Commit b620f633 authored by Matthew Wilcox (Oracle)'s avatar Matthew Wilcox (Oracle)
Browse files

mm: Add folio_put() 



If we know we have a folio, we can call folio_put() instead of put_page()
and save the overhead of calling compound_head().  Also skips the
devmap checks.

This commit looks like it should be a no-op, but actually saves 684 bytes
of text with the distro-derived config that I'm testing.  Some functions
grow a little while others shrink.  I presume the compiler is making
different inlining decisions.

Signed-off-by: default avatarMatthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: default avatarZi Yan <ziy@nvidia.com>
Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
Acked-by: default avatarJeff Layton <jlayton@kernel.org>
Acked-by: default avatarKirill A. Shutemov <kirill.shutemov@linux.intel.com>
Acked-by: default avatarVlastimil Babka <vbabka@suse.cz>
Reviewed-by: default avatarWilliam Kucharski <william.kucharski@oracle.com>
Reviewed-by: default avatarDavid Howells <dhowells@redhat.com>
Acked-by: default avatarMike Rapoport <rppt@linux.ibm.com>
parent c24016ac

include/linux/mm.h

+28 −5
Original line number Diff line number Diff line
@@ -748,6 +748,11 @@ static inline int put_page_testzero(struct page *page) 
	return page_ref_dec_and_test(page);

}



static inline int folio_put_testzero(struct folio *folio)

{

	return put_page_testzero(&folio->page);

}



/*

 * Try to grab a ref unless the page has a refcount of zero, return false if

 * that is the case.
@@ -1247,9 +1252,28 @@ static inline __must_check bool try_get_page(struct page *page) 
	return true;

}



/**

 * folio_put - Decrement the reference count on a folio.

 * @folio: The folio.

 *

 * If the folio's reference count reaches zero, the memory will be

 * released back to the page allocator and may be used by another

 * allocation immediately.  Do not access the memory or the struct folio

 * after calling folio_put() unless you can be sure that it wasn't the

 * last reference.

 *

 * Context: May be called in process or interrupt context, but not in NMI

 * context.  May be called while holding a spinlock.

 */

static inline void folio_put(struct folio *folio)

{

	if (folio_put_testzero(folio))

		__put_page(&folio->page);

}



static inline void put_page(struct page *page)

{

	page = compound_head(page);

	struct folio *folio = page_folio(page);



	/*

	 * For devmap managed pages we need to catch refcount transition from
@@ -1257,13 +1281,12 @@ static inline void put_page(struct page *page) 
	 * need to inform the device driver through callback. See

	 * include/linux/memremap.h and HMM for details.

	 */

	if (page_is_devmap_managed(page)) {

		put_devmap_managed_page(page);

	if (page_is_devmap_managed(&folio->page)) {

		put_devmap_managed_page(&folio->page);

		return;

	}



	if (put_page_testzero(page))

		__put_page(page);

	folio_put(folio);

}



/*