2 * Macros for manipulating and testing page->flags
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 */
15 * Various page->flags bits:
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)...
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.
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.
28 * PG_locked also pins a page in pagecache, and blocks truncation of the file
31 * page_waitqueue(page) is a wait queue of all tasks waiting for the page
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.
37 * PG_referenced, PG_reclaim are used for page reclaim for anonymous and
38 * file-backed pagecache (see mm/vmscan.c).
40 * PG_error is set to indicate that an I/O error occurred on this page.
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
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
51 * PG_buddy is set to indicate that the page is free and in the buddy system
52 * (see mm/page_alloc.c).
54 * PG_hwpoison indicates that a page got corrupted in hardware and contains
55 * data with incorrect ECC bits that triggered a machine check. Accessing is
56 * not safe since it may cause another machine check. Don't touch!
60 * Don't use the *_dontuse flags. Use the macros. Otherwise you'll break
61 * locked- and dirty-page accounting.
63 * The page flags field is split into two parts, the main flags area
64 * which extends from the low bits upwards, and the fields area which
65 * extends from the high bits downwards.
67 * | FIELD | ... | FLAGS |
71 * The fields area is reserved for fields mapping zone, node (for NUMA) and
72 * SPARSEMEM section (for variants of SPARSEMEM that require section ids like
73 * SPARSEMEM_EXTREME with !SPARSEMEM_VMEMMAP).
76 PG_locked, /* Page is locked. Don't touch. */
84 PG_owner_priv_1, /* Owner use. If pagecache, fs may use*/
87 PG_private, /* If pagecache, has fs-private data */
88 PG_private_2, /* If pagecache, has fs aux data */
89 PG_writeback, /* Page is under writeback */
90 #ifdef CONFIG_PAGEFLAGS_EXTENDED
91 PG_head, /* A head page */
92 PG_tail, /* A tail page */
94 PG_compound, /* A compound page */
96 PG_swapcache, /* Swap page: swp_entry_t in private */
97 PG_mappedtodisk, /* Has blocks allocated on-disk */
98 PG_reclaim, /* To be reclaimed asap */
99 PG_buddy, /* Page is free, on buddy lists */
100 PG_swapbacked, /* Page is backed by RAM/swap */
101 PG_unevictable, /* Page is "unevictable" */
103 PG_mlocked, /* Page is vma mlocked */
105 #ifdef CONFIG_ARCH_USES_PG_UNCACHED
106 PG_uncached, /* Page has been mapped as uncached */
108 #ifdef CONFIG_MEMORY_FAILURE
109 PG_hwpoison, /* hardware poisoned page. Don't touch */
111 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
117 PG_checked = PG_owner_priv_1,
119 /* Two page bits are conscripted by FS-Cache to maintain local caching
120 * state. These bits are set on pages belonging to the netfs's inodes
121 * when those inodes are being locally cached.
