1 /* SPDX-License-Identifier: GPL-2.0 */
3 * Macros for manipulating and testing page->flags
9 #include <linux/types.h>
10 #include <linux/bug.h>
11 #include <linux/mmdebug.h>
12 #ifndef __GENERATING_BOUNDS_H
13 #include <linux/mm_types.h>
14 #include <generated/bounds.h>
15 #endif /* !__GENERATING_BOUNDS_H */
18 * Various page->flags bits:
20 * PG_reserved is set for special pages. The "struct page" of such a page
21 * should in general not be touched (e.g. set dirty) except by its owner.
22 * Pages marked as PG_reserved include:
23 * - Pages part of the kernel image (including vDSO) and similar (e.g. BIOS,
25 * - Pages reserved or allocated early during boot (before the page allocator
26 * was initialized). This includes (depending on the architecture) the
27 * initial vmemmap, initial page tables, crashkernel, elfcorehdr, and much
28 * much more. Once (if ever) freed, PG_reserved is cleared and they will
29 * be given to the page allocator.
30 * - Pages falling into physical memory gaps - not IORESOURCE_SYSRAM. Trying
31 * to read/write these pages might end badly. Don't touch!
33 * - Pages not added to the page allocator when onlining a section because
34 * they were excluded via the online_page_callback() or because they are
36 * - Pages allocated in the context of kexec/kdump (loaded kernel image,
37 * control pages, vmcoreinfo)
38 * - MMIO/DMA pages. Some architectures don't allow to ioremap pages that are
39 * not marked PG_reserved (as they might be in use by somebody else who does
40 * not respect the caching strategy).
41 * - Pages part of an offline section (struct pages of offline sections should
42 * not be trusted as they will be initialized when first onlined).
44 * - Pages holding CPU notes for POWER Firmware Assisted Dump
45 * - Device memory (e.g. PMEM, DAX, HMM)
46 * Some PG_reserved pages will be excluded from the hibernation image.
47 * PG_reserved does in general not hinder anybody from dumping or swapping
48 * and is no longer required for remap_pfn_range(). ioremap might require it.
49 * Consequently, PG_reserved for a page mapped into user space can indicate
50 * the zero page, the vDSO, MMIO pages or device memory.
52 * The PG_private bitflag is set on pagecache pages if they contain filesystem
53 * specific data (which is normally at page->private). It can be used by
54 * private allocations for its own usage.
56 * During initiation of disk I/O, PG_locked is set. This bit is set before I/O
57 * and cleared when writeback _starts_ or when read _completes_. PG_writeback
58 * is set before writeback starts and cleared when it finishes.
60 * PG_locked also pins a page in pagecache, and blocks truncation of the file
63 * page_waitqueue(page) is a wait queue of all tasks waiting for the page
66 * PG_swapbacked is set when a page uses swap as a backing storage. This are
67 * usually PageAnon or shmem pages but please note that even anonymous pages
68 * might lose their PG_swapbacked flag when they simply can be dropped (e.g. as
69 * a result of MADV_FREE).
71 * PG_uptodate tells whether the page's contents is valid. When a read
72 * completes, the page becomes uptodate, unless a disk I/O error happened.
74 * PG_referenced, PG_reclaim are used for page reclaim for anonymous and
75 * file-backed pagecache (see mm/vmscan.c).
77 * PG_error is set to indicate that an I/O error occurred on this page.
79 * PG_arch_1 is an architecture specific page state bit. The generic code
80 * guarantees that this bit is cleared for a page when it first is entered into
83 * PG_hwpoison indicates that a page got corrupted in hardware and contains
84 * data with incorrect ECC bits that triggered a machine check. Accessing is
85 * not safe since it may cause another machine check. Don't touch!
89 * Don't use the pageflags directly. Use the PageFoo macros.
91 * The page flags field is split into two parts, the main flags area
92 * which extends from the low bits upwards, and the fields area which
93 * extends from the high bits downwards.
95 * | FIELD | ... | FLAGS |
99 * The fields area is reserved for fields mapping zone, node (for NUMA) and
100 * SPARSEMEM section (for variants of SPARSEMEM that require section ids like
101 * SPARSEMEM_EXTREME with !SPARSEMEM_VMEMMAP).
