xref: /linux-6.15/include/linux/page-flags.h (revision fc4fa6e1)
1 /*
2  * Macros for manipulating and testing page->flags
3  */
4 
5 #ifndef PAGE_FLAGS_H
6 #define PAGE_FLAGS_H
7 
8 #include <linux/types.h>
9 #include <linux/bug.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 */
15 
16 /*
17  * Various page->flags bits:
18  *
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)...
21  *
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.
25  *
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.
29  *
30  * PG_locked also pins a page in pagecache, and blocks truncation of the file
31  * while it is held.
32  *
33  * page_waitqueue(page) is a wait queue of all tasks waiting for the page
34  * to become unlocked.
35  *
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.
38  *
39  * PG_referenced, PG_reclaim are used for page reclaim for anonymous and
40  * file-backed pagecache (see mm/vmscan.c).
41  *
42  * PG_error is set to indicate that an I/O error occurred on this page.
43  *
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
46  * the page cache.
47  *
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
51  * address space...
52  *
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!
56  */
57 
58 /*
59  * Don't use the *_dontuse flags.  Use the macros.  Otherwise you'll break
60  * locked- and dirty-page accounting.
61  *
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.
65  *
66  *  | FIELD | ... | FLAGS |
67  *  N-1           ^       0
68  *               (NR_PAGEFLAGS)
69  *
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).
73  */
74 enum pageflags {
75 	PG_locked,		/* Page is locked. Don't touch. */
76 	PG_error,
77 	PG_referenced,
78 	PG_uptodate,
79 	PG_dirty,
80 	PG_lru,
81 	PG_active,
82 	PG_slab,
83 	PG_owner_priv_1,	/* Owner use. If pagecache, fs may use*/
84 	PG_arch_1,
85 	PG_reserved,
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 */
92 #else
93 	PG_compound,		/* A compound page */
94 #endif
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"  */
100 #ifdef CONFIG_MMU
101 	PG_mlocked,		/* Page is vma mlocked */
102 #endif
103 #ifdef CONFIG_ARCH_USES_PG_UNCACHED
104 	PG_uncached,		/* Page has been mapped as uncached */
105 #endif
106 #ifdef CONFIG_MEMORY_FAILURE
107 	PG_hwpoison,		/* hardware poisoned page. Don't touch */
108 #endif
109 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
110 	PG_compound_lock,
111 #endif
112 #if defined(CONFIG_IDLE_PAGE_TRACKING) && defined(CONFIG_64BIT)
113 	PG_young,
114 	PG_idle,
115 #endif
116 	__NR_PAGEFLAGS,
117 
118 	/* Filesystems */
119 	PG_checked = PG_owner_priv_1,
120 
121 	/* Two page bits are conscripted by FS-Cache to maintain local caching
122 	 * state.  These bits are set on pages belonging to the netfs's inodes
123 	 * when those inodes are being locally cached.
124 	 */
125 	PG_fscache = PG_private_2,	/* page backed by cache */
126 
127 	/* XEN */
128 	/* Pinned in Xen as a read-only pagetable page. */
129 	PG_pinned = PG_owner_priv_1,
130 	/* Pinned as part of domain save (see xen_mm_pin_all()). */
131 	PG_savepinned = PG_dirty,
132 	/* Has a grant mapping of another (foreign) domain's page. */
133 	PG_foreign = PG_owner_priv_1,
134 
135 	/* SLOB */
136 	PG_slob_free = PG_private,
137 };
138 
139 #ifndef __GENERATING_BOUNDS_H
140 
141 /*
142  * Macros to create function definitions for page flags
143  */
144 #define TESTPAGEFLAG(uname, lname)					\
145 static inline int Page##uname(const struct page *page)			\
146 			{ return test_bit(PG_##lname, &page->flags); }
147 
148 #define SETPAGEFLAG(uname, lname)					\
149 static inline void SetPage##uname(struct page *page)			\
