netdev - [PATCH 2/2] net/9p: Switch to wait_event

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Date:   Wed, 6 Sep 2017 17:59:08 +0300
From:   Tuomas Tynkkynen <tuomas@...era.com>
To:     Al Viro <viro@...iv.linux.org.uk>
CC:     <v9fs-developer@...ts.sourceforge.net>,
        Eric Van Hensbergen <ericvh@...il.com>,
        Ron Minnich <rminnich@...dia.gov>,
        Latchesar Ionkov <lucho@...kov.net>,
        "David S. Miller" <davem@...emloft.net>,
        <linux-kernel@...r.kernel.org>, <netdev@...r.kernel.org>,
        <linux-fsdevel@...r.kernel.org>,
        Tuomas Tynkkynen <tuomas@...era.com>, <stable@...r.kernel.org>
Subject: [PATCH 2/2] net/9p: Switch to wait_event_killable()

Because userspace gets Very Unhappy when calls like stat() and execve()
return -EINTR on 9p filesystem mounts. For instance, when bash is
looking in PATH for things to execute and some SIGCHLD interrupts
stat(), bash can throw a spurious 'command not found' since it doesn't
retry the stat().

In practice, hitting the problem is rare and needs a really
slow/bogged down 9p server.

Cc: stable@...r.kernel.org
Signed-off-by: Tuomas Tynkkynen <tuomas@...era.com>
---
 net/9p/client.c       |  3 +--
 net/9p/trans_virtio.c | 13 ++++++-------
 net/9p/trans_xen.c    |  4 ++--
 3 files changed, 9 insertions(+), 11 deletions(-)

diff --git a/net/9p/client.c b/net/9p/client.c
index 4674235b0d9b..1beb131dd3e1 100644
--- a/net/9p/client.c
+++ b/net/9p/client.c
@@ -773,8 +773,7 @@ p9_client_rpc(struct p9_client *c, int8_t type, const char *fmt, ...)
 	}
 again:
 	/* Wait for the response */
-	err = wait_event_interruptible(*req->wq,
-				       req->status >= REQ_STATUS_RCVD);
+	err = wait_event_killable(*req->wq, req->status >= REQ_STATUS_RCVD);
 
 	/*
 	 * Make sure our req is coherent with regard to updates in other
diff --git a/net/9p/trans_virtio.c b/net/9p/trans_virtio.c
index f24b25c25106..f3a4efcf1456 100644
--- a/net/9p/trans_virtio.c
+++ b/net/9p/trans_virtio.c
@@ -286,8 +286,8 @@ p9_virtio_request(struct p9_client *client, struct p9_req_t *req)
 		if (err == -ENOSPC) {
 			chan->ring_bufs_avail = 0;
 			spin_unlock_irqrestore(&chan->lock, flags);
-			err = wait_event_interruptible(*chan->vc_wq,
-							chan->ring_bufs_avail);
+			err = wait_event_killable(*chan->vc_wq,
+						  chan->ring_bufs_avail);
 			if (err  == -ERESTARTSYS)
 				return err;
 
@@ -327,7 +327,7 @@ static int p9_get_mapped_pages(struct virtio_chan *chan,
 		 * Other zc request to finish here
 		 */
 		if (atomic_read(&vp_pinned) >= chan->p9_max_pages) {
-			err = wait_event_interruptible(vp_wq,
+			err = wait_event_killable(vp_wq,
 			      (atomic_read(&vp_pinned) < chan->p9_max_pages));
 			if (err == -ERESTARTSYS)
 				return err;
@@ -471,8 +471,8 @@ p9_virtio_zc_request(struct p9_client *client, struct p9_req_t *req,
 		if (err == -ENOSPC) {
 			chan->ring_bufs_avail = 0;
 			spin_unlock_irqrestore(&chan->lock, flags);
-			err = wait_event_interruptible(*chan->vc_wq,
-						       chan->ring_bufs_avail);
+			err = wait_event_killable(*chan->vc_wq,
+						  chan->ring_bufs_avail);
 			if (err  == -ERESTARTSYS)
 				goto err_out;
 
@@ -489,8 +489,7 @@ p9_virtio_zc_request(struct p9_client *client, struct p9_req_t *req,
 	virtqueue_kick(chan->vq);
 	spin_unlock_irqrestore(&chan->lock, flags);
 	p9_debug(P9_DEBUG_TRANS, "virtio request kicked\n");
-	err = wait_event_interruptible(*req->wq,
-				       req->status >= REQ_STATUS_RCVD);
+	err = wait_event_killable(*req->wq, req->status >= REQ_STATUS_RCVD);
 	/*
 	 * Non kernel buffers are pinned, unpin them
 	 */
diff --git a/net/9p/trans_xen.c b/net/9p/trans_xen.c
index 6ad3e043c617..325c56043007 100644
--- a/net/9p/trans_xen.c
+++ b/net/9p/trans_xen.c
@@ -156,8 +156,8 @@ static int p9_xen_request(struct p9_client *client, struct p9_req_t *p9_req)
 	ring = &priv->rings[num];
 
 again:
-	while (wait_event_interruptible(ring->wq,
-					p9_xen_write_todo(ring, size)) != 0)
+	while (wait_event_killable(ring->wq,
+				   p9_xen_write_todo(ring, size)) != 0)
 		;
 
 	spin_lock_irqsave(&ring->lock, flags);
-- 
2.13.0