Commit 2f52578f authored by Matthew Wilcox (Oracle)'s avatar Matthew Wilcox (Oracle)
Browse files

mm/util: Add folio_mapping() and folio_file_mapping() 



These are the folio equivalent of page_mapping() and page_file_mapping().
Add an out-of-line page_mapping() wrapper around folio_mapping()
in order to prevent the page_folio() call from bloating every caller
of page_mapping().  Adjust page_file_mapping() and page_mapping_file()
to use folios internally.  Rename __page_file_mapping() to
swapcache_mapping() and change it to take a folio.

This ends up saving 122 bytes of text overall.  folio_mapping() is
45 bytes shorter than page_mapping() was, but the new page_mapping()
wrapper is 30 bytes.  The major reduction is a few bytes less in dozens
of nfs functions (which call page_file_mapping()).  Most of these appear
to be a slight change in gcc's register allocation decisions, which allow:

   48 8b 56 08         mov    0x8(%rsi),%rdx
   48 8d 42 ff         lea    -0x1(%rdx),%rax
   83 e2 01            and    $0x1,%edx
   48 0f 44 c6         cmove  %rsi,%rax

to become:

   48 8b 46 08         mov    0x8(%rsi),%rax
   48 8d 78 ff         lea    -0x1(%rax),%rdi
   a8 01               test   $0x1,%al
   48 0f 44 fe         cmove  %rsi,%rdi

for a reduction of a single byte.  Once the NFS client is converted to
use folios, this entire sequence will disappear.

Also add folio_mapping() documentation.

Signed-off-by: default avatarMatthew Wilcox (Oracle) <willy@infradead.org>
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>
parent 352b47a6

Documentation/core-api/mm-api.rst

+2 −0
Original line number Diff line number Diff line
@@ -101,3 +101,5 @@ More Memory Management Functions 
   :internal:

.. kernel-doc:: include/linux/page_ref.h

.. kernel-doc:: include/linux/mmzone.h

.. kernel-doc:: mm/util.c

   :functions: folio_mapping

include/linux/mm.h

+0 −14
Original line number Diff line number Diff line
@@ -1755,19 +1755,6 @@ void page_address_init(void); 


extern void *page_rmapping(struct page *page);

extern struct anon_vma *page_anon_vma(struct page *page);

extern struct address_space *page_mapping(struct page *page);



extern struct address_space *__page_file_mapping(struct page *);



static inline

struct address_space *page_file_mapping(struct page *page)

{

	if (unlikely(PageSwapCache(page)))

		return __page_file_mapping(page);



	return page->mapping;

}



extern pgoff_t __page_file_index(struct page *page);



/*
@@ -1782,7 +1769,6 @@ static inline pgoff_t page_index(struct page *page) 
}



bool page_mapped(struct page *page);

struct address_space *page_mapping(struct page *page);



/*

 * Return true only if the page has been allocated with

include/linux/pagemap.h

+33 −2
Original line number Diff line number Diff line
@@ -162,14 +162,45 @@ static inline void filemap_nr_thps_dec(struct address_space *mapping) 


void release_pages(struct page **pages, int nr);



struct address_space *page_mapping(struct page *);

struct address_space *folio_mapping(struct folio *);

struct address_space *swapcache_mapping(struct folio *);



/**

 * folio_file_mapping - Find the mapping this folio belongs to.

 * @folio: The folio.

 *

 * For folios which are in the page cache, return the mapping that this

 * page belongs to.  Folios in the swap cache return the mapping of the

 * swap file or swap device where the data is stored.  This is different

 * from the mapping returned by folio_mapping().  The only reason to

 * use it is if, like NFS, you return 0 from ->activate_swapfile.

 *

 * Do not call this for folios which aren't in the page cache or swap cache.

 */

static inline struct address_space *folio_file_mapping(struct folio *folio)

{

	if (unlikely(folio_test_swapcache(folio)))

		return swapcache_mapping(folio);



	return folio->mapping;

}



static inline struct address_space *page_file_mapping(struct page *page)

{

	return folio_file_mapping(page_folio(page));

}



/*

 * For file cache pages, return the address_space, otherwise return NULL

 */

static inline struct address_space *page_mapping_file(struct page *page)

{

	if (unlikely(PageSwapCache(page)))

	struct folio *folio = page_folio(page);



	if (unlikely(folio_test_swapcache(folio)))

		return NULL;

	return page_mapping(page);

	return folio_mapping(folio);

}



static inline bool page_cache_add_speculative(struct page *page, int count)

include/linux/swap.h

+6 −0
Original line number Diff line number Diff line
@@ -320,6 +320,12 @@ struct vma_swap_readahead { 
#endif

};



static inline swp_entry_t folio_swap_entry(struct folio *folio)

{

	swp_entry_t entry = { .val = page_private(&folio->page) };

	return entry;

}



/* linux/mm/workingset.c */

void workingset_age_nonresident(struct lruvec *lruvec, unsigned long nr_pages);

void *workingset_eviction(struct page *page, struct mem_cgroup *target_memcg);

mm/Makefile

+1 −1
Original line number Diff line number Diff line
@@ -46,7 +46,7 @@ mmu-$(CONFIG_MMU) += process_vm_access.o 
endif



obj-y			:= filemap.o mempool.o oom_kill.o fadvise.o \

			   maccess.o page-writeback.o \

			   maccess.o page-writeback.o folio-compat.o \

			   readahead.o swap.o truncate.o vmscan.o shmem.o \

			   util.o mmzone.o vmstat.o backing-dev.o \

			   mm_init.o percpu.o slab_common.o \