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Commit 5fd4ca2d authored by Matthew Wilcox's avatar Matthew Wilcox Committed by Linus Torvalds
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mm: page cache: store only head pages in i_pages 

Transparent Huge Pages are currently stored in i_pages as pointers to
consecutive subpages.  This patch changes that to storing consecutive
pointers to the head page in preparation for storing huge pages more
efficiently in i_pages.

Large parts of this are "inspired" by Kirill's patch
https://lore.kernel.org/lkml/20170126115819.58875-2-kirill.shutemov@linux.intel.com/

[willy@infradead.org: fix swapcache pages]
  Link: http://lkml.kernel.org/r/20190324155441.GF10344@bombadil.infradead.org
[kirill@shutemov.name: hugetlb stores pages in page cache differently]
  Link: http://lkml.kernel.org/r/20190404134553.vuvhgmghlkiw2hgl@kshutemo-mobl1
Link: http://lkml.kernel.org/r/20190307153051.18815-1-willy@infradead.org


Signed-off-by: default avatarMatthew Wilcox <willy@infradead.org>
Acked-by: default avatarJan Kara <jack@suse.cz>
Reviewed-by: default avatarKirill Shutemov <kirill@shutemov.name>
Reviewed-and-tested-by: default avatarSong Liu <songliubraving@fb.com>
Tested-by: default avatarWilliam Kucharski <william.kucharski@oracle.com>
Reviewed-by: default avatarWilliam Kucharski <william.kucharski@oracle.com>
Tested-by: default avatarQian Cai <cai@lca.pw>
Cc: Hugh Dickins <hughd@google.com>
Cc: Song Liu <liu.song.a23@gmail.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent cefdca0a

include/linux/pagemap.h

+13 −0
Original line number Diff line number Diff line
@@ -333,6 +333,19 @@ static inline struct page *grab_cache_page_nowait(struct address_space *mapping, 
			mapping_gfp_mask(mapping));

}



static inline struct page *find_subpage(struct page *page, pgoff_t offset)

{

	unsigned long mask;



	if (PageHuge(page))

		return page;



	VM_BUG_ON_PAGE(PageTail(page), page);



	mask = (1UL << compound_order(page)) - 1;

	return page + (offset & mask);

}



struct page *find_get_entry(struct address_space *mapping, pgoff_t offset);

struct page *find_lock_entry(struct address_space *mapping, pgoff_t offset);

unsigned find_get_entries(struct address_space *mapping, pgoff_t start,

mm/filemap.c

+62 −97
Original line number Diff line number Diff line
@@ -279,11 +279,11 @@ EXPORT_SYMBOL(delete_from_page_cache); 
 * @pvec: pagevec with pages to delete

 *

 * The function walks over mapping->i_pages and removes pages passed in @pvec

 * from the mapping. The function expects @pvec to be sorted by page index.

 * from the mapping. The function expects @pvec to be sorted by page index

 * and is optimised for it to be dense.

 * It tolerates holes in @pvec (mapping entries at those indices are not

 * modified). The function expects only THP head pages to be present in the

 * @pvec and takes care to delete all corresponding tail pages from the

 * mapping as well.

 * @pvec.

 *

 * The function expects the i_pages lock to be held.

 */
@@ -292,40 +292,44 @@ static void page_cache_delete_batch(struct address_space *mapping, 
{

	XA_STATE(xas, &mapping->i_pages, pvec->pages[0]->index);

	int total_pages = 0;

	int i = 0, tail_pages = 0;

	int i = 0;

	struct page *page;



	mapping_set_update(&xas, mapping);

	xas_for_each(&xas, page, ULONG_MAX) {

		if (i >= pagevec_count(pvec) && !tail_pages)

		if (i >= pagevec_count(pvec))

			break;



		/* A swap/dax/shadow entry got inserted? Skip it. */

		if (xa_is_value(page))

			continue;

		if (!tail_pages) {

		/*

			 * Some page got inserted in our range? Skip it. We

			 * have our pages locked so they are protected from

			 * being removed.

