[PATCH 13/37] FS-Cache: Provide an add_wait_queue_tail() function

David Howells
2008-02-08T17:02:04Z

Provide an add_wait_queue_tail() function to add a waiter to the back of a
wait queue instead of the front.

Signed-off-by: David Howells <dhowells@redhat.com>
---

include/linux/pagemap.h | 7 +++++--
include/linux/wait.h | 2 ++
kernel/wait.c | 18 ++++++++++++++++++
mm/filemap.c | 2 +-
4 files changed, 26 insertions(+), 3 deletions(-)

diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index 51c39f8..cecbace 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -225,8 +225,11 @@ static inline void wait_on_page_writeback(struct page *page)

extern void end_page_writeback(struct page *page);

-/*
- * Wait for a PG_owner_priv_2 to become clear
+/**
+ * wait_on_page_owner_priv_2 - Wait for PG_owner_priv_2 to become clear
+ * @page: The page to monitor
+ *
+ * Wait for a PG_owner_priv_2 to become clear on the specified page.
*/
static inline void wait_on_page_owner_priv_2(struct page *page)
{
diff --git a/include/linux/wait.h b/include/linux/wait.h
index 33a2aa9..5032ebb 100644
--- a/include/linux/wait.h
+++ b/include/linux/wait.h
@@ -118,6 +118,8 @@ static inline int waitqueue_active(wait_queue_head_t *q)
#define is_sync_wait(wait) (!(wait) || ((wait)->private))

extern void FASTCALL(add_wait_queue(wait_queue_head_t *q, wait_queue_t * wait));
+extern void FASTCALL(add_wait_queue_tail(wait_queue_head_t *q,
+ wait_queue_t *wait));
extern void FASTCALL(add_wait_queue_exclusive(wait_queue_head_t *q, wait_queue_t * wait));
extern void FASTCALL(remove_wait_queue(wait_queue_head_t *q, wait_queue_t * wait));

diff --git a/kernel/wait.c b/kernel/wait.c
index f987688..a82b012 100644
--- a/kernel/wait.c
+++ b/kernel/wait.c
@@ -29,6 +29,24 @@ void fastcall add_wait_queue(wait_queue_head_t *q, wait_queue_t *wait)
}
EXPORT_SYMBOL(add_wait_queue);

+/**
+ * add_wait_queue_tail - Add a waiter to the back of a waitqueue
+ * @q: the wait queue to append the waiter to
+ * @wait: the waiter to be queued
+ *
+ * Add a waiter to the back of a waitqueue so that it gets woken up last.
+ */
+void fastcall add_wait_queue_tail(wait_queue_head_t *q, wait_queue_t *wait)
+{
+ unsigned long flags;
+
+ wait->flags &= ~WQ_FLAG_EXCLUSIVE;
+ spin_lock_irqsave(&q->lock, flags);
+ __add_wait_queue_tail(q, wait);
+ spin_unlock_irqrestore(&q->lock, flags);
+}
+EXPORT_SYMBOL(add_wait_queue_tail);
+
void fastcall add_wait_queue_exclusive(wait_queue_head_t *q, wait_queue_t *wait)
{
unsigned long flags;
diff --git a/mm/filemap.c b/mm/filemap.c
index 138e791..8d64000 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -587,7 +587,7 @@ void end_page_writeback(struct page *page)
EXPORT_SYMBOL(end_page_writeback);

/**
- * end_page_own - Clear PG_owner_priv_2 and wake up any waiters
+ * end_page_owner_priv_2 - Clear PG_owner_priv_2 and wake up any waiters
* @page: the page
*
* Clear PG_owner_priv_2 and wake up any processes waiting for that event.