mm: split page_type out from _mapcount
We're already using a union of many fields here, so stop abusing the _mapcount and make page_type its own field. That implies renaming some of the machinery that creates PageBuddy, PageBalloon and PageKmemcg; bring back the PG_buddy, PG_balloon and PG_kmemcg names. As suggested by Kirill, make page_type a bitmask. Because it starts out life as -1 (thanks to sharing the storage with _mapcount), setting a page flag means clearing the appropriate bit. This gives us space for probably twenty or so extra bits (depending how paranoid we want to be about _mapcount underflow). Link: http://lkml.kernel.org/r/20180518194519.3820-3-willy@infradead.org Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com> Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Acked-by: Vlastimil Babka <vbabka@suse.cz> Cc: Christoph Lameter <cl@linux.com> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: Jérôme Glisse <jglisse@redhat.com> Cc: Lai Jiangshan <jiangshanlai@gmail.com> Cc: Martin Schwidefsky <schwidefsky@de.ibm.com> Cc: Pekka Enberg <penberg@kernel.org> Cc: Randy Dunlap <rdunlap@infradead.org> Cc: Andrey Ryabinin <aryabinin@virtuozzo.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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@ -96,6 +96,14 @@ struct page {
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};
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union {
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/*
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* If the page is neither PageSlab nor mappable to userspace,
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* the value stored here may help determine what this page
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* is used for. See page-flags.h for a list of page types
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* which are currently stored here.
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*/
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unsigned int page_type;
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_slub_counter_t counters;
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unsigned int active; /* SLAB */
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struct { /* SLUB */
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@ -109,11 +117,6 @@ struct page {
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/*
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* Count of ptes mapped in mms, to show when
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* page is mapped & limit reverse map searches.
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*
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* Extra information about page type may be
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* stored here for pages that are never mapped,
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* in which case the value MUST BE <= -2.
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* See page-flags.h for more details.
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*/
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atomic_t _mapcount;
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@ -642,49 +642,56 @@ PAGEFLAG_FALSE(DoubleMap)
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#endif
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/*
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* For pages that are never mapped to userspace, page->mapcount may be
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* used for storing extra information about page type. Any value used
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* for this purpose must be <= -2, but it's better start not too close
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* to -2 so that an underflow of the page_mapcount() won't be mistaken
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* for a special page.
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* For pages that are never mapped to userspace (and aren't PageSlab),
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* page_type may be used. Because it is initialised to -1, we invert the
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* sense of the bit, so __SetPageFoo *clears* the bit used for PageFoo, and
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* __ClearPageFoo *sets* the bit used for PageFoo. We reserve a few high and
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* low bits so that an underflow or overflow of page_mapcount() won't be
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* mistaken for a page type value.
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*/
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#define PAGE_MAPCOUNT_OPS(uname, lname) \
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#define PAGE_TYPE_BASE 0xf0000000
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/* Reserve 0x0000007f to catch underflows of page_mapcount */
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#define PG_buddy 0x00000080
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#define PG_balloon 0x00000100
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#define PG_kmemcg 0x00000200
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#define PageType(page, flag) \
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((page->page_type & (PAGE_TYPE_BASE | flag)) == PAGE_TYPE_BASE)
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#define PAGE_TYPE_OPS(uname, lname) \
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static __always_inline int Page##uname(struct page *page) \
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{ \
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return atomic_read(&page->_mapcount) == \
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PAGE_##lname##_MAPCOUNT_VALUE; \
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return PageType(page, PG_##lname); \
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} \
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static __always_inline void __SetPage##uname(struct page *page) \
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{ \
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VM_BUG_ON_PAGE(atomic_read(&page->_mapcount) != -1, page); \
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atomic_set(&page->_mapcount, PAGE_##lname##_MAPCOUNT_VALUE); \
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VM_BUG_ON_PAGE(!PageType(page, 0), page); \
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page->page_type &= ~PG_##lname; \
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} \
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static __always_inline void __ClearPage##uname(struct page *page) \
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{ \
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VM_BUG_ON_PAGE(!Page##uname(page), page); \
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atomic_set(&page->_mapcount, -1); \
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page->page_type |= PG_##lname; \
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}
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/*
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* PageBuddy() indicate that the page is free and in the buddy system
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* PageBuddy() indicates that the page is free and in the buddy system
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* (see mm/page_alloc.c).
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*/
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#define PAGE_BUDDY_MAPCOUNT_VALUE (-128)
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PAGE_MAPCOUNT_OPS(Buddy, BUDDY)
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PAGE_TYPE_OPS(Buddy, buddy)
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/*
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* PageBalloon() is set on pages that are on the balloon page list
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* PageBalloon() is true for pages that are on the balloon page list
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* (see mm/balloon_compaction.c).