123 PG_fscache = PG_private_2, /* page backed by cache */
126 PG_pinned = PG_owner_priv_1,
127 PG_savepinned = PG_dirty,
130 PG_slob_free = PG_private,
133 PG_slub_frozen = PG_active,
136 #ifndef __GENERATING_BOUNDS_H
139 * Macros to create function definitions for page flags
141 #define TESTPAGEFLAG(uname, lname) \
142 static inline int Page##uname(struct page *page) \
143 { return test_bit(PG_##lname, &page->flags); }
145 #define SETPAGEFLAG(uname, lname) \
146 static inline void SetPage##uname(struct page *page) \
147 { set_bit(PG_##lname, &page->flags); }
149 #define CLEARPAGEFLAG(uname, lname) \
150 static inline void ClearPage##uname(struct page *page) \
151 { clear_bit(PG_##lname, &page->flags); }
153 #define __SETPAGEFLAG(uname, lname) \
154 static inline void __SetPage##uname(struct page *page) \
155 { __set_bit(PG_##lname, &page->flags); }
157 #define __CLEARPAGEFLAG(uname, lname) \
158 static inline void __ClearPage##uname(struct page *page) \
159 { __clear_bit(PG_##lname, &page->flags); }
161 #define TESTSETFLAG(uname, lname) \
162 static inline int TestSetPage##uname(struct page *page) \
163 { return test_and_set_bit(PG_##lname, &page->flags); }
165 #define TESTCLEARFLAG(uname, lname) \
166 static inline int TestClearPage##uname(struct page *page) \
167 { return test_and_clear_bit(PG_##lname, &page->flags); }
169 #define __TESTCLEARFLAG(uname, lname) \
170 static inline int __TestClearPage##uname(struct page *page) \
171 { return __test_and_clear_bit(PG_##lname, &page->flags); }
173 #define PAGEFLAG(uname, lname) TESTPAGEFLAG(uname, lname) \
174 SETPAGEFLAG(uname, lname) CLEARPAGEFLAG(uname, lname)
176 #define __PAGEFLAG(uname, lname) TESTPAGEFLAG(uname, lname) \
177 __SETPAGEFLAG(uname, lname) __CLEARPAGEFLAG(uname, lname)
179 #define PAGEFLAG_FALSE(uname) \
180 static inline int Page##uname(struct page *page) \
183 #define TESTSCFLAG(uname, lname) \
184 TESTSETFLAG(uname, lname) TESTCLEARFLAG(uname, lname)
186 #define SETPAGEFLAG_NOOP(uname) \
187 static inline void SetPage##uname(struct page *page) { }
189 #define CLEARPAGEFLAG_NOOP(uname) \
190 static inline void ClearPage##uname(struct page *page) { }
192 #define __CLEARPAGEFLAG_NOOP(uname) \
193 static inline void __ClearPage##uname(struct page *page) { }
195 #define TESTCLEARFLAG_FALSE(uname) \
196 static inline int TestClearPage##uname(struct page *page) { return 0; }
198 #define __TESTCLEARFLAG_FALSE(uname) \
199 static inline int __TestClearPage##uname(struct page *page) { return 0; }
201 struct page; /* forward declaration */
203 TESTPAGEFLAG(Locked, locked) TESTSETFLAG(Locked, locked)
204 PAGEFLAG(Error, error) TESTCLEARFLAG(Error, error)
205 PAGEFLAG(Referenced, referenced) TESTCLEARFLAG(Referenced, referenced)
206 PAGEFLAG(Dirty, dirty) TESTSCFLAG(Dirty, dirty) __CLEARPAGEFLAG(Dirty, dirty)
207 PAGEFLAG(LRU, lru) __CLEARPAGEFLAG(LRU, lru)
208 PAGEFLAG(Active, active) __CLEARPAGEFLAG(Active, active)
209 TESTCLEARFLAG(Active, active)
210 __PAGEFLAG(Slab, slab)
211 PAGEFLAG(Checked, checked) /* Used by some filesystems */
212 PAGEFLAG(Pinned, pinned) TESTSCFLAG(Pinned, pinned) /* Xen */
213 PAGEFLAG(SavePinned, savepinned); /* Xen */
214 PAGEFLAG(Reserved, reserved) __CLEARPAGEFLAG(Reserved, reserved)
215 PAGEFLAG(SwapBacked, swapbacked) __CLEARPAGEFLAG(SwapBacked, swapbacked)
217 __PAGEFLAG(SlobFree, slob_free)
219 __PAGEFLAG(SlubFrozen, slub_frozen)
222 * Private page markings that may be used by the filesystem that owns the page
223 * for its own purposes.
