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aio: allow direct aio poll comletions for keyed wakeups

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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@lst.de>
Tested-by: Avi Kivity <avi@scylladb.com>
This commit is contained in:
Christoph Hellwig 2018-07-16 12:25:17 +02:00
parent bfe4037e72
commit e8693bcfa0
1 changed files with 15 additions and 2 deletions
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17
fs/aio.c
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@ -1672,13 +1672,26 @@ 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: */
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);