2 * Macros for manipulating and testing page->flags
8 #include <linux/types.h>
9 #include <linux/mm_types.h>
12 * Various page->flags bits:
14 * PG_reserved is set for special pages, which can never be swapped out. Some
15 * of them might not even exist (eg empty_bad_page)...
17 * The PG_private bitflag is set on pagecache pages if they contain filesystem
18 * specific data (which is normally at page->private). It can be used by
19 * private allocations for its own usage.
21 * During initiation of disk I/O, PG_locked is set. This bit is set before I/O
22 * and cleared when writeback _starts_ or when read _completes_. PG_writeback
23 * is set before writeback starts and cleared when it finishes.
25 * PG_locked also pins a page in pagecache, and blocks truncation of the file
28 * page_waitqueue(page) is a wait queue of all tasks waiting for the page
31 * PG_uptodate tells whether the page's contents is valid. When a read
32 * completes, the page becomes uptodate, unless a disk I/O error happened.
34 * PG_referenced, PG_reclaim are used for page reclaim for anonymous and
35 * file-backed pagecache (see mm/vmscan.c).
37 * PG_error is set to indicate that an I/O error occurred on this page.
39 * PG_arch_1 is an architecture specific page state bit. The generic code
40 * guarantees that this bit is cleared for a page when it first is entered into
43 * PG_highmem pages are not permanently mapped into the kernel virtual address
44 * space, they need to be kmapped separately for doing IO on the pages. The
45 * struct page (these bits with information) are always mapped into kernel
48 * PG_buddy is set to indicate that the page is free and in the buddy system
49 * (see mm/page_alloc.c).
54 * Don't use the *_dontuse flags. Use the macros. Otherwise you'll break
55 * locked- and dirty-page accounting.
57 * The page flags field is split into two parts, the main flags area
58 * which extends from the low bits upwards, and the fields area which
59 * extends from the high bits downwards.
61 * | FIELD | ... | FLAGS |
65 * The fields area is reserved for fields mapping zone, node and SPARSEMEM
66 * section. The boundry between these two areas is defined by
67 * FLAGS_RESERVED which defines the width of the fields section
68 * (see linux/mmzone.h). New flags must _not_ overlap with this area.
71 PG_locked, /* Page is locked. Don't touch. */
79 PG_owner_priv_1, /* Owner use. If pagecache, fs may use*/
80 PG_checked = PG_owner_priv_1, /* Used by some filesystems */
81 PG_pinned = PG_owner_priv_1, /* Xen pinned pagetable */
84 PG_private, /* If pagecache, has fs-private data */
85 PG_writeback, /* Page is under writeback */
86 PG_compound, /* A compound page */
87 PG_swapcache, /* Swap page: swp_entry_t in private */
88 PG_mappedtodisk, /* Has blocks allocated on-disk */
89 PG_reclaim, /* To be reclaimed asap */
90 /* PG_readahead is only used for file reads; PG_reclaim is only for writes */
91 PG_readahead = PG_reclaim, /* Reminder to do async read-ahead */
92 PG_buddy, /* Page is free, on buddy lists */
94 #if (BITS_PER_LONG > 32)
96 * 64-bit-only flags build down from bit 31
98 * 32 bit -------------------------------| FIELDS | FLAGS |
99 * 64 bit | FIELDS | ?????? FLAGS |
102 PG_uncached = 31, /* Page has been mapped as uncached */
108 * Manipulation of page state flags
110 #define PageLocked(page) \
111 test_bit(PG_locked, &(page)->flags)
112 #define SetPageLocked(page) \
113 set_bit(PG_locked, &(page)->flags)
114 #define TestSetPageLocked(page) \
115 test_and_set_bit(PG_locked, &(page)->flags)
116 #define ClearPageLocked(page) \
117 clear_bit(PG_locked, &(page)->flags)
118 #define TestClearPageLocked(page) \
119 test_and_clear_bit(PG_locked, &(page)->flags)
121 #define PageError(page) test_bit(PG_error, &(page)->flags)
122 #define SetPageError(page) set_bit(PG_error, &(page)->flags)
123 #define ClearPageError(page) clear_bit(PG_error, &(page)->flags)
125 #define PageReferenced(page) test_bit(PG_referenced, &(page)->flags)
126 #define SetPageReferenced(page) set_bit(PG_referenced, &(page)->flags)
127 #define ClearPageReferenced(page) clear_bit(PG_referenced, &(page)->flags)
128 #define TestClearPageReferenced(page) test_and_clear_bit(PG_referenced, &(page)->flags)
130 static inline int PageUptodate(struct page *page)
132 int ret = test_bit(PG_uptodate, &(page)->flags);
135 * Must ensure that the data we read out of the page is loaded
136 * _after_ we've loaded page->flags to check for PageUptodate.
