Commit be0ced5e authored by Matthew Wilcox (Oracle)'s avatar Matthew Wilcox (Oracle)
Browse files

filemap: Add filemap_get_folios() 



This is the equivalent of find_get_pages() but fills a folio_batch
instead of an array of pages.

Signed-off-by: default avatarMatthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
Acked-by: default avatarChristian Brauner (Microsoft) <brauner@kernel.org>
parent 2bb876b5

include/linux/pagemap.h

+2 −0
Original line number Diff line number Diff line
@@ -718,6 +718,8 @@ static inline struct page *find_subpage(struct page *head, pgoff_t index) 
	return head + (index & (thp_nr_pages(head) - 1));

}



unsigned filemap_get_folios(struct address_space *mapping, pgoff_t *start,

		pgoff_t end, struct folio_batch *fbatch);

unsigned find_get_pages_range(struct address_space *mapping, pgoff_t *start,

			pgoff_t end, unsigned int nr_pages,

			struct page **pages);

mm/filemap.c

+59 −0
Original line number Diff line number Diff line
@@ -2127,6 +2127,65 @@ unsigned find_lock_entries(struct address_space *mapping, pgoff_t start, 
	return folio_batch_count(fbatch);

}



/**

 * filemap_get_folios - Get a batch of folios

 * @mapping:	The address_space to search

 * @start:	The starting page index

 * @end:	The final page index (inclusive)

 * @fbatch:	The batch to fill.

 *

 * Search for and return a batch of folios in the mapping starting at

 * index @start and up to index @end (inclusive).  The folios are returned

 * in @fbatch with an elevated reference count.

 *

 * The first folio may start before @start; if it does, it will contain

 * @start.  The final folio may extend beyond @end; if it does, it will

 * contain @end.  The folios have ascending indices.  There may be gaps

 * between the folios if there are indices which have no folio in the

 * page cache.  If folios are added to or removed from the page cache

 * while this is running, they may or may not be found by this call.

 *

 * Return: The number of folios which were found.

 * We also update @start to index the next folio for the traversal.

 */

unsigned filemap_get_folios(struct address_space *mapping, pgoff_t *start,

		pgoff_t end, struct folio_batch *fbatch)

{

	XA_STATE(xas, &mapping->i_pages, *start);

	struct folio *folio;



	rcu_read_lock();

	while ((folio = find_get_entry(&xas, end, XA_PRESENT)) != NULL) {

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

		if (xa_is_value(folio))

			continue;

		if (!folio_batch_add(fbatch, folio)) {

			unsigned long nr = folio_nr_pages(folio);



			if (folio_test_hugetlb(folio))

				nr = 1;

			*start = folio->index + nr;

			goto out;

		}

	}



	/*

	 * We come here when there is no page beyond @end. We take care to not

	 * overflow the index @start as it confuses some of the callers. This

	 * breaks the iteration when there is a page at index -1 but that is

	 * already broken anyway.

	 */

	if (end == (pgoff_t)-1)

		*start = (pgoff_t)-1;

	else

		*start = end + 1;

out:

	rcu_read_unlock();



	return folio_batch_count(fbatch);

}

EXPORT_SYMBOL(filemap_get_folios);



static inline

bool folio_more_pages(struct folio *folio, pgoff_t index, pgoff_t max)

{