[PATCH v6 08/27] mm: Create FolioFlags

Matthew Wilcox (Oracle)
2021-03-31T18:51:56Z

These new functions are the folio analogues of the PageFlags functions.
If CONFIG_DEBUG_VM_PGFLAGS is enabled, we check the folio is not a tail
page at every invocation. Note that this will also catch the PagePoisoned
case as a poisoned page has every bit set, which would include PageTail.

This saves 1727 bytes of text with the distro-derived config that
I'm testing due to removing a double call to compound_head() in
PageSwapCache().

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---
include/linux/page-flags.h | 130 ++++++++++++++++++++++++++++++-------
1 file changed, 107 insertions(+), 23 deletions(-)

diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
index 04a34c08e0a6..b923a90b3ba5 100644
--- a/include/linux/page-flags.h
+++ b/include/linux/page-flags.h
@@ -212,6 +212,15 @@ static inline void page_init_poison(struct page *page, size_t size)
}
#endif

+static unsigned long *folio_flags(struct folio *folio, unsigned n)
+{
+ struct page *page = &folio->page;
+
+ VM_BUG_ON_PGFLAGS(PageTail(page), page);
+ VM_BUG_ON_PGFLAGS(n > 0 && !test_bit(PG_head, &page->flags), page);
+ return &page[n].flags;
+}
+
/*
* Page flags policies wrt compound pages
*
@@ -256,34 +265,56 @@ static inline void page_init_poison(struct page *page, size_t size)
VM_BUG_ON_PGFLAGS(!PageHead(page), page); \
PF_POISONED_CHECK(&page[1]); })

+/* Which page is the flag stored in */
+#define FOLIO_PF_ANY 0
+#define FOLIO_PF_HEAD 0
+#define FOLIO_PF_ONLY_HEAD 0
+#define FOLIO_PF_NO_TAIL 0
+#define FOLIO_PF_NO_COMPOUND 0
+#define FOLIO_PF_SECOND 1
+
/*
* Macros to create function definitions for page flags
*/
#define TESTPAGEFLAG(uname, lname, policy) \
+static __always_inline int Folio##uname(struct folio *folio) \
+ { return test_bit(PG_##lname, folio_flags(folio, FOLIO_##policy)); } \
static __always_inline int Page##uname(struct page *page) \
{ return test_bit(PG_##lname, &policy(page, 0)->flags); }

#define SETPAGEFLAG(uname, lname, policy) \
+static __always_inline void SetFolio##uname(struct folio *folio) \
+ { set_bit(PG_##lname, folio_flags(folio, FOLIO_##policy)); } \
static __always_inline void SetPage##uname(struct page *page) \
{ set_bit(PG_##lname, &policy(page, 1)->flags); }

#define CLEARPAGEFLAG(uname, lname, policy) \
+static __always_inline void ClearFolio##uname(struct folio *folio) \
+ { clear_bit(PG_##lname, folio_flags(folio, FOLIO_##policy)); } \
static __always_inline void ClearPage##uname(struct page *page) \
{ clear_bit(PG_##lname, &policy(page, 1)->flags); }

#define __SETPAGEFLAG(uname, lname, policy) \
+static __always_inline void __SetFolio##uname(struct folio *folio) \
+ { __set_bit(PG_##lname, folio_flags(folio, FOLIO_##policy)); } \
static __always_inline void __SetPage##uname(struct page *page) \
{ __set_bit(PG_##lname, &policy(page, 1)->flags); }

#define __CLEARPAGEFLAG(uname, lname, policy) \
+static __always_inline void __ClearFolio##uname(struct folio *folio) \
+ { __clear_bit(PG_##lname, folio_flags(folio, FOLIO_##policy)); } \
static __always_inline void __ClearPage##uname(struct page *page) \
{ __clear_bit(PG_##lname, &policy(page, 1)->flags); }

#define TESTSETFLAG(uname, lname, policy) \
+static __always_inline int TestSetFolio##uname(struct folio *folio) \
+ { return test_and_set_bit(PG_##lname, folio_flags(folio, FOLIO_##policy)); } \
static __always_inline int TestSetPage##uname(struct page *page) \
{ return test_and_set_bit(PG_##lname, &policy(page, 1)->flags); }

