iscsi-target: Fix potential deadlock on lock taken in timer

We need to disable BHs when taking sess_idr_lock because the
iscsit_handle_time2retain_timeout() timer function takes
se_tpg->session_lock, and iscsit_close_session() nests sess_idr_lock
inside se_tpg->session_lock.  So if the timer can run inside
sess_idr_lock, we have a potential AB-BA deadlock.

Fix this by disabling BHs when taking sess_idr_lock.  This was found
because of a lockdep warning, but it looks like a real (if highly
theoretical) deadlock.  In any case avoiding lockdep spew so that we can
find other issues is a worthy cause.

Signed-off-by: Roland Dreier <roland@purestorage.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

1 files changed, 2 insertions, 2 deletions

diff --git a/drivers/target/iscsi/iscsi_target_login.c b/drivers/target/iscsi/iscsi_target_login.c
index f8dbec05d5e5..3f34ecf87b1e 100644
--- a/drivers/target/iscsi/iscsi_target_login.c
+++ b/drivers/target/iscsi/iscsi_target_login.c
@@ -254,9 +254,9 @@ static int iscsi_login_zero_tsih_s1(
                 kfree(sess);
                 return -ENOMEM;
         }
-        spin_lock(&sess_idr_lock);
+        spin_lock_bh(&sess_idr_lock);
         ret = idr_get_new(&sess_idr, NULL, &sess->session_index);
-        spin_unlock(&sess_idr_lock);
+        spin_unlock_bh(&sess_idr_lock);
 
         if (ret < 0) {
                 pr_err("idr_get_new() for sess_idr failed\n");