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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 08/31] aio: implement IOCB_CMD_POLL
Date: Tue, 22 May 2018 13:30:45 +0200	[thread overview]
Message-ID: <20180522113108.25713-9-hch@lst.de> (raw)
In-Reply-To: <20180522113108.25713-1-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>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
---
 fs/aio.c                     | 134 ++++++++++++++++++++++++++++++++++-
 include/uapi/linux/aio_abi.h |   6 +-
 2 files changed, 135 insertions(+), 5 deletions(-)

diff --git a/fs/aio.c b/fs/aio.c
index 8991baa38d5d..4d1eabce6659 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.
  */
@@ -164,10 +165,22 @@ struct fsync_iocb {
 	bool			datasync;
 };
 
+struct poll_iocb {
+	struct file		*file;
+	__poll_t		events;
+	struct wait_queue_head	*head;
+
+	union {
+		struct wait_queue_entry	wait;
+		struct work_struct	work;
+	};
+};
+
 struct aio_kiocb {
 	union {
 		struct kiocb		rw;
 		struct fsync_iocb	fsync;
+		struct poll_iocb	poll;
 	};
 
 	struct kioctx		*ki_ctx;
@@ -1558,7 +1571,6 @@ static int aio_fsync(struct fsync_iocb *req, struct iocb *iocb, bool datasync)
 	if (unlikely(iocb->aio_buf || iocb->aio_offset || iocb->aio_nbytes ||
 			iocb->aio_rw_flags))
 		return -EINVAL;
-
 	req->file = fget(iocb->aio_fildes);
 	if (unlikely(!req->file))
 		return -EBADF;
@@ -1573,6 +1585,124 @@ static int aio_fsync(struct fsync_iocb *req, struct iocb *iocb, bool datasync)
 	return -EIOCBQUEUED;
 }
 
+/* need to use list_del_init so we can check if item was present */
+static inline bool __aio_poll_remove(struct poll_iocb *req)
+{
+	if (list_empty(&req->wait.entry))
+		return false;
+	list_del_init(&req->wait.entry);
+	return true;
+}
+
+static inline void __aio_poll_complete(struct poll_iocb *req, __poll_t mask)
+{
+	struct aio_kiocb *iocb = container_of(req, struct aio_kiocb, poll);
+
+	fput(req->file);
+	aio_complete(iocb, mangle_poll(mask), 0);
+}
+
+static void aio_poll_work(struct work_struct *work)
+{
+	struct poll_iocb *req = container_of(work, struct poll_iocb, work);
+
+	__aio_poll_complete(req, req->events);
+}
+
+static int aio_poll_cancel(struct kiocb *iocb)
+{
+	struct aio_kiocb *aiocb = container_of(iocb, struct aio_kiocb, rw);
+	struct poll_iocb *req = &aiocb->poll;
+	struct wait_queue_head *head = req->head;
+	bool found = false;
+
+	spin_lock(&head->lock);
+	found = __aio_poll_remove(req);
+	spin_unlock(&head->lock);
+
+	if (found) {
+		req->events = 0;
+		INIT_WORK(&req->work, aio_poll_work);
+		schedule_work(&req->work);
+	}
+	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 = file->f_op->poll_mask(file, req->events);
+	if (!mask)
+		return 0;
+
+	__aio_poll_remove(req);
+
+	req->events = mask;
+	INIT_WORK(&req->work, aio_poll_work);
+	schedule_work(&req->work);
+	return 1;
+}
+
+static ssize_t aio_poll(struct aio_kiocb *aiocb, struct iocb *iocb)
+{
+	struct kioctx *ctx = aiocb->ki_ctx;
+	struct poll_iocb *req = &aiocb->poll;
+	__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;
+	if (!file_has_poll_mask(req->file))
+		goto out_fail;
+
+	req->head = req->file->f_op->get_poll_head(req->file, req->events);
+	if (!req->head)
+		goto out_fail;
+	if (IS_ERR(req->head)) {
+		mask = EPOLLERR;
+		goto done;
+	}
+
+	init_waitqueue_func_entry(&req->wait, aio_poll_wake);
+	aiocb->ki_cancel = aio_poll_cancel;
+
+	spin_lock_irq(&ctx->ctx_lock);
+	list_add_tail(&aiocb->ki_list, &ctx->active_reqs);
+
+	spin_lock(&req->head->lock);
+	mask = req->file->f_op->poll_mask(req->file, req->events);
+	if (!mask)
+		__add_wait_queue(req->head, &req->wait);
+	spin_unlock(&req->head->lock);
+
+	spin_unlock_irq(&ctx->ctx_lock);
+done:
+	if (mask)
+		__aio_poll_complete(req, mask);
+	return -EIOCBQUEUED;
+out_fail:
+	fput(req->file);
+	return -EINVAL; /* same as no support for IOCB_CMD_POLL */
+}
+
 static int io_submit_one(struct kioctx *ctx, struct iocb __user *user_iocb,
 			 struct iocb *iocb, bool compat)
 {
@@ -1641,6 +1771,8 @@ static int io_submit_one(struct kioctx *ctx, struct iocb __user *user_iocb,
 		break;
 	case IOCB_CMD_FDSYNC:
 		ret = aio_fsync(&req->fsync, iocb, true);
+	case IOCB_CMD_POLL:
+		ret = aio_poll(req, iocb);
 		break;
 	default:
 		pr_debug("invalid aio operation %d\n", iocb->aio_lio_opcode);
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,
-- 
2.17.0

