Commit 9bf70167 authored by Matthew Wilcox (Oracle)'s avatar Matthew Wilcox (Oracle)
Browse files

mm/filemap: Add readahead_folio() 



The pointers stored in the page cache are folios, by definition.
This change comes with a behaviour change -- callers of readahead_folio()
are no longer required to put the page reference themselves.  This matches
how readpage works, rather than matching how readpages used to work.

Signed-off-by: default avatarMatthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
Reviewed-by: default avatarDavid Howells <dhowells@redhat.com>
Acked-by: default avatarVlastimil Babka <vbabka@suse.cz>
parent f705bf84

include/linux/pagemap.h

+39 −15
Original line number Diff line number Diff line
@@ -987,33 +987,57 @@ void page_cache_async_readahead(struct address_space *mapping, 
	page_cache_async_ra(&ractl, page, req_count);

}



static inline struct folio *__readahead_folio(struct readahead_control *ractl)

{

	struct folio *folio;



	BUG_ON(ractl->_batch_count > ractl->_nr_pages);

	ractl->_nr_pages -= ractl->_batch_count;

	ractl->_index += ractl->_batch_count;



	if (!ractl->_nr_pages) {

		ractl->_batch_count = 0;

		return NULL;

	}



	folio = xa_load(&ractl->mapping->i_pages, ractl->_index);

	VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio);

	ractl->_batch_count = folio_nr_pages(folio);



	return folio;

}



/**

 * readahead_page - Get the next page to read.

 * @rac: The current readahead request.

 * @ractl: The current readahead request.

 *

 * Context: The page is locked and has an elevated refcount.  The caller

 * should decreases the refcount once the page has been submitted for I/O

 * and unlock the page once all I/O to that page has completed.

 * Return: A pointer to the next page, or %NULL if we are done.

 */

static inline struct page *readahead_page(struct readahead_control *rac)

static inline struct page *readahead_page(struct readahead_control *ractl)

{

	struct page *page;

	struct folio *folio = __readahead_folio(ractl);



	BUG_ON(rac->_batch_count > rac->_nr_pages);

	rac->_nr_pages -= rac->_batch_count;

	rac->_index += rac->_batch_count;



	if (!rac->_nr_pages) {

		rac->_batch_count = 0;

		return NULL;

	return &folio->page;

}



	page = xa_load(&rac->mapping->i_pages, rac->_index);

	VM_BUG_ON_PAGE(!PageLocked(page), page);

	rac->_batch_count = thp_nr_pages(page);

/**

 * readahead_folio - Get the next folio to read.

 * @ractl: The current readahead request.

 *

 * Context: The folio is locked.  The caller should unlock the folio once

 * all I/O to that folio has completed.

 * Return: A pointer to the next folio, or %NULL if we are done.

 */

static inline struct folio *readahead_folio(struct readahead_control *ractl)

{

	struct folio *folio = __readahead_folio(ractl);



	return page;

	if (folio)

		folio_put(folio);

	return folio;

}



static inline unsigned int __readahead_batch(struct readahead_control *rac,