[PATCH v9 16/96] mm: Add folio flag manipulation functions

From: Matthew Wilcox (Oracle)
Date: Wed May 05 2021 - 11:26:15 EST

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These new functions are the folio analogues of the various PageFlags
functions. If CONFIG_DEBUG_VM_PGFLAGS is enabled, we check the folio
is not a tail page at every invocation. 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@xxxxxxxxxxxxx>
Reviewed-by: Christoph Hellwig <hch@xxxxxx>
Acked-by: Jeff Layton <jlayton@xxxxxxxxxx>
---
include/linux/page-flags.h | 203 +++++++++++++++++++++++++++----------
1 file changed, 148 insertions(+), 55 deletions(-)

diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
index e069aa8b11b7..ef8b7c6dc91c 100644
--- a/include/linux/page-flags.h
+++ b/include/linux/page-flags.h
@@ -140,6 +140,8 @@ enum pageflags {
#endif
__NR_PAGEFLAGS,

+ PG_readahead = PG_reclaim,
+
/* Filesystems */
PG_checked = PG_owner_priv_1,

@@ -239,6 +241,15 @@ 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
*
@@ -283,34 +294,62 @@ 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 bool folio_##lname(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 folio_set_##lname##_flag(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 folio_clear_##lname##_flag(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 __folio_set_##lname##_flag(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 __folio_clear_##lname##_flag(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 \
+bool folio_test_set_##lname##_flag(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 \
+bool folio_test_clear_##lname##_flag(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); }

@@ -328,29 +367,37 @@ static __always_inline int TestClearPage##uname(struct page *page) \
TESTSETFLAG(uname, lname, policy) \
TESTCLEARFLAG(uname, lname, policy)

-#define TESTPAGEFLAG_FALSE(uname) \
+#define TESTPAGEFLAG_FALSE(uname, lname) \
+static inline bool folio_##lname(const struct folio *folio) { return 0; } \
static inline int Page##uname(const struct page *page) { return 0; }

-#define SETPAGEFLAG_NOOP(uname) \
+#define SETPAGEFLAG_NOOP(uname, lname) \
+static inline void folio_set_##lname##_flag(struct folio *folio) { } \
static inline void SetPage##uname(struct page *page) { }

-#define CLEARPAGEFLAG_NOOP(uname) \
+#define CLEARPAGEFLAG_NOOP(uname, lname) \
+static inline void folio_clear_##lname##_flag(struct folio *folio) { } \
static inline void ClearPage##uname(struct page *page) { }

-#define __CLEARPAGEFLAG_NOOP(uname) \
+#define __CLEARPAGEFLAG_NOOP(uname, lname) \
+static inline void __folio_clear_##lname_flags(struct folio *folio) { } \
static inline void __ClearPage##uname(struct page *page) { }

-#define TESTSETFLAG_FALSE(uname) \
+#define TESTSETFLAG_FALSE(uname, lname) \
+static inline bool folio_test_set_##lname##_flag(struct folio *folio) \
+{ return 0; } \
static inline int TestSetPage##uname(struct page *page) { return 0; }

-#define TESTCLEARFLAG_FALSE(uname) \
+#define TESTCLEARFLAG_FALSE(uname, lname) \
+static inline bool folio_test_clear_##lname##_flag(struct folio *folio) \
+{ return 0; } \
static inline int TestClearPage##uname(struct page *page) { return 0; }

-#define PAGEFLAG_FALSE(uname) TESTPAGEFLAG_FALSE(uname) \
- SETPAGEFLAG_NOOP(uname) CLEARPAGEFLAG_NOOP(uname)
+#define PAGEFLAG_FALSE(uname, lname) TESTPAGEFLAG_FALSE(uname, lname) \
+ SETPAGEFLAG_NOOP(uname, lname) CLEARPAGEFLAG_NOOP(uname, lname)

