2 * Macros for manipulating and testing page->flags
8 #include <linux/types.h>
10 #include <linux/mmdebug.h>
11 #ifndef __GENERATING_BOUNDS_H
12 #include <linux/mm_types.h>
13 #include <generated/bounds.h>
14 #endif /* !__GENERATING_BOUNDS_H */
17 * Various page->flags bits:
19 * PG_reserved is set for special pages, which can never be swapped out. Some
20 * of them might not even exist (eg empty_bad_page)...
22 * The PG_private bitflag is set on pagecache pages if they contain filesystem
23 * specific data (which is normally at page->private). It can be used by
24 * private allocations for its own usage.
26 * During initiation of disk I/O, PG_locked is set. This bit is set before I/O
27 * and cleared when writeback _starts_ or when read _completes_. PG_writeback
28 * is set before writeback starts and cleared when it finishes.
30 * PG_locked also pins a page in pagecache, and blocks truncation of the file
33 * page_waitqueue(page) is a wait queue of all tasks waiting for the page
36 * PG_uptodate tells whether the page's contents is valid. When a read
37 * completes, the page becomes uptodate, unless a disk I/O error happened.
39 * PG_referenced, PG_reclaim are used for page reclaim for anonymous and
40 * file-backed pagecache (see mm/vmscan.c).
42 * PG_error is set to indicate that an I/O error occurred on this page.
44 * PG_arch_1 is an architecture specific page state bit. The generic code
45 * guarantees that this bit is cleared for a page when it first is entered into
48 * PG_highmem pages are not permanently mapped into the kernel virtual address
49 * space, they need to be kmapped separately for doing IO on the pages. The
50 * struct page (these bits with information) are always mapped into kernel
53 * PG_hwpoison indicates that a page got corrupted in hardware and contains
54 * data with incorrect ECC bits that triggered a machine check. Accessing is
55 * not safe since it may cause another machine check. Don't touch!
59 * Don't use the *_dontuse flags. Use the macros. Otherwise you'll break
60 * locked- and dirty-page accounting.
62 * The page flags field is split into two parts, the main flags area
63 * which extends from the low bits upwards, and the fields area which
64 * extends from the high bits downwards.
66 * | FIELD | ... | FLAGS |
70 * The fields area is reserved for fields mapping zone, node (for NUMA) and
71 * SPARSEMEM section (for variants of SPARSEMEM that require section ids like
72 * SPARSEMEM_EXTREME with !SPARSEMEM_VMEMMAP).
75 PG_locked, /* Page is locked. Don't touch. */
83 PG_owner_priv_1, /* Owner use. If pagecache, fs may use*/
86 PG_private, /* If pagecache, has fs-private data */
87 PG_private_2, /* If pagecache, has fs aux data */
88 PG_writeback, /* Page is under writeback */
89 #ifdef CONFIG_PAGEFLAGS_EXTENDED
90 PG_head, /* A head page */
91 PG_tail, /* A tail page */
93 PG_compound, /* A compound page */
95 PG_swapcache, /* Swap page: swp_entry_t in private */
96 PG_mappedtodisk, /* Has blocks allocated on-disk */
97 PG_reclaim, /* To be reclaimed asap */
98 PG_swapbacked, /* Page is backed by RAM/swap */
99 PG_unevictable, /* Page is "unevictable" */
101 PG_mlocked, /* Page is vma mlocked */
103 #ifdef CONFIG_ARCH_USES_PG_UNCACHED
104 PG_uncached, /* Page has been mapped as uncached */
106 #ifdef CONFIG_MEMORY_FAILURE
107 PG_hwpoison, /* hardware poisoned page. Don't touch */
109 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
115 PG_checked = PG_owner_priv_1,
117 /* Two page bits are conscripted by FS-Cache to maintain local caching
118 * state. These bits are set on pages belonging to the netfs's inodes
119 * when those inodes are being locally cached.