150 			{ set_bit(PG_##lname, &page->flags); }
151 
152 #define CLEARPAGEFLAG(uname, lname)					\
153 static inline void ClearPage##uname(struct page *page)			\
154 			{ clear_bit(PG_##lname, &page->flags); }
155 
156 #define __SETPAGEFLAG(uname, lname)					\
157 static inline void __SetPage##uname(struct page *page)			\
158 			{ __set_bit(PG_##lname, &page->flags); }
159 
160 #define __CLEARPAGEFLAG(uname, lname)					\
161 static inline void __ClearPage##uname(struct page *page)		\
162 			{ __clear_bit(PG_##lname, &page->flags); }
163 
164 #define TESTSETFLAG(uname, lname)					\
165 static inline int TestSetPage##uname(struct page *page)			\
166 		{ return test_and_set_bit(PG_##lname, &page->flags); }
167 
168 #define TESTCLEARFLAG(uname, lname)					\
169 static inline int TestClearPage##uname(struct page *page)		\
170 		{ return test_and_clear_bit(PG_##lname, &page->flags); }
171 
172 #define __TESTCLEARFLAG(uname, lname)					\
173 static inline int __TestClearPage##uname(struct page *page)		\
174 		{ return __test_and_clear_bit(PG_##lname, &page->flags); }
175 
176 #define PAGEFLAG(uname, lname) TESTPAGEFLAG(uname, lname)		\
177 	SETPAGEFLAG(uname, lname) CLEARPAGEFLAG(uname, lname)
178 
179 #define __PAGEFLAG(uname, lname) TESTPAGEFLAG(uname, lname)		\
180 	__SETPAGEFLAG(uname, lname)  __CLEARPAGEFLAG(uname, lname)
181 
182 #define TESTSCFLAG(uname, lname)					\
183 	TESTSETFLAG(uname, lname) TESTCLEARFLAG(uname, lname)
184 
185 #define TESTPAGEFLAG_FALSE(uname)					\
186 static inline int Page##uname(const struct page *page) { return 0; }
187 
188 #define SETPAGEFLAG_NOOP(uname)						\
189 static inline void SetPage##uname(struct page *page) {  }
190 
191 #define CLEARPAGEFLAG_NOOP(uname)					\
192 static inline void ClearPage##uname(struct page *page) {  }
193 
194 #define __CLEARPAGEFLAG_NOOP(uname)					\
195 static inline void __ClearPage##uname(struct page *page) {  }
196 
197 #define TESTSETFLAG_FALSE(uname)					\
198 static inline int TestSetPage##uname(struct page *page) { return 0; }
199 
200 #define TESTCLEARFLAG_FALSE(uname)					\
201 static inline int TestClearPage##uname(struct page *page) { return 0; }
202 
203 #define __TESTCLEARFLAG_FALSE(uname)					\
204 static inline int __TestClearPage##uname(struct page *page) { return 0; }
205 
206 #define PAGEFLAG_FALSE(uname) TESTPAGEFLAG_FALSE(uname)			\
207 	SETPAGEFLAG_NOOP(uname) CLEARPAGEFLAG_NOOP(uname)
208 
209 #define TESTSCFLAG_FALSE(uname)						\
210 	TESTSETFLAG_FALSE(uname) TESTCLEARFLAG_FALSE(uname)
211 
212 struct page;	/* forward declaration */
213 
214 TESTPAGEFLAG(Locked, locked)
215 PAGEFLAG(Error, error) TESTCLEARFLAG(Error, error)
216 PAGEFLAG(Referenced, referenced) TESTCLEARFLAG(Referenced, referenced)
217 	__SETPAGEFLAG(Referenced, referenced)
218 PAGEFLAG(Dirty, dirty) TESTSCFLAG(Dirty, dirty) __CLEARPAGEFLAG(Dirty, dirty)
219 PAGEFLAG(LRU, lru) __CLEARPAGEFLAG(LRU, lru)
220 PAGEFLAG(Active, active) __CLEARPAGEFLAG(Active, active)
221 	TESTCLEARFLAG(Active, active)
222 __PAGEFLAG(Slab, slab)
223 PAGEFLAG(Checked, checked)		/* Used by some filesystems */
224 PAGEFLAG(Pinned, pinned) TESTSCFLAG(Pinned, pinned)	/* Xen */
225 PAGEFLAG(SavePinned, savepinned);			/* Xen */
226 PAGEFLAG(Foreign, foreign);				/* Xen */
227 PAGEFLAG(Reserved, reserved) __CLEARPAGEFLAG(Reserved, reserved)
228 PAGEFLAG(SwapBacked, swapbacked) __CLEARPAGEFLAG(SwapBacked, swapbacked)
229 	__SETPAGEFLAG(SwapBacked, swapbacked)
230 
231 __PAGEFLAG(SlobFree, slob_free)
232 
233 /*
234  * Private page markings that may be used by the filesystem that owns the page
235  * for its own purposes.
