[patch 5/5] zfcp: Issue FCP command without holding SCSI host_lock

[Christof Schmitt <christof.schmitt@de.ibm.com>]

[-- Attachment #1: linux-2.6.36-zfcp-fcp-cmd-lock.patch --]
[-- Type: text/plain, Size: 4301 bytes --]

From: Christof Schmitt <christof.schmitt@de.ibm.com>

Interrupting the connection to the FCP channel while I/O requests are
being issues can lead to this deadlock. scsi_dispatch_cmd already
holds the host_lock while the recovery trigger tries to acquire the
host_lock again when iterating through the scsi_devices.

 INFO: lockdep is turned off.
 BUG: spinlock lockup on CPU#1, blast/9660, 0000000078f38878
 CPU: 1 Not tainted 2.6.35.7SWEN2 #2
 Process blast (pid: 9660, task: 0000000071f75940, ksp: 0000000074393ac0)
        0000000074393640 00000000743935c0 0000000000000002 0000000000000000
        0000000074393660 00000000743935d8 00000000743935d8 00000000005590c2
        0000000000000000 0000000078f38878 0000000026ede800 0000000078f38878
        000000000000000d 040000000000000c 0000000074393628 0000000000000000
        0000000000000000 0000000000100b2a 00000000743935c0 0000000074393600
 Call Trace:
 ([<0000000000100a32>] show_trace+0xee/0x144)
  [<00000000003be202>] do_raw_spin_lock+0x112/0x178
  [<000000000055d408>] _raw_spin_lock_irqsave+0x90/0xb0
  [<00000000003f1514>] __scsi_iterate_devices+0x38/0xbc
  [<00000000004849b0>] zfcp_erp_clear_adapter_status+0xd0/0x16c
  [<000000000048587a>] zfcp_erp_adapter_reopen+0x3a/0xb4
  [<0000000000489812>] zfcp_fsf_req_send+0x166/0x180
  [<000000000048c8d6>] zfcp_fsf_fcp_cmnd+0x272/0x408
  [<000000000048f864>] zfcp_scsi_queuecommand+0x11c/0x1e0
  [<00000000003f1f2a>] scsi_dispatch_cmd+0x1d6/0x324
  [<00000000003f9910>] scsi_request_fn+0x42c/0x56c
  [<00000000003828ae>] __blk_run_queue+0x86/0x140
  [<000000000037f742>] elv_insert+0x11a/0x208
  [<000000000038104c>] blk_insert_cloned_request+0x84/0xe4
  [<000003c0032b7c64>] dm_dispatch_request+0x6c/0x94 [dm_mod]
  [<000003c0032b7d5c>] map_request+0xd0/0x100 [dm_mod]
  [<000003c0032b9a78>] dm_request_fn+0xec/0x1bc [dm_mod]
  [<0000000000382c0e>] generic_unplug_device+0x5a/0x6c
  [<000003c0032b7f98>] dm_unplug_all+0x74/0x9c [dm_mod]
  [<00000000001d1272>] sync_page+0x76/0x9c
  [<00000000001d12ba>] sync_page_killable+0x22/0x60
  [<000000000055a768>] __wait_on_bit_lock+0xc0/0x124
  [<00000000001d1140>] __lock_page_killable+0x78/0x84
  [<00000000001d351c>] generic_file_aio_read+0x5a4/0x7e8
  [<0000000000228ec0>] do_sync_read+0xc8/0x12c
  [<0000000000229edc>] vfs_read+0xac/0x1ac
  [<000000000022a0d8>] SyS_read+0x58/0xa8
  [<00000000001146de>] sysc_noemu+0x10/0x16
  [<00000200000493c4>] 0x200000493c4
 INFO: lockdep is turned off.

Call zfcp_fsf_fcp_cmnd without the host_lock and disable the
interrupts when acquiring the req_q_lock.

Reviewed-by: Swen Schillig <swen@vnet.ibm.com>
Signed-off-by: Christof Schmitt <christof.schmitt@de.ibm.com>
---

 drivers/s390/scsi/zfcp_fsf.c  |    5 +++--
 drivers/s390/scsi/zfcp_scsi.c |    3 +++
 2 files changed, 6 insertions(+), 2 deletions(-)

--- a/drivers/s390/scsi/zfcp_fsf.c
+++ b/drivers/s390/scsi/zfcp_fsf.c
@@ -2170,12 +2170,13 @@ int zfcp_fsf_fcp_cmnd(struct scsi_cmnd *
 	struct zfcp_adapter *adapter = zfcp_sdev->port->adapter;
 	struct zfcp_qdio *qdio = adapter->qdio;
 	struct fsf_qtcb_bottom_io *io;
+	unsigned long flags;
 
 	if (unlikely(!(atomic_read(&zfcp_sdev->status) &
 		       ZFCP_STATUS_COMMON_UNBLOCKED)))
 		return -EBUSY;
 
-	spin_lock(&qdio->req_q_lock);
+	spin_lock_irqsave(&qdio->req_q_lock, flags);
 	if (atomic_read(&qdio->req_q_free) <= 0) {
 		atomic_inc(&qdio->req_q_full);
 		goto out;
@@ -2239,7 +2240,7 @@ failed_scsi_cmnd:
 	zfcp_fsf_req_free(req);
 	scsi_cmnd->host_scribble = NULL;
 out:
-	spin_unlock(&qdio->req_q_lock);
+	spin_unlock_irqrestore(&qdio->req_q_lock, flags);
 	return retval;
 }
 
--- a/drivers/s390/scsi/zfcp_scsi.c
+++ b/drivers/s390/scsi/zfcp_scsi.c
@@ -83,6 +83,7 @@ static int zfcp_scsi_queuecommand_lck(st
 	struct zfcp_adapter *adapter = zfcp_sdev->port->adapter;
 	struct fc_rport *rport = starget_to_rport(scsi_target(scpnt->device));
 	int    status, scsi_result, ret;
+	struct scsi_device *sdev = scpnt->device;
 
 	/* reset the status for this request */
 	scpnt->result = 0;
@@ -118,7 +119,9 @@ static int zfcp_scsi_queuecommand_lck(st
 		return 0;
 	}
 
+	spin_unlock_irq(sdev->host->host_lock);
 	ret = zfcp_fsf_fcp_cmnd(scpnt);
+	spin_lock_irq(sdev->host->host_lock);
 	if (unlikely(ret == -EBUSY))
 		return SCSI_MLQUEUE_DEVICE_BUSY;
 	else if (unlikely(ret < 0))