From: "Matthew Wilcox (Oracle)" <willy@infradead.org>
To: linux-mm@kvack.org, linux-fsdevel@vger.kernel.org,
akpm@linux-foundation.org
Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org>,
William Kucharski <william.kucharski@oracle.com>,
Vlastimil Babka <vbabka@suse.cz>,
Anshuman Khandual <anshuman.khandual@arm.com>
Subject: [PATCH 5/8] mm: Make compound_head const-preserving
Date: Fri, 30 Apr 2021 15:55:46 +0100 [thread overview]
Message-ID: <20210430145549.2662354-6-willy@infradead.org> (raw)
In-Reply-To: <20210430145549.2662354-1-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>
Reviewed-by: William Kucharski <william.kucharski@oracle.com>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com>
---
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:[~2021-04-30 15:04 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-30 14:55 [PATCH 0/8] Folio Prequel patches Matthew Wilcox (Oracle)
2021-04-30 14:55 ` [PATCH 1/8] mm: Optimise nth_page for contiguous memmap Matthew Wilcox (Oracle)
2021-04-30 14:55 ` [PATCH 2/8] mm: Make __dump_page static Matthew Wilcox (Oracle)
2021-04-30 14:55 ` [PATCH 3/8] mm/debug: Factor PagePoisoned out of __dump_page Matthew Wilcox (Oracle)
2021-05-12 3:29 ` Kefeng Wang
2021-05-12 3:38 ` Matthew Wilcox
2021-05-12 3:53 ` Kefeng Wang
2021-04-30 14:55 ` [PATCH 4/8] mm/page_owner: Constify dump_page_owner Matthew Wilcox (Oracle)
2021-04-30 14:55 ` Matthew Wilcox (Oracle) [this message]
2021-04-30 14:55 ` [PATCH 6/8] mm: Constify get_pfnblock_flags_mask and get_pfnblock_migratetype Matthew Wilcox (Oracle)
2021-04-30 14:55 ` [PATCH 7/8] mm: Constify page_count and page_ref_count Matthew Wilcox (Oracle)
2021-04-30 14:55 ` [PATCH 8/8] mm: Fix struct page layout on 32-bit systems Matthew Wilcox (Oracle)
2021-05-10 16:12 ` [PATCH 0/8] Folio Prequel patches Matteo Croce
2021-05-10 16:29 ` Matthew Wilcox
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