#define TESTCLEARFLAG(uname, lname, policy) \
+static __always_inline int TestClearFolio##uname(struct folio *folio) \
+ { return test_and_clear_bit(PG_##lname, folio_flags(folio, FOLIO_##policy)); } \
static __always_inline int TestClearPage##uname(struct page *page) \
{ return test_and_clear_bit(PG_##lname, &policy(page, 1)->flags); }

@@ -302,21 +333,27 @@ static __always_inline int TestClearPage##uname(struct page *page) \
TESTCLEARFLAG(uname, lname, policy)

#define TESTPAGEFLAG_FALSE(uname) \
+static inline int Folio##uname(const struct folio *folio) { return 0; } \
static inline int Page##uname(const struct page *page) { return 0; }

#define SETPAGEFLAG_NOOP(uname) \
+static inline void SetFolio##uname(struct folio *folio) { } \
static inline void SetPage##uname(struct page *page) { }

#define CLEARPAGEFLAG_NOOP(uname) \
+static inline void ClearFolio##uname(struct folio *folio) { } \
static inline void ClearPage##uname(struct page *page) { }

#define __CLEARPAGEFLAG_NOOP(uname) \
+static inline void __ClearFolio##uname(struct folio *folio) { } \
static inline void __ClearPage##uname(struct page *page) { }

#define TESTSETFLAG_FALSE(uname) \
+static inline int TestSetFolio##uname(struct folio *folio) { return 0; } \
static inline int TestSetPage##uname(struct page *page) { return 0; }

#define TESTCLEARFLAG_FALSE(uname) \
+static inline int TestClearFolio##uname(struct folio *folio) { return 0; } \
static inline int TestClearPage##uname(struct page *page) { return 0; }

#define PAGEFLAG_FALSE(uname) TESTPAGEFLAG_FALSE(uname) \
@@ -393,14 +430,18 @@ PAGEFLAG_FALSE(HighMem)
#endif

#ifdef CONFIG_SWAP
-static __always_inline int PageSwapCache(struct page *page)
+static __always_inline bool FolioSwapCache(struct folio *folio)
{
-#ifdef CONFIG_THP_SWAP
- page = compound_head(page);
-#endif
- return PageSwapBacked(page) && test_bit(PG_swapcache, &page->flags);
+ return FolioSwapBacked(folio) &&
+ test_bit(PG_swapcache, folio_flags(folio, 0));

}
+
+static __always_inline bool PageSwapCache(struct page *page)
+{
+ return FolioSwapCache(page_folio(page));
+}
+
SETPAGEFLAG(SwapCache, swapcache, PF_NO_TAIL)
CLEARPAGEFLAG(SwapCache, swapcache, PF_NO_TAIL)
#else
@@ -478,10 +519,14 @@ static __always_inline int PageMappingFlags(struct page *page)
return ((unsigned long)page->mapping & PAGE_MAPPING_FLAGS) != 0;
}

-static __always_inline int PageAnon(struct page *page)
+static __always_inline bool FolioAnon(struct folio *folio)
+{
+ return ((unsigned long)folio->mapping & PAGE_MAPPING_ANON) != 0;
+}
+
+static __always_inline bool PageAnon(struct page *page)
{
- page = compound_head(page);
- return ((unsigned long)page->mapping & PAGE_MAPPING_ANON) != 0;
+ return FolioAnon(page_folio(page));
}

static __always_inline int __PageMovable(struct page *page)
@@ -497,30 +542,32 @@ static __always_inline int __PageMovable(struct page *page)
* is found in VM_MERGEABLE vmas. It's a PageAnon page, pointing not to any
* anon_vma, but to that page's node of the stable tree.
*/
-static __always_inline int PageKsm(struct page *page)
+static __always_inline bool FolioKsm(struct folio *folio)
{
- page = compound_head(page);
- return ((unsigned long)page->mapping & PAGE_MAPPING_FLAGS) ==
+ return ((unsigned long)folio->mapping & PAGE_MAPPING_FLAGS) ==
PAGE_MAPPING_KSM;
}
+
+static __always_inline bool PageKsm(struct page *page)
+{
+ return FolioKsm(page_folio(page));
+}
#else
TESTPAGEFLAG_FALSE(Ksm)
#endif

u64 stable_page_flags(struct page *page);

