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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Mike Christie <mchristi@redhat.com>,
        Florian Westphal <fw@strlen.de>,
        Nicholas Bellinger <nab@linux-iscsi.org>
Subject: [PATCH 4.14 132/167] iscsi-target: make sure to wake up sleeping login worker
Date:   Wed, 21 Feb 2018 13:49:03 +0100
Message-Id: <20180221124531.859644775@linuxfoundation.org>
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4.14-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Florian Westphal <fw@strlen.de>

commit 1c130ae00b769a2e2df41bad3d6051ee8234b636 upstream.

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.

(Drop WARN_ON usage - nab)

Reported-by: Mike Christie <mchristi@redhat.com>
Bisected-by: Mike Christie <mchristi@redhat.com>
Tested-by: Mike Christie <mchristi@redhat.com>
Diagnosed-by: Nicholas Bellinger <nab@linux-iscsi.org>
Fixes: e7942d0633c4 ("tcp: remove prequeue support")
Signed-off-by: Florian Westphal <fw@strlen.de>
Cc: stable@vger.kernel.org # 4.14+
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/target/iscsi/iscsi_target_nego.c |    3 +++
 1 file changed, 3 insertions(+)

--- 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(s
 	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 (iscsi_target_sk_data_ready == conn->orig_data_ready)
+			return;
+		conn->orig_data_ready(sk);
 		return;
 	}