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 <linux/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 */
114 PG_checked = PG_owner_priv_1,
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.
120 PG_fscache = PG_private_2, /* page backed by cache */
123 PG_pinned = PG_owner_priv_1,
124 PG_savepinned = PG_dirty,
127 PG_slob_free = PG_private,
130 PG_slub_frozen = PG_active,
131 PG_slub_debug = PG_error,
134 #ifndef __GENERATING_BOUNDS_H
137 * Macros to create function definitions for page flags
139 #define TESTPAGEFLAG(uname, lname) \
140 static inline int Page##uname(struct page *page) \
141 { return test_bit(PG_##lname, &page->flags); }
143 #define SETPAGEFLAG(uname, lname) \
144 static inline void SetPage##uname(struct page *page) \
145 { set_bit(PG_##lname, &page->flags); }
147 #define CLEARPAGEFLAG(uname, lname) \
148 static inline void ClearPage##uname(struct page *page) \
149 { clear_bit(PG_##lname, &page->flags); }
151 #define __SETPAGEFLAG(uname, lname) \
152 static inline void __SetPage##uname(struct page *page) \
153 { __set_bit(PG_##lname, &page->flags); }
155 #define __CLEARPAGEFLAG(uname, lname) \
156 static inline void __ClearPage##uname(struct page *page) \
157 { __clear_bit(PG_##lname, &page->flags); }
159 #define TESTSETFLAG(uname, lname) \
160 static inline int TestSetPage##uname(struct page *page) \
161 { return test_and_set_bit(PG_##lname, &page->flags); }
163 #define TESTCLEARFLAG(uname, lname) \
164 static inline int TestClearPage##uname(struct page *page) \
165 { return test_and_clear_bit(PG_##lname, &page->flags); }
167 #define __TESTCLEARFLAG(uname, lname) \
168 static inline int __TestClearPage##uname(struct page *page) \
169 { return __test_and_clear_bit(PG_##lname, &page->flags); }
171 #define PAGEFLAG(uname, lname) TESTPAGEFLAG(uname, lname) \
172 SETPAGEFLAG(uname, lname) CLEARPAGEFLAG(uname, lname)
174 #define __PAGEFLAG(uname, lname) TESTPAGEFLAG(uname, lname) \
175 __SETPAGEFLAG(uname, lname) __CLEARPAGEFLAG(uname, lname)
177 #define PAGEFLAG_FALSE(uname) \
178 static inline int Page##uname(struct page *page) \
181 #define TESTSCFLAG(uname, lname) \
182 TESTSETFLAG(uname, lname) TESTCLEARFLAG(uname, lname)
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 TESTCLEARFLAG_FALSE(uname) \
194 static inline int TestClearPage##uname(struct page *page) { return 0; }
196 #define __TESTCLEARFLAG_FALSE(uname) \
197 static inline int __TestClearPage##uname(struct page *page) { return 0; }
199 struct page; /* forward declaration */
201 TESTPAGEFLAG(Locked, locked) TESTSETFLAG(Locked, locked)
202 PAGEFLAG(Error, error)
203 PAGEFLAG(Referenced, referenced) TESTCLEARFLAG(Referenced, referenced)
204 PAGEFLAG(Dirty, dirty) TESTSCFLAG(Dirty, dirty) __CLEARPAGEFLAG(Dirty, dirty)
205 PAGEFLAG(LRU, lru) __CLEARPAGEFLAG(LRU, lru)
206 PAGEFLAG(Active, active) __CLEARPAGEFLAG(Active, active)
207 TESTCLEARFLAG(Active, active)
208 __PAGEFLAG(Slab, slab)
209 PAGEFLAG(Checked, checked) /* Used by some filesystems */
210 PAGEFLAG(Pinned, pinned) TESTSCFLAG(Pinned, pinned) /* Xen */
211 PAGEFLAG(SavePinned, savepinned); /* Xen */
212 PAGEFLAG(Reserved, reserved) __CLEARPAGEFLAG(Reserved, reserved)
213 PAGEFLAG(SwapBacked, swapbacked) __CLEARPAGEFLAG(SwapBacked, swapbacked)
215 __PAGEFLAG(SlobFree, slob_free)
217 __PAGEFLAG(SlubFrozen, slub_frozen)
218 __PAGEFLAG(SlubDebug, slub_debug)
221 * Private page markings that may be used by the filesystem that owns the page
222 * for its own purposes.
