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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 07/36] aio: add delayed cancel support
Date: Wed, 17 Jan 2018 20:27:13 +0100	[thread overview]
Message-ID: <20180117192742.710-8-hch@lst.de> (raw)
In-Reply-To: <20180117192742.710-1-hch@lst.de>

The upcoming aio poll support would like to be able to complete the
iocb inline from the cancellation context, but that would cause
a lock order reversal.  Add support for optionally moving the cancelation
outside the context lock to avoid this reversal.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Jeff Moyer <jmoyer@redhat.com>
---
 fs/aio.c | 49 ++++++++++++++++++++++++++++++++++++++-----------
 1 file changed, 38 insertions(+), 11 deletions(-)

diff --git a/fs/aio.c b/fs/aio.c
index 0b6394b4e528..9d7d6e4cde87 100644
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -170,6 +170,10 @@ struct aio_kiocb {
 	struct list_head	ki_list;	/* the aio core uses this
 						 * for cancellation */
 
+	unsigned int		flags;		/* protected by ctx->ctx_lock */
+#define AIO_IOCB_DELAYED_CANCEL	(1 << 0)
+#define AIO_IOCB_CANCELLED	(1 << 1)
+
 	/*
 	 * If the aio_resfd field of the userspace iocb is not zero,
 	 * this is the underlying eventfd context to deliver events to.
@@ -536,9 +540,9 @@ static int aio_setup_ring(struct kioctx *ctx, unsigned int nr_events)
 #define AIO_EVENTS_FIRST_PAGE	((PAGE_SIZE - sizeof(struct aio_ring)) / sizeof(struct io_event))
 #define AIO_EVENTS_OFFSET	(AIO_EVENTS_PER_PAGE - AIO_EVENTS_FIRST_PAGE)
 
-void kiocb_set_cancel_fn(struct kiocb *iocb, kiocb_cancel_fn *cancel)
+static void __kiocb_set_cancel_fn(struct aio_kiocb *req,
+		kiocb_cancel_fn *cancel, unsigned int iocb_flags)
 {
-	struct aio_kiocb *req = container_of(iocb, struct aio_kiocb, rw);
 	struct kioctx *ctx = req->ki_ctx;
 	unsigned long flags;
 
@@ -548,8 +552,15 @@ void kiocb_set_cancel_fn(struct kiocb *iocb, kiocb_cancel_fn *cancel)
 	spin_lock_irqsave(&ctx->ctx_lock, flags);
 	list_add_tail(&req->ki_list, &ctx->active_reqs);
 	req->ki_cancel = cancel;
+	req->flags |= iocb_flags;
 	spin_unlock_irqrestore(&ctx->ctx_lock, flags);
 }
+
+void kiocb_set_cancel_fn(struct kiocb *iocb, kiocb_cancel_fn *cancel)
+{
+	return __kiocb_set_cancel_fn(container_of(iocb, struct aio_kiocb, rw),
+			cancel, 0);
+}
 EXPORT_SYMBOL(kiocb_set_cancel_fn);
 
 /*
@@ -603,17 +614,27 @@ static void free_ioctx_users(struct percpu_ref *ref)
 {
 	struct kioctx *ctx = container_of(ref, struct kioctx, users);
 	struct aio_kiocb *req;
+	LIST_HEAD(list);
 
 	spin_lock_irq(&ctx->ctx_lock);
-
 	while (!list_empty(&ctx->active_reqs)) {
 		req = list_first_entry(&ctx->active_reqs,
 				       struct aio_kiocb, ki_list);
-		kiocb_cancel(req);
-	}
 
+		if (req->flags & AIO_IOCB_DELAYED_CANCEL) {
+			req->flags |= AIO_IOCB_CANCELLED;
+			list_move_tail(&req->ki_list, &list);
+		} else {
+			kiocb_cancel(req);
+		}
+	}
 	spin_unlock_irq(&ctx->ctx_lock);
 
+	while (!list_empty(&list)) {
+		req = list_first_entry(&list, struct aio_kiocb, ki_list);
+		kiocb_cancel(req);
+	}
+
 	percpu_ref_kill(&ctx->reqs);
 	percpu_ref_put(&ctx->reqs);
 }
@@ -1785,15 +1806,22 @@ SYSCALL_DEFINE3(io_cancel, aio_context_t, ctx_id, struct iocb __user *, iocb,
 	if (unlikely(!ctx))
 		return -EINVAL;
 
-	spin_lock_irq(&ctx->ctx_lock);
+	ret = -EINVAL;
 
+	spin_lock_irq(&ctx->ctx_lock);
 	kiocb = lookup_kiocb(ctx, iocb, key);
+	if (kiocb) {
+		if (kiocb->flags & AIO_IOCB_DELAYED_CANCEL) {
+			kiocb->flags |= AIO_IOCB_CANCELLED;
+		} else {
+			ret = kiocb_cancel(kiocb);
+			kiocb = NULL;
+		}
+	}
+	spin_unlock_irq(&ctx->ctx_lock);
+
 	if (kiocb)
 		ret = kiocb_cancel(kiocb);
-	else
-		ret = -EINVAL;
-
-	spin_unlock_irq(&ctx->ctx_lock);
 
 	if (!ret) {
 		/*
@@ -1805,7 +1833,6 @@ SYSCALL_DEFINE3(io_cancel, aio_context_t, ctx_id, struct iocb __user *, iocb,
 	}
 
 	percpu_ref_put(&ctx->users);
-
 	return ret;
 }
 
-- 
2.14.2

  parent reply	other threads:[~2018-01-17 19:27 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 ` Christoph Hellwig [this message]
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 ` [PATCH 14/36] aio: implement IOCB_CMD_POLL Christoph Hellwig
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 07/36] aio: add delayed cancel support Christoph Hellwig
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 07/36] aio: add delayed cancel support Christoph Hellwig
2018-03-20  3:19   ` Darrick J. Wong
2018-03-20 15:20     ` Christoph Hellwig

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