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From: Christoph Hellwig <hch@lst.de>
To: viro@zeniv.linux.org.uk
Cc: Avi Kivity <avi@scylladb.com>,
	linux-aio@kvack.org, linux-fsdevel@vger.kernel.org,
	netdev@vger.kernel.org, linux-api@vger.kernel.org,
	linux-kernel@vger.kernel.org
Subject: [PATCH 14/36] aio: implement IOCB_CMD_POLL
Date: Wed, 17 Jan 2018 20:27:20 +0100	[thread overview]
Message-ID: <20180117192742.710-15-hch@lst.de> (raw)
In-Reply-To: <20180117192742.710-1-hch@lst.de>

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@lst.de>
---
 fs/aio.c                     | 98 ++++++++++++++++++++++++++++++++++++++++++++
 include/uapi/linux/aio_abi.h |  6 +--
 2 files changed, 100 insertions(+), 4 deletions(-)

diff --git a/fs/aio.c b/fs/aio.c
index da87cbf7c67a..0cddd24e7316 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 +1574,92 @@ 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 */
+	}
+
+	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);
+
+	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 +1723,9 @@ 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,
-- 
2.14.2

  parent reply	other threads:[~2018-01-17 19:28 UTC|newest]

Thread overview: 50+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-01-17 19:27 aio poll, io_pgetevents and a new in-kernel poll API V3 Christoph Hellwig
2018-01-17 19:27 ` [PATCH 01/36] aio: don't print the page size at boot time Christoph Hellwig
2018-01-17 19:27 ` [PATCH 02/36] aio: remove an outdated comment in aio_complete Christoph Hellwig
2018-01-17 19:27 ` [PATCH 03/36] aio: refactor read/write iocb setup Christoph Hellwig
2018-01-17 19:27 ` [PATCH 04/36] aio: sanitize ki_list handling Christoph Hellwig
2018-01-17 19:27 ` [PATCH 05/36] aio: simplify cancellation Christoph Hellwig
2018-01-17 19:27 ` [PATCH 06/36] aio: delete iocbs from the active_reqs list in kiocb_cancel Christoph Hellwig
2018-01-17 19:27 ` [PATCH 07/36] aio: add delayed cancel support Christoph Hellwig
2018-01-17 19:27 ` [PATCH 08/36] aio: implement io_pgetevents Christoph Hellwig
2018-01-17 19:27 ` [PATCH 09/36] fs: unexport poll_schedule_timeout Christoph Hellwig
2018-01-17 19:27 ` [PATCH 10/36] fs: cleanup do_pollfd Christoph Hellwig
2018-01-17 19:27 ` [PATCH 11/36] fs: update documentation for __poll_t Christoph Hellwig
2018-01-17 19:27 ` [PATCH 12/36] fs: add new vfs_poll and file_can_poll helpers Christoph Hellwig
2018-01-17 19:27 ` [PATCH 13/36] fs: introduce new ->get_poll_head and ->poll_mask methods Christoph Hellwig
2018-01-17 19:27 ` Christoph Hellwig [this message]
2018-01-17 19:27 ` [PATCH 15/36] net: refactor socket_poll Christoph Hellwig
2018-01-17 19:27 ` [PATCH 16/36] net: add support for ->poll_mask in proto_ops Christoph Hellwig
2018-01-17 19:27 ` [PATCH 17/36] net: remove sock_no_poll Christoph Hellwig
2018-01-17 19:27 ` [PATCH 18/36] net/tcp: convert to ->poll_mask Christoph Hellwig
2018-01-17 19:27 ` [PATCH 19/36] net/unix: " Christoph Hellwig
2018-01-17 19:27 ` [PATCH 20/36] net: convert datagram_poll users tp ->poll_mask Christoph Hellwig
2018-01-17 19:27 ` [PATCH 21/36] net/dccp: convert to ->poll_mask Christoph Hellwig
2018-01-17 19:27 ` [PATCH 22/36] net/atm: " Christoph Hellwig
2018-01-17 19:27 ` [PATCH 23/36] net/vmw_vsock: " Christoph Hellwig
2018-01-17 19:27 ` [PATCH 24/36] net/tipc: " Christoph Hellwig
2018-01-17 19:27 ` [PATCH 25/36] net/sctp: " Christoph Hellwig
2018-01-17 19:27 ` [PATCH 26/36] net/bluetooth: " Christoph Hellwig
2018-01-17 19:27 ` [PATCH 27/36] net/caif: " Christoph Hellwig
2018-01-17 19:27 ` [PATCH 28/36] net/nfc: " Christoph Hellwig
2018-01-17 19:27 ` [PATCH 29/36] net/phonet: " Christoph Hellwig
2018-01-17 19:27 ` [PATCH 30/36] net/iucv: " Christoph Hellwig
2018-01-17 19:27 ` [PATCH 31/36] net/rxrpc: " Christoph Hellwig
2018-01-17 19:27 ` [PATCH 32/36] crypto: af_alg: " Christoph Hellwig
2018-01-17 19:27 ` [PATCH 33/36] pipe: " Christoph Hellwig
2018-01-17 19:27 ` [PATCH 34/36] eventfd: switch " Christoph Hellwig
2018-01-17 19:27 ` [PATCH 35/36] timerfd: convert " Christoph Hellwig
2018-01-17 19:27 ` [PATCH 36/36] random: " Christoph Hellwig
2018-01-18 15:46 ` aio poll, io_pgetevents and a new in-kernel poll API V3 Jeff Moyer
2018-01-18 16:44   ` Jeff Moyer
2018-01-18 17:42     ` Christoph Hellwig
2018-01-18 17:59       ` Jeff Moyer
2018-01-18 17:55     ` Colin Walters
2018-01-18 18:53       ` Christoph Hellwig
2018-01-18 17:51   ` Avi Kivity
2018-01-18 17:52     ` Avi Kivity
2018-01-18 17:54     ` Jeff Moyer
2018-01-22 20:12 aio poll, io_pgetevents and a new in-kernel poll API V4 Christoph Hellwig
2018-01-22 20:12 ` [PATCH 14/36] aio: implement IOCB_CMD_POLL Christoph Hellwig
2018-01-24 19:24   ` Jeff Moyer
2018-03-05 21:27 aio poll, io_pgetevents and a new in-kernel poll API V5 Christoph Hellwig
2018-03-05 21:27 ` [PATCH 14/36] aio: implement IOCB_CMD_POLL Christoph Hellwig
2018-03-05 21:51   ` Jeff Moyer

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