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>
diff --git a/mm/Makefile b/mm/Makefile
index fc60a40..d6c0042 100644
--- a/mm/Makefile
+++ b/mm/Makefile
@@ -46,7 +46,7 @@
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 \
diff --git a/mm/folio-compat.c b/mm/folio-compat.c
new file mode 100644
index 0000000..5e107aa
--- /dev/null
+++ b/mm/folio-compat.c
@@ -0,0 +1,13 @@
+/*
+ * Compatibility functions which bloat the callers too much to make inline.
+ * All of the callers of these functions should be converted to use folios
+ * eventually.
+ */
+
+#include <linux/pagemap.h>
+
+struct address_space *page_mapping(struct page *page)
+{
+ return folio_mapping(page_folio(page));
+}
+EXPORT_SYMBOL(page_mapping);
diff --git a/mm/swapfile.c b/mm/swapfile.c
index 22d10f7..e3dcaee 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -3534,13 +3534,13 @@ struct swap_info_struct *page_swap_info(struct page *page)
}
/*
- * out-of-line __page_file_ methods to avoid include hell.
+ * out-of-line methods to avoid include hell.
*/
-struct address_space *__page_file_mapping(struct page *page)
+struct address_space *swapcache_mapping(struct folio *folio)
{
- return page_swap_info(page)->swap_file->f_mapping;
+ return page_swap_info(&folio->page)->swap_file->f_mapping;
}
-EXPORT_SYMBOL_GPL(__page_file_mapping);
+EXPORT_SYMBOL_GPL(swapcache_mapping);
pgoff_t __page_file_index(struct page *page)
{
diff --git a/mm/util.c b/mm/util.c
index bacabe4..6c1fe9b 100644
--- a/mm/util.c
+++ b/mm/util.c
@@ -705,30 +705,36 @@ struct anon_vma *page_anon_vma(struct page *page)
return __page_rmapping(page);
}
-struct address_space *page_mapping(struct page *page)
+/**
+ * folio_mapping - Find the mapping where this folio is stored.
+ * @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 swap mapping
+ * this page is stored in (which is different from the mapping for the
+ * swap file or swap device where the data is stored).
+ *
+ * You can call this for folios which aren't in the swap cache or page
+ * cache and it will return NULL.
+ */
+struct address_space *folio_mapping(struct folio *folio)
{
struct address_space *mapping;
- page = compound_head(page);
-
/* This happens if someone calls flush_dcache_page on slab page */
- if (unlikely(PageSlab(page)))
+ if (unlikely(folio_test_slab(folio)))
return NULL;
- if (unlikely(PageSwapCache(page))) {
- swp_entry_t entry;
+ if (unlikely(folio_test_swapcache(folio)))
+ return swap_address_space(folio_swap_entry(folio));
- entry.val = page_private(page);
- return swap_address_space(entry);
- }
-
- mapping = page->mapping;
+ mapping = folio->mapping;
if ((unsigned long)mapping & PAGE_MAPPING_ANON)
return NULL;
return (void *)((unsigned long)mapping & ~PAGE_MAPPING_FLAGS);
}
-EXPORT_SYMBOL(page_mapping);
+EXPORT_SYMBOL(folio_mapping);
/* Slow path of page_mapcount() for compound pages */
int __page_mapcount(struct page *page)