-#define TESTSCFLAG_FALSE(uname) \
- TESTSETFLAG_FALSE(uname) TESTCLEARFLAG_FALSE(uname)
+#define TESTSCFLAG_FALSE(uname, lname) \
+ TESTSETFLAG_FALSE(uname, lname) TESTCLEARFLAG_FALSE(uname, lname)

__PAGEFLAG(Locked, locked, PF_NO_TAIL)
PAGEFLAG(Waiters, waiters, PF_ONLY_HEAD) __CLEARPAGEFLAG(Waiters, waiters, PF_ONLY_HEAD)
@@ -406,8 +453,8 @@ PAGEFLAG(MappedToDisk, mappedtodisk, PF_NO_TAIL)
/* PG_readahead is only used for reads; PG_reclaim is only for writes */
PAGEFLAG(Reclaim, reclaim, PF_NO_TAIL)
TESTCLEARFLAG(Reclaim, reclaim, PF_NO_TAIL)
-PAGEFLAG(Readahead, reclaim, PF_NO_COMPOUND)
- TESTCLEARFLAG(Readahead, reclaim, PF_NO_COMPOUND)
+PAGEFLAG(Readahead, readahead, PF_NO_COMPOUND)
+ TESTCLEARFLAG(Readahead, readahead, PF_NO_COMPOUND)

#ifdef CONFIG_HIGHMEM
/*
@@ -416,22 +463,25 @@ PAGEFLAG(Readahead, reclaim, PF_NO_COMPOUND)
*/
#define PageHighMem(__p) is_highmem_idx(page_zonenum(__p))
#else
-PAGEFLAG_FALSE(HighMem)
+PAGEFLAG_FALSE(HighMem, highmem)
#endif

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

+static __always_inline bool PageSwapCache(struct page *page)
+{
+ return folio_swapcache(page_folio(page));
}
+
SETPAGEFLAG(SwapCache, swapcache, PF_NO_TAIL)
CLEARPAGEFLAG(SwapCache, swapcache, PF_NO_TAIL)
#else
-PAGEFLAG_FALSE(SwapCache)
+PAGEFLAG_FALSE(SwapCache, swapcache)
#endif

PAGEFLAG(Unevictable, unevictable, PF_HEAD)
@@ -443,14 +493,14 @@ PAGEFLAG(Mlocked, mlocked, PF_NO_TAIL)
__CLEARPAGEFLAG(Mlocked, mlocked, PF_NO_TAIL)
TESTSCFLAG(Mlocked, mlocked, PF_NO_TAIL)
#else
-PAGEFLAG_FALSE(Mlocked) __CLEARPAGEFLAG_NOOP(Mlocked)
- TESTSCFLAG_FALSE(Mlocked)
+PAGEFLAG_FALSE(Mlocked, mlocked) __CLEARPAGEFLAG_NOOP(Mlocked, mlocked)
+ TESTSCFLAG_FALSE(Mlocked, mlocked)
#endif

#ifdef CONFIG_ARCH_USES_PG_UNCACHED
PAGEFLAG(Uncached, uncached, PF_NO_COMPOUND)
#else
-PAGEFLAG_FALSE(Uncached)
+PAGEFLAG_FALSE(Uncached, uncached)
#endif

#ifdef CONFIG_MEMORY_FAILURE
@@ -459,7 +509,7 @@ TESTSCFLAG(HWPoison, hwpoison, PF_ANY)
#define __PG_HWPOISON (1UL << PG_hwpoison)
extern bool take_page_off_buddy(struct page *page);
#else
-PAGEFLAG_FALSE(HWPoison)
+PAGEFLAG_FALSE(HWPoison, hwpoison)
#define __PG_HWPOISON 0
#endif

@@ -505,10 +555,14 @@ 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 folio_anon(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 folio_anon(page_folio(page));
}

static __always_inline int __PageMovable(struct page *page)
@@ -524,30 +578,32 @@ 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 folio_ksm(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 folio_ksm(page_folio(page));
+}
#else
-TESTPAGEFLAG_FALSE(Ksm)
+TESTPAGEFLAG_FALSE(Ksm, ksm)
#endif

u64 stable_page_flags(struct page *page);

