Christoph Hellwig <hch@xxxxxx> writes: > Simple one-shot poll through the io_submit() interface. To poll for > a file descriptor the application should submit an iocb of type > IOCB_CMD_POLL. It will poll the fd for the events specified in the > the first 32 bits of the aio_buf field of the iocb. > > Unlike poll or epoll without EPOLLONESHOT this interface always works > in one shot mode, that is once the iocb is completed, it will have to be > resubmitted. > > Signed-off-by: Christoph Hellwig <hch@xxxxxx> Also acked this one in the last posting. Acked-by: Jeff Moyer <jmoyer@xxxxxxxxxx> > --- > fs/aio.c | 102 +++++++++++++++++++++++++++++++++++++++++++ > include/uapi/linux/aio_abi.h | 6 +-- > 2 files changed, 104 insertions(+), 4 deletions(-) > > diff --git a/fs/aio.c b/fs/aio.c > index da87cbf7c67a..0bafc4975d51 100644 > --- a/fs/aio.c > +++ b/fs/aio.c > @@ -5,6 +5,7 @@ > * Implements an efficient asynchronous io interface. > * > * Copyright 2000, 2001, 2002 Red Hat, Inc. All Rights Reserved. > + * Copyright 2018 Christoph Hellwig. > * > * See ../COPYING for licensing terms. > */ > @@ -156,9 +157,17 @@ struct kioctx { > unsigned id; > }; > > +struct poll_iocb { > + struct file *file; > + __poll_t events; > + struct wait_queue_head *head; > + struct wait_queue_entry wait; > +}; > + > struct aio_kiocb { > union { > struct kiocb rw; > + struct poll_iocb poll; > }; > > struct kioctx *ki_ctx; > @@ -1565,6 +1574,96 @@ static ssize_t aio_write(struct kiocb *req, struct iocb *iocb, bool vectored, > return ret; > } > > +static void __aio_complete_poll(struct poll_iocb *req, __poll_t mask) > +{ > + fput(req->file); > + aio_complete(container_of(req, struct aio_kiocb, poll), > + mangle_poll(mask), 0); > +} > + > +static void aio_complete_poll(struct poll_iocb *req, __poll_t mask) > +{ > + struct aio_kiocb *iocb = container_of(req, struct aio_kiocb, poll); > + > + if (!(iocb->flags & AIO_IOCB_CANCELLED)) > + __aio_complete_poll(req, mask); > +} > + > +static int aio_poll_cancel(struct kiocb *rw) > +{ > + struct aio_kiocb *iocb = container_of(rw, struct aio_kiocb, rw); > + > + remove_wait_queue(iocb->poll.head, &iocb->poll.wait); > + __aio_complete_poll(&iocb->poll, 0); /* no events to report */ > + return 0; > +} > + > +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 file *file = req->file; > + __poll_t mask = key_to_poll(key); > + > + assert_spin_locked(&req->head->lock); > + > + /* for instances that support it check for an event match first: */ > + if (mask && !(mask & req->events)) > + return 0; > + > + mask = vfs_poll_mask(file, req->events); > + if (!mask) > + return 0; > + > + __remove_wait_queue(req->head, &req->wait); > + aio_complete_poll(req, mask); > + return 1; > +} > + > +static ssize_t aio_poll(struct aio_kiocb *aiocb, struct iocb *iocb) > +{ > + struct poll_iocb *req = &aiocb->poll; > + unsigned long flags; > + __poll_t mask; > + > + /* reject any unknown events outside the normal event mask. */ > + if ((u16)iocb->aio_buf != iocb->aio_buf) > + return -EINVAL; > + /* reject fields that are not defined for poll */ > + if (iocb->aio_offset || iocb->aio_nbytes || iocb->aio_rw_flags) > + return -EINVAL; > + > + req->events = demangle_poll(iocb->aio_buf) | POLLERR | POLLHUP; > + req->file = fget(iocb->aio_fildes); > + if (unlikely(!req->file)) > + return -EBADF; > + > + req->head = vfs_get_poll_head(req->file, req->events); > + if (!req->head) { > + fput(req->file); > + return -EINVAL; /* same as no support for IOCB_CMD_POLL */ > + } > + if (IS_ERR(req->head)) { > + mask = PTR_TO_POLL(req->head); > + goto done; > + } > + > + init_waitqueue_func_entry(&req->wait, aio_poll_wake); > + > + spin_lock_irqsave(&req->head->lock, flags); > + mask = vfs_poll_mask(req->file, req->events); > + if (!mask) { > + __kiocb_set_cancel_fn(aiocb, aio_poll_cancel, > + AIO_IOCB_DELAYED_CANCEL); > + __add_wait_queue(req->head, &req->wait); > + } > + spin_unlock_irqrestore(&req->head->lock, flags); > +done: > + if (mask) > + aio_complete_poll(req, mask); > + return -EIOCBQUEUED; > +} > + > static int io_submit_one(struct kioctx *ctx, struct iocb __user *user_iocb, > struct iocb *iocb, bool compat) > { > @@ -1628,6 +1727,9 @@ static int io_submit_one(struct kioctx *ctx, struct iocb __user *user_iocb, > case IOCB_CMD_PWRITEV: > ret = aio_write(&req->rw, iocb, true, compat); > break; > + case IOCB_CMD_POLL: > + ret = aio_poll(req, iocb); > + break; > default: > pr_debug("invalid aio operation %d\n", iocb->aio_lio_opcode); > ret = -EINVAL; > diff --git a/include/uapi/linux/aio_abi.h b/include/uapi/linux/aio_abi.h > index 2c0a3415beee..ed0185945bb2 100644 > --- a/include/uapi/linux/aio_abi.h > +++ b/include/uapi/linux/aio_abi.h > @@ -39,10 +39,8 @@ enum { > IOCB_CMD_PWRITE = 1, > IOCB_CMD_FSYNC = 2, > IOCB_CMD_FDSYNC = 3, > - /* These two are experimental. > - * IOCB_CMD_PREADX = 4, > - * IOCB_CMD_POLL = 5, > - */ > + /* 4 was the experimental IOCB_CMD_PREADX */ > + IOCB_CMD_POLL = 5, > IOCB_CMD_NOOP = 6, > IOCB_CMD_PREADV = 7, > IOCB_CMD_PWRITEV = 8, -- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html