[3.11.y.z extended stable] Patch "sunrpc: don't wait for write before allowing reads from use-gss-proxy" has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

    sunrpc: don't wait for write before allowing reads from use-gss-proxy

to the linux-3.11.y-queue branch of the 3.11.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.11.y-queue

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.11.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From 4126d70acb762a8a31394e5f9a29f075e8f031b3 Mon Sep 17 00:00:00 2001
From: Jeff Layton <jlayton at redhat.com>
Date: Sat, 4 Jan 2014 07:18:03 -0500
Subject: sunrpc: don't wait for write before allowing reads from use-gss-proxy
 file

commit 1654a04cd702fd19c297c36300a6ab834cf8c072 upstream.

It doesn't make much sense to make reads from this procfile hang. As
far as I can tell, only gssproxy itself will open this file and it
never reads from it. Change it to just give the present setting of
sn->use_gss_proxy without waiting for anything.

Note that we do not want to call use_gss_proxy() in this codepath
since an inopportune read of this file could cause it to be disabled
prematurely.

Signed-off-by: Jeff Layton <jlayton at redhat.com>
Signed-off-by: J. Bruce Fields <bfields at redhat.com>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 net/sunrpc/auth_gss/gss_rpc_upcall.c |  2 --
 net/sunrpc/auth_gss/svcauth_gss.c    | 33 ++-------------------------------
 net/sunrpc/netns.h                   |  1 -
 3 files changed, 2 insertions(+), 34 deletions(-)

diff --git a/net/sunrpc/auth_gss/gss_rpc_upcall.c b/net/sunrpc/auth_gss/gss_rpc_upcall.c
index f1eb0d1..23fa3c1 100644
--- a/net/sunrpc/auth_gss/gss_rpc_upcall.c
+++ b/net/sunrpc/auth_gss/gss_rpc_upcall.c
@@ -137,7 +137,6 @@ void init_gssp_clnt(struct sunrpc_net *sn)
 {
 	mutex_init(&sn->gssp_lock);
 	sn->gssp_clnt = NULL;
-	init_waitqueue_head(&sn->gssp_wq);
 }

 int set_gssp_clnt(struct net *net)
@@ -154,7 +153,6 @@ int set_gssp_clnt(struct net *net)
 		sn->gssp_clnt = clnt;
 	}
 	mutex_unlock(&sn->gssp_lock);
-	wake_up(&sn->gssp_wq);
 	return ret;
 }

diff --git a/net/sunrpc/auth_gss/svcauth_gss.c b/net/sunrpc/auth_gss/svcauth_gss.c
index 09fb638..e18be86 100644
--- a/net/sunrpc/auth_gss/svcauth_gss.c
+++ b/net/sunrpc/auth_gss/svcauth_gss.c
@@ -1295,34 +1295,9 @@ static int set_gss_proxy(struct net *net, int type)
 	else
 		ret = -EBUSY;
 	spin_unlock(&use_gssp_lock);
-	wake_up(&sn->gssp_wq);
 	return ret;
 }

-static inline bool gssp_ready(struct sunrpc_net *sn)
-{
-	switch (sn->use_gss_proxy) {
-		case -1:
-			return false;
-		case 0:
-			return true;
-		case 1:
-			return sn->gssp_clnt;
-	}
-	WARN_ON_ONCE(1);
-	return false;
-}
-
-static int wait_for_gss_proxy(struct net *net, struct file *file)
-{
-	struct sunrpc_net *sn = net_generic(net, sunrpc_net_id);
-
-	if (file->f_flags & O_NONBLOCK && !gssp_ready(sn))
-		return -EAGAIN;
-	return wait_event_interruptible(sn->gssp_wq, gssp_ready(sn));
-}
-
-
 static ssize_t write_gssp(struct file *file, const char __user *buf,
 			 size_t count, loff_t *ppos)
 {
@@ -1355,16 +1330,12 @@ static ssize_t read_gssp(struct file *file, char __user *buf,
 			 size_t count, loff_t *ppos)
 {
 	struct net *net = PDE_DATA(file_inode(file));
+	struct sunrpc_net *sn = net_generic(net, sunrpc_net_id);
 	unsigned long p = *ppos;
 	char tbuf[10];
 	size_t len;
-	int ret;
-
-	ret = wait_for_gss_proxy(net, file);
-	if (ret)
-		return ret;

-	snprintf(tbuf, sizeof(tbuf), "%d\n", use_gss_proxy(net));
+	snprintf(tbuf, sizeof(tbuf), "%d\n", sn->use_gss_proxy);
 	len = strlen(tbuf);
 	if (p >= len)
 		return 0;
diff --git a/net/sunrpc/netns.h b/net/sunrpc/netns.h
index 779742c..3a260e4 100644
--- a/net/sunrpc/netns.h
+++ b/net/sunrpc/netns.h
@@ -26,7 +26,6 @@ struct sunrpc_net {
 	unsigned int rpcb_is_af_local : 1;

 	struct mutex gssp_lock;
-	wait_queue_head_t gssp_wq;
 	struct rpc_clnt *gssp_clnt;
 	int use_gss_proxy;
 	int pipe_version;
--
1.8.3.2