Prior to commit 1f4a4a19508d ("scsi: ibmvfc: Complete commands outside the host/queue lock") responses to commands were completed sequentially with the host lock held such that a command had a basic binary state of active or free. It was therefore a simple affair of ensuring the assocaiated ibmvfc_event to a VIOS response was valid by testing that it was not already free. The lock relexation work to complete commands outside the lock inadverdently made it a trinary command state such that a command is either in flight, received and being completed, or completed and now free. This breaks the stale command detection logic as a command may be still marked active and been placed on the delayed completion list when a second stale response for the same command arrives. This can lead to double completions and list corruption. This issue was exposed by a recent VIOS regression were a missing memory barrier could occasionally result in the ibmvfc client receiveing a duplicate response for the same command.

Fix the issue by introducing the atomic ibmvfc_event.active to track the trinary state of a command. The state is explicitly set to 1 when a command is successfully sent. The CRQ response handlers use atomic_dec_if_positive() to test for stale responses and correctly transition to the completion state when a active command is received. Finally, atomic_dec_and_test() is used to sanity check transistions when commands are freed as a result of a completion, or moved to the purge list as a result of error handling or adapter reset.

Cc: stable@vger.kernel.org Fixes: 1f4a4a19508d ("scsi: ibmvfc: Complete commands outside the host/queue lock") Signed-off-by: Tyrel Datwyler tyreld@linux.ibm.com --- drivers/scsi/ibmvscsi/ibmvfc.c | 19 +++++++++++++++++-- drivers/scsi/ibmvscsi/ibmvfc.h | 1 + 2 files changed, 18 insertions(+), 2 deletions(-)

diff --git a/drivers/scsi/ibmvscsi/ibmvfc.c b/drivers/scsi/ibmvscsi/ibmvfc.c index bee1bec49c09..935b01ee44b7 100644 --- a/drivers/scsi/ibmvscsi/ibmvfc.c +++ b/drivers/scsi/ibmvscsi/ibmvfc.c @@ -807,6 +807,13 @@ static int ibmvfc_init_event_pool(struct ibmvfc_host *vhost, for (i = 0; i < size; ++i) { struct ibmvfc_event *evt = &pool->events[i];

+ /* + * evt->active states + * 1 = in flight + * 0 = being completed + * -1 = free/freed + */ + atomic_set(&evt->active, -1); atomic_set(&evt->free, 1); evt->crq.valid = 0x80; evt->crq.ioba = cpu_to_be64(pool->iu_token + (sizeof(*evt->xfer_iu) * i)); @@ -1017,6 +1024,7 @@ static void ibmvfc_free_event(struct ibmvfc_event *evt)

BUG_ON(!ibmvfc_valid_event(pool, evt)); BUG_ON(atomic_inc_return(&evt->free) != 1); + BUG_ON(atomic_dec_and_test(&evt->active));

spin_lock_irqsave(&evt->queue->l_lock, flags); list_add_tail(&evt->queue_list, &evt->queue->free); @@ -1072,6 +1080,12 @@ static void ibmvfc_complete_purge(struct list_head *purge_list) **/ static void ibmvfc_fail_request(struct ibmvfc_event *evt, int error_code) { + /* + * Anything we are failing should still be active. Otherwise, it + * implies we already got a response for the command and are doing + * something bad like double completing it. + */ + BUG_ON(!atomic_dec_and_test(&evt->active)); if (evt->cmnd) { evt->cmnd->result = (error_code << 16); evt->done = ibmvfc_scsi_eh_done; @@ -1723,6 +1737,7 @@ static int ibmvfc_send_event(struct ibmvfc_event *evt,

evt->done(evt); } else { + atomic_set(&evt->active, 1); spin_unlock_irqrestore(&evt->queue->l_lock, flags); ibmvfc_trc_start(evt); } @@ -3251,7 +3266,7 @@ static void ibmvfc_handle_crq(struct ibmvfc_crq *crq, struct ibmvfc_host *vhost, return; }

- if (unlikely(atomic_read(&evt->free))) { + if (unlikely(atomic_dec_if_positive(&evt->active))) { dev_err(vhost->dev, "Received duplicate correlation_token 0x%08llx!\n", crq->ioba); return; @@ -3778,7 +3793,7 @@ static void ibmvfc_handle_scrq(struct ibmvfc_crq *crq, struct ibmvfc_host *vhost return; }

- if (unlikely(atomic_read(&evt->free))) { + if (unlikely(atomic_dec_if_positive(&evt->active))) { dev_err(vhost->dev, "Received duplicate correlation_token 0x%08llx!\n", crq->ioba); return; diff --git a/drivers/scsi/ibmvscsi/ibmvfc.h b/drivers/scsi/ibmvscsi/ibmvfc.h index 4f0f3baefae4..92fb889d7eb0 100644 --- a/drivers/scsi/ibmvscsi/ibmvfc.h +++ b/drivers/scsi/ibmvscsi/ibmvfc.h @@ -745,6 +745,7 @@ struct ibmvfc_event { struct ibmvfc_target *tgt; struct scsi_cmnd *cmnd; atomic_t free; + atomic_t active; union ibmvfc_iu *xfer_iu; void (*done)(struct ibmvfc_event *evt); void (*_done)(struct ibmvfc_event *evt);