Commit c7bad633 authored by Matthew Wilcox (Oracle)'s avatar Matthew Wilcox (Oracle) Committed by Linus Torvalds
Browse files

mm/filemap: add helper for finding pages 

There is a lot of common code in find_get_entries(),
find_get_pages_range() and find_get_pages_range_tag().  Factor out
find_get_entry() which simplifies all three functions.

[willy@infradead.org: remove VM_BUG_ON_PAGE()]
  Link: https://lkml.kernel.org/r/20201124041507.28996-2-willy@infradead.orgLink: https://lkml.kernel.org/r/20201112212641.27837-7-willy@infradead.org



Signed-off-by: default avatarMatthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: default avatarJan Kara <jack@suse.cz>
Reviewed-by: default avatarWilliam Kucharski <william.kucharski@oracle.com>
Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
Cc: Dave Chinner <dchinner@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Yang Shi <yang.shi@linux.alibaba.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent bc5a3011

mm/filemap.c

+42 −55
Original line number Diff line number Diff line
@@ -1825,6 +1825,42 @@ struct page *pagecache_get_page(struct address_space *mapping, pgoff_t index, 
}

EXPORT_SYMBOL(pagecache_get_page);



static inline struct page *find_get_entry(struct xa_state *xas, pgoff_t max,

		xa_mark_t mark)

{

	struct page *page;



retry:

	if (mark == XA_PRESENT)

		page = xas_find(xas, max);

	else

		page = xas_find_marked(xas, max, mark);



	if (xas_retry(xas, page))

		goto retry;

	/*

	 * A shadow entry of a recently evicted page, a swap

	 * entry from shmem/tmpfs or a DAX entry.  Return it

	 * without attempting to raise page count.

	 */

	if (!page || xa_is_value(page))

		return page;



	if (!page_cache_get_speculative(page))

		goto reset;



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

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

		put_page(page);

		goto reset;

	}



	return page;

reset:

	xas_reset(xas);

	goto retry;

}



/**

 * find_get_entries - gang pagecache lookup

 * @mapping:	The address_space to search
@@ -1864,42 +1900,21 @@ unsigned find_get_entries(struct address_space *mapping, 
		return 0;



	rcu_read_lock();

	xas_for_each(&xas, page, ULONG_MAX) {

		if (xas_retry(&xas, page))

			continue;

		/*

		 * A shadow entry of a recently evicted page, a swap

		 * entry from shmem/tmpfs or a DAX entry.  Return it

		 * without attempting to raise page count.

		 */

		if (xa_is_value(page))

			goto export;



		if (!page_cache_get_speculative(page))

			goto retry;



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

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

			goto put_page;



	while ((page = find_get_entry(&xas, ULONG_MAX, XA_PRESENT))) {

		/*

		 * Terminate early on finding a THP, to allow the caller to

		 * handle it all at once; but continue if this is hugetlbfs.

		 */

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

		if (!xa_is_value(page) && PageTransHuge(page) &&

				!PageHuge(page)) {

			page = find_subpage(page, xas.xa_index);

			nr_entries = ret + 1;

		}

export:



		indices[ret] = xas.xa_index;

		entries[ret] = page;

		if (++ret == nr_entries)

			break;

		continue;

put_page:

		put_page(page);

retry:

		xas_reset(&xas);

	}

	rcu_read_unlock();

	return ret;
@@ -1938,30 +1953,16 @@ unsigned find_get_pages_range(struct address_space *mapping, pgoff_t *start, 
		return 0;



	rcu_read_lock();

	xas_for_each(&xas, page, end) {

		if (xas_retry(&xas, page))

			continue;

	while ((page = find_get_entry(&xas, end, XA_PRESENT))) {

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

		if (xa_is_value(page))

			continue;



		if (!page_cache_get_speculative(page))

			goto retry;



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

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

			goto put_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(page);

retry:

		xas_reset(&xas);

	}



	/*
@@ -2061,9 +2062,7 @@ unsigned find_get_pages_range_tag(struct address_space *mapping, pgoff_t *index, 
		return 0;



	rcu_read_lock();

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

		if (xas_retry(&xas, page))

			continue;

	while ((page = find_get_entry(&xas, end, tag))) {

		/*

		 * Shadow entries should never be tagged, but this iteration

		 * is lockless so there is a window for page reclaim to evict
@@ -2072,23 +2071,11 @@ unsigned find_get_pages_range_tag(struct address_space *mapping, pgoff_t *index, 
		if (xa_is_value(page))

			continue;



		if (!page_cache_get_speculative(page))

			goto retry;



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

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

			goto put_page;



		pages[ret] = page;

		if (++ret == nr_pages) {

			*index = page->index + thp_nr_pages(page);

			goto out;

		}

		continue;

put_page:

		put_page(page);

retry:

		xas_reset(&xas);

	}



	/*