104 PG_locked, /* Page is locked. Don't touch. */
111 PG_waiters, /* Page has waiters, check its waitqueue. Must be bit #7 and in the same byte as "PG_locked" */
114 PG_owner_priv_1, /* Owner use. If pagecache, fs may use*/
117 PG_private, /* If pagecache, has fs-private data */
118 PG_private_2, /* If pagecache, has fs aux data */
119 PG_writeback, /* Page is under writeback */
120 PG_head, /* A head page */
121 PG_mappedtodisk, /* Has blocks allocated on-disk */
122 PG_reclaim, /* To be reclaimed asap */
123 PG_swapbacked, /* Page is backed by RAM/swap */
124 PG_unevictable, /* Page is "unevictable" */
126 PG_mlocked, /* Page is vma mlocked */
128 #ifdef CONFIG_ARCH_USES_PG_UNCACHED
129 PG_uncached, /* Page has been mapped as uncached */
131 #ifdef CONFIG_MEMORY_FAILURE
132 PG_hwpoison, /* hardware poisoned page. Don't touch */
134 #if defined(CONFIG_IDLE_PAGE_TRACKING) && defined(CONFIG_64BIT)
141 #ifdef CONFIG_KASAN_HW_TAGS
142 PG_skip_kasan_poison,
147 PG_checked = PG_owner_priv_1,
150 PG_swapcache = PG_owner_priv_1, /* Swap page: swp_entry_t in private */
152 /* Two page bits are conscripted by FS-Cache to maintain local caching
153 * state. These bits are set on pages belonging to the netfs's inodes
154 * when those inodes are being locally cached.
156 PG_fscache = PG_private_2, /* page backed by cache */
159 /* Pinned in Xen as a read-only pagetable page. */
160 PG_pinned = PG_owner_priv_1,
161 /* Pinned as part of domain save (see xen_mm_pin_all()). */
162 PG_savepinned = PG_dirty,
163 /* Has a grant mapping of another (foreign) domain's page. */
164 PG_foreign = PG_owner_priv_1,
165 /* Remapped by swiotlb-xen. */
166 PG_xen_remapped = PG_owner_priv_1,
169 PG_slob_free = PG_private,
171 /* Compound pages. Stored in first tail page's flags */
172 PG_double_map = PG_workingset,
174 /* non-lru isolated movable page */
175 PG_isolated = PG_reclaim,
177 /* Only valid for buddy pages. Used to track pages that are reported */
178 PG_reported = PG_uptodate,
181 #ifndef __GENERATING_BOUNDS_H
183 static inline unsigned long _compound_head(const struct page *page)
185 unsigned long head = READ_ONCE(page->compound_head);
187 if (unlikely(head & 1))
189 return (unsigned long)page;
192 #define compound_head(page) ((typeof(page))_compound_head(page))
194 static __always_inline int PageTail(struct page *page)
196 return READ_ONCE(page->compound_head) & 1;
199 static __always_inline int PageCompound(struct page *page)
201 return test_bit(PG_head, &page->flags) || PageTail(page);
204 #define PAGE_POISON_PATTERN -1l
205 static inline int PagePoisoned(const struct page *page)
207 return page->flags == PAGE_POISON_PATTERN;
210 #ifdef CONFIG_DEBUG_VM
211 void page_init_poison(struct page *page, size_t size);
213 static inline void page_init_poison(struct page *page, size_t size)
219 * Page flags policies wrt compound pages
222 * check if this struct page poisoned/uninitialized
225 * the page flag is relevant for small, head and tail pages.
228 * for compound page all operations related to the page flag applied to
232 * for compound page, callers only ever operate on the head page.
235 * modifications of the page flag must be done on small or head pages,
236 * checks can be done on tail pages too.
239 * the page flag is not relevant for compound pages.
242 * the page flag is stored in the first tail page.
