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author | Matthew Wilcox (Oracle) <willy@infradead.org> | 2021-06-28 19:41:19 -0700 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2021-06-29 10:53:53 -0700 |
commit | 0f2317e34e2c7b97efd4600122115410795ebeea (patch) | |
tree | a859330e4c960baf2fc0f3d8a2379870f8d59d8b | |
parent | 8bf6f451bded5db7840b3b2932ef48be5dce6b38 (diff) | |
download | linux-0f2317e34e2c7b97efd4600122115410795ebeea.tar.bz2 |
mm: make compound_head const-preserving
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.
Link: https://lkml.kernel.org/r/20210416231531.2521383-5-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com>
Reviewed-by: William Kucharski <william.kucharski@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r-- | include/linux/page-flags.h | 10 |
1 files 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; |