137 * We can skip the barrier if the page is not uptodate, because
138 * we wouldn't be reading anything from it.
140 * See SetPageUptodate() for the other side of the story.
148 static inline void __SetPageUptodate(struct page *page)
151 __set_bit(PG_uptodate, &(page)->flags);
153 page_clear_dirty(page);
157 static inline void SetPageUptodate(struct page *page)
160 if (!test_and_set_bit(PG_uptodate, &page->flags))
161 page_clear_dirty(page);
164 * Memory barrier must be issued before setting the PG_uptodate bit,
165 * so that all previous stores issued in order to bring the page
166 * uptodate are actually visible before PageUptodate becomes true.
168 * s390 doesn't need an explicit smp_wmb here because the test and
169 * set bit already provides full barriers.
172 set_bit(PG_uptodate, &(page)->flags);
176 #define ClearPageUptodate(page) clear_bit(PG_uptodate, &(page)->flags)
178 #define PageDirty(page) test_bit(PG_dirty, &(page)->flags)
179 #define SetPageDirty(page) set_bit(PG_dirty, &(page)->flags)
180 #define TestSetPageDirty(page) test_and_set_bit(PG_dirty, &(page)->flags)
181 #define ClearPageDirty(page) clear_bit(PG_dirty, &(page)->flags)
182 #define __ClearPageDirty(page) __clear_bit(PG_dirty, &(page)->flags)
183 #define TestClearPageDirty(page) test_and_clear_bit(PG_dirty, &(page)->flags)
185 #define PageLRU(page) test_bit(PG_lru, &(page)->flags)
186 #define SetPageLRU(page) set_bit(PG_lru, &(page)->flags)
187 #define ClearPageLRU(page) clear_bit(PG_lru, &(page)->flags)
188 #define __ClearPageLRU(page) __clear_bit(PG_lru, &(page)->flags)
190 #define PageActive(page) test_bit(PG_active, &(page)->flags)
191 #define SetPageActive(page) set_bit(PG_active, &(page)->flags)
192 #define ClearPageActive(page) clear_bit(PG_active, &(page)->flags)
193 #define __ClearPageActive(page) __clear_bit(PG_active, &(page)->flags)
195 #define PageSlab(page) test_bit(PG_slab, &(page)->flags)
196 #define __SetPageSlab(page) __set_bit(PG_slab, &(page)->flags)
197 #define __ClearPageSlab(page) __clear_bit(PG_slab, &(page)->flags)
199 #ifdef CONFIG_HIGHMEM
200 #define PageHighMem(page) is_highmem(page_zone(page))
202 #define PageHighMem(page) 0 /* needed to optimize away at compile time */
205 #define PageChecked(page) test_bit(PG_checked, &(page)->flags)
206 #define SetPageChecked(page) set_bit(PG_checked, &(page)->flags)
207 #define ClearPageChecked(page) clear_bit(PG_checked, &(page)->flags)
209 #define PagePinned(page) test_bit(PG_pinned, &(page)->flags)
210 #define SetPagePinned(page) set_bit(PG_pinned, &(page)->flags)
211 #define ClearPagePinned(page) clear_bit(PG_pinned, &(page)->flags)
213 #define PageReserved(page) test_bit(PG_reserved, &(page)->flags)
214 #define SetPageReserved(page) set_bit(PG_reserved, &(page)->flags)
215 #define ClearPageReserved(page) clear_bit(PG_reserved, &(page)->flags)
216 #define __ClearPageReserved(page) __clear_bit(PG_reserved, &(page)->flags)
218 #define SetPagePrivate(page) set_bit(PG_private, &(page)->flags)
219 #define ClearPagePrivate(page) clear_bit(PG_private, &(page)->flags)
220 #define PagePrivate(page) test_bit(PG_private, &(page)->flags)
221 #define __SetPagePrivate(page) __set_bit(PG_private, &(page)->flags)
222 #define __ClearPagePrivate(page) __clear_bit(PG_private, &(page)->flags)
225 * Only test-and-set exist for PG_writeback. The unconditional operators are
226 * risky: they bypass page accounting.
