Commit 503670ee authored by Vishal Moola (Oracle)'s avatar Vishal Moola (Oracle) Committed by Andrew Morton
Browse files

mm/gup.c: reorganize try_get_folio() 

try_get_folio() takes in a page, then chooses to do some folio operations
based on the flags (either FOLL_GET or FOLL_PIN).  We can rewrite this
function to be more purpose oriented.

After calling try_get_folio(), if neither FOLL_GET nor FOLL_PIN are set,
warn and fail.  If FOLL_GET is set we can return the result.  If FOLL_GET
is not set then FOLL_PIN is set, so we pin the folio.

This change assists with folio conversions, and makes the function more
readable.

Link: https://lkml.kernel.org/r/20230614021312.34085-5-vishal.moola@gmail.com


Signed-off-by: default avatarVishal Moola (Oracle) <vishal.moola@gmail.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent c9223a4a

mm/gup.c

+43 −43
Original line number Diff line number Diff line
@@ -124,13 +124,22 @@ static inline struct folio *try_get_folio(struct page *page, int refs) 
 */

struct folio *try_grab_folio(struct page *page, int refs, unsigned int flags)

{

	struct folio *folio;



	if (WARN_ON_ONCE((flags & (FOLL_GET | FOLL_PIN)) == 0))

		return NULL;



	if (unlikely(!(flags & FOLL_PCI_P2PDMA) && is_pci_p2pdma_page(page)))

		return NULL;



	folio = try_get_folio(page, refs);



	if (flags & FOLL_GET)

		return try_get_folio(page, refs);

	else if (flags & FOLL_PIN) {

		struct folio *folio;

		return folio;



	/* FOLL_PIN is set */

	if (!folio)

		return NULL;



	/*

	 * Can't do FOLL_LONGTERM + FOLL_PIN gup fast path if not in a
@@ -138,16 +147,11 @@ struct folio *try_grab_folio(struct page *page, int refs, unsigned int flags) 
	 * path.

	 */

	if (unlikely((flags & FOLL_LONGTERM) &&

			     !is_longterm_pinnable_page(page)))

			return NULL;



		/*

		 * CAUTION: Don't use compound_head() on the page before this

		 * point, the result won't be stable.

		 */

		folio = try_get_folio(page, refs);

		if (!folio)

		     !folio_is_longterm_pinnable(folio))) {

		if (!put_devmap_managed_page_refs(&folio->page, refs))

			folio_put_refs(folio, refs);

		return NULL;

	}



	/*

	 * When pinning a large folio, use an exact count to track it.
@@ -174,10 +178,6 @@ struct folio *try_grab_folio(struct page *page, int refs, unsigned int flags) 
	return folio;

}



	WARN_ON_ONCE(1);

	return NULL;

}



static void gup_put_folio(struct folio *folio, int refs, unsigned int flags)

{

	if (flags & FOLL_PIN) {