Commit 084a8990 authored by Matthew Wilcox's avatar Matthew Wilcox
Browse files

dax: Convert dax_layout_busy_page to XArray 



Instead of using a pagevec, just use the XArray iterators.  Add a
conditional rescheduling point which probably should have been there in
the original.

Signed-off-by: default avatarMatthew Wilcox <willy@infradead.org>
parent cfc93c6c

fs/dax.c

+21 −43
Original line number Diff line number Diff line
@@ -722,11 +722,10 @@ static void *grab_mapping_entry(struct address_space *mapping, pgoff_t index, 
 */

struct page *dax_layout_busy_page(struct address_space *mapping)

{

	pgoff_t	indices[PAGEVEC_SIZE];

	XA_STATE(xas, &mapping->i_pages, 0);

	void *entry;

	unsigned int scanned = 0;

	struct page *page = NULL;

	struct pagevec pvec;

	pgoff_t	index, end;

	unsigned i;



	/*

	 * In the 'limited' case get_user_pages() for dax is disabled.
@@ -737,13 +736,9 @@ struct page *dax_layout_busy_page(struct address_space *mapping) 
	if (!dax_mapping(mapping) || !mapping_mapped(mapping))

		return NULL;



	pagevec_init(&pvec);

	index = 0;

	end = -1;



	/*

	 * If we race get_user_pages_fast() here either we'll see the

	 * elevated page count in the pagevec_lookup and wait, or

	 * elevated page count in the iteration and wait, or

	 * get_user_pages_fast() will see that the page it took a reference

	 * against is no longer mapped in the page tables and bail to the

	 * get_user_pages() slow path.  The slow path is protected by
@@ -755,43 +750,26 @@ struct page *dax_layout_busy_page(struct address_space *mapping) 
	 */

	unmap_mapping_range(mapping, 0, 0, 1);



	while (index < end && pagevec_lookup_entries(&pvec, mapping, index,

				min(end - index, (pgoff_t)PAGEVEC_SIZE),

				indices)) {

		for (i = 0; i < pagevec_count(&pvec); i++) {

			struct page *pvec_ent = pvec.pages[i];

			void *entry;



			index = indices[i];

			if (index >= end)

				break;



			if (WARN_ON_ONCE(!xa_is_value(pvec_ent)))

	xas_lock_irq(&xas);

	xas_for_each(&xas, entry, ULONG_MAX) {

		if (WARN_ON_ONCE(!xa_is_value(entry)))

			continue;



			xa_lock_irq(&mapping->i_pages);

			entry = get_unlocked_mapping_entry(mapping, index, NULL);

		if (unlikely(dax_is_locked(entry)))

			entry = get_unlocked_entry(&xas);

		if (entry)

			page = dax_busy_page(entry);

			put_unlocked_mapping_entry(mapping, index, entry);

			xa_unlock_irq(&mapping->i_pages);

		put_unlocked_entry(&xas, entry);

		if (page)

			break;

		}



		/*

		 * We don't expect normal struct page entries to exist in our

		 * tree, but we keep these pagevec calls so that this code is

		 * consistent with the common pattern for handling pagevecs

		 * throughout the kernel.

		 */

		pagevec_remove_exceptionals(&pvec);

		pagevec_release(&pvec);

		index++;

		if (++scanned % XA_CHECK_SCHED)

			continue;



		if (page)

			break;

		xas_pause(&xas);

		xas_unlock_irq(&xas);

		cond_resched();

		xas_lock_irq(&xas);

	}

	xas_unlock_irq(&xas);

	return page;

}

EXPORT_SYMBOL_GPL(dax_layout_busy_page);