netdev - [PATCH target-pending] iscsi-target: make sure to wake up sleeping login worker

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Message-Id: <20180119133629.14812-1-fw@strlen.de>
Date:   Fri, 19 Jan 2018 14:36:29 +0100
From:   Florian Westphal <fw@...len.de>
To:     target-devel@...r.kernel.org
Cc:     mchristi@...hat.com, nab@...ux-iscsi.org, netdev@...r.kernel.org,
        linux-scsi@...r.kernel.org, Florian Westphal <fw@...len.de>
Subject: [PATCH target-pending] iscsi-target: make sure to wake up sleeping login worker

Mike Christie reports:
  Starting in 4.14 iscsi logins will fail around 50% of the time.

Problem appears to be that iscsi_target_sk_data_ready() callback may
return without doing anything in case it finds the login work queue
is still blocked in sock_recvmsg().

Nicholas Bellinger says:
  It would indicate users providing their own ->sk_data_ready() callback
  must be responsible for waking up a kthread context blocked on
  sock_recvmsg(..., MSG_WAITALL), when a second ->sk_data_ready() is
  received before the first sock_recvmsg(..., MSG_WAITALL) completes.

So, do this and invoke the original data_ready() callback -- in
case of tcp sockets this takes care of waking the thread.

Disclaimer: I do not understand why this problem did not show up before
tcp prequeue removal.

Reported-by: Mike Christie <mchristi@...hat.com>
Bisected-by: Mike Christie <mchristi@...hat.com>
Tested-by: Mike Christie <mchristi@...hat.com>
Diagnosed-by: Nicholas Bellinger <nab@...ux-iscsi.org>
Fixes: e7942d0633c4 ("tcp: remove prequeue support")
Signed-off-by: Florian Westphal <fw@...len.de>
---
 drivers/target/iscsi/iscsi_target_nego.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/target/iscsi/iscsi_target_nego.c b/drivers/target/iscsi/iscsi_target_nego.c
index b686e2ce9c0e..3723f8f419aa 100644
--- a/drivers/target/iscsi/iscsi_target_nego.c
+++ b/drivers/target/iscsi/iscsi_target_nego.c
@@ -432,6 +432,9 @@ static void iscsi_target_sk_data_ready(struct sock *sk)
 	if (test_and_set_bit(LOGIN_FLAGS_READ_ACTIVE, &conn->login_flags)) {
 		write_unlock_bh(&sk->sk_callback_lock);
 		pr_debug("Got LOGIN_FLAGS_READ_ACTIVE=1, conn: %p >>>>\n", conn);
+		if (WARN_ON(iscsi_target_sk_data_ready == conn->orig_data_ready))
+			return;
+		conn->orig_data_ready(sk);
 		return;
 	}

-- 
2.13.6