244 #define PF_POISONED_CHECK(page) ({ \
245 VM_BUG_ON_PGFLAGS(PagePoisoned(page), page); \
247 #define PF_ANY(page, enforce) PF_POISONED_CHECK(page)
248 #define PF_HEAD(page, enforce) PF_POISONED_CHECK(compound_head(page))
249 #define PF_ONLY_HEAD(page, enforce) ({ \
250 VM_BUG_ON_PGFLAGS(PageTail(page), page); \
251 PF_POISONED_CHECK(page); })
252 #define PF_NO_TAIL(page, enforce) ({ \
253 VM_BUG_ON_PGFLAGS(enforce && PageTail(page), page); \
254 PF_POISONED_CHECK(compound_head(page)); })
255 #define PF_NO_COMPOUND(page, enforce) ({ \
256 VM_BUG_ON_PGFLAGS(enforce && PageCompound(page), page); \
257 PF_POISONED_CHECK(page); })
258 #define PF_SECOND(page, enforce) ({ \
259 VM_BUG_ON_PGFLAGS(!PageHead(page), page); \
260 PF_POISONED_CHECK(&page[1]); })
263 * Macros to create function definitions for page flags
265 #define TESTPAGEFLAG(uname, lname, policy) \
266 static __always_inline int Page##uname(struct page *page) \
267 { return test_bit(PG_##lname, &policy(page, 0)->flags); }
269 #define SETPAGEFLAG(uname, lname, policy) \
270 static __always_inline void SetPage##uname(struct page *page) \
271 { set_bit(PG_##lname, &policy(page, 1)->flags); }
273 #define CLEARPAGEFLAG(uname, lname, policy) \
274 static __always_inline void ClearPage##uname(struct page *page) \
275 { clear_bit(PG_##lname, &policy(page, 1)->flags); }
277 #define __SETPAGEFLAG(uname, lname, policy) \
278 static __always_inline void __SetPage##uname(struct page *page) \
279 { __set_bit(PG_##lname, &policy(page, 1)->flags); }
281 #define __CLEARPAGEFLAG(uname, lname, policy) \
282 static __always_inline void __ClearPage##uname(struct page *page) \
283 { __clear_bit(PG_##lname, &policy(page, 1)->flags); }
285 #define TESTSETFLAG(uname, lname, policy) \
286 static __always_inline int TestSetPage##uname(struct page *page) \
287 { return test_and_set_bit(PG_##lname, &policy(page, 1)->flags); }
289 #define TESTCLEARFLAG(uname, lname, policy) \
290 static __always_inline int TestClearPage##uname(struct page *page) \
291 { return test_and_clear_bit(PG_##lname, &policy(page, 1)->flags); }
293 #define PAGEFLAG(uname, lname, policy) \
294 TESTPAGEFLAG(uname, lname, policy) \
295 SETPAGEFLAG(uname, lname, policy) \
296 CLEARPAGEFLAG(uname, lname, policy)
298 #define __PAGEFLAG(uname, lname, policy) \
299 TESTPAGEFLAG(uname, lname, policy) \
300 __SETPAGEFLAG(uname, lname, policy) \
301 __CLEARPAGEFLAG(uname, lname, policy)
303 #define TESTSCFLAG(uname, lname, policy) \
304 TESTSETFLAG(uname, lname, policy) \
305 TESTCLEARFLAG(uname, lname, policy)
307 #define TESTPAGEFLAG_FALSE(uname) \
308 static inline int Page##uname(const struct page *page) { return 0; }
310 #define SETPAGEFLAG_NOOP(uname) \
311 static inline void SetPage##uname(struct page *page) { }
313 #define CLEARPAGEFLAG_NOOP(uname) \
314 static inline void ClearPage##uname(struct page *page) { }
316 #define __CLEARPAGEFLAG_NOOP(uname) \
317 static inline void __ClearPage##uname(struct page *page) { }
319 #define TESTSETFLAG_FALSE(uname) \
