linux/Documentation/core-api/mm-api.rst
Matthew Wilcox (Oracle) 2f52578f9c 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: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Acked-by: Jeff Layton <jlayton@kernel.org>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: William Kucharski <william.kucharski@oracle.com>
Reviewed-by: David Howells <dhowells@redhat.com>
2021-09-27 09:27:30 -04:00

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======================
Memory Management APIs
======================
User Space Memory Access
========================
.. kernel-doc:: arch/x86/include/asm/uaccess.h
:internal:
.. kernel-doc:: arch/x86/lib/usercopy_32.c
:export:
.. kernel-doc:: mm/gup.c
:functions: get_user_pages_fast
.. _mm-api-gfp-flags:
Memory Allocation Controls
==========================
.. kernel-doc:: include/linux/gfp.h
:internal:
.. kernel-doc:: include/linux/gfp.h
:doc: Page mobility and placement hints
.. kernel-doc:: include/linux/gfp.h
:doc: Watermark modifiers
.. kernel-doc:: include/linux/gfp.h
:doc: Reclaim modifiers
.. kernel-doc:: include/linux/gfp.h
:doc: Useful GFP flag combinations
The Slab Cache
==============
.. kernel-doc:: include/linux/slab.h
:internal:
.. kernel-doc:: mm/slab.c
:export:
.. kernel-doc:: mm/slab_common.c
:export:
.. kernel-doc:: mm/util.c
:functions: kfree_const kvmalloc_node kvfree
Virtually Contiguous Mappings
=============================
.. kernel-doc:: mm/vmalloc.c
:export:
File Mapping and Page Cache
===========================
.. kernel-doc:: mm/readahead.c
:export:
.. kernel-doc:: mm/filemap.c
:export:
.. kernel-doc:: mm/page-writeback.c
:export:
.. kernel-doc:: mm/truncate.c
:export:
.. kernel-doc:: include/linux/pagemap.h
:internal:
Memory pools
============
.. kernel-doc:: mm/mempool.c
:export:
DMA pools
=========
.. kernel-doc:: mm/dmapool.c
:export:
More Memory Management Functions
================================
.. kernel-doc:: mm/memory.c
:export:
.. kernel-doc:: mm/page_alloc.c
.. kernel-doc:: mm/mempolicy.c
.. kernel-doc:: include/linux/mm_types.h
:internal:
.. kernel-doc:: include/linux/mm_inline.h
.. kernel-doc:: include/linux/page-flags.h
.. kernel-doc:: include/linux/mm.h
:internal:
.. kernel-doc:: include/linux/page_ref.h
.. kernel-doc:: include/linux/mmzone.h
.. kernel-doc:: mm/util.c
:functions: folio_mapping