[SCSI] fnic: fnic driver may hit BUG_ON on device reset

The issue was observed when LUN Reset is issued through IOCTL or sg_reset
utility.

fnic driver issues LUN RESET to firmware. On successful completion of device
reset, driver cleans up all the pending IOs that were issued prior to device
reset. These pending IOs are expected to be in ABTS_PENDING state. This works
fine, when the device reset operation resulted from midlayer, but not when
device reset was triggered from IOCTL path as the pending IOs were not in
ABTS_PENDING state. execution path hits panic if the pending IO is not in
ABTS_PENDING state.

Changes:
The fix replaces BUG_ON check in fnic_clean_pending_aborts() with marking
pending IOs as ABTS_PENDING if they were not in ABTS_PENDING state and skips
if they were already in ABTS_PENDING state. An extra check is added to validate
the abort status of the commands after a delay of 2 * E_D_TOV using a
helper function. The helper function returns 1 if it finds any pending IO in
ABTS_PENDING state, belong to the LUN on which device reset was issued else 0.
With this, device reset operation returns success only if the helper funciton
returns 0, otherwise it returns failure.

Other changes:
- Removed code in fnic_clean_pending_aborts() that returns failure if it finds
  io_req NULL, instead of returning failure added code to continue with next io
- Added device reset flags for debugging in fnic_terminate_rport_io,
  fnic_rport_exch_reset, and fnic_clean_pending_aborts
Signed-off-by: Narsimhulu Musini <nmusini@cisco.com>
Signed-off-by: Hiral Patel <hiralpat@cisco.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>

drivers/scsi/fnic/fnic.h

@@ -303,6 +303,8 @@ const char *fnic_state_to_str(unsigned int state);
 void fnic_log_q_error(struct fnic *fnic);
 void fnic_handle_link_event(struct fnic *fnic);
 
+int fnic_is_abts_pending(struct fnic *, struct scsi_cmnd *);
+
 static inline int
 fnic_chk_state_flags_locked(struct fnic *fnic, unsigned long st_flags)
 {

drivers/scsi/fnic/fnic_scsi.c

@@ -1271,6 +1271,7 @@ static void fnic_rport_exch_reset(struct fnic *fnic, u32 port_id)
 			spin_unlock_irqrestore(io_lock, flags);
 		} else {
 			spin_lock_irqsave(io_lock, flags);
+			if (CMD_FLAGS(sc) & FNIC_DEVICE_RESET)
 				CMD_FLAGS(sc) |= FNIC_DEV_RST_TERM_ISSUED;
 			spin_unlock_irqrestore(io_lock, flags);
 		}
@@ -1379,6 +1380,7 @@ void fnic_terminate_rport_io(struct fc_rport *rport)
 			spin_unlock_irqrestore(io_lock, flags);
 		} else {
 			spin_lock_irqsave(io_lock, flags);
+			if (CMD_FLAGS(sc) & FNIC_DEVICE_RESET)
 				CMD_FLAGS(sc) |= FNIC_DEV_RST_TERM_ISSUED;
 			spin_unlock_irqrestore(io_lock, flags);
 		}
@@ -1592,7 +1594,7 @@ static inline int fnic_queue_dr_io_req(struct fnic *fnic,
 static int fnic_clean_pending_aborts(struct fnic *fnic,
 				     struct scsi_cmnd *lr_sc)
 {
-	int tag;
+	int tag, abt_tag;
 	struct fnic_io_req *io_req;
 	spinlock_t *io_lock;
 	unsigned long flags;
@@ -1601,6 +1603,7 @@ static int fnic_clean_pending_aborts(struct fnic *fnic,
 	struct scsi_lun fc_lun;
 	struct scsi_device *lun_dev = lr_sc->device;
 	DECLARE_COMPLETION_ONSTACK(tm_done);
+	enum fnic_ioreq_state old_ioreq_state;
 
 	for (tag = 0; tag < FNIC_MAX_IO_REQ; tag++) {
 		sc = scsi_host_find_tag(fnic->lport->host, tag);
@@ -1629,7 +1632,41 @@ static int fnic_clean_pending_aborts(struct fnic *fnic,
 			      "Found IO in %s on lun\n",
 			      fnic_ioreq_state_to_str(CMD_STATE(sc)));
 
-		BUG_ON(CMD_STATE(sc) != FNIC_IOREQ_ABTS_PENDING);
+		if (CMD_STATE(sc) == FNIC_IOREQ_ABTS_PENDING) {
+			spin_unlock_irqrestore(io_lock, flags);
+			continue;
+		}
+		if ((CMD_FLAGS(sc) & FNIC_DEVICE_RESET) &&
+			(!(CMD_FLAGS(sc) & FNIC_DEV_RST_PENDING))) {
+			FNIC_SCSI_DBG(KERN_INFO, fnic->lport->host,
+				"%s dev rst not pending sc 0x%p\n", __func__,
+				sc);
+			spin_unlock_irqrestore(io_lock, flags);
+			continue;
+		}
+		old_ioreq_state = CMD_STATE(sc);
+		/*
+		 * Any pending IO issued prior to reset is expected to be
+		 * in abts pending state, if not we need to set
+		 * FNIC_IOREQ_ABTS_PENDING to indicate the IO is abort pending.
+		 * When IO is completed, the IO will be handed over and
+		 * handled in this function.
+		 */
+		CMD_STATE(sc) = FNIC_IOREQ_ABTS_PENDING;
+
+		if (io_req->abts_done)
+			shost_printk(KERN_ERR, fnic->lport->host,
+			  "%s: io_req->abts_done is set state is %s\n",
+			  __func__, fnic_ioreq_state_to_str(CMD_STATE(sc)));
+
+		BUG_ON(io_req->abts_done);
+
+		abt_tag = tag;
+		if (CMD_FLAGS(sc) & FNIC_DEVICE_RESET) {
+			abt_tag |= FNIC_TAG_DEV_RST;
+			FNIC_SCSI_DBG(KERN_INFO, fnic->lport->host,
+				  "%s: dev rst sc 0x%p\n", __func__, sc);
+		}
 
