*/
enum pageflags {
PG_locked, /* Page is locked. Don't touch. */
+ PG_waiters, /* Page has waiters, check its waitqueue */
PG_error,
PG_referenced,
PG_uptodate,
* for compound page all operations related to the page flag applied to
* head page.
*
+ * PF_ONLY_HEAD:
+ * for compound page, callers only ever operate on the head page.
+ *
* PF_NO_TAIL:
* modifications of the page flag must be done on small or head pages,
* checks can be done on tail pages too.
*/
#define PF_ANY(page, enforce) page
#define PF_HEAD(page, enforce) compound_head(page)
+#define PF_ONLY_HEAD(page, enforce) ({ \
+ VM_BUG_ON_PGFLAGS(PageTail(page), page); \
+ page;})
#define PF_NO_TAIL(page, enforce) ({ \
VM_BUG_ON_PGFLAGS(enforce && PageTail(page), page); \
compound_head(page);})
TESTSETFLAG_FALSE(uname) TESTCLEARFLAG_FALSE(uname)
__PAGEFLAG(Locked, locked, PF_NO_TAIL)
+PAGEFLAG(Waiters, waiters, PF_ONLY_HEAD) __CLEARPAGEFLAG(Waiters, waiters, PF_ONLY_HEAD)
PAGEFLAG(Error, error, PF_NO_COMPOUND) TESTCLEARFLAG(Error, error, PF_NO_COMPOUND)
PAGEFLAG(Referenced, referenced, PF_HEAD)
TESTCLEARFLAG(Referenced, referenced, PF_HEAD)
#undef PF_ANY
#undef PF_HEAD
+#undef PF_ONLY_HEAD
#undef PF_NO_TAIL
#undef PF_NO_COMPOUND
#endif /* !__GENERATING_BOUNDS_H */
* at a cost of "thundering herd" phenomena during rare hash
* collisions.
*/
-wait_queue_head_t *page_waitqueue(struct page *page)
+#define PAGE_WAIT_TABLE_BITS 8
+#define PAGE_WAIT_TABLE_SIZE (1 << PAGE_WAIT_TABLE_BITS)
+static wait_queue_head_t page_wait_table[PAGE_WAIT_TABLE_SIZE] __cacheline_aligned;
+
+static wait_queue_head_t *page_waitqueue(struct page *page)
{
- return bit_waitqueue(page, 0);
+ return &page_wait_table[hash_ptr(page, PAGE_WAIT_TABLE_BITS)];
}
-EXPORT_SYMBOL(page_waitqueue);
-void wait_on_page_bit(struct page *page, int bit_nr)
+void __init pagecache_init(void)
{
- DEFINE_WAIT_BIT(wait, &page->flags, bit_nr);
+ int i;
- if (test_bit(bit_nr, &page->flags))
- __wait_on_bit(page_waitqueue(page), &wait, bit_wait_io,
- TASK_UNINTERRUPTIBLE);
+ for (i = 0; i < PAGE_WAIT_TABLE_SIZE; i++)
+ init_waitqueue_head(&page_wait_table[i]);
+
+ page_writeback_init();
}
-EXPORT_SYMBOL(wait_on_page_bit);
-int wait_on_page_bit_killable(struct page *page, int bit_nr)
+struct wait_page_key {
+ struct page *page;
+ int bit_nr;
+ int page_match;
+};
+
+struct wait_page_queue {
+ struct page *page;
+ int bit_nr;
+ wait_queue_t wait;
+};
+
+static int wake_page_function(wait_queue_t *wait, unsigned mode, int sync, void *arg)
{
- DEFINE_WAIT_BIT(wait, &page->flags, bit_nr);
+ struct wait_page_key *key = arg;
+ struct wait_page_queue *wait_page
+ = container_of(wait, struct wait_page_queue, wait);
+
+ if (wait_page->page != key->page)
+ return 0;
+ key->page_match = 1;
- if (!test_bit(bit_nr, &page->flags))
+ if (wait_page->bit_nr != key->bit_nr)
+ return 0;
+ if (test_bit(key->bit_nr, &key->page->flags))
return 0;
- return __wait_on_bit(page_waitqueue(page), &wait,
- bit_wait_io, TASK_KILLABLE);
+ return autoremove_wake_function(wait, mode, sync, key);
}
-int wait_on_page_bit_killable_timeout(struct page *page,
- int bit_nr, unsigned long timeout)
+void wake_up_page_bit(struct page *page, int bit_nr)
{
- DEFINE_WAIT_BIT(wait, &page->flags, bit_nr);
+ wait_queue_head_t *q = page_waitqueue(page);
+ struct wait_page_key key;
+ unsigned long flags;
- wait.key.timeout = jiffies + timeout;
- if (!test_bit(bit_nr, &page->flags))
- return 0;
- return __wait_on_bit(page_waitqueue(page), &wait,
- bit_wait_io_timeout, TASK_KILLABLE);
+ key.page = page;
+ key.bit_nr = bit_nr;
+ key.page_match = 0;
+
+ spin_lock_irqsave(&q->lock, flags);
+ __wake_up_locked_key(q, TASK_NORMAL, &key);
+ /*
+ * It is possible for other pages to have collided on the waitqueue
+ * hash, so in that case check for a page match. That prevents a long-
+ * term waiter
+ *
+ * It is still possible to miss a case here, when we woke page waiters
+ * and removed them from the waitqueue, but there are still other
+ * page waiters.
