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authorChristoph Hellwig <hch@lst.de>2018-05-20 20:19:30 +0300
committerChristoph Hellwig <hch@lst.de>2018-05-26 10:16:44 +0300
commit1962da0d2198a00a056a2915fbc6ec684c3bef0a (patch)
treeaec374beb42fb7e8d6dc95a602a1cd257df3ba82
parent2c14fa838cbefc23cf1c73ca167ed85b274b2913 (diff)
downloadlinux-1962da0d2198a00a056a2915fbc6ec684c3bef0a.tar.xz
aio: try to complete poll iocbs without context switch
If we can acquire ctx_lock without spinning we can just remove our iocb from the active_reqs list, and thus complete the iocbs from the wakeup context. Signed-off-by: Christoph Hellwig <hch@lst.de>
-rw-r--r--fs/aio.c20
1 files changed, 17 insertions, 3 deletions
diff --git a/fs/aio.c b/fs/aio.c
index bd711cfa4a1f..8274d09d44a2 100644
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -1633,6 +1633,7 @@ 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);
struct file *file = req->file;
__poll_t mask = key_to_poll(key);
@@ -1648,9 +1649,22 @@ static int aio_poll_wake(struct wait_queue_entry *wait, unsigned mode, int sync,
__aio_poll_remove(req);
- req->events = mask;
- INIT_WORK(&req->work, aio_poll_work);
- schedule_work(&req->work);
+ /*
+ * Try completing without a context switch if we can acquire ctx_lock
+ * without spinning. Otherwise we need to defer to a workqueue to
+ * avoid a deadlock due to the lock order.
+ */
+ if (spin_trylock(&iocb->ki_ctx->ctx_lock)) {
+ list_del_init(&iocb->ki_list);
+ spin_unlock(&iocb->ki_ctx->ctx_lock);
+
+ __aio_poll_complete(req, mask);
+ } else {
+ req->events = mask;
+ INIT_WORK(&req->work, aio_poll_work);
+ schedule_work(&req->work);
+ }
+
return 1;
}