-static inline int PageUptodate(struct page *page)
+static inline int FolioUptodate(struct folio *folio)
{
- int ret;
- page = compound_head(page);
- ret = test_bit(PG_uptodate, &(page)->flags);
+ int ret = test_bit(PG_uptodate, folio_flags(folio, 0));
/*
* Must ensure that the data we read out of the page is loaded
* _after_ we've loaded page->flags to check for PageUptodate.
* We can skip the barrier if the page is not uptodate, because
* we wouldn't be reading anything from it.
*
- * See SetPageUptodate() for the other side of the story.
+ * See SetFolioUptodate() for the other side of the story.
*/
if (ret)
smp_rmb();
@@ -528,23 +575,36 @@ static inline int PageUptodate(struct page *page)
return ret;
}

-static __always_inline void __SetPageUptodate(struct page *page)
+static inline int PageUptodate(struct page *page)
+{
+ return FolioUptodate(page_folio(page));
+}
+
+static __always_inline void __SetFolioUptodate(struct folio *folio)
{
- VM_BUG_ON_PAGE(PageTail(page), page);
smp_wmb();
- __set_bit(PG_uptodate, &page->flags);
+ __set_bit(PG_uptodate, folio_flags(folio, 0));
}

-static __always_inline void SetPageUptodate(struct page *page)
+static __always_inline void SetFolioUptodate(struct folio *folio)
{
- VM_BUG_ON_PAGE(PageTail(page), page);
/*
* Memory barrier must be issued before setting the PG_uptodate bit,
* so that all previous stores issued in order to bring the page
* uptodate are actually visible before PageUptodate becomes true.
*/
smp_wmb();
- set_bit(PG_uptodate, &page->flags);
+ set_bit(PG_uptodate, folio_flags(folio, 0));
+}
+
+static __always_inline void __SetPageUptodate(struct page *page)
+{
+ __SetFolioUptodate((struct folio *)page);
+}
+
+static __always_inline void SetPageUptodate(struct page *page)
+{
+ SetFolioUptodate((struct folio *)page);
}

CLEARPAGEFLAG(Uptodate, uptodate, PF_NO_TAIL)
@@ -569,6 +629,17 @@ static inline void set_page_writeback_keepwrite(struct page *page)

__PAGEFLAG(Head, head, PF_ANY) CLEARPAGEFLAG(Head, head, PF_ANY)

+/* Whether there are one or multiple pages in a folio */
+static inline bool FolioSingle(struct folio *folio)
+{
+ return !FolioHead(folio);
+}
+
+static inline bool FolioMulti(struct folio *folio)
+{
+ return FolioHead(folio);
+}
+
static __always_inline void set_compound_head(struct page *page, struct page *head)
{
WRITE_ONCE(page->compound_head, (unsigned long)head + 1);
@@ -592,12 +663,15 @@ static inline void ClearPageCompound(struct page *page)
#ifdef CONFIG_HUGETLB_PAGE
int PageHuge(struct page *page);
int PageHeadHuge(struct page *page);
+static inline bool FolioHuge(struct folio *folio)
+{
+ return PageHeadHuge(&folio->page);
+}
#else
TESTPAGEFLAG_FALSE(Huge)
TESTPAGEFLAG_FALSE(HeadHuge)
#endif

-
#ifdef CONFIG_TRANSPARENT_HUGEPAGE
/*
* PageHuge() only returns true for hugetlbfs pages, but not for
@@ -613,6 +687,11 @@ static inline int PageTransHuge(struct page *page)
return PageHead(page);
}

+static inline bool FolioTransHuge(struct folio *folio)
+{
+ return FolioHead(folio);
+}
+
/*
* PageTransCompound returns true for both transparent huge pages
* and hugetlbfs pages, so it should only be called when it's known
@@ -844,6 +923,11 @@ static inline int page_has_private(struct page *page)
return !!(page->flags & PAGE_FLAGS_PRIVATE);
}

+static inline bool folio_has_private(struct folio *folio)
+{
+ return page_has_private(&folio->page);
+}
+
#undef PF_ANY
#undef PF_HEAD
#undef PF_ONLY_HEAD
--
2.30.2