320 static inline int TestSetPage##uname(struct page *page) { return 0; }
322 #define TESTCLEARFLAG_FALSE(uname) \
323 static inline int TestClearPage##uname(struct page *page) { return 0; }
325 #define PAGEFLAG_FALSE(uname) TESTPAGEFLAG_FALSE(uname) \
326 SETPAGEFLAG_NOOP(uname) CLEARPAGEFLAG_NOOP(uname)
328 #define TESTSCFLAG_FALSE(uname) \
329 TESTSETFLAG_FALSE(uname) TESTCLEARFLAG_FALSE(uname)
331 __PAGEFLAG(Locked, locked, PF_NO_TAIL)
332 PAGEFLAG(Waiters, waiters, PF_ONLY_HEAD) __CLEARPAGEFLAG(Waiters, waiters, PF_ONLY_HEAD)
333 PAGEFLAG(Error, error, PF_NO_TAIL) TESTCLEARFLAG(Error, error, PF_NO_TAIL)
334 PAGEFLAG(Referenced, referenced, PF_HEAD)
335 TESTCLEARFLAG(Referenced, referenced, PF_HEAD)
336 __SETPAGEFLAG(Referenced, referenced, PF_HEAD)
337 PAGEFLAG(Dirty, dirty, PF_HEAD) TESTSCFLAG(Dirty, dirty, PF_HEAD)
338 __CLEARPAGEFLAG(Dirty, dirty, PF_HEAD)
339 PAGEFLAG(LRU, lru, PF_HEAD) __CLEARPAGEFLAG(LRU, lru, PF_HEAD)
340 TESTCLEARFLAG(LRU, lru, PF_HEAD)
341 PAGEFLAG(Active, active, PF_HEAD) __CLEARPAGEFLAG(Active, active, PF_HEAD)
342 TESTCLEARFLAG(Active, active, PF_HEAD)
343 PAGEFLAG(Workingset, workingset, PF_HEAD)
344 TESTCLEARFLAG(Workingset, workingset, PF_HEAD)
345 __PAGEFLAG(Slab, slab, PF_NO_TAIL)
346 __PAGEFLAG(SlobFree, slob_free, PF_NO_TAIL)
347 PAGEFLAG(Checked, checked, PF_NO_COMPOUND) /* Used by some filesystems */
350 PAGEFLAG(Pinned, pinned, PF_NO_COMPOUND)
351 TESTSCFLAG(Pinned, pinned, PF_NO_COMPOUND)
352 PAGEFLAG(SavePinned, savepinned, PF_NO_COMPOUND);
353 PAGEFLAG(Foreign, foreign, PF_NO_COMPOUND);
354 PAGEFLAG(XenRemapped, xen_remapped, PF_NO_COMPOUND)
355 TESTCLEARFLAG(XenRemapped, xen_remapped, PF_NO_COMPOUND)
357 PAGEFLAG(Reserved, reserved, PF_NO_COMPOUND)
358 __CLEARPAGEFLAG(Reserved, reserved, PF_NO_COMPOUND)
359 __SETPAGEFLAG(Reserved, reserved, PF_NO_COMPOUND)
360 PAGEFLAG(SwapBacked, swapbacked, PF_NO_TAIL)
361 __CLEARPAGEFLAG(SwapBacked, swapbacked, PF_NO_TAIL)
362 __SETPAGEFLAG(SwapBacked, swapbacked, PF_NO_TAIL)
365 * Private page markings that may be used by the filesystem that owns the page
366 * for its own purposes.
367 * - PG_private and PG_private_2 cause releasepage() and co to be invoked
369 PAGEFLAG(Private, private, PF_ANY)
370 PAGEFLAG(Private2, private_2, PF_ANY) TESTSCFLAG(Private2, private_2, PF_ANY)
371 PAGEFLAG(OwnerPriv1, owner_priv_1, PF_ANY)
372 TESTCLEARFLAG(OwnerPriv1, owner_priv_1, PF_ANY)
375 * Only test-and-set exist for PG_writeback. The unconditional operators are
376 * risky: they bypass page accounting.
378 TESTPAGEFLAG(Writeback, writeback, PF_NO_TAIL)
379 TESTSCFLAG(Writeback, writeback, PF_NO_TAIL)
380 PAGEFLAG(MappedToDisk, mappedtodisk, PF_NO_TAIL)
382 /* PG_readahead is only used for reads; PG_reclaim is only for writes */
383 PAGEFLAG(Reclaim, reclaim, PF_NO_TAIL)
384 TESTCLEARFLAG(Reclaim, reclaim, PF_NO_TAIL)
385 PAGEFLAG(Readahead, reclaim, PF_NO_COMPOUND)
386 TESTCLEARFLAG(Readahead, reclaim, PF_NO_COMPOUND)
388 #ifdef CONFIG_HIGHMEM
390 * Must use a macro here due to header dependency issues. page_zone() is not
391 * available at this point.