121 PG_fscache = PG_private_2, /* page backed by cache */
124 /* Pinned in Xen as a read-only pagetable page. */
125 PG_pinned = PG_owner_priv_1,
126 /* Pinned as part of domain save (see xen_mm_pin_all()). */
127 PG_savepinned = PG_dirty,
128 /* Has a grant mapping of another (foreign) domain's page. */
129 PG_foreign = PG_owner_priv_1,
132 PG_slob_free = PG_private,
135 #ifndef __GENERATING_BOUNDS_H
138 * Macros to create function definitions for page flags
140 #define TESTPAGEFLAG(uname, lname) \
141 static inline int Page##uname(const struct page *page) \
142 { return test_bit(PG_##lname, &page->flags); }
144 #define SETPAGEFLAG(uname, lname) \
145 static inline void SetPage##uname(struct page *page) \
146 { set_bit(PG_##lname, &page->flags); }
148 #define CLEARPAGEFLAG(uname, lname) \
149 static inline void ClearPage##uname(struct page *page) \
150 { clear_bit(PG_##lname, &page->flags); }
152 #define __SETPAGEFLAG(uname, lname) \
153 static inline void __SetPage##uname(struct page *page) \
154 { __set_bit(PG_##lname, &page->flags); }
156 #define __CLEARPAGEFLAG(uname, lname) \
157 static inline void __ClearPage##uname(struct page *page) \
158 { __clear_bit(PG_##lname, &page->flags); }
160 #define TESTSETFLAG(uname, lname) \
161 static inline int TestSetPage##uname(struct page *page) \
162 { return test_and_set_bit(PG_##lname, &page->flags); }
164 #define TESTCLEARFLAG(uname, lname) \
165 static inline int TestClearPage##uname(struct page *page) \
166 { return test_and_clear_bit(PG_##lname, &page->flags); }
168 #define __TESTCLEARFLAG(uname, lname) \
169 static inline int __TestClearPage##uname(struct page *page) \
170 { return __test_and_clear_bit(PG_##lname, &page->flags); }
172 #define PAGEFLAG(uname, lname) TESTPAGEFLAG(uname, lname) \
173 SETPAGEFLAG(uname, lname) CLEARPAGEFLAG(uname, lname)
175 #define __PAGEFLAG(uname, lname) TESTPAGEFLAG(uname, lname) \
176 __SETPAGEFLAG(uname, lname) __CLEARPAGEFLAG(uname, lname)
178 #define TESTSCFLAG(uname, lname) \
179 TESTSETFLAG(uname, lname) TESTCLEARFLAG(uname, lname)
181 #define TESTPAGEFLAG_FALSE(uname) \
182 static inline int Page##uname(const struct page *page) { return 0; }
184 #define SETPAGEFLAG_NOOP(uname) \
185 static inline void SetPage##uname(struct page *page) { }
187 #define CLEARPAGEFLAG_NOOP(uname) \
188 static inline void ClearPage##uname(struct page *page) { }
190 #define __CLEARPAGEFLAG_NOOP(uname) \
191 static inline void __ClearPage##uname(struct page *page) { }
193 #define TESTSETFLAG_FALSE(uname) \
194 static inline int TestSetPage##uname(struct page *page) { return 0; }
196 #define TESTCLEARFLAG_FALSE(uname) \
197 static inline int TestClearPage##uname(struct page *page) { return 0; }
199 #define __TESTCLEARFLAG_FALSE(uname) \
200 static inline int __TestClearPage##uname(struct page *page) { return 0; }
202 #define PAGEFLAG_FALSE(uname) TESTPAGEFLAG_FALSE(uname) \
203 SETPAGEFLAG_NOOP(uname) CLEARPAGEFLAG_NOOP(uname)
205 #define TESTSCFLAG_FALSE(uname) \
206 TESTSETFLAG_FALSE(uname) TESTCLEARFLAG_FALSE(uname)
