dm verity: add "panic_on_corruption" error handling mode

Samsung smart phones may need the ability to panic on corruption. Not
all devices provide the bootloader support needed to use the existing
"restart_on_corruption" mode. Additional details for why Samsung needs
this new mode can be found here:
https://www.redhat.com/archives/dm-devel/2020-June/msg00235.html

Signed-off-by: jhs2.lee <[e-mail]>
Signed-off-by: Mike Snitzer <[e-mail]>

Documentation/admin-guide/device-mapper/verity.rst

···
     not compatible with ignore_corruption and requires user space support to
     avoid restart loops.
 
+panic_on_corruption
+    Panic the device when a corrupted block is discovered. This option is
+    not compatible with ignore_corruption and restart_on_corruption.
+
 ignore_zero_blocks
     Do not verify blocks that are expected to contain zeroes and always return
     zeroes instead. This may be useful if the partition contains unused blocks

drivers/md/dm-verity-target.c

···
 
 #define DM_VERITY_OPT_LOGGING		"ignore_corruption"
 #define DM_VERITY_OPT_RESTART		"restart_on_corruption"
+#define DM_VERITY_OPT_PANIC		"panic_on_corruption"
 #define DM_VERITY_OPT_IGN_ZEROES	"ignore_zero_blocks"
 #define DM_VERITY_OPT_AT_MOST_ONCE	"check_at_most_once"
 
···
 
 	if (v->mode == DM_VERITY_MODE_RESTART)
 		kernel_restart("dm-verity device corrupted");
+
+	if (v->mode == DM_VERITY_MODE_PANIC)
+		panic("dm-verity device corrupted");
 
 	return 1;
 }
···
 			case DM_VERITY_MODE_RESTART:
 				DMEMIT(DM_VERITY_OPT_RESTART);
 				break;
+			case DM_VERITY_MODE_PANIC:
+				DMEMIT(DM_VERITY_OPT_PANIC);
+				break;
 			default:
 				BUG();
 			}
···
 
 		} else if (!strcasecmp(arg_name, DM_VERITY_OPT_RESTART)) {
 			v->mode = DM_VERITY_MODE_RESTART;
+			continue;
+
+		} else if (!strcasecmp(arg_name, DM_VERITY_OPT_PANIC)) {
+			v->mode = DM_VERITY_MODE_PANIC;
 			continue;
 
 		} else if (!strcasecmp(arg_name, DM_VERITY_OPT_IGN_ZEROES)) {
···
 
 static struct target_type verity_target = {
 	.name		= "verity",
-	.version	= {1, 6, 0},
+	.version	= {1, 7, 0},
 	.module		= THIS_MODULE,
 	.ctr		= verity_ctr,
 	.dtr		= verity_dtr,

drivers/md/dm-verity.h

···
 enum verity_mode {
 	DM_VERITY_MODE_EIO,
 	DM_VERITY_MODE_LOGGING,
-	DM_VERITY_MODE_RESTART
+	DM_VERITY_MODE_RESTART,
+	DM_VERITY_MODE_PANIC
 };
 
 enum verity_block_type {