393 #define PageHighMem(__p) is_highmem_idx(page_zonenum(__p))
395 PAGEFLAG_FALSE(HighMem)
399 static __always_inline int PageSwapCache(struct page *page)
401 #ifdef CONFIG_THP_SWAP
402 page = compound_head(page);
404 return PageSwapBacked(page) && test_bit(PG_swapcache, &page->flags);
407 SETPAGEFLAG(SwapCache, swapcache, PF_NO_TAIL)
408 CLEARPAGEFLAG(SwapCache, swapcache, PF_NO_TAIL)
410 PAGEFLAG_FALSE(SwapCache)
413 PAGEFLAG(Unevictable, unevictable, PF_HEAD)
414 __CLEARPAGEFLAG(Unevictable, unevictable, PF_HEAD)
415 TESTCLEARFLAG(Unevictable, unevictable, PF_HEAD)
418 PAGEFLAG(Mlocked, mlocked, PF_NO_TAIL)
419 __CLEARPAGEFLAG(Mlocked, mlocked, PF_NO_TAIL)
420 TESTSCFLAG(Mlocked, mlocked, PF_NO_TAIL)
422 PAGEFLAG_FALSE(Mlocked) __CLEARPAGEFLAG_NOOP(Mlocked)
423 TESTSCFLAG_FALSE(Mlocked)
426 #ifdef CONFIG_ARCH_USES_PG_UNCACHED
427 PAGEFLAG(Uncached, uncached, PF_NO_COMPOUND)
429 PAGEFLAG_FALSE(Uncached)
432 #ifdef CONFIG_MEMORY_FAILURE
433 PAGEFLAG(HWPoison, hwpoison, PF_ANY)
434 TESTSCFLAG(HWPoison, hwpoison, PF_ANY)
435 #define __PG_HWPOISON (1UL << PG_hwpoison)
436 extern bool take_page_off_buddy(struct page *page);
438 PAGEFLAG_FALSE(HWPoison)
439 #define __PG_HWPOISON 0
442 #if defined(CONFIG_IDLE_PAGE_TRACKING) && defined(CONFIG_64BIT)
443 TESTPAGEFLAG(Young, young, PF_ANY)
444 SETPAGEFLAG(Young, young, PF_ANY)
445 TESTCLEARFLAG(Young, young, PF_ANY)
446 PAGEFLAG(Idle, idle, PF_ANY)
449 #ifdef CONFIG_KASAN_HW_TAGS
450 PAGEFLAG(SkipKASanPoison, skip_kasan_poison, PF_HEAD)
452 PAGEFLAG_FALSE(SkipKASanPoison)
456 * PageReported() is used to track reported free pages within the Buddy
457 * allocator. We can use the non-atomic version of the test and set
458 * operations as both should be shielded with the zone lock to prevent
459 * any possible races on the setting or clearing of the bit.
461 __PAGEFLAG(Reported, reported, PF_NO_COMPOUND)
464 * On an anonymous page mapped into a user virtual memory area,
465 * page->mapping points to its anon_vma, not to a struct address_space;
466 * with the PAGE_MAPPING_ANON bit set to distinguish it. See rmap.h.
468 * On an anonymous page in a VM_MERGEABLE area, if CONFIG_KSM is enabled,
469 * the PAGE_MAPPING_MOVABLE bit may be set along with the PAGE_MAPPING_ANON
470 * bit; and then page->mapping points, not to an anon_vma, but to a private
471 * structure which KSM associates with that merged page. See ksm.h.
473 * PAGE_MAPPING_KSM without PAGE_MAPPING_ANON is used for non-lru movable
474 * page and then page->mapping points a struct address_space.
476 * Please note that, confusingly, "page_mapping" refers to the inode
477 * address_space which maps the page from disk; whereas "page_mapped"
478 * refers to user virtual address space into which the page is mapped.
