iscsi-target: make sure to wake up sleeping login worker

Web:        https://git.kernel.org/torvalds/c/1c130ae00b769a2e2df41bad3d6051ee8234b636
Commit:     1c130ae00b769a2e2df41bad3d6051ee8234b636
Parent:     85fae482a9dd3560b9dcd35136fb29ccab6fae48
Refname:    refs/heads/master
Author:     Florian Westphal <[email protected]>
AuthorDate: Fri Jan 19 14:36:29 2018 +0100
Committer:  Nicholas Bellinger <[email protected]>
CommitDate: Tue Jan 23 23:03:54 2018 -0800

    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.
    
    (Drop WARN_ON usage - nab)
    
    Reported-by: Mike Christie <[email protected]>
    Bisected-by: Mike Christie <[email protected]>
    Tested-by: Mike Christie <[email protected]>
    Diagnosed-by: Nicholas Bellinger <[email protected]>
    Fixes: e7942d0633c4 ("tcp: remove prequeue support")
    Signed-off-by: Florian Westphal <[email protected]>
    Cc: [email protected] # 4.14+
    Signed-off-by: Nicholas Bellinger <[email protected]>
---
 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..8a5e8d17a942 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 (iscsi_target_sk_data_ready == conn->orig_data_ready)
+			return;
+		conn->orig_data_ready(sk);
 		return;
 	}
 
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