mm: remove page_maybe_dma_pinned()

After the last user of page_maybe_dma_pinned() is converted to
folio_maybe_dma_pinned(), remove page_maybe_dma_pinned() and update the
document and comment.

[wangkefeng.wang@huawei.com: fix pin_user_pages.rst underlining]
  Link: https://lkml.kernel.org/r/61b256c7-4989-44ec-83db-f34a1bd4be2d@huawei.com
Link: https://lkml.kernel.org/r/20240604114822.2089819-3-wangkefeng.wang@huawei.comSigned-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Acked-by: David Hildenbrand <david@redhat.com>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Helge Deller <deller@gmx.de>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Documentation/core-api/pin_user_pages.rst

@@ -196,20 +196,20 @@ INCORRECT (uses FOLL_GET calls):
     write to the data within the pages
     put_page()
 
-page_maybe_dma_pinned(): the whole point of pinning
-===================================================
+folio_maybe_dma_pinned(): the whole point of pinning
+====================================================
 
-The whole point of marking pages as "DMA-pinned" or "gup-pinned" is to be able
-to query, "is this page DMA-pinned?" That allows code such as page_mkclean()
+The whole point of marking folios as "DMA-pinned" or "gup-pinned" is to be able
+to query, "is this folio DMA-pinned?" That allows code such as page_mkclean()
 (and file system writeback code in general) to make informed decisions about
-what to do when a page cannot be unmapped due to such pins.
+what to do when a folio cannot be unmapped due to such pins.
 
 What to do in those cases is the subject of a years-long series of discussions
 and debates (see the References at the end of this document). It's a TODO item
 here: fill in the details once that's worked out. Meanwhile, it's safe to say
 that having this available: ::
 
-        static inline bool page_maybe_dma_pinned(struct page *page)
+        static inline bool folio_maybe_dma_pinned(struct folio *folio)
 
 ...is a prerequisite to solving the long-running gup+DMA problem.
 

include/linux/mm.h

@@ -1918,8 +1918,8 @@ static inline struct folio *pfn_folio(unsigned long pfn)
  *
  * For more information, please see Documentation/core-api/pin_user_pages.rst.
  *
- * Return: True, if it is likely that the page has been "dma-pinned".
- * False, if the page is definitely not dma-pinned.
+ * Return: True, if it is likely that the folio has been "dma-pinned".
+ * False, if the folio is definitely not dma-pinned.
  */
 static inline bool folio_maybe_dma_pinned(struct folio *folio)
 {
@@ -1938,11 +1938,6 @@ static inline bool folio_maybe_dma_pinned(struct folio *folio)
 		GUP_PIN_COUNTING_BIAS;
 }
 
-static inline bool page_maybe_dma_pinned(struct page *page)
-{
-	return folio_maybe_dma_pinned(page_folio(page));
-}
-
 /*
  * This should most likely only be called during fork() to see whether we
  * should break the cow immediately for an anon page on the src mm.