[PATCH] mm: remove page_mapping()

[PATCH] mm: remove page_mapping()

[Matthew Wilcox (Oracle)]

All callers are now converted, delete this compatibility wrapper.
Also fix up some comments which referred to page_mapping.

Link: https://lkml.kernel.org/r/20240423225552.4113447-7-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: David Hildenbrand <david@redhat.com>
Cc: Eric Biggers <ebiggers@google.com>
Cc: Sidhartha Kumar <sidhartha.kumar@oracle.com>
---
 arch/arm/include/asm/cacheflush.h   |  2 +-
 arch/arm64/include/asm/cacheflush.h |  2 +-
 arch/mips/mm/cache.c                |  2 +-
 arch/sparc/mm/init_64.c             |  2 +-
 include/linux/buffer_head.h         |  2 +-
 include/linux/page-flags.h          | 23 ++++++++++++-----------
 include/linux/pagemap.h             |  1 -
 mm/folio-compat.c                   |  6 ------
 8 files changed, 17 insertions(+), 23 deletions(-)

diff --git a/arch/arm/include/asm/cacheflush.h b/arch/arm/include/asm/cacheflush.h
index 1075534b0a2e..8ed8b9a24efe 100644
--- a/arch/arm/include/asm/cacheflush.h
+++ b/arch/arm/include/asm/cacheflush.h
@@ -283,7 +283,7 @@ void flush_cache_pages(struct vm_area_struct *vma, unsigned long user_addr,
  * flush_dcache_page is used when the kernel has written to the page
  * cache page at virtual address page->virtual.
  *
- * If this page isn't mapped (ie, page_mapping == NULL), or it might
+ * If this page isn't mapped (ie, folio_mapping == NULL), or it might
  * have userspace mappings, then we _must_ always clean + invalidate
  * the dcache entries associated with the kernel mapping.
  *
diff --git a/arch/arm64/include/asm/cacheflush.h b/arch/arm64/include/asm/cacheflush.h
index fefac75fa009..28ab96e808ef 100644
--- a/arch/arm64/include/asm/cacheflush.h
+++ b/arch/arm64/include/asm/cacheflush.h
@@ -117,7 +117,7 @@ extern void copy_to_user_page(struct vm_area_struct *, struct page *,
  * flush_dcache_folio is used when the kernel has written to the page
  * cache page at virtual address page->virtual.
  *
- * If this page isn't mapped (ie, page_mapping == NULL), or it might
+ * If this page isn't mapped (ie, folio_mapping == NULL), or it might
  * have userspace mappings, then we _must_ always clean + invalidate
  * the dcache entries associated with the kernel mapping.
  *
diff --git a/arch/mips/mm/cache.c b/arch/mips/mm/cache.c
index df1ced4fc3b5..bf9a37c60e9f 100644
--- a/arch/mips/mm/cache.c
+++ b/arch/mips/mm/cache.c
@@ -112,7 +112,7 @@ void __flush_dcache_pages(struct page *page, unsigned int nr)
 	}
 
 	/*
-	 * We could delay the flush for the !page_mapping case too.  But that
+	 * We could delay the flush for the !folio_mapping case too.  But that
 	 * case is for exec env/arg pages and those are %99 certainly going to
 	 * get faulted into the tlb (and thus flushed) anyways.
 	 */
diff --git a/arch/sparc/mm/init_64.c b/arch/sparc/mm/init_64.c
index 00b247d924a9..53d7cb5bbffe 100644
--- a/arch/sparc/mm/init_64.c
+++ b/arch/sparc/mm/init_64.c
@@ -490,7 +490,7 @@ void flush_dcache_folio(struct folio *folio)
 		}
 		set_dcache_dirty(folio, this_cpu);
 	} else {
-		/* We could delay the flush for the !page_mapping
+		/* We could delay the flush for the !folio_mapping
 		 * case too.  But that case is for exec env/arg
 		 * pages and those are %99 certainly going to get
 		 * faulted into the tlb (and thus flushed) anyways.
diff --git a/include/linux/buffer_head.h b/include/linux/buffer_head.h
index e022e40b099e..14acf1bbe0ce 100644
--- a/include/linux/buffer_head.h
+++ b/include/linux/buffer_head.h
@@ -53,7 +53,7 @@ typedef void (bh_end_io_t)(struct buffer_head *bh, int uptodate);
  * filesystem and block layers.  Nowadays the basic I/O unit
  * is the bio, and buffer_heads are used for extracting block
  * mappings (via a get_block_t call), for tracking state within
- * a page (via a page_mapping) and for wrapping bio submission
+ * a folio (via a folio_mapping) and for wrapping bio submission
  * for backward compatibility reasons (e.g. submit_bh).
  */
 struct buffer_head {
diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
index 104078afe0b1..d1bdbaaccc96 100644
--- a/include/linux/page-flags.h
+++ b/include/linux/page-flags.h
@@ -655,27 +655,28 @@ PAGEFLAG_FALSE(VmemmapSelfHosted, vmemmap_self_hosted)
 #endif
 