+ */
+ if (!waitqueue_active(q) || !key.page_match) {
+ ClearPageWaiters(page);
+ /*
+ * It's possible to miss clearing Waiters here, when we woke
+ * our page waiters, but the hashed waitqueue has waiters for
+ * other pages on it.
+ *
+ * That's okay, it's a rare case. The next waker will clear it.
+ */
+ }
+ spin_unlock_irqrestore(&q->lock, flags);
+}
+EXPORT_SYMBOL(wake_up_page_bit);
+
+static inline int wait_on_page_bit_common(wait_queue_head_t *q,
+ struct page *page, int bit_nr, int state, bool lock)
+{
+ struct wait_page_queue wait_page;
+ wait_queue_t *wait = &wait_page.wait;
+ int ret = 0;
+
+ init_wait(wait);
+ wait->func = wake_page_function;
+ wait_page.page = page;
+ wait_page.bit_nr = bit_nr;
+
+ for (;;) {
+ spin_lock_irq(&q->lock);
+
+ if (likely(list_empty(&wait->task_list))) {
+ if (lock)
+ __add_wait_queue_tail_exclusive(q, wait);
+ else
+ __add_wait_queue(q, wait);
+ SetPageWaiters(page);
+ }
+
+ set_current_state(state);
+
+ spin_unlock_irq(&q->lock);
+
+ if (likely(test_bit(bit_nr, &page->flags))) {
+ io_schedule();
+ if (unlikely(signal_pending_state(state, current))) {
+ ret = -EINTR;
+ break;
+ }
+ }
+
+ if (lock) {
+ if (!test_and_set_bit_lock(bit_nr, &page->flags))
+ break;
+ } else {
+ if (!test_bit(bit_nr, &page->flags))
+ break;
+ }
+ }
+
+ finish_wait(q, wait);
+
+ /*
+ * A signal could leave PageWaiters set. Clearing it here if
+ * !waitqueue_active would be possible (by open-coding finish_wait),
+ * but still fail to catch it in the case of wait hash collision. We
+ * already can fail to clear wait hash collision cases, so don't
+ * bother with signals either.
+ */
+
+ return ret;
+}
+
+void wait_on_page_bit(struct page *page, int bit_nr)
+{
+ wait_queue_head_t *q = page_waitqueue(page);
+ wait_on_page_bit_common(q, page, bit_nr, TASK_UNINTERRUPTIBLE, false);
+}
+EXPORT_SYMBOL(wait_on_page_bit);
+
+int wait_on_page_bit_killable(struct page *page, int bit_nr)
+{
+ wait_queue_head_t *q = page_waitqueue(page);
+ return wait_on_page_bit_common(q, page, bit_nr, TASK_KILLABLE, false);
}
-EXPORT_SYMBOL_GPL(wait_on_page_bit_killable_timeout);
/**
* add_page_wait_queue - Add an arbitrary waiter to a page's wait queue
spin_lock_irqsave(&q->lock, flags);
__add_wait_queue(q, waiter);
+ SetPageWaiters(page);
spin_unlock_irqrestore(&q->lock, flags);
}
EXPORT_SYMBOL_GPL(add_page_wait_queue);
* __lock_page - get a lock on the page, assuming we need to sleep to get it
* @page: the page to lock
*/
-void __lock_page(struct page *page)
+void __lock_page(struct page *__page)
{
- struct page *page_head = compound_head(page);
- DEFINE_WAIT_BIT(wait, &page_head->flags, PG_locked);
-
- __wait_on_bit_lock(page_waitqueue(page_head), &wait, bit_wait_io,
- TASK_UNINTERRUPTIBLE);
+ struct page *page = compound_head(__page);
+ wait_queue_head_t *q = page_waitqueue(page);
+ wait_on_page_bit_common(q, page, PG_locked, TASK_UNINTERRUPTIBLE, true);
}
EXPORT_SYMBOL(__lock_page);
-int __lock_page_killable(struct page *page)
+int __lock_page_killable(struct page *__page)
{
- struct page *page_head = compound_head(page);
- DEFINE_WAIT_BIT(wait, &page_head->flags, PG_locked);
-
- return __wait_on_bit_lock(page_waitqueue(page_head), &wait,
- bit_wait_io, TASK_KILLABLE);
+ struct page *page = compound_head(__page);
+ wait_queue_head_t *q = page_waitqueue(page);
+ return wait_on_page_bit_common(q, page, PG_locked, TASK_KILLABLE, true);
}
EXPORT_SYMBOL_GPL(__lock_page_killable);
projects / linux-beck.git / commitdiff