236  * - PG_private and PG_private_2 cause releasepage() and co to be invoked
237  */
238 PAGEFLAG(Private, private) __SETPAGEFLAG(Private, private)
239 	__CLEARPAGEFLAG(Private, private)
240 PAGEFLAG(Private2, private_2) TESTSCFLAG(Private2, private_2)
241 PAGEFLAG(OwnerPriv1, owner_priv_1) TESTCLEARFLAG(OwnerPriv1, owner_priv_1)
242 
243 /*
244  * Only test-and-set exist for PG_writeback.  The unconditional operators are
245  * risky: they bypass page accounting.
246  */
247 TESTPAGEFLAG(Writeback, writeback) TESTSCFLAG(Writeback, writeback)
248 PAGEFLAG(MappedToDisk, mappedtodisk)
249 
250 /* PG_readahead is only used for reads; PG_reclaim is only for writes */
251 PAGEFLAG(Reclaim, reclaim) TESTCLEARFLAG(Reclaim, reclaim)
252 PAGEFLAG(Readahead, reclaim) TESTCLEARFLAG(Readahead, reclaim)
253 
254 #ifdef CONFIG_HIGHMEM
255 /*
256  * Must use a macro here due to header dependency issues. page_zone() is not
257  * available at this point.
258  */
259 #define PageHighMem(__p) is_highmem_idx(page_zonenum(__p))
260 #else
261 PAGEFLAG_FALSE(HighMem)
262 #endif
263 
264 #ifdef CONFIG_SWAP
265 PAGEFLAG(SwapCache, swapcache)
266 #else
267 PAGEFLAG_FALSE(SwapCache)
268 #endif
269 
270 PAGEFLAG(Unevictable, unevictable) __CLEARPAGEFLAG(Unevictable, unevictable)
271 	TESTCLEARFLAG(Unevictable, unevictable)
272 
273 #ifdef CONFIG_MMU
274 PAGEFLAG(Mlocked, mlocked) __CLEARPAGEFLAG(Mlocked, mlocked)
275 	TESTSCFLAG(Mlocked, mlocked) __TESTCLEARFLAG(Mlocked, mlocked)
276 #else
277 PAGEFLAG_FALSE(Mlocked) __CLEARPAGEFLAG_NOOP(Mlocked)
278 	TESTSCFLAG_FALSE(Mlocked) __TESTCLEARFLAG_FALSE(Mlocked)
279 #endif
280 
281 #ifdef CONFIG_ARCH_USES_PG_UNCACHED
282 PAGEFLAG(Uncached, uncached)
283 #else
284 PAGEFLAG_FALSE(Uncached)
285 #endif
286 
287 #ifdef CONFIG_MEMORY_FAILURE
288 PAGEFLAG(HWPoison, hwpoison)
289 TESTSCFLAG(HWPoison, hwpoison)
290 #define __PG_HWPOISON (1UL << PG_hwpoison)
291 #else
292 PAGEFLAG_FALSE(HWPoison)
293 #define __PG_HWPOISON 0
294 #endif
295 
296 #if defined(CONFIG_IDLE_PAGE_TRACKING) && defined(CONFIG_64BIT)
297 TESTPAGEFLAG(Young, young)
298 SETPAGEFLAG(Young, young)
299 TESTCLEARFLAG(Young, young)
300 PAGEFLAG(Idle, idle)
301 #endif
302 
303 /*
304  * On an anonymous page mapped into a user virtual memory area,
305  * page->mapping points to its anon_vma, not to a struct address_space;
306  * with the PAGE_MAPPING_ANON bit set to distinguish it.  See rmap.h.
307  *
308  * On an anonymous page in a VM_MERGEABLE area, if CONFIG_KSM is enabled,
309  * the PAGE_MAPPING_KSM bit may be set along with the PAGE_MAPPING_ANON bit;
310  * and then page->mapping points, not to an anon_vma, but to a private
311  * structure which KSM associates with that merged page.  See ksm.h.
312  *
313  * PAGE_MAPPING_KSM without PAGE_MAPPING_ANON is currently never used.
314  *
315  * Please note that, confusingly, "page_mapping" refers to the inode
316  * address_space which maps the page from disk; whereas "page_mapped"
317  * refers to user virtual address space into which the page is mapped.
