[Devel] [PATCH RHEL COMMIT] sunrpc: pending tasks kill helper added

[Konstantin Khorenko]

The commit is pushed to "branch-rh9-5.14.vz9.1.x-ovz" and will appear at https://src.openvz.org/scm/ovz/vzkernel.git
after ark-5.14
------>
commit 8c8eb5292bae57a202cfe6b3240fe1e885585b3a
Author: Stanislav Kinsburskiy <skinsbursky at virtuozzo.com>
Date:   Tue Sep 28 14:42:40 2021 +0300

    sunrpc: pending tasks kill helper added
    
    This patch aborts SUNRPC tasks upon raise of per-net "kill_tasks" toggle.
    This is needed to abort pernding tasks, which are waiting for timeout.
    
    There could be a situation, when RPC task is not yet sleeping, but already
    passed the check for "kill_tasks" in __rpc_execute().
    There is a race in such a case, because task will fall into sleep anyway.
    This patch makes this probability a little bit less.
    
    https://jira.sw.ru/browse/PSBM-66510
    https://jira.sw.ru/browse/PSBM-68214
    
    rpc_killall_tasks helper is much better.
    First, is's in upsteam (I wrote it, but forgot :( ).
    Second, it kills *all* tasks (including sleeping in other than "pending"
    queues).
    
    Signed-off-by: Stanislav Kinsburskiy <skinsbursky at virtuozzo.com>
    
    (cherry-picked from vz8 commit 67bab1f08957 ("sunrpc: pending tasks kill
    helper added"))
    
    Signed-off-by: Nikita Yushchenko <nikita.yushchenko at virtuozzo.com>
---
 net/sunrpc/clnt.c | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/net/sunrpc/clnt.c b/net/sunrpc/clnt.c
index c1415984a21e..7ec1b4a06515 100644
--- a/net/sunrpc/clnt.c
+++ b/net/sunrpc/clnt.c
@@ -3072,11 +3072,23 @@ rpc_clnt_swap_deactivate(struct rpc_clnt *clnt)
 EXPORT_SYMBOL_GPL(rpc_clnt_swap_deactivate);
 #endif /* CONFIG_SUNRPC_SWAP */
 
+static void rpc_kill_tasks(struct net *net)
+{
+	struct rpc_clnt *clnt;
+	struct sunrpc_net *sn = net_generic(net, sunrpc_net_id);
+
+	spin_lock(&sn->rpc_client_lock);
+	list_for_each_entry(clnt, &sn->all_clients, cl_clients)
+		rpc_killall_tasks(clnt);
+	spin_unlock(&sn->rpc_client_lock);
+}
+
 static ssize_t write_kill_tasks(struct file *file, const char __user *buf,
 			 size_t count, loff_t *ppos)
 {
 	struct net *net = PDE_DATA(file->f_path.dentry->d_inode);
 	struct sunrpc_net *sn = net_generic(net, sunrpc_net_id);
+	bool prev_kill_tasks = sn->kill_tasks;
 	char tbuf[20];
 	unsigned long kill_tasks;
 	int res;
@@ -3092,6 +3104,11 @@ static ssize_t write_kill_tasks(struct file *file, const char __user *buf,
 		return res;
 
 	sn->kill_tasks = !!kill_tasks;
+
+	/* Kill pending tasks */
+	if (sn->kill_tasks && !prev_kill_tasks)
+		rpc_kill_tasks(net);
+
 	return count;
 }