Fix error recovery behavior in the pass(4) driver.

After FreeBSD SVN revision 236814, the pass(4) driver changed from
only doing error recovery when the CAM_PASS_ERR_RECOVER flag was
set on a CCB to sometimes doing error recovery if the passed in
retry count was non-zero.

Error recovery would happen if two conditions were met:

1.  The error recovery action was simply a retry.  (Which is most
    cases.)
2.  The retry_count is non-zero. (Which happened a lot because of
    cut-and-pasted code.)

This explains a bug I noticed in with camcontrol:

# camcontrol tur da34 -v
Unit is ready
# camcontrol reset da34
Reset of 1:172:0 was successful

At this point, there should be a Unit Attention:

# camcontrol tur da34 -v
Unit is ready

No Unit Attention.

Try it again:

# camcontrol reset da34
Reset of 1:172:0 was successful

Now set the retry_count to 0 for the TUR:

# camcontrol tur da34 -v -C 0
Unit is not ready
(pass42:mps1:0:172:0): TEST UNIT READY. CDB: 00 00 00 00 00 00
(pass42:mps1:0:172:0): CAM status: SCSI Status Error
(pass42:mps1:0:172:0): SCSI status: Check Condition
(pass42:mps1:0:172:0): SCSI sense: UNIT ATTENTION asc:29,2 (SCSI bus reset occurred)
(pass42:mps1:0:172:0): Field Replaceable Unit: 2

There is the unit attention. camcontrol(8) has a default
retry_count of 1, in case someone sets the -E flag without
setting -C.

The CAM_PASS_ERR_RECOVER behavior was only broken with the
CAMIOCOMMAND ioctl, which is the synchronous pass(4) API.  It has
worked as intended (error recovery is only done when the flag
is set) in the asynchronous API (CAMIOQUEUE ioctl).

sys/cam/scsi/scsi_pass.c:
	In passsendccb(), when calling cam_periph_runccb(), only
	specify the error routine when CAM_PASS_ERR_RECOVER is set.

share/man/man4/pass.4:
	Document that CAM_PASS_ERR_RECOVER is needed to enable
	error recovery.

Reported by:	Terry Kennedy <TERRY@glaver.org>
PR:		kern/218572
MFC after:	1 week
Sponsored by:	Spectra Logic

share/man/man4/pass.4

@@ -27,7 +27,7 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd March 17, 2015
+.Dd May 3, 2017
 .Dt PASS 4
 .Os
 .Sh NAME
@@ -85,6 +85,11 @@ Some examples of xpt-only CCBs are XPT_SCAN_BUS,
 XPT_DEV_MATCH, XPT_RESET_BUS, XPT_SCAN_LUN, XPT_ENG_INQ, and XPT_ENG_EXEC.
 These CCB types have various attributes that make it illogical or
 impossible to service them through the passthrough interface.
+.Pp
+If the user would like the kernel to do error recovery, the
+.Dv CAM_PASS_ERR_RECOVER
+flag must be set on the CCB, and the retry_count field set to the number
+of retries.
 .It CAMGETPASSTHRU union ccb *
 This ioctl takes an XPT_GDEVLIST CCB, and returns the passthrough device
 corresponding to the device in question.
@@ -160,6 +165,11 @@ available for userland use with the
 and
 .Dv CAMIOGET
 ioctls and will be preserved across calls.
+.Pp
+If the user would like the kernel to do error recovery, the
+.Dv CAM_PASS_ERR_RECOVER
+flag must be set on the CCB, and the retry_count field set to the number
+of retries.
 .It CAMIOGET union ccb *
 Retrieve completed CAM CCBs queued via the
 .Dv CAMIOQUEUE

sys/cam/scsi/scsi_pass.c

@@ -2229,9 +2229,9 @@ passsendccb(struct cam_periph *periph, union ccb *ccb, union ccb *inccb)
 	 * that request.  Otherwise, it's up to the user to perform any
 	 * error recovery.
 	 */
-	cam_periph_runccb(ccb, passerror, /* cam_flags */ CAM_RETRY_SELTO,
-	    /* sense_flags */ ((ccb->ccb_h.flags & CAM_PASS_ERR_RECOVER) ?
-	     SF_RETRY_UA : SF_NO_RECOVERY) | SF_NO_PRINT,
+	cam_periph_runccb(ccb, (ccb->ccb_h.flags & CAM_PASS_ERR_RECOVER) ? 
+	    passerror : NULL, /* cam_flags */ CAM_RETRY_SELTO,
+	    /* sense_flags */ SF_RETRY_UA | SF_NO_PRINT,
 	    softc->device_stats);
 
 	cam_periph_unmapmem(ccb, &mapinfo);