi <nao.horiguchi@gmail.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent aed8adb7

include/linux/pagemap.h

+12 −0
Original line number Diff line number Diff line
@@ -398,6 +398,18 @@ static inline struct page *read_mapping_page(struct address_space *mapping, 
	return read_cache_page(mapping, index, filler, data);

}



/*

 * Get the offset in PAGE_SIZE.

 * (TODO: hugepage should have ->index in PAGE_SIZE)

 */

static inline pgoff_t page_to_pgoff(struct page *page)

{

	if (unlikely(PageHeadHuge(page)))

		return page->index << compound_order(page);

	else

		return page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);

}



/*

 * Return byte-offset into filesystem object for page.

 */

mm/memory-failure.c

+2 −2
Original line number Diff line number Diff line
@@ -435,7 +435,7 @@ static void collect_procs_anon(struct page *page, struct list_head *to_kill, 
	if (av == NULL)	/* Not actually mapped anymore */

		return;



	pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);

	pgoff = page_to_pgoff(page);

	read_lock(&tasklist_lock);

	for_each_process (tsk) {

		struct anon_vma_chain *vmac;
@@ -469,7 +469,7 @@ static void collect_procs_file(struct page *page, struct list_head *to_kill, 
	mutex_lock(&mapping->i_mmap_mutex);

	read_lock(&tasklist_lock);

	for_each_process(tsk) {

		pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);

		pgoff_t pgoff = page_to_pgoff(page);

		struct task_struct *t = task_early_kill(tsk, force_early);



		if (!t)

mm/rmap.c

+3 −7
Original line number Diff line number Diff line
@@ -517,11 +517,7 @@ void page_unlock_anon_vma_read(struct anon_vma *anon_vma) 
static inline unsigned long

__vma_address(struct page *page, struct vm_area_struct *vma)

{

	pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);



	if (unlikely(is_vm_hugetlb_page(vma)))

		pgoff = page->index << huge_page_order(page_hstate(page));



	pgoff_t pgoff = page_to_pgoff(page);

	return vma->vm_start + ((pgoff - vma->vm_pgoff) << PAGE_SHIFT);

}
@@ -1639,7 +1635,7 @@ static struct anon_vma *rmap_walk_anon_lock(struct page *page, 
static int rmap_walk_anon(struct page *page, struct rmap_walk_control *rwc)

{

	struct anon_vma *anon_vma;

	pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);

	pgoff_t pgoff = page_to_pgoff(page);

	struct anon_vma_chain *avc;

	int ret = SWAP_AGAIN;
@@ -1680,7 +1676,7 @@ static int rmap_walk_anon(struct page *page, struct rmap_walk_control *rwc) 
static int rmap_walk_file(struct page *page, struct rmap_walk_control *rwc)

{

	struct address_space *mapping = page->mapping;

	pgoff_t pgoff = page->index << compound_order(page);

	pgoff_t pgoff = page_to_pgoff(page);

	struct vm_area_struct *vma;

	int ret = SWAP_AGAIN;