		 * A page got inserted in our range? Skip it. We have our

		 * pages locked so they are protected from being removed.

		 * If we see a page whose index is higher than ours, it

		 * means our page has been removed, which shouldn't be

		 * possible because we're holding the PageLock.

		 */

		if (page != pvec->pages[i]) {

				VM_BUG_ON_PAGE(page->index >

						pvec->pages[i]->index, page);

			VM_BUG_ON_PAGE(page->index > pvec->pages[i]->index,

					page);

			continue;

		}



		WARN_ON_ONCE(!PageLocked(page));

			if (PageTransHuge(page) && !PageHuge(page))

				tail_pages = HPAGE_PMD_NR - 1;



		if (page->index == xas.xa_index)

			page->mapping = NULL;

		/* Leave page->index set: truncation lookup relies on it */



		/*

			 * Leave page->index set: truncation lookup relies

			 * upon it

		 * Move to the next page in the vector if this is a regular

		 * page or the index is of the last sub-page of this compound

		 * page.

		 */

		if (page->index + (1UL << compound_order(page)) - 1 ==

				xas.xa_index)

			i++;

		} else {

			VM_BUG_ON_PAGE(page->index + HPAGE_PMD_NR - tail_pages

					!= pvec->pages[i]->index, page);

			tail_pages--;

		}

		xas_store(&xas, NULL);

		total_pages++;

	}
@@ -1491,7 +1495,7 @@ EXPORT_SYMBOL(page_cache_prev_miss); 
struct page *find_get_entry(struct address_space *mapping, pgoff_t offset)

{

	XA_STATE(xas, &mapping->i_pages, offset);

	struct page *head, *page;

	struct page *page;



	rcu_read_lock();

repeat:
@@ -1506,25 +1510,19 @@ struct page *find_get_entry(struct address_space *mapping, pgoff_t offset) 
	if (!page || xa_is_value(page))

		goto out;



	head = compound_head(page);

	if (!page_cache_get_speculative(head))

	if (!page_cache_get_speculative(page))

		goto repeat;



	/* The page was split under us? */

	if (compound_head(page) != head) {

		put_page(head);

		goto repeat;

	}



	/*

	 * Has the page moved?

	 * Has the page moved or been split?

	 * This is part of the lockless pagecache protocol. See

	 * include/linux/pagemap.h for details.

	 */

	if (unlikely(page != xas_reload(&xas))) {

		put_page(head);

		put_page(page);

		goto repeat;

	}

	page = find_subpage(page, offset);

out:

	rcu_read_unlock();
@@ -1706,7 +1704,6 @@ unsigned find_get_entries(struct address_space *mapping, 


	rcu_read_lock();

	xas_for_each(&xas, page, ULONG_MAX) {

		struct page *head;

		if (xas_retry(&xas, page))

			continue;

		/*
@@ -1717,17 +1714,13 @@ unsigned find_get_entries(struct address_space *mapping, 
		if (xa_is_value(page))

			goto export;



		head = compound_head(page);

		if (!page_cache_get_speculative(head))

		if (!page_cache_get_speculative(page))

			goto retry;



		/* The page was split under us? */

		if (compound_head(page) != head)

			goto put_page;



		/* Has the page moved? */

		/* Has the page moved or been split? */

		if (unlikely(page != xas_reload(&xas)))

			goto put_page;

		page = find_subpage(page, xas.xa_index);



export:

		indices[ret] = xas.xa_index;
@@ -1736,7 +1729,7 @@ unsigned find_get_entries(struct address_space *mapping, 
			break;

		continue;

put_page:

		put_page(head);

		put_page(page);

retry:

		xas_reset(&xas);