318  */
319 #define PAGE_MAPPING_ANON	1
320 #define PAGE_MAPPING_KSM	2
321 #define PAGE_MAPPING_FLAGS	(PAGE_MAPPING_ANON | PAGE_MAPPING_KSM)
322 
323 static inline int PageAnon(struct page *page)
324 {
325 	return ((unsigned long)page->mapping & PAGE_MAPPING_ANON) != 0;
326 }
327 
328 #ifdef CONFIG_KSM
329 /*
330  * A KSM page is one of those write-protected "shared pages" or "merged pages"
331  * which KSM maps into multiple mms, wherever identical anonymous page content
332  * is found in VM_MERGEABLE vmas.  It's a PageAnon page, pointing not to any
333  * anon_vma, but to that page's node of the stable tree.
334  */
335 static inline int PageKsm(struct page *page)
336 {
337 	return ((unsigned long)page->mapping & PAGE_MAPPING_FLAGS) ==
338 				(PAGE_MAPPING_ANON | PAGE_MAPPING_KSM);
339 }
340 #else
341 TESTPAGEFLAG_FALSE(Ksm)
342 #endif
343 
344 u64 stable_page_flags(struct page *page);
345 
346 static inline int PageUptodate(struct page *page)
347 {
348 	int ret = test_bit(PG_uptodate, &(page)->flags);
349 
350 	/*
351 	 * Must ensure that the data we read out of the page is loaded
352 	 * _after_ we've loaded page->flags to check for PageUptodate.
353 	 * We can skip the barrier if the page is not uptodate, because
354 	 * we wouldn't be reading anything from it.
355 	 *
356 	 * See SetPageUptodate() for the other side of the story.
357 	 */
358 	if (ret)
359 		smp_rmb();
360 
361 	return ret;
362 }
363 
364 static inline void __SetPageUptodate(struct page *page)
365 {
366 	smp_wmb();
367 	__set_bit(PG_uptodate, &(page)->flags);
368 }
369 
370 static inline void SetPageUptodate(struct page *page)
371 {
372 	/*
373 	 * Memory barrier must be issued before setting the PG_uptodate bit,
374 	 * so that all previous stores issued in order to bring the page
375 	 * uptodate are actually visible before PageUptodate becomes true.
376 	 */
377 	smp_wmb();
378 	set_bit(PG_uptodate, &(page)->flags);
379 }
380 
381 CLEARPAGEFLAG(Uptodate, uptodate)
382 
383 int test_clear_page_writeback(struct page *page);
384 int __test_set_page_writeback(struct page *page, bool keep_write);
385 
386 #define test_set_page_writeback(page)			\
387 	__test_set_page_writeback(page, false)
388 #define test_set_page_writeback_keepwrite(page)	\
389 	__test_set_page_writeback(page, true)
390 
391 static inline void set_page_writeback(struct page *page)
392 {
393 	test_set_page_writeback(page);
394 }
395 
396 static inline void set_page_writeback_keepwrite(struct page *page)
397 {
398 	test_set_page_writeback_keepwrite(page);
399 }
400 
401 #ifdef CONFIG_PAGEFLAGS_EXTENDED
402 /*
403  * System with lots of page flags available. This allows separate
404  * flags for PageHead() and PageTail() checks of compound pages so that bit
405  * tests can be used in performance sensitive paths. PageCompound is
406  * generally not used in hot code paths except arch/powerpc/mm/init_64.c
407  * and arch/powerpc/kvm/book3s_64_vio_hv.c which use it to detect huge pages
408  * and avoid handling those in real mode.
409  */
410 __PAGEFLAG(Head, head) CLEARPAGEFLAG(Head, head)
411 __PAGEFLAG(Tail, tail)
412 
413 static inline int PageCompound(struct page *page)
414 {
415 	return page->flags & ((1L << PG_head) | (1L << PG_tail));
416 
417 }
418 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
419 static inline void ClearPageCompound(struct page *page)
420 {
421 	BUG_ON(!PageHead(page));
422 	ClearPageHead(page);
423 }
424 #endif
425 
426 #define PG_head_mask ((1L << PG_head))
427 
428 #else
429 /*
430  * Reduce page flag use as much as possible by overlapping
431  * compound page flags with the flags used for page cache pages. Possible
432  * because PageCompound is always set for compound pages and not for
433  * pages on the LRU and/or pagecache.