223 * - PG_private and PG_private_2 cause releasepage() and co to be invoked
225 PAGEFLAG(Private, private) __SETPAGEFLAG(Private, private)
226 __CLEARPAGEFLAG(Private, private)
227 PAGEFLAG(Private2, private_2) TESTSCFLAG(Private2, private_2)
228 PAGEFLAG(OwnerPriv1, owner_priv_1) TESTCLEARFLAG(OwnerPriv1, owner_priv_1)
231 * Only test-and-set exist for PG_writeback. The unconditional operators are
232 * risky: they bypass page accounting.
234 TESTPAGEFLAG(Writeback, writeback) TESTSCFLAG(Writeback, writeback)
235 __PAGEFLAG(Buddy, buddy)
236 PAGEFLAG(MappedToDisk, mappedtodisk)
238 /* PG_readahead is only used for file reads; PG_reclaim is only for writes */
239 PAGEFLAG(Reclaim, reclaim) TESTCLEARFLAG(Reclaim, reclaim)
240 PAGEFLAG(Readahead, reclaim) /* Reminder to do async read-ahead */
242 #ifdef CONFIG_HIGHMEM
244 * Must use a macro here due to header dependency issues. page_zone() is not
245 * available at this point.
247 #define PageHighMem(__p) is_highmem(page_zone(__p))
249 PAGEFLAG_FALSE(HighMem)
253 PAGEFLAG(SwapCache, swapcache)
255 PAGEFLAG_FALSE(SwapCache)
256 SETPAGEFLAG_NOOP(SwapCache) CLEARPAGEFLAG_NOOP(SwapCache)
259 PAGEFLAG(Unevictable, unevictable) __CLEARPAGEFLAG(Unevictable, unevictable)
260 TESTCLEARFLAG(Unevictable, unevictable)
263 PAGEFLAG(Mlocked, mlocked) __CLEARPAGEFLAG(Mlocked, mlocked)
264 TESTSCFLAG(Mlocked, mlocked) __TESTCLEARFLAG(Mlocked, mlocked)
266 PAGEFLAG_FALSE(Mlocked) SETPAGEFLAG_NOOP(Mlocked)
267 TESTCLEARFLAG_FALSE(Mlocked) __TESTCLEARFLAG_FALSE(Mlocked)
270 #ifdef CONFIG_ARCH_USES_PG_UNCACHED
271 PAGEFLAG(Uncached, uncached)
273 PAGEFLAG_FALSE(Uncached)
276 #ifdef CONFIG_MEMORY_FAILURE
277 PAGEFLAG(HWPoison, hwpoison)
278 TESTSETFLAG(HWPoison, hwpoison)
279 #define __PG_HWPOISON (1UL << PG_hwpoison)
281 PAGEFLAG_FALSE(HWPoison)
282 #define __PG_HWPOISON 0
285 static inline int PageUptodate(struct page *page)
287 int ret = test_bit(PG_uptodate, &(page)->flags);
290 * Must ensure that the data we read out of the page is loaded
291 * _after_ we've loaded page->flags to check for PageUptodate.
292 * We can skip the barrier if the page is not uptodate, because
293 * we wouldn't be reading anything from it.
295 * See SetPageUptodate() for the other side of the story.
303 static inline void __SetPageUptodate(struct page *page)
306 __set_bit(PG_uptodate, &(page)->flags);
309 static inline void SetPageUptodate(struct page *page)
312 if (!test_and_set_bit(PG_uptodate, &page->flags))
313 page_clear_dirty(page);
316 * Memory barrier must be issued before setting the PG_uptodate bit,
317 * so that all previous stores issued in order to bring the page
318 * uptodate are actually visible before PageUptodate becomes true.