208 struct page; /* forward declaration */
210 TESTPAGEFLAG(Locked, locked)
211 PAGEFLAG(Error, error) TESTCLEARFLAG(Error, error)
212 PAGEFLAG(Referenced, referenced) TESTCLEARFLAG(Referenced, referenced)
213 __SETPAGEFLAG(Referenced, referenced)
214 PAGEFLAG(Dirty, dirty) TESTSCFLAG(Dirty, dirty) __CLEARPAGEFLAG(Dirty, dirty)
215 PAGEFLAG(LRU, lru) __CLEARPAGEFLAG(LRU, lru)
216 PAGEFLAG(Active, active) __CLEARPAGEFLAG(Active, active)
217 TESTCLEARFLAG(Active, active)
218 __PAGEFLAG(Slab, slab)
219 PAGEFLAG(Checked, checked) /* Used by some filesystems */
220 PAGEFLAG(Pinned, pinned) TESTSCFLAG(Pinned, pinned) /* Xen */
221 PAGEFLAG(SavePinned, savepinned); /* Xen */
222 PAGEFLAG(Foreign, foreign); /* Xen */
223 PAGEFLAG(Reserved, reserved) __CLEARPAGEFLAG(Reserved, reserved)
224 PAGEFLAG(SwapBacked, swapbacked) __CLEARPAGEFLAG(SwapBacked, swapbacked)
225 __SETPAGEFLAG(SwapBacked, swapbacked)
227 __PAGEFLAG(SlobFree, slob_free)
230 * Private page markings that may be used by the filesystem that owns the page
231 * for its own purposes.
232 * - PG_private and PG_private_2 cause releasepage() and co to be invoked
234 PAGEFLAG(Private, private) __SETPAGEFLAG(Private, private)
235 __CLEARPAGEFLAG(Private, private)
236 PAGEFLAG(Private2, private_2) TESTSCFLAG(Private2, private_2)
237 PAGEFLAG(OwnerPriv1, owner_priv_1) TESTCLEARFLAG(OwnerPriv1, owner_priv_1)
240 * Only test-and-set exist for PG_writeback. The unconditional operators are
241 * risky: they bypass page accounting.
243 TESTPAGEFLAG(Writeback, writeback) TESTSCFLAG(Writeback, writeback)
244 PAGEFLAG(MappedToDisk, mappedtodisk)
246 /* PG_readahead is only used for reads; PG_reclaim is only for writes */
247 PAGEFLAG(Reclaim, reclaim) TESTCLEARFLAG(Reclaim, reclaim)
248 PAGEFLAG(Readahead, reclaim) TESTCLEARFLAG(Readahead, reclaim)
250 #ifdef CONFIG_HIGHMEM
252 * Must use a macro here due to header dependency issues. page_zone() is not
253 * available at this point.
255 #define PageHighMem(__p) is_highmem(page_zone(__p))
257 PAGEFLAG_FALSE(HighMem)
261 PAGEFLAG(SwapCache, swapcache)
263 PAGEFLAG_FALSE(SwapCache)
266 PAGEFLAG(Unevictable, unevictable) __CLEARPAGEFLAG(Unevictable, unevictable)
267 TESTCLEARFLAG(Unevictable, unevictable)
270 PAGEFLAG(Mlocked, mlocked) __CLEARPAGEFLAG(Mlocked, mlocked)
271 TESTSCFLAG(Mlocked, mlocked) __TESTCLEARFLAG(Mlocked, mlocked)
273 PAGEFLAG_FALSE(Mlocked) __CLEARPAGEFLAG_NOOP(Mlocked)
274 TESTSCFLAG_FALSE(Mlocked) __TESTCLEARFLAG_FALSE(Mlocked)
277 #ifdef CONFIG_ARCH_USES_PG_UNCACHED
278 PAGEFLAG(Uncached, uncached)
280 PAGEFLAG_FALSE(Uncached)
283 #ifdef CONFIG_MEMORY_FAILURE
284 PAGEFLAG(HWPoison, hwpoison)
285 TESTSCFLAG(HWPoison, hwpoison)
286 #define __PG_HWPOISON (1UL << PG_hwpoison)
288 PAGEFLAG_FALSE(HWPoison)
289 #define __PG_HWPOISON 0
293 * On an anonymous page mapped into a user virtual memory area,
294 * page->mapping points to its anon_vma, not to a struct address_space;
295 * with the PAGE_MAPPING_ANON bit set to distinguish it. See rmap.h.
