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 #ifndef __GENERATING_BOUNDS_H
11 #include <linux/mm_types.h>
12 #include <generated/bounds.h>
13 #endif /* !__GENERATING_BOUNDS_H */
14
15 /*
16 * Various page->flags bits:
17 *
18 * PG_reserved is set for special pages, which can never be swapped out. Some
19 * of them might not even exist (eg empty_bad_page)...
20 *
21 * The PG_private bitflag is set on pagecache pages if they contain filesystem
22 * specific data (which is normally at page->private). It can be used by
23 * private allocations for its own usage.
24 *
25 * During initiation of disk I/O, PG_locked is set. This bit is set before I/O
26 * and cleared when writeback _starts_ or when read _completes_. PG_writeback
27 * is set before writeback starts and cleared when it finishes.
28 *
29 * PG_locked also pins a page in pagecache, and blocks truncation of the file
30 * while it is held.
31 *
32 * page_waitqueue(page) is a wait queue of all tasks waiting for the page
33 * to become unlocked.
34 *
35 * PG_uptodate tells whether the page's contents is valid. When a read
36 * completes, the page becomes uptodate, unless a disk I/O error happened.
37 *
38 * PG_referenced, PG_reclaim are used for page reclaim for anonymous and
39 * file-backed pagecache (see mm/vmscan.c).
40 *
41 * PG_error is set to indicate that an I/O error occurred on this page.
42 *
43 * PG_arch_1 is an architecture specific page state bit. The generic code
44 * guarantees that this bit is cleared for a page when it first is entered into
45 * the page cache.
46 *
47 * PG_highmem pages are not permanently mapped into the kernel virtual address
48 * space, they need to be kmapped separately for doing IO on the pages. The
49 * struct page (these bits with information) are always mapped into kernel
50 * address space...
51 *
52 * PG_hwpoison indicates that a page got corrupted in hardware and contains
53 * data with incorrect ECC bits that triggered a machine check. Accessing is
54 * not safe since it may cause another machine check. Don't touch!
55 */
56
57 /*
58 * Don't use the *_dontuse flags. Use the macros. Otherwise you'll break
59 * locked- and dirty-page accounting.
60 *
61 * The page flags field is split into two parts, the main flags area
62 * which extends from the low bits upwards, and the fields area which
63 * extends from the high bits downwards.
64 *
65 * | FIELD | ... | FLAGS |
66 * N-1 ^ 0
67 * (NR_PAGEFLAGS)
68 *
69 * The fields area is reserved for fields mapping zone, node (for NUMA) and
70 * SPARSEMEM section (for variants of SPARSEMEM that require section ids like
71 * SPARSEMEM_EXTREME with !SPARSEMEM_VMEMMAP).
72 */
73 enum pageflags {
74 PG_locked, /* Page is locked. Don't touch. */
75 PG_error,
76 PG_referenced,
77 PG_uptodate,
78 PG_dirty,
79 PG_lru,
80 PG_active,
81 PG_slab,
82 PG_owner_priv_1, /* Owner use. If pagecache, fs may use*/
83 PG_arch_1,
84 PG_reserved,
85 PG_private, /* If pagecache, has fs-private data */
86 PG_private_2, /* If pagecache, has fs aux data */
87 PG_writeback, /* Page is under writeback */
88 #ifdef CONFIG_PAGEFLAGS_EXTENDED
89 PG_head, /* A head page */
90 PG_tail, /* A tail page */
91 #else
92 PG_compound, /* A compound page */
93 #endif
94 PG_swapcache, /* Swap page: swp_entry_t in private */
95 PG_mappedtodisk, /* Has blocks allocated on-disk */
96 PG_reclaim, /* To be reclaimed asap */
97 PG_swapbacked, /* Page is backed by RAM/swap */
98 PG_unevictable, /* Page is "unevictable" */
99 #ifdef CONFIG_MMU
100 PG_mlocked, /* Page is vma mlocked */
101 #endif
102 #ifdef CONFIG_ARCH_USES_PG_UNCACHED
103 PG_uncached, /* Page has been mapped as uncached */
104 #endif
105 #ifdef CONFIG_MEMORY_FAILURE
106 PG_hwpoison, /* hardware poisoned page. Don't touch */
107 #endif
108 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
109 PG_compound_lock,
110 #endif
111 __NR_PAGEFLAGS,
112
113 /* Filesystems */
114 PG_checked = PG_owner_priv_1,
115
116 /* Two page bits are conscripted by FS-Cache to maintain local caching
117 * state. These bits are set on pages belonging to the netfs's inodes
118 * when those inodes are being locally cached.