320 * s390 doesn't need an explicit smp_wmb here because the test and
321 * set bit already provides full barriers.
324 set_bit(PG_uptodate, &(page)->flags);
328 CLEARPAGEFLAG(Uptodate, uptodate)
330 extern void cancel_dirty_page(struct page *page, unsigned int account_size);
332 int test_clear_page_writeback(struct page *page);
333 int test_set_page_writeback(struct page *page);
335 static inline void set_page_writeback(struct page *page)
337 test_set_page_writeback(page);
340 #ifdef CONFIG_PAGEFLAGS_EXTENDED
342 * System with lots of page flags available. This allows separate
343 * flags for PageHead() and PageTail() checks of compound pages so that bit
344 * tests can be used in performance sensitive paths. PageCompound is
345 * generally not used in hot code paths.
347 __PAGEFLAG(Head, head)
348 __PAGEFLAG(Tail, tail)
350 static inline int PageCompound(struct page *page)
352 return page->flags & ((1L << PG_head) | (1L << PG_tail));
357 * Reduce page flag use as much as possible by overlapping
358 * compound page flags with the flags used for page cache pages. Possible
359 * because PageCompound is always set for compound pages and not for
360 * pages on the LRU and/or pagecache.
362 TESTPAGEFLAG(Compound, compound)
363 __PAGEFLAG(Head, compound)
366 * PG_reclaim is used in combination with PG_compound to mark the
367 * head and tail of a compound page. This saves one page flag
368 * but makes it impossible to use compound pages for the page cache.
369 * The PG_reclaim bit would have to be used for reclaim or readahead
370 * if compound pages enter the page cache.
372 * PG_compound & PG_reclaim => Tail page
373 * PG_compound & ~PG_reclaim => Head page
375 #define PG_head_tail_mask ((1L << PG_compound) | (1L << PG_reclaim))
377 static inline int PageTail(struct page *page)
379 return ((page->flags & PG_head_tail_mask) == PG_head_tail_mask);
382 static inline void __SetPageTail(struct page *page)
384 page->flags |= PG_head_tail_mask;
387 static inline void __ClearPageTail(struct page *page)
389 page->flags &= ~PG_head_tail_mask;
392 #endif /* !PAGEFLAGS_EXTENDED */
395 #define __PG_MLOCKED (1 << PG_mlocked)
397 #define __PG_MLOCKED 0
401 * Flags checked when a page is freed. Pages being freed should not have
402 * these flags set. It they are, there is a problem.
404 #define PAGE_FLAGS_CHECK_AT_FREE \
405 (1 << PG_lru | 1 << PG_locked | \
406 1 << PG_private | 1 << PG_private_2 | \
407 1 << PG_buddy | 1 << PG_writeback | 1 << PG_reserved | \
408 1 << PG_slab | 1 << PG_swapcache | 1 << PG_active | \
409 1 << PG_unevictable | __PG_MLOCKED | __PG_HWPOISON)
412 * Flags checked when a page is prepped for return by the page allocator.
413 * Pages being prepped should not have any flags set. It they are set,
414 * there has been a kernel bug or struct page corruption.
416 #define PAGE_FLAGS_CHECK_AT_PREP ((1 << NR_PAGEFLAGS) - 1)
418 #define PAGE_FLAGS_PRIVATE \
419 (1 << PG_private | 1 << PG_private_2)
421 * page_has_private - Determine if page has private stuff
422 * @page: The page to be checked
424 * Determine if a page has private stuff, indicating that release routines
425 * should be invoked upon it.
427 static inline int page_has_private(struct page *page)
429 return !!(page->flags & PAGE_FLAGS_PRIVATE);
432 #endif /* !__GENERATING_BOUNDS_H */
434 #endif /* PAGE_FLAGS_H */