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*/
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#define PAGE_BALLOON_MAPCOUNT_VALUE (-256)
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PAGE_MAPCOUNT_OPS(Balloon, BALLOON)
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PAGE_TYPE_OPS(Balloon, balloon)
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/*
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* If kmemcg is enabled, the buddy allocator will set PageKmemcg() on
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* pages allocated with __GFP_ACCOUNT. It gets cleared on page free.
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*/
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#define PAGE_KMEMCG_MAPCOUNT_VALUE (-512)
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PAGE_MAPCOUNT_OPS(Kmemcg, KMEMCG)
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PAGE_TYPE_OPS(Kmemcg, kmemcg)
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extern bool is_free_buddy_page(struct page *page);
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@ -460,6 +460,7 @@ static int __init crash_save_vmcoreinfo_init(void)
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VMCOREINFO_NUMBER(PG_hwpoison);
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#endif
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VMCOREINFO_NUMBER(PG_head_mask);
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#define PAGE_BUDDY_MAPCOUNT_VALUE (~PG_buddy)
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VMCOREINFO_NUMBER(PAGE_BUDDY_MAPCOUNT_VALUE);
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#ifdef CONFIG_HUGETLB_PAGE
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VMCOREINFO_NUMBER(HUGETLB_PAGE_DTOR);
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@ -705,16 +705,14 @@ static inline void rmv_page_order(struct page *page)
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/*
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* This function checks whether a page is free && is the buddy
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* we can do coalesce a page and its buddy if
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* we can coalesce a page and its buddy if
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* (a) the buddy is not in a hole (check before calling!) &&
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* (b) the buddy is in the buddy system &&
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* (c) a page and its buddy have the same order &&
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* (d) a page and its buddy are in the same zone.
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*
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* For recording whether a page is in the buddy system, we set ->_mapcount
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* PAGE_BUDDY_MAPCOUNT_VALUE.
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* Setting, clearing, and testing _mapcount PAGE_BUDDY_MAPCOUNT_VALUE is
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* serialized by zone->lock.
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* For recording whether a page is in the buddy system, we set PageBuddy.
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* Setting, clearing, and testing PageBuddy is serialized by zone->lock.
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*
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* For recording page's order, we use page_private(page).
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*/
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@ -759,9 +757,8 @@ static inline int page_is_buddy(struct page *page, struct page *buddy,
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* as necessary, plus some accounting needed to play nicely with other
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* parts of the VM system.
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* At each level, we keep a list of pages, which are heads of continuous
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* free pages of length of (1 << order) and marked with _mapcount
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* PAGE_BUDDY_MAPCOUNT_VALUE. Page's order is recorded in page_private(page)
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* field.
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* free pages of length of (1 << order) and marked with PageBuddy.
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* Page's order is recorded in page_private(page) field.
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* So when we are allocating or freeing one, we can derive the state of the
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* other. That is, if we allocate a small block, and both were
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* free, the remainder of the region must be split into blocks.
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@ -179,9 +179,9 @@ regex_c=(
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'/\<CLEARPAGEFLAG_NOOP(\([[:alnum:]_]*\).*/ClearPage\1/'
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'/\<__CLEARPAGEFLAG_NOOP(\([[:alnum:]_]*\).*/__ClearPage\1/'
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'/\<TESTCLEARFLAG_FALSE(\([[:alnum:]_]*\).*/TestClearPage\1/'
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'/^PAGE_MAPCOUNT_OPS(\([[:alnum:]_]*\).*/Page\1/'
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'/^PAGE_MAPCOUNT_OPS(\([[:alnum:]_]*\).*/__SetPage\1/'
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'/^PAGE_MAPCOUNT_OPS(\([[:alnum:]_]*\).*/__ClearPage\1/'
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'/^PAGE_TYPE_OPS(\([[:alnum:]_]*\).*/Page\1/'
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'/^PAGE_TYPE_OPS(\([[:alnum:]_]*\).*/__SetPage\1/'
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'/^PAGE_TYPE_OPS(\([[:alnum:]_]*\).*/__ClearPage\1/'
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'/^TASK_PFA_TEST([^,]*, *\([[:alnum:]_]*\))/task_\1/'
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'/^TASK_PFA_SET([^,]*, *\([[:alnum:]_]*\))/task_set_\1/'
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'/^TASK_PFA_CLEAR([^,]*, *\([[:alnum:]_]*\))/task_clear_\1/'
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