mm: add private field of first tail to struct page and struct folio

[ Upstream commit d340625 ]

Allow struct folio to store hugetlb metadata that is contained in the
private field of the first tail page.  On 32-bit, _private_1 aligns with
page[1].private.

Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Sidhartha Kumar <[email protected]>
Acked-by: Mike Kravetz <[email protected]>
Cc: Arnd Bergmann <[email protected]>
Cc: Colin Cross <[email protected]>
Cc: David Howells <[email protected]>
Cc: "Eric W . Biederman" <[email protected]>
Cc: Hugh Dickins <[email protected]>
Cc: kernel test robot <[email protected]>
Cc: Matthew Wilcox <[email protected]>
Cc: Muchun Song <[email protected]>
Cc: Peter Xu <[email protected]>
Cc: Vlastimil Babka <[email protected]>
Cc: William Kucharski <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Stable-dep-of: b76b469 ("mm/hugetlb: fix missing hugetlb_lock for resv uncharge")
Signed-off-by: Sasha Levin <[email protected]>

Author: sidkumar99

include/linux/mm_types.h

@@ -144,6 +144,7 @@ struct page {
 			atomic_t compound_pincount;
 #ifdef CONFIG_64BIT
 			unsigned int compound_nr; /* 1 << compound_order */
+			unsigned long _private_1;
 #endif
 		};
 		struct {	/* Second tail page of compound page */
@@ -264,6 +265,7 @@ struct page {
  * @_total_mapcount: Do not use directly, call folio_entire_mapcount().
  * @_pincount: Do not use directly, call folio_maybe_dma_pinned().
  * @_folio_nr_pages: Do not use directly, call folio_nr_pages().
+ * @_private_1: Do not use directly, call folio_get_private_1().
  *
  * A folio is a physically, virtually and logically contiguous set
  * of bytes.  It is a power-of-two in size, and it is aligned to that
@@ -311,6 +313,7 @@ struct folio {
 #ifdef CONFIG_64BIT
 	unsigned int _folio_nr_pages;
 #endif
+	unsigned long _private_1;
 };
 
 #define FOLIO_MATCH(pg, fl)						\
@@ -338,6 +341,7 @@ FOLIO_MATCH(compound_mapcount, _total_mapcount);
 FOLIO_MATCH(compound_pincount, _pincount);
 #ifdef CONFIG_64BIT
 FOLIO_MATCH(compound_nr, _folio_nr_pages);
+FOLIO_MATCH(_private_1, _private_1);
 #endif
 #undef FOLIO_MATCH
 
@@ -383,6 +387,16 @@ static inline void *folio_get_private(struct folio *folio)
 	return folio->private;
 }
 
+static inline void folio_set_private_1(struct folio *folio, unsigned long private)
+{
+	folio->_private_1 = private;
+}
+
+static inline unsigned long folio_get_private_1(struct folio *folio)
+{
+	return folio->_private_1;
+}
+
 struct page_frag_cache {
 	void * va;
 #if (PAGE_SIZE < PAGE_FRAG_CACHE_MAX_SIZE)