119 */
120 PG_fscache = PG_private_2, /* page backed by cache */
121
122 /* XEN */
123 PG_pinned = PG_owner_priv_1,
124 PG_savepinned = PG_dirty,
125
126 /* SLOB */
127 PG_slob_free = PG_private,
128 };
129
130 #ifndef __GENERATING_BOUNDS_H
131
132 /*
133 * Macros to create function definitions for page flags
134 */
135 #define TESTPAGEFLAG(uname, lname) \
136 static inline int Page##uname(const struct page *page) \
137 { return test_bit(PG_##lname, &page->flags); }
138
139 #define SETPAGEFLAG(uname, lname) \
140 static inline void SetPage##uname(struct page *page) \
141 { set_bit(PG_##lname, &page->flags); }
142
143 #define CLEARPAGEFLAG(uname, lname) \
144 static inline void ClearPage##uname(struct page *page) \
145 { clear_bit(PG_##lname, &page->flags); }
146
147 #define __SETPAGEFLAG(uname, lname) \
148 static inline void __SetPage##uname(struct page *page) \
149 { __set_bit(PG_##lname, &page->flags); }
150
151 #define __CLEARPAGEFLAG(uname, lname) \
152 static inline void __ClearPage##uname(struct page *page) \
153 { __clear_bit(PG_##lname, &page->flags); }
154
155 #define TESTSETFLAG(uname, lname) \
156 static inline int TestSetPage##uname(struct page *page) \
157 { return test_and_set_bit(PG_##lname, &page->flags); }
158
159 #define TESTCLEARFLAG(uname, lname) \
160 static inline int TestClearPage##uname(struct page *page) \
161 { return test_and_clear_bit(PG_##lname, &page->flags); }
162
163 #define __TESTCLEARFLAG(uname, lname) \
164 static inline int __TestClearPage##uname(struct page *page) \
165 { return __test_and_clear_bit(PG_##lname, &page->flags); }
166
167 #define PAGEFLAG(uname, lname) TESTPAGEFLAG(uname, lname) \
168 SETPAGEFLAG(uname, lname) CLEARPAGEFLAG(uname, lname)
169
170 #define __PAGEFLAG(uname, lname) TESTPAGEFLAG(uname, lname) \
171 __SETPAGEFLAG(uname, lname) __CLEARPAGEFLAG(uname, lname)
172
173 #define PAGEFLAG_FALSE(uname) \
174 static inline int Page##uname(const struct page *page) \
175 { return 0; }
176
177 #define TESTSCFLAG(uname, lname) \
178 TESTSETFLAG(uname, lname) TESTCLEARFLAG(uname, lname)
179
180 #define SETPAGEFLAG_NOOP(uname) \
181 static inline void SetPage##uname(struct page *page) { }
182
183 #define CLEARPAGEFLAG_NOOP(uname) \
184 static inline void ClearPage##uname(struct page *page) { }
185
186 #define __CLEARPAGEFLAG_NOOP(uname) \
187 static inline void __ClearPage##uname(struct page *page) { }
188
189 #define TESTCLEARFLAG_FALSE(uname) \
190 static inline int TestClearPage##uname(struct page *page) { return 0; }
191
192 #define __TESTCLEARFLAG_FALSE(uname) \
193 static inline int __TestClearPage##uname(struct page *page) { return 0; }
194
195 struct page; /* forward declaration */
196
197 TESTPAGEFLAG(Locked, locked)
198 PAGEFLAG(Error, error) TESTCLEARFLAG(Error, error)
199 PAGEFLAG(Referenced, referenced) TESTCLEARFLAG(Referenced, referenced)
200 PAGEFLAG(Dirty, dirty) TESTSCFLAG(Dirty, dirty) __CLEARPAGEFLAG(Dirty, dirty)
201 PAGEFLAG(LRU, lru) __CLEARPAGEFLAG(LRU, lru)
202 PAGEFLAG(Active, active) __CLEARPAGEFLAG(Active, active)
203 TESTCLEARFLAG(Active, active)
204 __PAGEFLAG(Slab, slab)
205 PAGEFLAG(Checked, checked) /* Used by some filesystems */
206 PAGEFLAG(Pinned, pinned) TESTSCFLAG(Pinned, pinned) /* Xen */
207 PAGEFLAG(SavePinned, savepinned); /* Xen */
208 PAGEFLAG(Reserved, reserved) __CLEARPAGEFLAG(Reserved, reserved)
209 PAGEFLAG(SwapBacked, swapbacked) __CLEARPAGEFLAG(SwapBacked, swapbacked)
210
211 __PAGEFLAG(SlobFree, slob_free)
212
213 /*
214 * Private page markings that may be used by the filesystem that owns the page
215 * for its own purposes.
