linux-kernel - [PATCH v3 2/6] mm: add private field of first tail to struct page and struct folio

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Message-Id: <20220908193706.1716548-3-sidhartha.kumar@oracle.com>
Date:   Thu,  8 Sep 2022 12:37:02 -0700
From:   Sidhartha Kumar <sidhartha.kumar@...cle.com>
To:     linux-kernel@...r.kernel.org, linux-mm@...ck.org
Cc:     akpm@...ux-foundation.org, songmuchun@...edance.com,
        mike.kravetz@...cle.com, willy@...radead.org, vbabka@...e.cz,
        william.kucharski@...cle.com, dhowells@...hat.com,
        peterx@...hat.com, arnd@...db.de, ccross@...gle.com,
        hughd@...gle.com, ebiederm@...ssion.com,
        Sidhartha Kumar <sidhartha.kumar@...cle.com>
Subject: [PATCH v3 2/6] mm: add private field of first tail to struct page and struct folio

Allows 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.

Signed-off-by: Sidhartha Kumar <sidhartha.kumar@...cle.com>
---
 include/linux/mm_types.h | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index 8a9ee9d24973..7a33171a05b6 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -143,6 +143,7 @@ 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 */
@@ -251,6 +252,7 @@ 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
@@ -298,6 +300,7 @@ struct folio {
 #ifdef CONFIG_64BIT
 	unsigned int _folio_nr_pages;
 #endif
+	unsigned long _private_1;
 };
 
 #define FOLIO_MATCH(pg, fl)						\
@@ -325,6 +328,7 @@ 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
 
@@ -370,6 +374,16 @@ 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)
-- 
2.31.1