[patch 18/22] pollfs: check if a AIO event ring is empty

[Davi Arnaut <davi@haxent.com.br>]

[-- Attachment #1: pollfs-aio-ring-empty.patch --]
[-- Type: text/plain, Size: 1604 bytes --]

The aio_ring_empty() function returns true if the AIO event ring has no
elements, false otherwise.

Signed-off-by: Davi E. M. Arnaut <davi@haxent.com.br>

---
 fs/aio.c            |   17 +++++++++++++++++
 include/linux/aio.h |    1 +
 2 files changed, 18 insertions(+)

Index: linux-2.6/fs/aio.c
===================================================================
--- linux-2.6.orig/fs/aio.c
+++ linux-2.6/fs/aio.c
@@ -1004,6 +1004,23 @@ put_rq:
 	return ret;
 }
 
+int fastcall aio_ring_empty(struct kioctx *ioctx)
+{
+	struct aio_ring_info *info = &ioctx->ring_info;
+	struct aio_ring *ring;
+	unsigned long flags;
+	int ret = 0;
+
+	spin_lock_irqsave(&ioctx->ctx_lock, flags);
+	ring = kmap_atomic(info->ring_pages[0], KM_IRQ1);
+	if (ring->head == ring->tail)
+		ret = 1;
+	kunmap_atomic(ring, KM_IRQ1);
+	spin_unlock_irqrestore(&ioctx->ctx_lock, flags);
+
+	return ret;
+}
+
 /* aio_read_evt
  *	Pull an event off of the ioctx's event ring.  Returns the number of 
  *	events fetched (0 or 1 ;-)
Index: linux-2.6/include/linux/aio.h
===================================================================
--- linux-2.6.orig/include/linux/aio.h
+++ linux-2.6/include/linux/aio.h
@@ -202,6 +202,7 @@ extern unsigned aio_max_size;
 
 extern ssize_t FASTCALL(wait_on_sync_kiocb(struct kiocb *iocb));
 extern int FASTCALL(aio_put_req(struct kiocb *iocb));
+extern int FASTCALL(aio_ring_empty(struct kioctx *ioctx));
 extern void FASTCALL(kick_iocb(struct kiocb *iocb));
 extern int FASTCALL(aio_complete(struct kiocb *iocb, long res, long res2));
 extern void FASTCALL(__put_ioctx(struct kioctx *ctx));

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