 /*
- * On an anonymous page mapped into a user virtual memory area,
- * page->mapping points to its anon_vma, not to a struct address_space;
+ * On an anonymous folio mapped into a user virtual memory area,
+ * folio->mapping points to its anon_vma, not to a struct address_space;
  * with the PAGE_MAPPING_ANON bit set to distinguish it.  See rmap.h.
  *
  * On an anonymous page in a VM_MERGEABLE area, if CONFIG_KSM is enabled,
  * the PAGE_MAPPING_MOVABLE bit may be set along with the PAGE_MAPPING_ANON
- * bit; and then page->mapping points, not to an anon_vma, but to a private
+ * bit; and then folio->mapping points, not to an anon_vma, but to a private
  * structure which KSM associates with that merged page.  See ksm.h.
  *
  * PAGE_MAPPING_KSM without PAGE_MAPPING_ANON is used for non-lru movable
- * page and then page->mapping points to a struct movable_operations.
+ * page and then folio->mapping points to a struct movable_operations.
  *
- * Please note that, confusingly, "page_mapping" refers to the inode
- * address_space which maps the page from disk; whereas "page_mapped"
- * refers to user virtual address space into which the page is mapped.
+ * Please note that, confusingly, "folio_mapping" refers to the inode
+ * address_space which maps the folio from disk; whereas "folio_mapped"
+ * refers to user virtual address space into which the folio is mapped.
  *
  * For slab pages, since slab reuses the bits in struct page to store its
- * internal states, the page->mapping does not exist as such, nor do these
- * flags below.  So in order to avoid testing non-existent bits, please
- * make sure that PageSlab(page) actually evaluates to false before calling
- * the following functions (e.g., PageAnon).  See mm/slab.h.
+ * internal states, the folio->mapping does not exist as such, nor do
+ * these flags below.  So in order to avoid testing non-existent bits,
+ * please make sure that folio_test_slab(folio) actually evaluates to
+ * false before calling the following functions (e.g., folio_test_anon).
+ * See mm/slab.h.
  */
 #define PAGE_MAPPING_ANON	0x1
 #define PAGE_MAPPING_MOVABLE	0x2
diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index 3d69589c00a4..e8ac3b910746 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -401,7 +401,6 @@ static inline void filemap_nr_thps_dec(struct address_space *mapping)
 #endif
 }
 
-struct address_space *page_mapping(struct page *);
 struct address_space *folio_mapping(struct folio *);
 struct address_space *swapcache_mapping(struct folio *);
 
diff --git a/mm/folio-compat.c b/mm/folio-compat.c
index f31e0ce65b11..f05906006b3c 100644
--- a/mm/folio-compat.c
+++ b/mm/folio-compat.c
@@ -10,12 +10,6 @@
 #include <linux/swap.h>
 #include "internal.h"
 
-struct address_space *page_mapping(struct page *page)
-{
-	return folio_mapping(page_folio(page));
-}
-EXPORT_SYMBOL(page_mapping);
-
 void unlock_page(struct page *page)
 {
 	return folio_unlock(page_folio(page));
-- 
2.43.0

Re: [PATCH] mm: remove page_mapping()

[Matthew Wilcox]

On Fri, May 24, 2024 at 07:18:10PM +0100, Matthew Wilcox (Oracle) wrote:
> All callers are now converted, delete this compatibility wrapper.
> Also fix up some comments which referred to page_mapping.
> 
> Link: https://lkml.kernel.org/r/20240423225552.4113447-7-willy@infradead.org
> Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
> Reviewed-by: David Hildenbrand <david@redhat.com>
> Cc: Eric Biggers <ebiggers@google.com>
> Cc: Sidhartha Kumar <sidhartha.kumar@oracle.com>

For context, an earlier version of this patch was sent, but had an
unnoticed dependency on a patch in the s390 tree.  To avoid unnecessary
dependencies, we agreed to drop this patch and reapply it after s390
had sent their pull request.

I added the comment changes while reviewing the state of the tree.