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https://github.com/AuxXxilium/linux_dsm_epyc7002.git
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sunrpc: get rid of use_gssp_lock
We can achieve the same result with a cmpxchg(). This also fixes a potential race in use_gss_proxy(). The value of sn->use_gss_proxy could go from -1 to 1 just after we check it in use_gss_proxy() but before we acquire the spinlock. The procfile write would end up returning success but the value would flip to 0 soon afterward. With this method we not only avoid locking but the first "setter" always wins. Signed-off-by: Jeff Layton <jlayton@redhat.com> Signed-off-by: J. Bruce Fields <bfields@redhat.com>
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@ -1263,41 +1263,35 @@ static int svcauth_gss_proxy_init(struct svc_rqst *rqstp,
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return ret;
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}
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DEFINE_SPINLOCK(use_gssp_lock);
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/*
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* Try to set the sn->use_gss_proxy variable to a new value. We only allow
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* it to be changed if it's currently undefined (-1). If it's any other value
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* then return -EBUSY unless the type wouldn't have changed anyway.
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*/
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static int set_gss_proxy(struct net *net, int type)
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{
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struct sunrpc_net *sn = net_generic(net, sunrpc_net_id);
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int ret;
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WARN_ON_ONCE(type != 0 && type != 1);
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ret = cmpxchg(&sn->use_gss_proxy, -1, type);
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if (ret != -1 && ret != type)
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return -EBUSY;
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return 0;
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}
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static bool use_gss_proxy(struct net *net)
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{
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struct sunrpc_net *sn = net_generic(net, sunrpc_net_id);
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if (sn->use_gss_proxy != -1)
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return sn->use_gss_proxy;
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spin_lock(&use_gssp_lock);
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/*
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* If you wanted gss-proxy, you should have said so before
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* starting to accept requests:
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*/
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sn->use_gss_proxy = 0;
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spin_unlock(&use_gssp_lock);
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return 0;
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/* If use_gss_proxy is still undefined, then try to disable it */
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if (sn->use_gss_proxy == -1)
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set_gss_proxy(net, 0);
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return sn->use_gss_proxy;
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}
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#ifdef CONFIG_PROC_FS
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static int set_gss_proxy(struct net *net, int type)
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{
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struct sunrpc_net *sn = net_generic(net, sunrpc_net_id);
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int ret = 0;
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WARN_ON_ONCE(type != 0 && type != 1);
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spin_lock(&use_gssp_lock);
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if (sn->use_gss_proxy == -1 || sn->use_gss_proxy == type)
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sn->use_gss_proxy = type;
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else
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ret = -EBUSY;
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spin_unlock(&use_gssp_lock);
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return ret;
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}
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static ssize_t write_gssp(struct file *file, const char __user *buf,
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size_t count, loff_t *ppos)
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{
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