228 #define PageWriteback(page) test_bit(PG_writeback, &(page)->flags)
229 #define TestSetPageWriteback(page) test_and_set_bit(PG_writeback, \
231 #define TestClearPageWriteback(page) test_and_clear_bit(PG_writeback, \
234 #define PageBuddy(page) test_bit(PG_buddy, &(page)->flags)
235 #define __SetPageBuddy(page) __set_bit(PG_buddy, &(page)->flags)
236 #define __ClearPageBuddy(page) __clear_bit(PG_buddy, &(page)->flags)
238 #define PageMappedToDisk(page) test_bit(PG_mappedtodisk, &(page)->flags)
239 #define SetPageMappedToDisk(page) set_bit(PG_mappedtodisk, &(page)->flags)
240 #define ClearPageMappedToDisk(page) clear_bit(PG_mappedtodisk, &(page)->flags)
242 #define PageReadahead(page) test_bit(PG_readahead, &(page)->flags)
243 #define SetPageReadahead(page) set_bit(PG_readahead, &(page)->flags)
244 #define ClearPageReadahead(page) clear_bit(PG_readahead, &(page)->flags)
246 #define PageReclaim(page) test_bit(PG_reclaim, &(page)->flags)
247 #define SetPageReclaim(page) set_bit(PG_reclaim, &(page)->flags)
248 #define ClearPageReclaim(page) clear_bit(PG_reclaim, &(page)->flags)
249 #define TestClearPageReclaim(page) test_and_clear_bit(PG_reclaim, &(page)->flags)
251 #define PageCompound(page) test_bit(PG_compound, &(page)->flags)
252 #define __SetPageCompound(page) __set_bit(PG_compound, &(page)->flags)
253 #define __ClearPageCompound(page) __clear_bit(PG_compound, &(page)->flags)
256 * PG_reclaim is used in combination with PG_compound to mark the
257 * head and tail of a compound page
259 * PG_compound & PG_reclaim => Tail page
260 * PG_compound & ~PG_reclaim => Head page
263 #define PG_head_tail_mask ((1L << PG_compound) | (1L << PG_reclaim))
265 #define PageTail(page) (((page)->flags & PG_head_tail_mask) \
266 == PG_head_tail_mask)
268 static inline void __SetPageTail(struct page *page)
270 page->flags |= PG_head_tail_mask;
273 static inline void __ClearPageTail(struct page *page)
275 page->flags &= ~PG_head_tail_mask;
278 #define PageHead(page) (((page)->flags & PG_head_tail_mask) \
279 == (1L << PG_compound))
280 #define __SetPageHead(page) __SetPageCompound(page)
281 #define __ClearPageHead(page) __ClearPageCompound(page)
284 #define PageSwapCache(page) test_bit(PG_swapcache, &(page)->flags)
285 #define SetPageSwapCache(page) set_bit(PG_swapcache, &(page)->flags)
286 #define ClearPageSwapCache(page) clear_bit(PG_swapcache, &(page)->flags)
288 #define PageSwapCache(page) 0
291 #define PageUncached(page) test_bit(PG_uncached, &(page)->flags)
292 #define SetPageUncached(page) set_bit(PG_uncached, &(page)->flags)
293 #define ClearPageUncached(page) clear_bit(PG_uncached, &(page)->flags)
295 struct page; /* forward declaration */
297 extern void cancel_dirty_page(struct page *page, unsigned int account_size);
299 int test_clear_page_writeback(struct page *page);
300 int test_set_page_writeback(struct page *page);
302 static inline void set_page_writeback(struct page *page)
304 test_set_page_writeback(page);
307 #endif /* PAGE_FLAGS_H */