-static inline int PageUptodate(struct page *page)
+static inline bool folio_uptodate(struct folio *folio)
{
- int ret;
- page = compound_head(page);
- ret = test_bit(PG_uptodate, &(page)->flags);
+ bool 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
+ * Must ensure that the data we read out of the folio is loaded
+ * _after_ we've loaded folio->flags to check the uptodate bit.
+ * We can skip the barrier if the folio is not uptodate, because
* we wouldn't be reading anything from it.
*
- * See SetPageUptodate() for the other side of the story.
+ * See folio_mark_uptodate() for the other side of the story.
*/
if (ret)
smp_rmb();
@@ -555,23 +611,36 @@ 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 folio_uptodate(page_folio(page));
+}
+
+static __always_inline void __folio_mark_uptodate(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 folio_mark_uptodate(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.
+ * so that all previous stores issued in order to bring the folio
+ * uptodate are actually visible before folio_uptodate 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)
+{
+ __folio_mark_uptodate((struct folio *)page);
+}
+
+static __always_inline void SetPageUptodate(struct page *page)
+{
+ folio_mark_uptodate((struct folio *)page);
}

CLEARPAGEFLAG(Uptodate, uptodate, PF_NO_TAIL)
@@ -596,6 +665,17 @@ 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 folio_single(struct folio *folio)
+{
+ return !folio_head(folio);
+}
+
+static inline bool folio_multi(struct folio *folio)
+{
+ return folio_head(folio);
+}
+
static __always_inline void set_compound_head(struct page *page, struct page *head)
{
WRITE_ONCE(page->compound_head, (unsigned long)head + 1);
@@ -619,12 +699,15 @@ static inline void ClearPageCompound(struct page *page)
#ifdef CONFIG_HUGETLB_PAGE
int PageHuge(struct page *page);
int PageHeadHuge(struct page *page);
+static inline bool folio_hugetlb(struct folio *folio)
+{
+ return PageHeadHuge(&folio->page);
+}
#else
-TESTPAGEFLAG_FALSE(Huge)
-TESTPAGEFLAG_FALSE(HeadHuge)
+TESTPAGEFLAG_FALSE(Huge, hugetlb)
+TESTPAGEFLAG_FALSE(HeadHuge, headhuge)
#endif

-
#ifdef CONFIG_TRANSPARENT_HUGEPAGE
/*
* PageHuge() only returns true for hugetlbfs pages, but not for
@@ -640,6 +723,11 @@ static inline int PageTransHuge(struct page *page)
return PageHead(page);
}

+static inline bool folio_transhuge(struct folio *folio)
+{
+ return folio_head(folio);
+}
+
/*
* PageTransCompound returns true for both transparent huge pages
* and hugetlbfs pages, so it should only be called when it's known
@@ -713,12 +801,12 @@ static inline int PageTransTail(struct page *page)
PAGEFLAG(DoubleMap, double_map, PF_SECOND)
TESTSCFLAG(DoubleMap, double_map, PF_SECOND)
#else
-TESTPAGEFLAG_FALSE(TransHuge)
-TESTPAGEFLAG_FALSE(TransCompound)
-TESTPAGEFLAG_FALSE(TransCompoundMap)
-TESTPAGEFLAG_FALSE(TransTail)
-PAGEFLAG_FALSE(DoubleMap)
- TESTSCFLAG_FALSE(DoubleMap)
+TESTPAGEFLAG_FALSE(TransHuge, transhuge)
+TESTPAGEFLAG_FALSE(TransCompound, transcompound)
+TESTPAGEFLAG_FALSE(TransCompoundMap, transcompoundmap)
+TESTPAGEFLAG_FALSE(TransTail, transtail)
+PAGEFLAG_FALSE(DoubleMap, double_map)
+ TESTSCFLAG_FALSE(DoubleMap, double_map)
#endif

/*
@@ -871,6 +959,11 @@ 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

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