If we get a keyed wakeup for a aio poll waitqueue and wake can acquire the
ctx_lock without spinning we can just complete the iocb straight from the
wakeup callback to avoid a context switch.
Signed-off-by: Christoph Hellwig <hch@xxxxxx>
Tested-by: Avi Kivity <avi@xxxxxxxxxxxx>
---
Fix a subject line typo and improve a comment.
fs/aio.c | 20 ++++++++++++++++++--
1 file changed, 18 insertions(+), 2 deletions(-)
diff --git a/fs/aio.c b/fs/aio.c
index 2fd19521d8a8..5943098a87c6 100644
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -1672,13 +1672,29 @@ static int aio_poll_wake(struct wait_queue_entry *wait, unsigned mode, int sync,
void *key)
{
struct poll_iocb *req = container_of(wait, struct poll_iocb, wait);
+ struct aio_kiocb *iocb = container_of(req, struct aio_kiocb, poll);
__poll_t mask = key_to_poll(key);
req->woken = true;
/* for instances that support it check for an event match first: */
- if (mask && !(mask & req->events))
- return 0;
+ if (mask) {
+ if (!(mask & req->events))
+ return 0;
+
+ /*
+ * Try to complete the iocb inline if we can to avoid a costly
+ * context switch.
+ */
+ if (spin_trylock(&iocb->ki_ctx->ctx_lock)) {
+ list_del(&iocb->ki_list);
+ spin_unlock(&iocb->ki_ctx->ctx_lock);
+
+ list_del_init(&req->wait.entry);
+ aio_poll_complete(iocb, mask);
+ return 1;
+ }
+ }
list_del_init(&req->wait.entry);
schedule_work(&req->work);
--
2.18.0