216 * - PG_private and PG_private_2 cause releasepage() and co to be invoked
217 */
218 PAGEFLAG(Private, private) __SETPAGEFLAG(Private, private)
219 __CLEARPAGEFLAG(Private, private)
220 PAGEFLAG(Private2, private_2) TESTSCFLAG(Private2, private_2)
221 PAGEFLAG(OwnerPriv1, owner_priv_1) TESTCLEARFLAG(OwnerPriv1, owner_priv_1)
222
223 /*
224 * Only test-and-set exist for PG_writeback. The unconditional operators are
225 * risky: they bypass page accounting.
226 */
227 TESTPAGEFLAG(Writeback, writeback) TESTSCFLAG(Writeback, writeback)
228 PAGEFLAG(MappedToDisk, mappedtodisk)
229
230 /* PG_readahead is only used for file reads; PG_reclaim is only for writes */
231 PAGEFLAG(Reclaim, reclaim) TESTCLEARFLAG(Reclaim, reclaim)
232 PAGEFLAG(Readahead, reclaim) /* Reminder to do async read-ahead */
233
234 #ifdef CONFIG_HIGHMEM
235 /*
236 * Must use a macro here due to header dependency issues. page_zone() is not
237 * available at this point.
238 */
239 #define PageHighMem(__p) is_highmem(page_zone(__p))
240 #else
241 PAGEFLAG_FALSE(HighMem)
242 #endif
243
244 #ifdef CONFIG_SWAP
245 PAGEFLAG(SwapCache, swapcache)
246 #else
247 PAGEFLAG_FALSE(SwapCache)
248 SETPAGEFLAG_NOOP(SwapCache) CLEARPAGEFLAG_NOOP(SwapCache)
249 #endif
250
251 PAGEFLAG(Unevictable, unevictable) __CLEARPAGEFLAG(Unevictable, unevictable)
252 TESTCLEARFLAG(Unevictable, unevictable)
253
254 #ifdef CONFIG_MMU
255 PAGEFLAG(Mlocked, mlocked) __CLEARPAGEFLAG(Mlocked, mlocked)
256 TESTSCFLAG(Mlocked, mlocked) __TESTCLEARFLAG(Mlocked, mlocked)
257 #else
258 PAGEFLAG_FALSE(Mlocked) SETPAGEFLAG_NOOP(Mlocked)
259 TESTCLEARFLAG_FALSE(Mlocked) __TESTCLEARFLAG_FALSE(Mlocked)
260 #endif
261
262 #ifdef CONFIG_ARCH_USES_PG_UNCACHED
263 PAGEFLAG(Uncached, uncached)
264 #else
265 PAGEFLAG_FALSE(Uncached)
266 #endif
267
268 #ifdef CONFIG_MEMORY_FAILURE
269 PAGEFLAG(HWPoison, hwpoison)
270 TESTSCFLAG(HWPoison, hwpoison)
271 #define __PG_HWPOISON (1UL << PG_hwpoison)
272 #else
273 PAGEFLAG_FALSE(HWPoison)
274 #define __PG_HWPOISON 0
275 #endif
276
277 u64 stable_page_flags(struct page *page);
278
PageUptodate(struct page * page)279 static inline int PageUptodate(struct page *page)
280 {
281 int ret = test_bit(PG_uptodate, &(page)->flags);
282
283 /*
284 * Must ensure that the data we read out of the page is loaded
285 * _after_ we've loaded page->flags to check for PageUptodate.