224 * - PG_private and PG_private_2 cause releasepage() and co to be invoked
226 PAGEFLAG(Private, private) __SETPAGEFLAG(Private, private)
227 __CLEARPAGEFLAG(Private, private)
228 PAGEFLAG(Private2, private_2) TESTSCFLAG(Private2, private_2)
229 PAGEFLAG(OwnerPriv1, owner_priv_1) TESTCLEARFLAG(OwnerPriv1, owner_priv_1)
232 * Only test-and-set exist for PG_writeback. The unconditional operators are
233 * risky: they bypass page accounting.
235 TESTPAGEFLAG(Writeback, writeback) TESTSCFLAG(Writeback, writeback)
236 __PAGEFLAG(Buddy, buddy)
237 PAGEFLAG(MappedToDisk, mappedtodisk)
239 /* PG_readahead is only used for file reads; PG_reclaim is only for writes */
240 PAGEFLAG(Reclaim, reclaim) TESTCLEARFLAG(Reclaim, reclaim)
241 PAGEFLAG(Readahead, reclaim) /* Reminder to do async read-ahead */
243 #ifdef CONFIG_HIGHMEM
245 * Must use a macro here due to header dependency issues. page_zone() is not
246 * available at this point.
248 #define PageHighMem(__p) is_highmem(page_zone(__p))
250 PAGEFLAG_FALSE(HighMem)
254 PAGEFLAG(SwapCache, swapcache)
256 PAGEFLAG_FALSE(SwapCache)
257 SETPAGEFLAG_NOOP(SwapCache) CLEARPAGEFLAG_NOOP(SwapCache)
260 PAGEFLAG(Unevictable, unevictable) __CLEARPAGEFLAG(Unevictable, unevictable)
261 TESTCLEARFLAG(Unevictable, unevictable)
264 PAGEFLAG(Mlocked, mlocked) __CLEARPAGEFLAG(Mlocked, mlocked)
265 TESTSCFLAG(Mlocked, mlocked) __TESTCLEARFLAG(Mlocked, mlocked)
267 PAGEFLAG_FALSE(Mlocked) SETPAGEFLAG_NOOP(Mlocked)
268 TESTCLEARFLAG_FALSE(Mlocked) __TESTCLEARFLAG_FALSE(Mlocked)
271 #ifdef CONFIG_ARCH_USES_PG_UNCACHED
272 PAGEFLAG(Uncached, uncached)
274 PAGEFLAG_FALSE(Uncached)
277 #ifdef CONFIG_MEMORY_FAILURE
278 PAGEFLAG(HWPoison, hwpoison)
279 TESTSCFLAG(HWPoison, hwpoison)
280 #define __PG_HWPOISON (1UL << PG_hwpoison)
282 PAGEFLAG_FALSE(HWPoison)
283 #define __PG_HWPOISON 0
286 u64 stable_page_flags(struct page *page);
288 static inline int PageUptodate(struct page *page)
290 int ret = test_bit(PG_uptodate, &(page)->flags);
293 * Must ensure that the data we read out of the page is loaded
294 * _after_ we've loaded page->flags to check for PageUptodate.
295 * We can skip the barrier if the page is not uptodate, because
296 * we wouldn't be reading anything from it.
298 * See SetPageUptodate() for the other side of the story.
306 static inline void __SetPageUptodate(struct page *page)
309 __set_bit(PG_uptodate, &(page)->flags);
312 static inline void SetPageUptodate(struct page *page)
315 if (!test_and_set_bit(PG_uptodate, &page->flags))
316 page_clear_dirty(page, 0);
319 * Memory barrier must be issued before setting the PG_uptodate bit,
320 * so that all previous stores issued in order to bring the page
321 * uptodate are actually visible before PageUptodate becomes true.
323 * s390 doesn't need an explicit smp_wmb here because the test and
324 * set bit already provides full barriers.
