diff mbox series

[v5,04/38] mm: Add folio_flush_mapping()

Message ID 20230710204339.3554919-5-willy@infradead.org
State New
Headers
Series New page table range API |

Commit Message

Matthew Wilcox July 10, 2023, 8:43 p.m. UTC 
  This is the folio equivalent of page_mapping_file(), but rename it
to make it clear that it's very different from page_file_mapping().
Theoretically, there's nothing flush-only about it, but there are no
other users today, and I doubt there will be; it's almost always more
useful to know the swapfile's mapping or the swapcache's mapping.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Acked-by: Mike Rapoport (IBM) <rppt@kernel.org>
Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com>
---
 include/linux/pagemap.h | 26 +++++++++++++++++++++-----
 1 file changed, 21 insertions(+), 5 deletions(-)

Comments

Andrew Morton July 10, 2023, 11:17 p.m. UTC | #1 
On Mon, 10 Jul 2023 21:43:05 +0100 "Matthew Wilcox (Oracle)" <willy@infradead.org> wrote:

> This is the folio equivalent of page_mapping_file(), but rename it
> to make it clear that it's very different from page_file_mapping().
> Theoretically, there's nothing flush-only about it, but there are no
> other users today, and I doubt there will be; it's almost always more
> useful to know the swapfile's mapping or the swapcache's mapping.
> 
> Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
> +++ b/include/linux/pagemap.h
> @@ -389,6 +389,26 @@ static inline struct address_space *folio_file_mapping(struct folio *folio)
>  	return folio->mapping;
>  }
>  
> +/**
> + * folio_flush_mapping - Find the file mapping this folio belongs to.
> + * @folio: The folio.
> + *
> + * For folios which are in the page cache, return the mapping that this
> + * page belongs to.  Anonymous folios return NULL, even if they're in
> + * the swap cache.  Other kinds of folio also return NULL.
> + *
> + * This is ONLY used by architecture cache flushing code.  If you aren't
> + * writing cache flushing code, you want either folio_mapping() or
> + * folio_file_mapping().
> + */
> +static inline struct address_space *folio_flush_mapping(struct folio *folio)
> +{
> +	if (unlikely(folio_test_swapcache(folio)))
> +		return NULL;
> +
> +	return folio_mapping(folio);
> +}

The name makes it sound like it flushes something.  Wouldn't
folio_flushable_mapping() be clearer?

>  static inline struct address_space *page_file_mapping(struct page *page)
>  {
>  	return folio_file_mapping(page_folio(page));
> @@ -399,11 +419,7 @@ static inline struct address_space *page_file_mapping(struct page *page)
>   */
>  static inline struct address_space *page_mapping_file(struct page *page)
>  {
> -	struct folio *folio = page_folio(page);
> -
> -	if (unlikely(folio_test_swapcache(folio)))
> -		return NULL;
> -	return folio_mapping(folio);
> +	return folio_flush_mapping(page_folio(page));
>  }
Matthew Wilcox July 11, 2023, 2:33 a.m. UTC | #2 
On Mon, Jul 10, 2023 at 04:17:27PM -0700, Andrew Morton wrote:
> On Mon, 10 Jul 2023 21:43:05 +0100 "Matthew Wilcox (Oracle)" <willy@infradead.org> wrote:
> > +static inline struct address_space *folio_flush_mapping(struct folio *folio)
> > +{
> > +	if (unlikely(folio_test_swapcache(folio)))
> > +		return NULL;
> > +
> > +	return folio_mapping(folio);
> > +}
> 
> The name makes it sound like it flushes something.  Wouldn't
> folio_flushable_mapping() be clearer?

Yes; I wasn't a big fan of the name, but I wasn't a fan of perpetuating
the page_file_mapping / page_mapping_file confusio either.  Do you want
me to send you a set of fixup patches, or will you run them through sed
-i ?  ;-)
Andrew Morton July 11, 2023, 4:01 p.m. UTC | #3 
On Tue, 11 Jul 2023 03:33:42 +0100 Matthew Wilcox <willy@infradead.org> wrote:

> On Mon, Jul 10, 2023 at 04:17:27PM -0700, Andrew Morton wrote:
> > On Mon, 10 Jul 2023 21:43:05 +0100 "Matthew Wilcox (Oracle)" <willy@infradead.org> wrote:
> > > +static inline struct address_space *folio_flush_mapping(struct folio *folio)
> > > +{
> > > +	if (unlikely(folio_test_swapcache(folio)))
> > > +		return NULL;
> > > +
> > > +	return folio_mapping(folio);
> > > +}
> > 
> > The name makes it sound like it flushes something.  Wouldn't
> > folio_flushable_mapping() be clearer?
> 
> Yes; I wasn't a big fan of the name, but I wasn't a fan of perpetuating
> the page_file_mapping / page_mapping_file confusio either.  Do you want
> me to send you a set of fixup patches, or will you run them through sed
> -i ?  ;-)

I sedded.
diff mbox series

Patch

diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index 69b99b61ed72..794e4e55dc38 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -389,6 +389,26 @@  static inline struct address_space *folio_file_mapping(struct folio *folio)
 	return folio->mapping;
 }
 
+/**
+ * folio_flush_mapping - Find the file mapping this folio belongs to.
+ * @folio: The folio.
+ *
+ * For folios which are in the page cache, return the mapping that this
+ * page belongs to.  Anonymous folios return NULL, even if they're in
+ * the swap cache.  Other kinds of folio also return NULL.
+ *
+ * This is ONLY used by architecture cache flushing code.  If you aren't
+ * writing cache flushing code, you want either folio_mapping() or
+ * folio_file_mapping().
+ */
+static inline struct address_space *folio_flush_mapping(struct folio *folio)
+{
+	if (unlikely(folio_test_swapcache(folio)))
+		return NULL;
+
+	return folio_mapping(folio);
+}
+
 static inline struct address_space *page_file_mapping(struct page *page)
 {
 	return folio_file_mapping(page_folio(page));
@@ -399,11 +419,7 @@  static inline struct address_space *page_file_mapping(struct page *page)
  */
 static inline struct address_space *page_mapping_file(struct page *page)
 {
-	struct folio *folio = page_folio(page);
-
-	if (unlikely(folio_test_swapcache(folio)))
-		return NULL;
-	return folio_mapping(folio);
+	return folio_flush_mapping(page_folio(page));
 }
 
 /**