297 * On an anonymous page in a VM_MERGEABLE area, if CONFIG_KSM is enabled,
298 * the PAGE_MAPPING_KSM bit may be set along with the PAGE_MAPPING_ANON bit;
299 * and then page->mapping points, not to an anon_vma, but to a private
300 * structure which KSM associates with that merged page. See ksm.h.
302 * PAGE_MAPPING_KSM without PAGE_MAPPING_ANON is currently never used.
304 * Please note that, confusingly, "page_mapping" refers to the inode
305 * address_space which maps the page from disk; whereas "page_mapped"
306 * refers to user virtual address space into which the page is mapped.
308 #define PAGE_MAPPING_ANON 1
309 #define PAGE_MAPPING_KSM 2
310 #define PAGE_MAPPING_FLAGS (PAGE_MAPPING_ANON | PAGE_MAPPING_KSM)
312 static inline int PageAnon(struct page *page)
314 return ((unsigned long)page->mapping & PAGE_MAPPING_ANON) != 0;
319 * A KSM page is one of those write-protected "shared pages" or "merged pages"
320 * which KSM maps into multiple mms, wherever identical anonymous page content
321 * is found in VM_MERGEABLE vmas. It's a PageAnon page, pointing not to any
322 * anon_vma, but to that page's node of the stable tree.
324 static inline int PageKsm(struct page *page)
326 return ((unsigned long)page->mapping & PAGE_MAPPING_FLAGS) ==
327 (PAGE_MAPPING_ANON | PAGE_MAPPING_KSM);
330 TESTPAGEFLAG_FALSE(Ksm)
333 u64 stable_page_flags(struct page *page);
335 static inline int PageUptodate(struct page *page)
337 int ret = test_bit(PG_uptodate, &(page)->flags);
340 * Must ensure that the data we read out of the page is loaded
341 * _after_ we've loaded page->flags to check for PageUptodate.
342 * We can skip the barrier if the page is not uptodate, because
343 * we wouldn't be reading anything from it.
345 * See SetPageUptodate() for the other side of the story.
353 static inline void __SetPageUptodate(struct page *page)
356 __set_bit(PG_uptodate, &(page)->flags);
359 static inline void SetPageUptodate(struct page *page)
362 * Memory barrier must be issued before setting the PG_uptodate bit,
363 * so that all previous stores issued in order to bring the page
364 * uptodate are actually visible before PageUptodate becomes true.
367 set_bit(PG_uptodate, &(page)->flags);
370 CLEARPAGEFLAG(Uptodate, uptodate)
372 int test_clear_page_writeback(struct page *page);
373 int __test_set_page_writeback(struct page *page, bool keep_write);
375 #define test_set_page_writeback(page) \
376 __test_set_page_writeback(page, false)
377 #define test_set_page_writeback_keepwrite(page) \
378 __test_set_page_writeback(page, true)
380 static inline void set_page_writeback(struct page *page)
382 test_set_page_writeback(page);
385 static inline void set_page_writeback_keepwrite(struct page *page)
387 test_set_page_writeback_keepwrite(page);
390 #ifdef CONFIG_PAGEFLAGS_EXTENDED
392 * System with lots of page flags available. This allows separate
393 * flags for PageHead() and PageTail() checks of compound pages so that bit
394 * tests can be used in performance sensitive paths. PageCompound is
395 * generally not used in hot code paths except arch/powerpc/mm/init_64.c
396 * and arch/powerpc/kvm/book3s_64_vio_hv.c which use it to detect huge pages
397 * and avoid handling those in real mode.