480 #define PAGE_MAPPING_ANON 0x1
481 #define PAGE_MAPPING_MOVABLE 0x2
482 #define PAGE_MAPPING_KSM (PAGE_MAPPING_ANON | PAGE_MAPPING_MOVABLE)
483 #define PAGE_MAPPING_FLAGS (PAGE_MAPPING_ANON | PAGE_MAPPING_MOVABLE)
485 static __always_inline int PageMappingFlags(struct page *page)
487 return ((unsigned long)page->mapping & PAGE_MAPPING_FLAGS) != 0;
490 static __always_inline int PageAnon(struct page *page)
492 page = compound_head(page);
493 return ((unsigned long)page->mapping & PAGE_MAPPING_ANON) != 0;
496 static __always_inline int __PageMovable(struct page *page)
498 return ((unsigned long)page->mapping & PAGE_MAPPING_FLAGS) ==
499 PAGE_MAPPING_MOVABLE;
504 * A KSM page is one of those write-protected "shared pages" or "merged pages"
505 * which KSM maps into multiple mms, wherever identical anonymous page content
506 * is found in VM_MERGEABLE vmas. It's a PageAnon page, pointing not to any
507 * anon_vma, but to that page's node of the stable tree.
509 static __always_inline int PageKsm(struct page *page)
511 page = compound_head(page);
512 return ((unsigned long)page->mapping & PAGE_MAPPING_FLAGS) ==
516 TESTPAGEFLAG_FALSE(Ksm)
519 u64 stable_page_flags(struct page *page);
521 static inline int PageUptodate(struct page *page)
524 page = compound_head(page);
525 ret = test_bit(PG_uptodate, &(page)->flags);
527 * Must ensure that the data we read out of the page is loaded
528 * _after_ we've loaded page->flags to check for PageUptodate.
529 * We can skip the barrier if the page is not uptodate, because
530 * we wouldn't be reading anything from it.
532 * See SetPageUptodate() for the other side of the story.
540 static __always_inline void __SetPageUptodate(struct page *page)
542 VM_BUG_ON_PAGE(PageTail(page), page);
544 __set_bit(PG_uptodate, &page->flags);
547 static __always_inline void SetPageUptodate(struct page *page)
549 VM_BUG_ON_PAGE(PageTail(page), page);
551 * Memory barrier must be issued before setting the PG_uptodate bit,
552 * so that all previous stores issued in order to bring the page
553 * uptodate are actually visible before PageUptodate becomes true.
556 set_bit(PG_uptodate, &page->flags);
559 CLEARPAGEFLAG(Uptodate, uptodate, PF_NO_TAIL)
561 int test_clear_page_writeback(struct page *page);
562 int __test_set_page_writeback(struct page *page, bool keep_write);
564 #define test_set_page_writeback(page) \
565 __test_set_page_writeback(page, false)
566 #define test_set_page_writeback_keepwrite(page) \
567 __test_set_page_writeback(page, true)
569 static inline void set_page_writeback(struct page *page)
571 test_set_page_writeback(page);
574 static inline void set_page_writeback_keepwrite(struct page *page)
576 test_set_page_writeback_keepwrite(page);
579 __PAGEFLAG(Head, head, PF_ANY) CLEARPAGEFLAG(Head, head, PF_ANY)
581 static __always_inline void set_compound_head(struct page *page, struct page *head)
583 WRITE_ONCE(page->compound_head, (unsigned long)head + 1);
586 static __always_inline void clear_compound_head(struct page *page)
588 WRITE_ONCE(page->compound_head, 0);
591 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
592 static inline void ClearPageCompound(struct page *page)
594 BUG_ON(!PageHead(page));
599 #define PG_head_mask ((1UL << PG_head))
601 #ifdef CONFIG_HUGETLB_PAGE
602 int PageHuge(struct page *page);
603 int PageHeadHuge(struct page *page);
605 TESTPAGEFLAG_FALSE(Huge)
606 TESTPAGEFLAG_FALSE(HeadHuge)
610 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
612 * PageHuge() only returns true for hugetlbfs pages, but not for
613 * normal or transparent huge pages.
615 * PageTransHuge() returns true for both transparent huge and
616 * hugetlbfs pages, but not normal pages. PageTransHuge() can only be
617 * called only in the core VM paths where hugetlbfs pages can't exist.
