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