399 __PAGEFLAG(Head, head) CLEARPAGEFLAG(Head, head)
400 __PAGEFLAG(Tail, tail)
402 static inline int PageCompound(struct page *page)
404 return page->flags & ((1L << PG_head) | (1L << PG_tail));
407 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
408 static inline void ClearPageCompound(struct page *page)
410 BUG_ON(!PageHead(page));
415 #define PG_head_mask ((1L << PG_head))
419 * Reduce page flag use as much as possible by overlapping
420 * compound page flags with the flags used for page cache pages. Possible
421 * because PageCompound is always set for compound pages and not for
422 * pages on the LRU and/or pagecache.
424 TESTPAGEFLAG(Compound, compound)
425 __SETPAGEFLAG(Head, compound) __CLEARPAGEFLAG(Head, compound)
428 * PG_reclaim is used in combination with PG_compound to mark the
429 * head and tail of a compound page. This saves one page flag
430 * but makes it impossible to use compound pages for the page cache.
431 * The PG_reclaim bit would have to be used for reclaim or readahead
432 * if compound pages enter the page cache.
434 * PG_compound & PG_reclaim => Tail page
435 * PG_compound & ~PG_reclaim => Head page
437 #define PG_head_mask ((1L << PG_compound))
438 #define PG_head_tail_mask ((1L << PG_compound) | (1L << PG_reclaim))
440 static inline int PageHead(struct page *page)
442 return ((page->flags & PG_head_tail_mask) == PG_head_mask);
445 static inline int PageTail(struct page *page)
447 return ((page->flags & PG_head_tail_mask) == PG_head_tail_mask);
450 static inline void __SetPageTail(struct page *page)
452 page->flags |= PG_head_tail_mask;
455 static inline void __ClearPageTail(struct page *page)
457 page->flags &= ~PG_head_tail_mask;
460 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
461 static inline void ClearPageCompound(struct page *page)
463 BUG_ON((page->flags & PG_head_tail_mask) != (1 << PG_compound));
464 clear_bit(PG_compound, &page->flags);
468 #endif /* !PAGEFLAGS_EXTENDED */
470 #ifdef CONFIG_HUGETLB_PAGE
471 int PageHuge(struct page *page);
472 int PageHeadHuge(struct page *page);
473 bool page_huge_active(struct page *page);
475 TESTPAGEFLAG_FALSE(Huge)
476 TESTPAGEFLAG_FALSE(HeadHuge)
478 static inline bool page_huge_active(struct page *page)
485 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
487 * PageHuge() only returns true for hugetlbfs pages, but not for
488 * normal or transparent huge pages.
490 * PageTransHuge() returns true for both transparent huge and
491 * hugetlbfs pages, but not normal pages. PageTransHuge() can only be
492 * called only in the core VM paths where hugetlbfs pages can't exist.
494 static inline int PageTransHuge(struct page *page)
496 VM_BUG_ON_PAGE(PageTail(page), page);
497 return PageHead(page);
501 * PageTransCompound returns true for both transparent huge pages
502 * and hugetlbfs pages, so it should only be called when it's known
503 * that hugetlbfs pages aren't involved.
505 static inline int PageTransCompound(struct page *page)
507 return PageCompound(page);
511 * PageTransTail returns true for both transparent huge pages
512 * and hugetlbfs pages, so it should only be called when it's known
513 * that hugetlbfs pages aren't involved.
515 static inline int PageTransTail(struct page *page)
517 return PageTail(page);
522 static inline int PageTransHuge(struct page *page)
527 static inline int PageTransCompound(struct page *page)
532 static inline int PageTransTail(struct page *page)
539 * PageBuddy() indicate that the page is free and in the buddy system
540 * (see mm/page_alloc.c).
542 * PAGE_BUDDY_MAPCOUNT_VALUE must be <= -2 but better not too close to
543 * -2 so that an underflow of the page_mapcount() won't be mistaken
544 * for a genuine PAGE_BUDDY_MAPCOUNT_VALUE. -128 can be created very
545 * efficiently by most CPU architectures.