  parent reply	other threads:[~2018-05-22 11:31 UTC|newest]

Thread overview: 38+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-05-22 11:30 aio poll and a new in-kernel poll API V12 Christoph Hellwig
2018-05-22 11:30 ` [PATCH 01/31] fs: unexport poll_schedule_timeout Christoph Hellwig
2018-05-22 11:30 ` [PATCH 02/31] fs: cleanup do_pollfd Christoph Hellwig
2018-05-22 11:30 ` [PATCH 03/31] fs: update documentation to mention __poll_t and match the code Christoph Hellwig
2018-05-22 11:30 ` [PATCH 04/31] fs: add new vfs_poll and file_can_poll helpers Christoph Hellwig
2018-05-22 11:30 ` [PATCH 05/31] fs: introduce new ->get_poll_head and ->poll_mask methods Christoph Hellwig
2018-05-22 11:30 ` [PATCH 06/31] aio: simplify KIOCB_KEY handling Christoph Hellwig
2018-05-22 11:30 ` [PATCH 07/31] aio: simplify cancellation Christoph Hellwig
2018-05-22 11:30 ` Christoph Hellwig [this message]
2018-05-22 22:05   ` [PATCH 08/31] aio: implement IOCB_CMD_POLL Al Viro
2018-05-23  0:45     ` Al Viro
2018-05-23  0:49       ` Al Viro
2018-05-23  1:43         ` YAaioRace (was Re: [PATCH 08/31] aio: implement IOCB_CMD_POLL) Al Viro
2018-05-22 11:30 ` [PATCH 09/31] aio: try to complete poll iocbs without context switch Christoph Hellwig
2018-05-22 11:30 ` [PATCH 10/31] net: refactor socket_poll Christoph Hellwig
2018-05-22 11:30 ` [PATCH 11/31] net: add support for ->poll_mask in proto_ops Christoph Hellwig
2018-05-22 11:30 ` [PATCH 12/31] net: remove sock_no_poll Christoph Hellwig
2018-05-22 11:30 ` [PATCH 13/31] net/tcp: convert to ->poll_mask Christoph Hellwig
2018-05-22 11:30 ` [PATCH 14/31] net/unix: " Christoph Hellwig
2018-05-22 11:30 ` [PATCH 15/31] net: convert datagram_poll users tp ->poll_mask Christoph Hellwig
2018-05-22 11:30 ` [PATCH 16/31] net/dccp: convert to ->poll_mask Christoph Hellwig
2018-05-22 11:30 ` [PATCH 17/31] net/atm: " Christoph Hellwig
2018-05-22 11:30 ` [PATCH 18/31] net/vmw_vsock: " Christoph Hellwig
2018-05-22 11:30 ` [PATCH 19/31] net/tipc: " Christoph Hellwig
2018-05-22 11:30 ` [PATCH 20/31] net/sctp: " Christoph Hellwig
2018-05-22 11:30 ` [PATCH 21/31] net/bluetooth: " Christoph Hellwig
2018-05-22 11:30 ` [PATCH 22/31] net/caif: " Christoph Hellwig
2018-05-22 11:31 ` [PATCH 23/31] net/nfc: " Christoph Hellwig
2018-05-22 11:31 ` [PATCH 24/31] net/phonet: " Christoph Hellwig
2018-05-22 11:31 ` [PATCH 25/31] net/iucv: " Christoph Hellwig
2018-05-22 11:31 ` [PATCH 26/31] net/rxrpc: " Christoph Hellwig
2018-05-22 11:31 ` [PATCH 27/31] crypto: af_alg: " Christoph Hellwig
2018-05-22 11:31 ` [PATCH 28/31] pipe: " Christoph Hellwig
2018-05-22 11:31 ` [PATCH 29/31] eventfd: switch " Christoph Hellwig
2018-05-22 11:31 ` [PATCH 30/31] timerfd: convert " Christoph Hellwig
2018-05-22 16:59   ` Sergei Shtylyov
2018-05-22 11:31 ` [PATCH 31/31] random: " Christoph Hellwig
2018-05-22 22:07 ` aio poll and a new in-kernel poll API V12 Al Viro

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