 		CMD_ABTS_STATUS(sc) = FCPIO_INVALID_CODE;
 		io_req->abts_done = &tm_done;
@@ -1638,16 +1675,23 @@ static int fnic_clean_pending_aborts(struct fnic *fnic,
 		/* Now queue the abort command to firmware */
 		int_to_scsilun(sc->device->lun, &fc_lun);
 
-		if (fnic_queue_abort_io_req(fnic, tag,
+		if (fnic_queue_abort_io_req(fnic, abt_tag,
 					    FCPIO_ITMF_ABT_TASK_TERM,
 					    fc_lun.scsi_lun, io_req)) {
 			spin_lock_irqsave(io_lock, flags);
 			io_req = (struct fnic_io_req *)CMD_SP(sc);
 			if (io_req)
 				io_req->abts_done = NULL;
+			if (CMD_STATE(sc) == FNIC_IOREQ_ABTS_PENDING)
+				CMD_STATE(sc) = old_ioreq_state;
 			spin_unlock_irqrestore(io_lock, flags);
 			ret = 1;
 			goto clean_pending_aborts_end;
+		} else {
+			spin_lock_irqsave(io_lock, flags);
+			if (CMD_FLAGS(sc) & FNIC_DEVICE_RESET)
+				CMD_FLAGS(sc) |= FNIC_DEV_RST_TERM_ISSUED;
+			spin_unlock_irqrestore(io_lock, flags);
 		}
 
 		wait_for_completion_timeout(&tm_done,
@@ -1659,8 +1703,7 @@ static int fnic_clean_pending_aborts(struct fnic *fnic,
 		io_req = (struct fnic_io_req *)CMD_SP(sc);
 		if (!io_req) {
 			spin_unlock_irqrestore(io_lock, flags);
-			ret = 1;
-			goto clean_pending_aborts_end;
+			continue;
 		}
 
 		io_req->abts_done = NULL;
@@ -1678,6 +1721,12 @@ static int fnic_clean_pending_aborts(struct fnic *fnic,
 		mempool_free(io_req, fnic->io_req_pool);
 	}
 
+	schedule_timeout(msecs_to_jiffies(2 * fnic->config.ed_tov));
+
+	/* walk again to check, if IOs are still pending in fw */
+	if (fnic_is_abts_pending(fnic, lr_sc))
+		ret = FAILED;
+
 clean_pending_aborts_end:
 	return ret;
 }
@@ -2142,3 +2191,61 @@ void fnic_exch_mgr_reset(struct fc_lport *lp, u32 sid, u32 did)
 	fc_exch_mgr_reset(lp, sid, did);
 
 }
+
+/*
+ * fnic_is_abts_pending() is a helper function that
+ * walks through tag map to check if there is any IOs pending,if there is one,
+ * then it returns 1 (true), otherwise 0 (false)
+ * if @lr_sc is non NULL, then it checks IOs specific to particular LUN,
+ * otherwise, it checks for all IOs.
+ */
+int fnic_is_abts_pending(struct fnic *fnic, struct scsi_cmnd *lr_sc)
+{
+	int tag;
+	struct fnic_io_req *io_req;
+	spinlock_t *io_lock;
+	unsigned long flags;
+	int ret = 0;
+	struct scsi_cmnd *sc;
+	struct scsi_device *lun_dev = NULL;
+
+	if (lr_sc)
+		lun_dev = lr_sc->device;
+
+	/* walk again to check, if IOs are still pending in fw */
+	for (tag = 0; tag < FNIC_MAX_IO_REQ; tag++) {
+		sc = scsi_host_find_tag(fnic->lport->host, tag);
+		/*
+		 * ignore this lun reset cmd or cmds that do not belong to
+		 * this lun
+		 */
+		if (!sc || (lr_sc && (sc->device != lun_dev || sc == lr_sc)))
+			continue;
+
+		io_lock = fnic_io_lock_hash(fnic, sc);
+		spin_lock_irqsave(io_lock, flags);
+
+		io_req = (struct fnic_io_req *)CMD_SP(sc);
+
+		if (!io_req || sc->device != lun_dev) {
+			spin_unlock_irqrestore(io_lock, flags);
+			continue;
+		}
+
+		/*
+		 * Found IO that is still pending with firmware and
+		 * belongs to the LUN that we are resetting
+		 */
+		FNIC_SCSI_DBG(KERN_INFO, fnic->lport->host,
+			      "Found IO in %s on lun\n",
+			      fnic_ioreq_state_to_str(CMD_STATE(sc)));
+
+		if (CMD_STATE(sc) == FNIC_IOREQ_ABTS_PENDING) {
+			spin_unlock_irqrestore(io_lock, flags);
+			ret = 1;
+			continue;
+		}
+	}
+
+	return ret;
+}