1 files changed, 146 insertions, 35 deletions

diff --git a/mm/filemap.c b/mm/filemap.c
index 32be3c8f3a11..82f26cde830c 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -739,45 +739,159 @@ EXPORT_SYMBOL(__page_cache_alloc);
  * 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
@@ -793,6 +907,7 @@ void add_page_wait_queue(struct page *page, wait_queue_t *waiter)
 
 	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);
@@ -874,23 +989,19 @@ EXPORT_SYMBOL_GPL(page_endio);
  * __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);