libfc: fixup command abort handling

From: Hannes Reinecke <[email protected]>

Hi all,

when testing command timeout with the help of XDP I found that scsi_try_to_abort_cmd() would always return 'SUCCESS' for FCoE, even if no commands could be sent over the wire. Which is not only surprising, but also can lead to data corruption as commands were never aborted.
Root cause was that aborts had been sent twice, once from FC error recovery and once from SCSI EH, with the former inducing the latter to assume that the command was already aborted.

As usual, comments and reviews are welcome.

Hannes Reinecke (3):
libfc: don't schedule abort twice
libfc: Fixup timeout error in fc_fcp_rec_error()
libfc: map FC_TIMED_OUT to DID_TIME_OUT

 drivers/scsi/libfc/fc_fcp.c | 22 ++++++++++++++--------
 1 file changed, 14 insertions(+), 8 deletions(-)

2.35.3

From: Hannes Reinecke <[email protected]>

The current FC error recovery is sending up to three REC (recovery) frames in 10 second intervals, and as a final step sending an ABTS after 30 seconds for the command itself.
Unfortunately sending an ABTS is also the action for the SCSI abort handler, and the default timeout for scsi commands is also 30 seconds. This causes two ABTS to be scheduled, with the libfc one slightly earlier. The ABTS scheduled by SCSI EH then sees the command to be already aborted, and will always return with a 'GOOD' status irrespective on the actual result from the first ABTS. This causes the SCSI EH abort handler to always succeed, and SCSI EH never to be engaged.
Fix this by not issuing an ABTS when a SCSI command is present for the exchange, but rather wait for the abort scheduled from SCSI EH.
And warn if an abort is already scheduled to avoid similar errors in the future.

---
 drivers/scsi/libfc/fc_fcp.c | 16 +++++++++++-----
 1 file changed, 11 insertions(+), 5 deletions(-)

index 945adca5e72f..3f189cedf6db 100644
@@ -265,6 +265,11 @@ static int fc_fcp_send_abort(struct fc_fcp_pkt *fsp)
 	if (!fsp->seq_ptr)
 		return -EINVAL;
 
+	if (fsp->state & FC_SRB_ABORT_PENDING) {
+		FC_FCP_DBG(fsp, "abort already pending\n");
+		return -EBUSY;
+	}
+
 	this_cpu_inc(fsp->lp->stats->FcpPktAborts);
 
 	fsp->state |= FC_SRB_ABORT_PENDING;

@@ -1690,11 +1695,12 @@ static void fc_fcp_recovery(struct fc_fcp_pkt *fsp, u8 code)
 	fsp->status_code = code;
 	fsp->cdb_status = 0;
 	fsp->io_status = 0;
-	/*
-	 * if this fails then we let the scsi command timer fire and
-	 * scsi-ml escalate.
-	 */
-	fc_fcp_send_abort(fsp);
+	if (!fsp->cmd)
+		/*
+		 * Only abort non-scsi commands; otherwise let the
+		 * scsi command timer fire and scsi-ml escalate.
+		 */
+		fc_fcp_send_abort(fsp);
 }
 
 /**

2.35.3

Looks good:

From: Hannes Reinecke <[email protected]>

We should set the status to FC_TIMED_OUT when a timeout error is passed to fc_fcp_rec_error().

---
 drivers/scsi/libfc/fc_fcp.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

index 3f189cedf6db..05be0810b5e3 100644
@@ -1676,7 +1676,7 @@ static void fc_fcp_rec_error(struct fc_fcp_pkt *fsp, struct fc_frame *fp)
 		if (fsp->recov_retry++ < FC_MAX_RECOV_RETRY)
 			fc_fcp_rec(fsp);
 		else
-			fc_fcp_recovery(fsp, FC_ERROR);
+			fc_fcp_recovery(fsp, FC_TIMED_OUT);
 		break;
 	}
 	fc_fcp_unlock_pkt(fsp);

2.35.3

Looks good:

From: Hannes Reinecke <[email protected]>

When an exchange is completed with FC_TIMED_OUT we should map it to DID_TIME_OUT to inform the SCSI midlayer that this was a command timeout; DID_BUS_BUSY implies that the command was never sent which is not the case here.

---
 drivers/scsi/libfc/fc_fcp.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

index 05be0810b5e3..80be3a936d92 100644
@@ -2062,9 +2062,9 @@ static void fc_io_compl(struct fc_fcp_pkt *fsp)
 		sc_cmd->result = (DID_PARITY << 16);
 		break;
 	case FC_TIMED_OUT:
-		FC_FCP_DBG(fsp, "Returning DID_BUS_BUSY to scsi-ml "
+		FC_FCP_DBG(fsp, "Returning DID_TIME_OUT to scsi-ml "
 			   "due to FC_TIMED_OUT\n");
-		sc_cmd->result = (DID_BUS_BUSY << 16) | fsp->io_status;
+		sc_cmd->result = (DID_TIME_OUT << 16);
 		break;
 	default:
 		FC_FCP_DBG(fsp, "Returning DID_ERROR to scsi-ml "

2.35.3

Looks good:

Applied to 6.8/scsi-queue, thanks!

[1/3] libfc: don't schedule abort twice

      https://git.kernel.org/mkp/scsi/c/b57c4db5d23b
[2/3] libfc: Fixup timeout error in fc_fcp_rec_error()
      https://git.kernel.org/mkp/scsi/c/53122a49f497
[3/3] libfc: map FC_TIMED_OUT to DID_TIME_OUT
      https://git.kernel.org/mkp/scsi/c/be40572c22cc

Martin K. Petersen	Oracle Linux Engineering