linux-kernel - [PATCH AUTOSEL 4.14 46/57] scsi: libfc: fixup 'sleeping function called from invalid context'

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Message-ID: <20180915013223.179909-46-alexander.levin@microsoft.com>
Date:   Sat, 15 Sep 2018 01:32:58 +0000
From:   Sasha Levin <Alexander.Levin@...rosoft.com>
To:     "stable@...r.kernel.org" <stable@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC:     Hannes Reinecke <hare@...e.de>, Hannes Reinecke <hare@...e.com>,
        "Martin K . Petersen" <martin.petersen@...cle.com>,
        Sasha Levin <Alexander.Levin@...rosoft.com>
Subject: [PATCH AUTOSEL 4.14 46/57] scsi: libfc: fixup 'sleeping function
 called from invalid context'

From: Hannes Reinecke <hare@...e.de>

[ Upstream commit fa519f701d27198a2858bb108fc18ea9d8c106a7 ]

fc_rport_login() will be calling mutex_lock() while running inside an
RCU-protected section, triggering the warning 'sleeping function called
from invalid context'.  To fix this we can drop the rcu functions here
altogether as the disc mutex protecting the list itself is already held,
preventing any list manipulation.

Fixes: a407c593398c ("scsi: libfc: Fixup disc_mutex handling")
Signed-off-by: Hannes Reinecke <hare@...e.com>
Acked-by: Johannes Thumshirn <jth@...nel.org>
Signed-off-by: Martin K. Petersen <martin.petersen@...cle.com>
Signed-off-by: Sasha Levin <alexander.levin@...rosoft.com>
---
 drivers/scsi/libfc/fc_disc.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/scsi/libfc/fc_disc.c b/drivers/scsi/libfc/fc_disc.c
index 8660f923ace0..bb9c1c016643 100644
--- a/drivers/scsi/libfc/fc_disc.c
+++ b/drivers/scsi/libfc/fc_disc.c
@@ -294,9 +294,11 @@ static void fc_disc_done(struct fc_disc *disc, enum fc_disc_event event)
 	 * discovery, reverify or log them in.	Otherwise, log them out.
 	 * Skip ports which were never discovered.  These are the dNS port
 	 * and ports which were created by PLOGI.
+	 *
+	 * We don't need to use the _rcu variant here as the rport list
+	 * is protected by the disc mutex which is already held on entry.
 	 */
-	rcu_read_lock();
-	list_for_each_entry_rcu(rdata, &disc->rports, peers) {
+	list_for_each_entry(rdata, &disc->rports, peers) {
 		if (!kref_get_unless_zero(&rdata->kref))
 			continue;
 		if (rdata->disc_id) {
@@ -307,7 +309,6 @@ static void fc_disc_done(struct fc_disc *disc, enum fc_disc_event event)
 		}
 		kref_put(&rdata->kref, fc_rport_destroy);
 	}
-	rcu_read_unlock();
 	mutex_unlock(&disc->disc_mutex);
 	disc->disc_callback(lport, event);
 	mutex_lock(&disc->disc_mutex);
-- 
2.17.1