327 set_bit(PG_uptodate, &(page)->flags);
331 CLEARPAGEFLAG(Uptodate, uptodate)
333 extern void cancel_dirty_page(struct page *page, unsigned int account_size);
335 int test_clear_page_writeback(struct page *page);
336 int test_set_page_writeback(struct page *page);
338 static inline void set_page_writeback(struct page *page)
340 test_set_page_writeback(page);
343 #ifdef CONFIG_PAGEFLAGS_EXTENDED
345 * System with lots of page flags available. This allows separate
346 * flags for PageHead() and PageTail() checks of compound pages so that bit
347 * tests can be used in performance sensitive paths. PageCompound is
348 * generally not used in hot code paths.
350 __PAGEFLAG(Head, head) CLEARPAGEFLAG(Head, head)
351 __PAGEFLAG(Tail, tail)
353 static inline int PageCompound(struct page *page)
355 return page->flags & ((1L << PG_head) | (1L << PG_tail));
358 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
359 static inline void ClearPageCompound(struct page *page)
361 BUG_ON(!PageHead(page));
367 * Reduce page flag use as much as possible by overlapping
368 * compound page flags with the flags used for page cache pages. Possible
369 * because PageCompound is always set for compound pages and not for
370 * pages on the LRU and/or pagecache.
372 TESTPAGEFLAG(Compound, compound)
373 __PAGEFLAG(Head, compound)
376 * PG_reclaim is used in combination with PG_compound to mark the
377 * head and tail of a compound page. This saves one page flag
378 * but makes it impossible to use compound pages for the page cache.
379 * The PG_reclaim bit would have to be used for reclaim or readahead
380 * if compound pages enter the page cache.
382 * PG_compound & PG_reclaim => Tail page
383 * PG_compound & ~PG_reclaim => Head page
385 #define PG_head_tail_mask ((1L << PG_compound) | (1L << PG_reclaim))
387 static inline int PageTail(struct page *page)
389 return ((page->flags & PG_head_tail_mask) == PG_head_tail_mask);
392 static inline void __SetPageTail(struct page *page)
394 page->flags |= PG_head_tail_mask;
397 static inline void __ClearPageTail(struct page *page)
399 page->flags &= ~PG_head_tail_mask;
402 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
403 static inline void ClearPageCompound(struct page *page)
405 BUG_ON((page->flags & PG_head_tail_mask) != (1 << PG_compound));
406 clear_bit(PG_compound, &page->flags);
410 #endif /* !PAGEFLAGS_EXTENDED */
413 #define __PG_MLOCKED (1 << PG_mlocked)
415 #define __PG_MLOCKED 0
418 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
419 #define __PG_COMPOUND_LOCK (1 << PG_compound_lock)
421 #define __PG_COMPOUND_LOCK 0
425 * Flags checked when a page is freed. Pages being freed should not have
426 * these flags set. It they are, there is a problem.
428 #define PAGE_FLAGS_CHECK_AT_FREE \
429 (1 << PG_lru | 1 << PG_locked | \
430 1 << PG_private | 1 << PG_private_2 | \
431 1 << PG_buddy | 1 << PG_writeback | 1 << PG_reserved | \
432 1 << PG_slab | 1 << PG_swapcache | 1 << PG_active | \
433 1 << PG_unevictable | __PG_MLOCKED | __PG_HWPOISON | \
437 * Flags checked when a page is prepped for return by the page allocator.
438 * Pages being prepped should not have any flags set. It they are set,
439 * there has been a kernel bug or struct page corruption.
441 #define PAGE_FLAGS_CHECK_AT_PREP ((1 << NR_PAGEFLAGS) - 1)
443 #define PAGE_FLAGS_PRIVATE \
444 (1 << PG_private | 1 << PG_private_2)
446 * page_has_private - Determine if page has private stuff
447 * @page: The page to be checked
449 * Determine if a page has private stuff, indicating that release routines
450 * should be invoked upon it.
452 static inline int page_has_private(struct page *page)
454 return !!(page->flags & PAGE_FLAGS_PRIVATE);
457 #endif /* !__GENERATING_BOUNDS_H */
459 #endif /* PAGE_FLAGS_H */