434  */
435 TESTPAGEFLAG(Compound, compound)
436 __SETPAGEFLAG(Head, compound)  __CLEARPAGEFLAG(Head, compound)
437 
438 /*
439  * PG_reclaim is used in combination with PG_compound to mark the
440  * head and tail of a compound page. This saves one page flag
441  * but makes it impossible to use compound pages for the page cache.
442  * The PG_reclaim bit would have to be used for reclaim or readahead
443  * if compound pages enter the page cache.
444  *
445  * PG_compound & PG_reclaim	=> Tail page
446  * PG_compound & ~PG_reclaim	=> Head page
447  */
448 #define PG_head_mask ((1L << PG_compound))
449 #define PG_head_tail_mask ((1L << PG_compound) | (1L << PG_reclaim))
450 
451 static inline int PageHead(struct page *page)
452 {
453 	return ((page->flags & PG_head_tail_mask) == PG_head_mask);
454 }
455 
456 static inline int PageTail(struct page *page)
457 {
458 	return ((page->flags & PG_head_tail_mask) == PG_head_tail_mask);
459 }
460 
461 static inline void __SetPageTail(struct page *page)
462 {
463 	page->flags |= PG_head_tail_mask;
464 }
465 
466 static inline void __ClearPageTail(struct page *page)
467 {
468 	page->flags &= ~PG_head_tail_mask;
469 }
470 
471 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
472 static inline void ClearPageCompound(struct page *page)
473 {
474 	BUG_ON((page->flags & PG_head_tail_mask) != (1 << PG_compound));
475 	clear_bit(PG_compound, &page->flags);
476 }
477 #endif
478 
479 #endif /* !PAGEFLAGS_EXTENDED */
480 
481 #ifdef CONFIG_HUGETLB_PAGE
482 int PageHuge(struct page *page);
483 int PageHeadHuge(struct page *page);
484 bool page_huge_active(struct page *page);
485 #else
486 TESTPAGEFLAG_FALSE(Huge)
487 TESTPAGEFLAG_FALSE(HeadHuge)
488 
489 static inline bool page_huge_active(struct page *page)
490 {
491 	return 0;
492 }
493 #endif
494 
495 
496 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
497 /*
498  * PageHuge() only returns true for hugetlbfs pages, but not for
499  * normal or transparent huge pages.
500  *
501  * PageTransHuge() returns true for both transparent huge and
502  * hugetlbfs pages, but not normal pages. PageTransHuge() can only be
503  * called only in the core VM paths where hugetlbfs pages can't exist.
504  */
505 static inline int PageTransHuge(struct page *page)
506 {
507 	VM_BUG_ON_PAGE(PageTail(page), page);
508 	return PageHead(page);
509 }
510 
511 /*
512  * PageTransCompound returns true for both transparent huge pages
513  * and hugetlbfs pages, so it should only be called when it's known
514  * that hugetlbfs pages aren't involved.
515  */
516 static inline int PageTransCompound(struct page *page)
517 {
518 	return PageCompound(page);
519 }
520 
521 /*
522  * PageTransTail returns true for both transparent huge pages
523  * and hugetlbfs pages, so it should only be called when it's known
524  * that hugetlbfs pages aren't involved.
525  */
526 static inline int PageTransTail(struct page *page)
527 {
528 	return PageTail(page);
529 }
530 
531 #else
532 
533 static inline int PageTransHuge(struct page *page)
534 {
535 	return 0;
536 }
537 
538 static inline int PageTransCompound(struct page *page)
539 {
540 	return 0;
541 }
542 
543 static inline int PageTransTail(struct page *page)
544 {
545 	return 0;
546 }
547 #endif
548 
549 /*
550  * PageBuddy() indicate that the page is free and in the buddy system
551  * (see mm/page_alloc.c).
552  *
553  * PAGE_BUDDY_MAPCOUNT_VALUE must be <= -2 but better not too close to
554  * -2 so that an underflow of the page_mapcount() won't be mistaken
555  * for a genuine PAGE_BUDDY_MAPCOUNT_VALUE. -128 can be created very
556  * efficiently by most CPU architectures.
