From: "Matthew Wilcox (Oracle)" <willy@infradead.org>
To: linux-mm@kvack.org
Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org>,
Andrew Morton <akpm@linux-foundation.org>,
linux-kernel@vger.kernel.org
Subject: [PATCH 4/6] mm: Make compound_head const-preserving
Date: Sat, 17 Apr 2021 00:15:29 +0100 [thread overview]
Message-ID: <20210416231531.2521383-5-willy@infradead.org> (raw)
In-Reply-To: <20210416231531.2521383-1-willy@infradead.org>
If you pass a const pointer to compound_head(), you get a const pointer
back; if you pass a mutable pointer, you get a mutable pointer back.
Also remove an unnecessary forward definition of struct page; we're about
to dereference page->compound_head, so it must already have been defined.
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---
include/linux/page-flags.h | 10 +++++-----
1 file changed, 5 insertions(+), 5 deletions(-)
diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
index 04a34c08e0a6..d8e26243db25 100644
--- a/include/linux/page-flags.h
+++ b/include/linux/page-flags.h
@@ -177,17 +177,17 @@ enum pageflags {
#ifndef __GENERATING_BOUNDS_H
-struct page; /* forward declaration */
-
-static inline struct page *compound_head(struct page *page)
+static inline unsigned long _compound_head(const struct page *page)
{
unsigned long head = READ_ONCE(page->compound_head);
if (unlikely(head & 1))
- return (struct page *) (head - 1);
- return page;
+ return head - 1;
+ return (unsigned long)page;
}
+#define compound_head(page) ((typeof(page))_compound_head(page))
+
static __always_inline int PageTail(struct page *page)
{
return READ_ONCE(page->compound_head) & 1;
--
2.30.2
next prev parent reply other threads:[~2021-04-16 23:17 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-16 23:15 [RESEND][PATCH 0/6] Constify struct page arguments Matthew Wilcox (Oracle)
2021-04-16 23:15 ` [PATCH 1/6] mm: Make __dump_page static Matthew Wilcox (Oracle)
2021-04-23 14:49 ` Vlastimil Babka
2021-04-27 3:30 ` Anshuman Khandual
2021-04-16 23:15 ` [PATCH 2/6] mm/debug: Factor PagePoisoned out of __dump_page Matthew Wilcox (Oracle)
2021-04-23 14:52 ` Vlastimil Babka
2021-04-27 3:30 ` Anshuman Khandual
2021-04-16 23:15 ` [PATCH 3/6] mm/page_owner: Constify dump_page_owner Matthew Wilcox (Oracle)
2021-04-23 14:53 ` Vlastimil Babka
2021-04-27 3:31 ` Anshuman Khandual
2021-04-16 23:15 ` Matthew Wilcox (Oracle) [this message]
2021-04-23 14:58 ` [PATCH 4/6] mm: Make compound_head const-preserving Vlastimil Babka
2021-04-27 3:31 ` Anshuman Khandual
2021-04-16 23:15 ` [PATCH 5/6] mm: Constify get_pfnblock_flags_mask and get_pfnblock_migratetype Matthew Wilcox (Oracle)
2021-04-23 14:59 ` Vlastimil Babka
2021-04-27 3:32 ` Anshuman Khandual
2021-04-16 23:15 ` [PATCH 6/6] mm: Constify page_count and page_ref_count Matthew Wilcox (Oracle)
2021-04-23 15:01 ` Vlastimil Babka
2021-04-27 3:32 ` Anshuman Khandual
2021-04-17 7:14 ` [RESEND][PATCH 0/6] Constify struct page arguments William Kucharski
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