[PATCH AUTOSEL 4.14 09/25] scsi: RDMA/srp: Fix a sleep-in-invalid-context bug

[PATCH AUTOSEL 4.14 09/25] scsi: RDMA/srp: Fix a sleep-in-invalid-context bug

[Sasha Levin]

From: Bart Van Assche <bvanassche@acm.org>

[ Upstream commit fd56141244066a6a21ef458670071c58b6402035 ]

The previous patch guarantees that srp_queuecommand() does not get
invoked while reconnecting occurs. Hence remove the code from
srp_queuecommand() that prevents command queueing while reconnecting.
This patch avoids that the following can appear in the kernel log:

BUG: sleeping function called from invalid context at kernel/locking/mutex.c:747
in_atomic(): 1, irqs_disabled(): 0, pid: 5600, name: scsi_eh_9
1 lock held by scsi_eh_9/5600:
 #0:  (rcu_read_lock){....}, at: [<00000000cbb798c7>] __blk_mq_run_hw_queue+0xf1/0x1e0
Preemption disabled at:
[<00000000139badf2>] __blk_mq_delay_run_hw_queue+0x78/0xf0
CPU: 9 PID: 5600 Comm: scsi_eh_9 Tainted: G        W        4.15.0-rc4-dbg+ #1
Hardware name: Dell Inc. PowerEdge R720/0VWT90, BIOS 2.5.4 01/22/2016
Call Trace:
 dump_stack+0x67/0x99
 ___might_sleep+0x16a/0x250 [ib_srp]
 __mutex_lock+0x46/0x9d0
 srp_queuecommand+0x356/0x420 [ib_srp]
 scsi_dispatch_cmd+0xf6/0x3f0
 scsi_queue_rq+0x4a8/0x5f0
 blk_mq_dispatch_rq_list+0x73/0x440
 blk_mq_sched_dispatch_requests+0x109/0x1a0
 __blk_mq_run_hw_queue+0x131/0x1e0
 __blk_mq_delay_run_hw_queue+0x9a/0xf0
 blk_mq_run_hw_queue+0xc0/0x1e0
 blk_mq_start_hw_queues+0x2c/0x40
 scsi_run_queue+0x18e/0x2d0
 scsi_run_host_queues+0x22/0x40
 scsi_error_handler+0x18d/0x5f0
 kthread+0x11c/0x140
 ret_from_fork+0x24/0x30

Reviewed-by: Hannes Reinecke <hare@suse.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Laurence Oberman <loberman@redhat.com>
Cc: Jason Gunthorpe <jgg@mellanox.com>
Cc: Leon Romanovsky <leonro@mellanox.com>
Cc: Doug Ledford <dledford@redhat.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/infiniband/ulp/srp/ib_srp.c | 21 ++-------------------
 1 file changed, 2 insertions(+), 19 deletions(-)

diff --git a/drivers/infiniband/ulp/srp/ib_srp.c b/drivers/infiniband/ulp/srp/ib_srp.c
index 3f5b5893792cd..78e6e3b040305 100644
--- a/drivers/infiniband/ulp/srp/ib_srp.c
+++ b/drivers/infiniband/ulp/srp/ib_srp.c
@@ -2132,7 +2132,6 @@ static void srp_handle_qp_err(struct ib_cq *cq, struct ib_wc *wc,
 static int srp_queuecommand(struct Scsi_Host *shost, struct scsi_cmnd *scmnd)
 {
 	struct srp_target_port *target = host_to_target(shost);
-	struct srp_rport *rport = target->rport;
 	struct srp_rdma_ch *ch;
 	struct srp_request *req;
 	struct srp_iu *iu;
@@ -2142,16 +2141,6 @@ static int srp_queuecommand(struct Scsi_Host *shost, struct scsi_cmnd *scmnd)
 	u32 tag;
 	u16 idx;
 	int len, ret;
-	const bool in_scsi_eh = !in_interrupt() && current == shost->ehandler;
-
-	/*
-	 * The SCSI EH thread is the only context from which srp_queuecommand()
-	 * can get invoked for blocked devices (SDEV_BLOCK /
-	 * SDEV_CREATED_BLOCK). Avoid racing with srp_reconnect_rport() by
-	 * locking the rport mutex if invoked from inside the SCSI EH.
-	 */
-	if (in_scsi_eh)
-		mutex_lock(&rport->mutex);
 
 	scmnd->result = srp_chkready(target->rport);
 	if (unlikely(scmnd->result))
@@ -2213,13 +2202,7 @@ static int srp_queuecommand(struct Scsi_Host *shost, struct scsi_cmnd *scmnd)
 		goto err_unmap;
 	}
 