	}
@@ -1778,33 +1771,27 @@ unsigned find_get_pages_range(struct address_space *mapping, pgoff_t *start, 


	rcu_read_lock();

	xas_for_each(&xas, page, end) {

		struct page *head;

		if (xas_retry(&xas, page))

			continue;

		/* Skip over shadow, swap and DAX entries */

		if (xa_is_value(page))

			continue;



		head = compound_head(page);

		if (!page_cache_get_speculative(head))

		if (!page_cache_get_speculative(page))

			goto retry;



		/* The page was split under us? */

		if (compound_head(page) != head)

			goto put_page;



		/* Has the page moved? */

		/* Has the page moved or been split? */

		if (unlikely(page != xas_reload(&xas)))

			goto put_page;



		pages[ret] = page;

		pages[ret] = find_subpage(page, xas.xa_index);

		if (++ret == nr_pages) {

			*start = xas.xa_index + 1;

			goto out;

		}

		continue;

put_page:

		put_page(head);

		put_page(page);

retry:

		xas_reset(&xas);

	}
@@ -1849,7 +1836,6 @@ unsigned find_get_pages_contig(struct address_space *mapping, pgoff_t index, 


	rcu_read_lock();

	for (page = xas_load(&xas); page; page = xas_next(&xas)) {

		struct page *head;

		if (xas_retry(&xas, page))

			continue;

		/*
@@ -1859,24 +1845,19 @@ unsigned find_get_pages_contig(struct address_space *mapping, pgoff_t index, 
		if (xa_is_value(page))

			break;



		head = compound_head(page);

		if (!page_cache_get_speculative(head))

		if (!page_cache_get_speculative(page))

			goto retry;



		/* The page was split under us? */

		if (compound_head(page) != head)

			goto put_page;



		/* Has the page moved? */

		/* Has the page moved or been split? */

		if (unlikely(page != xas_reload(&xas)))

			goto put_page;



		pages[ret] = page;

		pages[ret] = find_subpage(page, xas.xa_index);

		if (++ret == nr_pages)

			break;

		continue;

put_page:

		put_page(head);

		put_page(page);

retry:

		xas_reset(&xas);

	}
@@ -1912,7 +1893,6 @@ unsigned find_get_pages_range_tag(struct address_space *mapping, pgoff_t *index, 


	rcu_read_lock();

	xas_for_each_marked(&xas, page, end, tag) {

		struct page *head;

		if (xas_retry(&xas, page))

			continue;

		/*
@@ -1923,26 +1903,21 @@ unsigned find_get_pages_range_tag(struct address_space *mapping, pgoff_t *index, 
		if (xa_is_value(page))

			continue;



		head = compound_head(page);

		if (!page_cache_get_speculative(head))

		if (!page_cache_get_speculative(page))

			goto retry;



		/* The page was split under us? */

		if (compound_head(page) != head)

			goto put_page;



		/* Has the page moved? */

		/* Has the page moved or been split? */

		if (unlikely(page != xas_reload(&xas)))

			goto put_page;



		pages[ret] = page;

		pages[ret] = find_subpage(page, xas.xa_index);

		if (++ret == nr_pages) {

			*index = xas.xa_index + 1;

			goto out;

		}

		continue;

put_page:

		put_page(head);

		put_page(page);

retry:

		xas_reset(&xas);

	}
@@ -1991,7 +1966,6 @@ unsigned find_get_entries_tag(struct address_space *mapping, pgoff_t start, 


	rcu_read_lock();

	xas_for_each_marked(&xas, page, ULONG_MAX, tag) {

		struct page *head;

		if (xas_retry(&xas, page))

			continue;

		/*
@@ -2002,17 +1976,13 @@ unsigned find_get_entries_tag(struct address_space *mapping, pgoff_t start, 
		if (xa_is_value(page))

			goto export;



		head = compound_head(page);

		if (!page_cache_get_speculative(head))

		if (!page_cache_get_speculative(page))

			goto retry;