547 #define PAGE_BUDDY_MAPCOUNT_VALUE (-128)
549 static inline int PageBuddy(struct page *page)
551 return atomic_read(&page->_mapcount) == PAGE_BUDDY_MAPCOUNT_VALUE;
554 static inline void __SetPageBuddy(struct page *page)
556 VM_BUG_ON_PAGE(atomic_read(&page->_mapcount) != -1, page);
557 atomic_set(&page->_mapcount, PAGE_BUDDY_MAPCOUNT_VALUE);
560 static inline void __ClearPageBuddy(struct page *page)
562 VM_BUG_ON_PAGE(!PageBuddy(page), page);
563 atomic_set(&page->_mapcount, -1);
566 #define PAGE_BALLOON_MAPCOUNT_VALUE (-256)
568 static inline int PageBalloon(struct page *page)
570 return atomic_read(&page->_mapcount) == PAGE_BALLOON_MAPCOUNT_VALUE;
573 static inline void __SetPageBalloon(struct page *page)
575 VM_BUG_ON_PAGE(atomic_read(&page->_mapcount) != -1, page);
576 atomic_set(&page->_mapcount, PAGE_BALLOON_MAPCOUNT_VALUE);
579 static inline void __ClearPageBalloon(struct page *page)
581 VM_BUG_ON_PAGE(!PageBalloon(page), page);
582 atomic_set(&page->_mapcount, -1);
586 * If network-based swap is enabled, sl*b must keep track of whether pages
587 * were allocated from pfmemalloc reserves.
589 static inline int PageSlabPfmemalloc(struct page *page)
591 VM_BUG_ON_PAGE(!PageSlab(page), page);
592 return PageActive(page);
595 static inline void SetPageSlabPfmemalloc(struct page *page)
597 VM_BUG_ON_PAGE(!PageSlab(page), page);
601 static inline void __ClearPageSlabPfmemalloc(struct page *page)
603 VM_BUG_ON_PAGE(!PageSlab(page), page);
604 __ClearPageActive(page);
607 static inline void ClearPageSlabPfmemalloc(struct page *page)
609 VM_BUG_ON_PAGE(!PageSlab(page), page);
610 ClearPageActive(page);
614 #define __PG_MLOCKED (1 << PG_mlocked)
616 #define __PG_MLOCKED 0
619 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
620 #define __PG_COMPOUND_LOCK (1 << PG_compound_lock)
622 #define __PG_COMPOUND_LOCK 0
626 * Flags checked when a page is freed. Pages being freed should not have
627 * these flags set. It they are, there is a problem.
629 #define PAGE_FLAGS_CHECK_AT_FREE \
630 (1 << PG_lru | 1 << PG_locked | \
631 1 << PG_private | 1 << PG_private_2 | \
632 1 << PG_writeback | 1 << PG_reserved | \
633 1 << PG_slab | 1 << PG_swapcache | 1 << PG_active | \
634 1 << PG_unevictable | __PG_MLOCKED | \
638 * Flags checked when a page is prepped for return by the page allocator.
639 * Pages being prepped should not have these flags set. It they are set,
640 * there has been a kernel bug or struct page corruption.
642 * __PG_HWPOISON is exceptional because it needs to be kept beyond page's
643 * alloc-free cycle to prevent from reusing the page.
645 #define PAGE_FLAGS_CHECK_AT_PREP \
646 (((1 << NR_PAGEFLAGS) - 1) & ~__PG_HWPOISON)
648 #define PAGE_FLAGS_PRIVATE \
649 (1 << PG_private | 1 << PG_private_2)
651 * page_has_private - Determine if page has private stuff
652 * @page: The page to be checked
654 * Determine if a page has private stuff, indicating that release routines
655 * should be invoked upon it.
657 static inline int page_has_private(struct page *page)
659 return !!(page->flags & PAGE_FLAGS_PRIVATE);
662 #endif /* !__GENERATING_BOUNDS_H */
664 #endif /* PAGE_FLAGS_H */