* PG_reserved is set for special pages, which can never be swapped out. Some
* of them might not even exist (eg empty_bad_page)...
*
- * The PG_private bitflag is set if page->private contains a valid value.
+ * The PG_private bitflag is set on pagecache pages if they contain filesystem
+ * specific data (which is normally at page->private). It can be used by
+ * private allocations for its own usage.
*
- * During disk I/O, PG_locked is used. This bit is set before I/O and
- * reset when I/O completes. page_waitqueue(page) is a wait queue of all tasks
- * waiting for the I/O on this page to complete.
+ * During initiation of disk I/O, PG_locked is set. This bit is set before I/O
+ * and cleared when writeback _starts_ or when read _completes_. PG_writeback
+ * is set before writeback starts and cleared when it finishes.
+ *
+ * PG_locked also pins a page in pagecache, and blocks truncation of the file
+ * while it is held.
+ *
+ * page_waitqueue(page) is a wait queue of all tasks waiting for the page
+ * to become unlocked.
*
* PG_uptodate tells whether the page's contents is valid. When a read
* completes, the page becomes uptodate, unless a disk I/O error happened.
*
- * For choosing which pages to swap out, inode pages carry a PG_referenced bit,
- * which is set any time the system accesses that page through the (mapping,
- * index) hash table. This referenced bit, together with the referenced bit
- * in the page tables, is used to manipulate page->age and move the page across
- * the active, inactive_dirty and inactive_clean lists.
- *
- * Note that the referenced bit, the page->lru list_head and the active,
- * inactive_dirty and inactive_clean lists are protected by the
- * zone->lru_lock, and *NOT* by the usual PG_locked bit!
+ * PG_referenced, PG_reclaim are used for page reclaim for anonymous and
+ * file-backed pagecache (see mm/vmscan.c).
*
* PG_error is set to indicate that an I/O error occurred on this page.
*
* space, they need to be kmapped separately for doing IO on the pages. The
* struct page (these bits with information) are always mapped into kernel
* address space...
+ *
+ * PG_buddy is set to indicate that the page is free and in the buddy system
+ * (see mm/page_alloc.c).
+ *
*/
/*
#define PG_checked 8 /* kill me in 2.5.<early>. */
#define PG_arch_1 9
#define PG_reserved 10
-#define PG_private 11 /* Has something at ->private */
+#define PG_private 11 /* If pagecache, has fs-private data */
#define PG_writeback 12 /* Page is under writeback */
#define PG_nosave 13 /* Used for system suspend/resume */
#define PG_mappedtodisk 16 /* Has blocks allocated on-disk */
#define PG_reclaim 17 /* To be reclaimed asap */
-#define PG_nosave_free 18 /* Free, should not be written */
+#define PG_nosave_free 18 /* Used for system suspend/resume */
#define PG_buddy 19 /* Page is free, on buddy lists */
#define PageUptodate(page) test_bit(PG_uptodate, &(page)->flags)
#ifdef CONFIG_S390
-#define SetPageUptodate(_page) \
- do { \
- struct page *__page = (_page); \
- if (!test_and_set_bit(PG_uptodate, &__page->flags)) \
- page_test_and_clear_dirty(_page); \
- } while (0)
+static inline void SetPageUptodate(struct page *page)
+{
+ if (!test_and_set_bit(PG_uptodate, &page->flags))
+ page_test_and_clear_dirty(page);
+}
#else
#define SetPageUptodate(page) set_bit(PG_uptodate, &(page)->flags)
#endif
do { \
if (!test_and_set_bit(PG_writeback, \
&(page)->flags)) \
- inc_page_state(nr_writeback); \
+ inc_zone_page_state(page, NR_WRITEBACK); \
} while (0)
#define TestSetPageWriteback(page) \
({ \
ret = test_and_set_bit(PG_writeback, \
&(page)->flags); \
if (!ret) \
- inc_page_state(nr_writeback); \
+ inc_zone_page_state(page, NR_WRITEBACK); \
ret; \
})
#define ClearPageWriteback(page) \
do { \
if (test_and_clear_bit(PG_writeback, \
&(page)->flags)) \
- dec_page_state(nr_writeback); \
+ dec_zone_page_state(page, NR_WRITEBACK); \
} while (0)
#define TestClearPageWriteback(page) \
({ \
ret = test_and_clear_bit(PG_writeback, \
&(page)->flags); \
if (ret) \
- dec_page_state(nr_writeback); \
+ dec_zone_page_state(page, NR_WRITEBACK); \
ret; \
})
git://ftp.safe.ca / safe / jmp / linux-2.6 / blobdiff