fs/proc: move page_mapcount() to fs/proc/internal.h

...  and rename it to folio_precise_page_mapcount().  fs/proc is the last
remaining user, and that should stay that way.

While at it, cleanup kpagecount_read() a bit: there are still some legacy
leftovers -- when the interface was introduced it returned the page
refcount, but was changed briefly afterwards to return the page mapcount. 
Further, some simple folio conversion.

Once we stop using the per-page mapcounts of large folios, all
folio_precise_page_mapcount() users will have to implement an alternative
way to achieve what they are trying to achieve, possibly in a less precise
way.

[dan.carpenter@linaro.org: fix uninitialized variable in pagemap_pmd_range()]
  Link: https://lkml.kernel.org/r/9d6eaba7-92f8-4a70-8765-38a519680a87@moroto.mountain
Link: https://lkml.kernel.org/r/20240607122357.115423-6-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Lance Yang <ioworker0@gmail.com>
Cc: Oscar Salvador <osalvador@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

1 files changed, 1 insertions, 26 deletions

diff --git a/include/linux/mm.h b/include/linux/mm.h
index f4bf94ca99e3..7f864d5f52b7 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1202,8 +1202,7 @@ static inline int is_vmalloc_or_module_addr(const void *x)
 /*
  * How many times the entire folio is mapped as a single unit (eg by a
  * PMD or PUD entry).  This is probably not what you want, except for
- * debugging purposes - it does not include PTE-mapped sub-pages; look
- * at folio_mapcount() or page_mapcount() instead.
+ * debugging purposes or implementation of other core folio_*() primitives.
  */
 static inline int folio_entire_mapcount(const struct folio *folio)
 {
@@ -1221,30 +1220,6 @@ static inline void page_mapcount_reset(struct page *page)
 	atomic_set(&(page)->_mapcount, -1);
 }
 
-/**
- * page_mapcount() - Number of times this precise page is mapped.
- * @page: The page.
- *
- * The number of times this page is mapped.  If this page is part of
- * a large folio, it includes the number of times this page is mapped
- * as part of that folio.
- *
- * Will report 0 for pages which cannot be mapped into userspace, eg
- * slab, page tables and similar.
- */
-static inline int page_mapcount(struct page *page)
-{
-	int mapcount = atomic_read(&page->_mapcount) + 1;
-
-	/* Handle page_has_type() pages */
-	if (mapcount < PAGE_MAPCOUNT_RESERVE + 1)
-		mapcount = 0;
-	if (unlikely(PageCompound(page)))
-		mapcount += folio_entire_mapcount(page_folio(page));
-
-	return mapcount;
-}
-
 static inline int folio_large_mapcount(const struct folio *folio)
 {
 	VM_WARN_ON_FOLIO(!folio_test_large(folio), folio);