619 static inline int PageTransHuge(struct page *page)
621 VM_BUG_ON_PAGE(PageTail(page), page);
622 return PageHead(page);
626 * PageTransCompound returns true for both transparent huge pages
627 * and hugetlbfs pages, so it should only be called when it's known
628 * that hugetlbfs pages aren't involved.
630 static inline int PageTransCompound(struct page *page)
632 return PageCompound(page);
636 * PageTransCompoundMap is the same as PageTransCompound, but it also
637 * guarantees the primary MMU has the entire compound page mapped
638 * through pmd_trans_huge, which in turn guarantees the secondary MMUs
639 * can also map the entire compound page. This allows the secondary
640 * MMUs to call get_user_pages() only once for each compound page and
641 * to immediately map the entire compound page with a single secondary
642 * MMU fault. If there will be a pmd split later, the secondary MMUs
643 * will get an update through the MMU notifier invalidation through
646 * Unlike PageTransCompound, this is safe to be called only while
647 * split_huge_pmd() cannot run from under us, like if protected by the
648 * MMU notifier, otherwise it may result in page->_mapcount check false
651 * We have to treat page cache THP differently since every subpage of it
652 * would get _mapcount inc'ed once it is PMD mapped. But, it may be PTE
653 * mapped in the current process so comparing subpage's _mapcount to
654 * compound_mapcount to filter out PTE mapped case.
656 static inline int PageTransCompoundMap(struct page *page)
660 if (!PageTransCompound(page))
664 return atomic_read(&page->_mapcount) < 0;
666 head = compound_head(page);
667 /* File THP is PMD mapped and not PTE mapped */
668 return atomic_read(&page->_mapcount) ==
669 atomic_read(compound_mapcount_ptr(head));
673 * PageTransTail returns true for both transparent huge pages
674 * and hugetlbfs pages, so it should only be called when it's known
675 * that hugetlbfs pages aren't involved.
677 static inline int PageTransTail(struct page *page)
679 return PageTail(page);
683 * PageDoubleMap indicates that the compound page is mapped with PTEs as well
686 * This is required for optimization of rmap operations for THP: we can postpone
687 * per small page mapcount accounting (and its overhead from atomic operations)
688 * until the first PMD split.
690 * For the page PageDoubleMap means ->_mapcount in all sub-pages is offset up
691 * by one. This reference will go away with last compound_mapcount.
693 * See also __split_huge_pmd_locked() and page_remove_anon_compound_rmap().
695 PAGEFLAG(DoubleMap, double_map, PF_SECOND)
696 TESTSCFLAG(DoubleMap, double_map, PF_SECOND)
698 TESTPAGEFLAG_FALSE(TransHuge)
699 TESTPAGEFLAG_FALSE(TransCompound)
700 TESTPAGEFLAG_FALSE(TransCompoundMap)
701 TESTPAGEFLAG_FALSE(TransTail)
702 PAGEFLAG_FALSE(DoubleMap)
703 TESTSCFLAG_FALSE(DoubleMap)
707 * For pages that are never mapped to userspace (and aren't PageSlab),
708 * page_type may be used. Because it is initialised to -1, we invert the
709 * sense of the bit, so __SetPageFoo *clears* the bit used for PageFoo, and
710 * __ClearPageFoo *sets* the bit used for PageFoo. We reserve a few high and
711 * low bits so that an underflow or overflow of page_mapcount() won't be
712 * mistaken for a page type value.
715 #define PAGE_TYPE_BASE 0xf0000000
716 /* Reserve 0x0000007f to catch underflows of page_mapcount */
717 #define PAGE_MAPCOUNT_RESERVE -128
718 #define PG_buddy 0x00000080
719 #define PG_offline 0x00000100
720 #define PG_table 0x00000200
721 #define PG_guard 0x00000400
723 #define PageType(page, flag) \
724 ((page->page_type & (PAGE_TYPE_BASE | flag)) == PAGE_TYPE_BASE)
726 static inline int page_has_type(struct page *page)
728 return (int)page->page_type < PAGE_MAPCOUNT_RESERVE;
731 #define PAGE_TYPE_OPS(uname, lname) \
732 static __always_inline int Page##uname(struct page *page) \
734 return PageType(page, PG_##lname); \
736 static __always_inline void __SetPage##uname(struct page *page) \
738 VM_BUG_ON_PAGE(!PageType(page, 0), page); \
739 page->page_type &= ~PG_##lname; \
741 static __always_inline void __ClearPage##uname(struct page *page) \
743 VM_BUG_ON_PAGE(!Page##uname(page), page); \
744 page->page_type |= PG_##lname; \
748 * PageBuddy() indicates that the page is free and in the buddy system
749 * (see mm/page_alloc.c).
