[PATCH AUTOSEL 4.19 08/12] scsi: ibmvfc: Set default timeout to avoid crash during migration

[PATCH AUTOSEL 4.19 08/12] scsi: ibmvfc: Set default timeout to avoid crash during migration

[Sasha Levin]

From: Brian King <brking@linux.vnet.ibm.com>

[ Upstream commit 764907293edc1af7ac857389af9dc858944f53dc ]

While testing live partition mobility, we have observed occasional crashes
of the Linux partition. What we've seen is that during the live migration,
for specific configurations with large amounts of memory, slow network
links, and workloads that are changing memory a lot, the partition can end
up being suspended for 30 seconds or longer. This resulted in the following
scenario:

CPU 0                          CPU 1
-------------------------------  ----------------------------------
scsi_queue_rq                    migration_store
 -> blk_mq_start_request          -> rtas_ibm_suspend_me
  -> blk_add_timer                 -> on_each_cpu(rtas_percpu_suspend_me
              _______________________________________V
             |
             V
    -> IPI from CPU 1
     -> rtas_percpu_suspend_me
                                     -> __rtas_suspend_last_cpu

-- Linux partition suspended for > 30 seconds --
                                      -> for_each_online_cpu(cpu)
                                           plpar_hcall_norets(H_PROD
 -> scsi_dispatch_cmd
                                      -> scsi_times_out
                                       -> scsi_abort_command
                                        -> queue_delayed_work
  -> ibmvfc_queuecommand_lck
   -> ibmvfc_send_event
    -> ibmvfc_send_crq
     - returns H_CLOSED
   <- returns SCSI_MLQUEUE_HOST_BUSY
-> __blk_mq_requeue_request

                                      -> scmd_eh_abort_handler
                                       -> scsi_try_to_abort_cmd
                                         - returns SUCCESS
                                       -> scsi_queue_insert

Normally, the SCMD_STATE_COMPLETE bit would protect against the command
completion and the timeout, but that doesn't work here, since we don't
check that at all in the SCSI_MLQUEUE_HOST_BUSY path.

In this case we end up calling scsi_queue_insert on a request that has
already been queued, or possibly even freed, and we crash.

The patch below simply increases the default I/O timeout to avoid this race
condition. This is also the timeout value that nearly all IBM SAN storage
recommends setting as the default value.

Link: https://lore.kernel.org/r/1610463998-19791-1-git-send-email-brking@linux.vnet.ibm.com
Signed-off-by: Brian King <brking@linux.vnet.ibm.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/scsi/ibmvscsi/ibmvfc.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/scsi/ibmvscsi/ibmvfc.c b/drivers/scsi/ibmvscsi/ibmvfc.c
index 090ab377f65e5..50078a199fea0 100644
--- a/drivers/scsi/ibmvscsi/ibmvfc.c
+++ b/drivers/scsi/ibmvscsi/ibmvfc.c
@@ -2890,8 +2890,10 @@ static int ibmvfc_slave_configure(struct scsi_device *sdev)
 	unsigned long flags = 0;
 
 	spin_lock_irqsave(shost->host_lock, flags);
-	if (sdev->type == TYPE_DISK)
+	if (sdev->type == TYPE_DISK) {
 		sdev->allow_restart = 1;
+		blk_queue_rq_timeout(sdev->request_queue, 120 * HZ);
+	}
 	spin_unlock_irqrestore(shost->host_lock, flags);
 	return 0;
 }
-- 
2.27.0

[PATCH AUTOSEL 4.19 09/12] selftests/powerpc: Only test lwm/stmw on big endian

[Sasha Levin]

From: Michael Ellerman <mpe@ellerman.id.au>

[ Upstream commit dd3a44c06f7b4f14e90065bf05d62c255b20005f ]

Newer binutils (>= 2.36) refuse to assemble lmw/stmw when building in
little endian mode. That breaks compilation of our alignment handler
test:

  /tmp/cco4l14N.s: Assembler messages:
  /tmp/cco4l14N.s:1440: Error: `lmw' invalid when little-endian
  /tmp/cco4l14N.s:1814: Error: `stmw' invalid when little-endian
  make[2]: *** [../../lib.mk:139: /output/kselftest/powerpc/alignment/alignment_handler] Error 1

These tests do pass on little endian machines, as the kernel will
still emulate those instructions even when running little
endian (which is arguably a kernel bug).

But we don't really need to test that case, so ifdef those
instructions out to get the alignment test building again.

Reported-by: Libor Pechacek <lpechacek@suse.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Tested-by: Libor Pechacek <lpechacek@suse.com>
Link: https://lore.kernel.org/r/20210119041800.3093047-1-mpe@ellerman.id.au
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 .../testing/selftests/powerpc/alignment/alignment_handler.c  | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/powerpc/alignment/alignment_handler.c b/tools/testing/selftests/powerpc/alignment/alignment_handler.c
index 169a8b9719fb9..4f8335e0c9858 100644
--- a/tools/testing/selftests/powerpc/alignment/alignment_handler.c
+++ b/tools/testing/selftests/powerpc/alignment/alignment_handler.c
@@ -384,7 +384,6 @@ int test_alignment_handler_integer(void)
 	LOAD_DFORM_TEST(ldu);
 	LOAD_XFORM_TEST(ldx);
 	LOAD_XFORM_TEST(ldux);
-	LOAD_DFORM_TEST(lmw);
 	STORE_DFORM_TEST(stb);
 	STORE_XFORM_TEST(stbx);
 	STORE_DFORM_TEST(stbu);
@@ -403,7 +402,11 @@ int test_alignment_handler_integer(void)
 	STORE_XFORM_TEST(stdx);
 	STORE_DFORM_TEST(stdu);
 	STORE_XFORM_TEST(stdux);
+
+#ifdef __BIG_ENDIAN__
+	LOAD_DFORM_TEST(lmw);
 	STORE_DFORM_TEST(stmw);
+#endif
 
 	return rc;
 }
-- 
2.27.0