-	ret = 0;
-
-unlock_rport:
-	if (in_scsi_eh)
-		mutex_unlock(&rport->mutex);
-
-	return ret;
+	return 0;
 
 err_unmap:
 	srp_unmap_data(scmnd, ch, req);
@@ -2241,7 +2224,7 @@ static int srp_queuecommand(struct Scsi_Host *shost, struct scsi_cmnd *scmnd)
 		ret = SCSI_MLQUEUE_HOST_BUSY;
 	}
 
-	goto unlock_rport;
+	return ret;
 }
 
 /*
-- 
2.20.1

[PATCH AUTOSEL 4.14 23/25] RDMA/iwcm: Fix a lock inversion issue

[Sasha Levin]

From: Bart Van Assche <bvanassche@acm.org>

[ Upstream commit b66f31efbdad95ec274345721d99d1d835e6de01 ]

This patch fixes the lock inversion complaint:

============================================
WARNING: possible recursive locking detected
5.3.0-rc7-dbg+ #1 Not tainted
--------------------------------------------
kworker/u16:6/171 is trying to acquire lock:
00000000035c6e6c (&id_priv->handler_mutex){+.+.}, at: rdma_destroy_id+0x78/0x4a0 [rdma_cm]

but task is already holding lock:
00000000bc7c307d (&id_priv->handler_mutex){+.+.}, at: iw_conn_req_handler+0x151/0x680 [rdma_cm]

other info that might help us debug this:
 Possible unsafe locking scenario:

       CPU0
       ----
  lock(&id_priv->handler_mutex);
  lock(&id_priv->handler_mutex);

 *** DEADLOCK ***

 May be due to missing lock nesting notation

3 locks held by kworker/u16:6/171:
 #0: 00000000e2eaa773 ((wq_completion)iw_cm_wq){+.+.}, at: process_one_work+0x472/0xac0
 #1: 000000001efd357b ((work_completion)(&work->work)#3){+.+.}, at: process_one_work+0x476/0xac0
 #2: 00000000bc7c307d (&id_priv->handler_mutex){+.+.}, at: iw_conn_req_handler+0x151/0x680 [rdma_cm]

stack backtrace:
CPU: 3 PID: 171 Comm: kworker/u16:6 Not tainted 5.3.0-rc7-dbg+ #1
Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
Workqueue: iw_cm_wq cm_work_handler [iw_cm]
Call Trace:
 dump_stack+0x8a/0xd6
 __lock_acquire.cold+0xe1/0x24d
 lock_acquire+0x106/0x240
 __mutex_lock+0x12e/0xcb0
 mutex_lock_nested+0x1f/0x30
 rdma_destroy_id+0x78/0x4a0 [rdma_cm]
 iw_conn_req_handler+0x5c9/0x680 [rdma_cm]
 cm_work_handler+0xe62/0x1100 [iw_cm]
 process_one_work+0x56d/0xac0
 worker_thread+0x7a/0x5d0
 kthread+0x1bc/0x210
 ret_from_fork+0x24/0x30

This is not a bug as there are actually two lock classes here.

Link: https://lore.kernel.org/r/20190930231707.48259-3-bvanassche@acm.org
Fixes: de910bd92137 ("RDMA/cma: Simplify locking needed for serialization of callbacks")
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Reviewed-by: Jason Gunthorpe <jgg@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/infiniband/core/cma.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/infiniband/core/cma.c b/drivers/infiniband/core/cma.c
index 7c5eca312aa88..f698c6a28c142 100644
--- a/drivers/infiniband/core/cma.c
+++ b/drivers/infiniband/core/cma.c
@@ -2212,9 +2212,10 @@ static int iw_conn_req_handler(struct iw_cm_id *cm_id,
 		conn_id->cm_id.iw = NULL;
 		cma_exch(conn_id, RDMA_CM_DESTROYING);
 		mutex_unlock(&conn_id->handler_mutex);
+		mutex_unlock(&listen_id->handler_mutex);
 		cma_deref_id(conn_id);
 		rdma_destroy_id(&conn_id->id);
-		goto out;
+		return ret;
 	}
 
 	mutex_unlock(&conn_id->handler_mutex);
-- 
2.20.1