751 PAGE_TYPE_OPS(Buddy, buddy)
754 * PageOffline() indicates that the page is logically offline although the
755 * containing section is online. (e.g. inflated in a balloon driver or
756 * not onlined when onlining the section).
757 * The content of these pages is effectively stale. Such pages should not
758 * be touched (read/write/dump/save) except by their owner.
760 * If a driver wants to allow to offline unmovable PageOffline() pages without
761 * putting them back to the buddy, it can do so via the memory notifier by
762 * decrementing the reference count in MEM_GOING_OFFLINE and incrementing the
763 * reference count in MEM_CANCEL_OFFLINE. When offlining, the PageOffline()
764 * pages (now with a reference count of zero) are treated like free pages,
765 * allowing the containing memory block to get offlined. A driver that
766 * relies on this feature is aware that re-onlining the memory block will
767 * require to re-set the pages PageOffline() and not giving them to the
768 * buddy via online_page_callback_t.
770 PAGE_TYPE_OPS(Offline, offline)
773 * Marks pages in use as page tables.
775 PAGE_TYPE_OPS(Table, table)
778 * Marks guardpages used with debug_pagealloc.
780 PAGE_TYPE_OPS(Guard, guard)
782 extern bool is_free_buddy_page(struct page *page);
784 __PAGEFLAG(Isolated, isolated, PF_ANY);
787 * If network-based swap is enabled, sl*b must keep track of whether pages
788 * were allocated from pfmemalloc reserves.
790 static inline int PageSlabPfmemalloc(struct page *page)
792 VM_BUG_ON_PAGE(!PageSlab(page), page);
793 return PageActive(page);
796 static inline void SetPageSlabPfmemalloc(struct page *page)
798 VM_BUG_ON_PAGE(!PageSlab(page), page);
802 static inline void __ClearPageSlabPfmemalloc(struct page *page)
804 VM_BUG_ON_PAGE(!PageSlab(page), page);
805 __ClearPageActive(page);
808 static inline void ClearPageSlabPfmemalloc(struct page *page)
810 VM_BUG_ON_PAGE(!PageSlab(page), page);
811 ClearPageActive(page);
815 #define __PG_MLOCKED (1UL << PG_mlocked)
817 #define __PG_MLOCKED 0
821 * Flags checked when a page is freed. Pages being freed should not have
822 * these flags set. If they are, there is a problem.
824 #define PAGE_FLAGS_CHECK_AT_FREE \
825 (1UL << PG_lru | 1UL << PG_locked | \
826 1UL << PG_private | 1UL << PG_private_2 | \
827 1UL << PG_writeback | 1UL << PG_reserved | \
828 1UL << PG_slab | 1UL << PG_active | \
829 1UL << PG_unevictable | __PG_MLOCKED)
832 * Flags checked when a page is prepped for return by the page allocator.
833 * Pages being prepped should not have these flags set. If they are set,
834 * there has been a kernel bug or struct page corruption.
836 * __PG_HWPOISON is exceptional because it needs to be kept beyond page's
837 * alloc-free cycle to prevent from reusing the page.
839 #define PAGE_FLAGS_CHECK_AT_PREP \
840 (((1UL << NR_PAGEFLAGS) - 1) & ~__PG_HWPOISON)
842 #define PAGE_FLAGS_PRIVATE \
843 (1UL << PG_private | 1UL << PG_private_2)
845 * page_has_private - Determine if page has private stuff
846 * @page: The page to be checked
848 * Determine if a page has private stuff, indicating that release routines
849 * should be invoked upon it.
851 static inline int page_has_private(struct page *page)
853 return !!(page->flags & PAGE_FLAGS_PRIVATE);
860 #undef PF_NO_COMPOUND
862 #endif /* !__GENERATING_BOUNDS_H */
864 #endif /* PAGE_FLAGS_H */