286 * We can skip the barrier if the page is not uptodate, because
287 * we wouldn't be reading anything from it.
288 *
289 * See SetPageUptodate() for the other side of the story.
290 */
291 if (ret)
292 smp_rmb();
293
294 return ret;
295 }
296
__SetPageUptodate(struct page * page)297 static inline void __SetPageUptodate(struct page *page)
298 {
299 smp_wmb();
300 __set_bit(PG_uptodate, &(page)->flags);
301 }
302
SetPageUptodate(struct page * page)303 static inline void SetPageUptodate(struct page *page)
304 {
305 #ifdef CONFIG_S390
306 if (!test_and_set_bit(PG_uptodate, &page->flags))
307 page_set_storage_key(page_to_phys(page), PAGE_DEFAULT_KEY, 0);
308 #else
309 /*
310 * Memory barrier must be issued before setting the PG_uptodate bit,
311 * so that all previous stores issued in order to bring the page
312 * uptodate are actually visible before PageUptodate becomes true.
313 *
314 * s390 doesn't need an explicit smp_wmb here because the test and
315 * set bit already provides full barriers.
316 */
317 smp_wmb();
318 set_bit(PG_uptodate, &(page)->flags);
319 #endif
320 }
321
322 CLEARPAGEFLAG(Uptodate, uptodate)
323
324 extern void cancel_dirty_page(struct page *page, unsigned int account_size);
325
326 int test_clear_page_writeback(struct page *page);
327 int test_set_page_writeback(struct page *page);
328
set_page_writeback(struct page * page)329 static inline void set_page_writeback(struct page *page)
330 {
331 test_set_page_writeback(page);
332 }
333
334 #ifdef CONFIG_PAGEFLAGS_EXTENDED
335 /*
336 * System with lots of page flags available. This allows separate
337 * flags for PageHead() and PageTail() checks of compound pages so that bit
338 * tests can be used in performance sensitive paths. PageCompound is
339 * generally not used in hot code paths.
340 */
__PAGEFLAG(Head,head)341 __PAGEFLAG(Head, head) CLEARPAGEFLAG(Head, head)
342 __PAGEFLAG(Tail, tail)
343
344 static inline int PageCompound(struct page *page)
345 {
346 return page->flags & ((1L << PG_head) | (1L << PG_tail));
347
348 }
349 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
ClearPageCompound(struct page * page)350 static inline void ClearPageCompound(struct page *page)
351 {
352 BUG_ON(!PageHead(page));
353 ClearPageHead(page);
354 }
355 #endif
356 #else
357 /*
358 * Reduce page flag use as much as possible by overlapping
359 * compound page flags with the flags used for page cache pages. Possible
360 * because PageCompound is always set for compound pages and not for
361 * pages on the LRU and/or pagecache.
362 */
TESTPAGEFLAG(Compound,compound)363 TESTPAGEFLAG(Compound, compound)
364 __SETPAGEFLAG(Head, compound) __CLEARPAGEFLAG(Head, compound)
365
366 /*
367 * PG_reclaim is used in combination with PG_compound to mark the
368 * head and tail of a compound page. This saves one page flag
369 * but makes it impossible to use compound pages for the page cache.
370 * The PG_reclaim bit would have to be used for reclaim or readahead
371 * if compound pages enter the page cache.