		/* The page was split under us? */

		if (compound_head(page) != head)

			goto put_page;



		/* Has the page moved? */

		/* Has the page moved or been split? */

		if (unlikely(page != xas_reload(&xas)))

			goto put_page;

		page = find_subpage(page, xas.xa_index);



export:

		indices[ret] = xas.xa_index;
@@ -2021,7 +1991,7 @@ unsigned find_get_entries_tag(struct address_space *mapping, pgoff_t start, 
			break;

		continue;

put_page:

		put_page(head);

		put_page(page);

retry:

		xas_reset(&xas);

	}
@@ -2691,7 +2661,7 @@ void filemap_map_pages(struct vm_fault *vmf, 
	pgoff_t last_pgoff = start_pgoff;

	unsigned long max_idx;

	XA_STATE(xas, &mapping->i_pages, start_pgoff);

	struct page *head, *page;

	struct page *page;



	rcu_read_lock();

	xas_for_each(&xas, page, end_pgoff) {
@@ -2700,24 +2670,19 @@ void filemap_map_pages(struct vm_fault *vmf, 
		if (xa_is_value(page))

			goto next;



		head = compound_head(page);



		/*

		 * Check for a locked page first, as a speculative

		 * reference may adversely influence page migration.

		 */

		if (PageLocked(head))

		if (PageLocked(page))

			goto next;

		if (!page_cache_get_speculative(head))

		if (!page_cache_get_speculative(page))

			goto next;



		/* The page was split under us? */

		if (compound_head(page) != head)

			goto skip;



		/* Has the page moved? */

		/* Has the page moved or been split? */

		if (unlikely(page != xas_reload(&xas)))

			goto skip;

		page = find_subpage(page, xas.xa_index);



		if (!PageUptodate(page) ||

				PageReadahead(page) ||

mm/huge_memory.c

+3 −0
Original line number Diff line number Diff line
@@ -2496,6 +2496,9 @@ static void __split_huge_page(struct page *page, struct list_head *list, 
			if (IS_ENABLED(CONFIG_SHMEM) && PageSwapBacked(head))

				shmem_uncharge(head->mapping->host, 1);

			put_page(head + i);

		} else if (!PageAnon(page)) {

			__xa_store(&head->mapping->i_pages, head[i].index,

					head + i, 0);

		}

	}

mm/khugepaged.c

+2 −2
Original line number Diff line number Diff line
@@ -1374,7 +1374,7 @@ static void collapse_shmem(struct mm_struct *mm, 
				result = SCAN_FAIL;

				goto xa_locked;

			}

			xas_store(&xas, new_page + (index % HPAGE_PMD_NR));

			xas_store(&xas, new_page);

			nr_none++;

			continue;

		}
@@ -1450,7 +1450,7 @@ static void collapse_shmem(struct mm_struct *mm, 
		list_add_tail(&page->lru, &pagelist);



		/* Finally, replace with the new page. */

		xas_store(&xas, new_page + (index % HPAGE_PMD_NR));

		xas_store(&xas, new_page);

		continue;

out_unlock:

		unlock_page(page);

mm/memfd.c

+2 −0
Original line number Diff line number Diff line
@@ -39,6 +39,7 @@ static void memfd_tag_pins(struct xa_state *xas) 
	xas_for_each(xas, page, ULONG_MAX) {

		if (xa_is_value(page))

			continue;

		page = find_subpage(page, xas->xa_index);

		if (page_count(page) - page_mapcount(page) > 1)

			xas_set_mark(xas, MEMFD_TAG_PINNED);
@@ -88,6 +89,7 @@ static int memfd_wait_for_pins(struct address_space *mapping) 
			bool clear = true;

			if (xa_is_value(page))

				continue;

			page = find_subpage(page, xas.xa_index);

			if (page_count(page) - page_mapcount(page) != 1) {

				/*

				 * On the last scan, we clean up all those tags