557  */
558 #define PAGE_BUDDY_MAPCOUNT_VALUE (-128)
559 
560 static inline int PageBuddy(struct page *page)
561 {
562 	return atomic_read(&page->_mapcount) == PAGE_BUDDY_MAPCOUNT_VALUE;
563 }
564 
565 static inline void __SetPageBuddy(struct page *page)
566 {
567 	VM_BUG_ON_PAGE(atomic_read(&page->_mapcount) != -1, page);
568 	atomic_set(&page->_mapcount, PAGE_BUDDY_MAPCOUNT_VALUE);
569 }
570 
571 static inline void __ClearPageBuddy(struct page *page)
572 {
573 	VM_BUG_ON_PAGE(!PageBuddy(page), page);
574 	atomic_set(&page->_mapcount, -1);
575 }
576 
577 #define PAGE_BALLOON_MAPCOUNT_VALUE (-256)
578 
579 static inline int PageBalloon(struct page *page)
580 {
581 	return atomic_read(&page->_mapcount) == PAGE_BALLOON_MAPCOUNT_VALUE;
582 }
583 
584 static inline void __SetPageBalloon(struct page *page)
585 {
586 	VM_BUG_ON_PAGE(atomic_read(&page->_mapcount) != -1, page);
587 	atomic_set(&page->_mapcount, PAGE_BALLOON_MAPCOUNT_VALUE);
588 }
589 
590 static inline void __ClearPageBalloon(struct page *page)
591 {
592 	VM_BUG_ON_PAGE(!PageBalloon(page), page);
593 	atomic_set(&page->_mapcount, -1);
594 }
595 
596 /*
597  * If network-based swap is enabled, sl*b must keep track of whether pages
598  * were allocated from pfmemalloc reserves.
599  */
600 static inline int PageSlabPfmemalloc(struct page *page)
601 {
602 	VM_BUG_ON_PAGE(!PageSlab(page), page);
603 	return PageActive(page);
604 }
605 
606 static inline void SetPageSlabPfmemalloc(struct page *page)
607 {
608 	VM_BUG_ON_PAGE(!PageSlab(page), page);
609 	SetPageActive(page);
610 }
611 
612 static inline void __ClearPageSlabPfmemalloc(struct page *page)
613 {
614 	VM_BUG_ON_PAGE(!PageSlab(page), page);
615 	__ClearPageActive(page);
616 }
617 
618 static inline void ClearPageSlabPfmemalloc(struct page *page)
619 {
620 	VM_BUG_ON_PAGE(!PageSlab(page), page);
621 	ClearPageActive(page);
622 }
623 
624 #ifdef CONFIG_MMU
625 #define __PG_MLOCKED		(1 << PG_mlocked)
626 #else
627 #define __PG_MLOCKED		0
628 #endif
629 
630 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
631 #define __PG_COMPOUND_LOCK		(1 << PG_compound_lock)
632 #else
633 #define __PG_COMPOUND_LOCK		0
634 #endif
635 
636 /*
637  * Flags checked when a page is freed.  Pages being freed should not have
638  * these flags set.  It they are, there is a problem.
639  */
640 #define PAGE_FLAGS_CHECK_AT_FREE \
641 	(1 << PG_lru	 | 1 << PG_locked    | \
642 	 1 << PG_private | 1 << PG_private_2 | \
643 	 1 << PG_writeback | 1 << PG_reserved | \
644 	 1 << PG_slab	 | 1 << PG_swapcache | 1 << PG_active | \
645 	 1 << PG_unevictable | __PG_MLOCKED | \
646 	 __PG_COMPOUND_LOCK)
647 
648 /*
649  * Flags checked when a page is prepped for return by the page allocator.
650  * Pages being prepped should not have these flags set.  It they are set,
651  * there has been a kernel bug or struct page corruption.
652  *
653  * __PG_HWPOISON is exceptional because it needs to be kept beyond page's
654  * alloc-free cycle to prevent from reusing the page.
655  */
656 #define PAGE_FLAGS_CHECK_AT_PREP	\
657 	(((1 << NR_PAGEFLAGS) - 1) & ~__PG_HWPOISON)
658 
659 #define PAGE_FLAGS_PRIVATE				\
660 	(1 << PG_private | 1 << PG_private_2)
661 /**
662  * page_has_private - Determine if page has private stuff
663  * @page: The page to be checked
664  *
665  * Determine if a page has private stuff, indicating that release routines
666  * should be invoked upon it.
667  */
668 static inline int page_has_private(struct page *page)
669 {
670 	return !!(page->flags & PAGE_FLAGS_PRIVATE);
671 }
672 
673 #endif /* !__GENERATING_BOUNDS_H */
674 
675 #endif	/* PAGE_FLAGS_H */
676