372 *
373 * PG_compound & PG_reclaim => Tail page
374 * PG_compound & ~PG_reclaim => Head page
375 */
376 #define PG_head_mask ((1L << PG_compound))
377 #define PG_head_tail_mask ((1L << PG_compound) | (1L << PG_reclaim))
378
379 static inline int PageHead(struct page *page)
380 {
381 return ((page->flags & PG_head_tail_mask) == PG_head_mask);
382 }
383
PageTail(struct page * page)384 static inline int PageTail(struct page *page)
385 {
386 return ((page->flags & PG_head_tail_mask) == PG_head_tail_mask);
387 }
388
__SetPageTail(struct page * page)389 static inline void __SetPageTail(struct page *page)
390 {
391 page->flags |= PG_head_tail_mask;
392 }
393
__ClearPageTail(struct page * page)394 static inline void __ClearPageTail(struct page *page)
395 {
396 page->flags &= ~PG_head_tail_mask;
397 }
398
399 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
ClearPageCompound(struct page * page)400 static inline void ClearPageCompound(struct page *page)
401 {
402 BUG_ON((page->flags & PG_head_tail_mask) != (1 << PG_compound));
403 clear_bit(PG_compound, &page->flags);
404 }
405 #endif
406
407 #endif /* !PAGEFLAGS_EXTENDED */
408
409 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
410 /*
411 * PageHuge() only returns true for hugetlbfs pages, but not for
412 * normal or transparent huge pages.
413 *
414 * PageTransHuge() returns true for both transparent huge and
415 * hugetlbfs pages, but not normal pages. PageTransHuge() can only be
416 * called only in the core VM paths where hugetlbfs pages can't exist.
417 */
PageTransHuge(struct page * page)418 static inline int PageTransHuge(struct page *page)
419 {
420 VM_BUG_ON(PageTail(page));
421 return PageHead(page);
422 }
423
424 /*
425 * PageTransCompound returns true for both transparent huge pages
426 * and hugetlbfs pages, so it should only be called when it's known
427 * that hugetlbfs pages aren't involved.
428 */
PageTransCompound(struct page * page)429 static inline int PageTransCompound(struct page *page)
430 {
431 return PageCompound(page);
432 }
433
434 /*
435 * PageTransTail returns true for both transparent huge pages
436 * and hugetlbfs pages, so it should only be called when it's known
437 * that hugetlbfs pages aren't involved.
438 */
PageTransTail(struct page * page)439 static inline int PageTransTail(struct page *page)
440 {
441 return PageTail(page);
442 }
443
444 #else
445
PageTransHuge(struct page * page)446 static inline int PageTransHuge(struct page *page)
447 {
448 return 0;
449 }
450
PageTransCompound(struct page * page)451 static inline int PageTransCompound(struct page *page)
452 {
453 return 0;
454 }
455
PageTransTail(struct page * page)456 static inline int PageTransTail(struct page *page)
457 {
458 return 0;
459 }
460 #endif
461
462 #ifdef CONFIG_MMU
463 #define __PG_MLOCKED (1 << PG_mlocked)
464 #else
465 #define __PG_MLOCKED 0
466 #endif
467
468 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
469 #define __PG_COMPOUND_LOCK (1 << PG_compound_lock)
470 #else
471 #define __PG_COMPOUND_LOCK 0
472 #endif
473
474 /*
475 * Flags checked when a page is freed. Pages being freed should not have
476 * these flags set. It they are, there is a problem.
477 */
478 #define PAGE_FLAGS_CHECK_AT_FREE \
479 (1 << PG_lru | 1 << PG_locked | \
480 1 << PG_private | 1 << PG_private_2 | \
481 1 << PG_writeback | 1 << PG_reserved | \
482 1 << PG_slab | 1 << PG_swapcache | 1 << PG_active | \
483 1 << PG_unevictable | __PG_MLOCKED | __PG_HWPOISON | \
484 __PG_COMPOUND_LOCK)
485
486 /*
487 * Flags checked when a page is prepped for return by the page allocator.
488 * Pages being prepped should not have any flags set. It they are set,
489 * there has been a kernel bug or struct page corruption.
490 */
491 #define PAGE_FLAGS_CHECK_AT_PREP ((1 << NR_PAGEFLAGS) - 1)
492
493 #define PAGE_FLAGS_PRIVATE \
494 (1 << PG_private | 1 << PG_private_2)
495 /**
496 * page_has_private - Determine if page has private stuff
497 * @page: The page to be checked
498 *
499 * Determine if a page has private stuff, indicating that release routines
500 * should be invoked upon it.
501 */
page_has_private(struct page * page)502 static inline int page_has_private(struct page *page)
503 {
504 return !!(page->flags & PAGE_FLAGS_PRIVATE);
505 }
506
507 #endif /* !__GENERATING_BOUNDS_H */
508
509 #endif /* PAGE_FLAGS_H */
510