blkid: make PART_ENTRY_* tags optional (add --no-part-details)

blkid(8) returns information from partition table also for empty
partitions. This is necessary for example for udev, but it could be
confusing if you care about on-device content only.

Default:
 # blkid -p /dev/md0p1; echo $?
 /dev/md0p1: PART_ENTRY_SCHEME="dos" PART_ENTRY_UUID="6d8796b1-01" PART_ENTRY_TYPE="0x83" PART_ENTRY_NUMBER="1" PART_ENTRY_OFFSET="2048" PART_ENTRY_SIZE="204800" PART_ENTRY_DISK="9:0"
 0

With --no-part-details:
 # blkid -p /dev/md0p1 --no-part-details; echo $?
 2

Addresses: https://bugzilla.redhat.com/show_bug.cgi?id=1653413
Signed-off-by: Karel Zak <[email protected]>

misc-utils/blkid.8

@@ -35,6 +35,7 @@ blkid \- locate/print block device attributes
 .IR list ]
 .RB [ \-\-usages
 .IR list ]
+.RB [ \-\-no\-part\-details ]
 .IR device " ..."
 
 .IP \fBblkid\fR
@@ -114,6 +115,9 @@ Don't encode non-printing characters.  The non-printing characters are encoded
 by ^ and M- notation by default.  Note that the \fB\-\-output udev\fR output format uses
 a different encoding which cannot be disabled.
 .TP
+\fB\-D\fR, \fB\-\-no\-part\-details\fR 
+Don't print information (PART_ENTRY_* tags) from partition table in low-level probing mode.
+.TP
 \fB\-g\fR, \fB\-\-garbage\-collect\fR
 Perform a garbage collection pass on the blkid cache to remove
 devices which no longer exist.
@@ -224,7 +228,7 @@ Note that low-level probing also returns information about partition table type
 (PTTYPE tag) and partitions (PART_ENTRY_* tags). The tag names produced by
 low-level probing are based on names used internally by libblkid and it may be
 different than when executed without \fB\-\-probe\fR (for example PART_ENTRY_UUID= vs
-PARTUUID=).
+PARTUUID=). See also \fB\-\-no\-part\-details\fR.
 .TP
 \fB\-s\fR, \fB\-\-match\-tag\fR \fItag\fR
 For each (specified) device, show only the tags that match

misc-utils/blkid.c

@@ -58,6 +58,7 @@ struct blkid_control {
 		lowprobe:1,
 		lowprobe_superblocks:1,
 		lowprobe_topology:1,
+		no_part_details:1,
 		raw_chars:1;
 };
 
@@ -101,6 +102,7 @@ static void __attribute__((__noreturn__)) usage(void)
 	fputs(_(	" -O, --offset <offset>      probe at the given offset\n"), out);
 	fputs(_(	" -u, --usages <list>        filter by \"usage\" (e.g. -u filesystem,raid)\n"), out);
 	fputs(_(	" -n, --match-types <list>   filter by filesystem type (e.g. -n vfat,ext3)\n"), out);
+	fputs(_(        " -D, --no-part-details      don't print info from partition table\n"), out);
 
 	fputs(USAGE_SEPARATOR, out);
 	printf(USAGE_HELP_OPTIONS(28));
@@ -444,7 +446,7 @@ static int print_udev_ambivalent(blkid_probe pr)
 	return rc;
 }
 
-static int lowprobe_superblocks(blkid_probe pr)
+static int lowprobe_superblocks(blkid_probe pr, struct blkid_control *ctl)
 {
 	struct stat st;
 	int rc, fd = blkid_probe_get_fd(pr);
@@ -470,7 +472,8 @@ static int lowprobe_superblocks(blkid_probe pr)
 			return 0;	/* partition table detected */
 	}
 
-	blkid_probe_set_partitions_flags(pr, BLKID_PARTS_ENTRY_DETAILS);
+	if (!ctl->no_part_details)
+		blkid_probe_set_partitions_flags(pr, BLKID_PARTS_ENTRY_DETAILS);
 	blkid_probe_enable_superblocks(pr, 1);
 
 	return blkid_do_safeprobe(pr);
@@ -509,7 +512,7 @@ static int lowprobe_device(blkid_probe pr, const char *devname,
 	if (ctl->lowprobe_topology)
 		rc = lowprobe_topology(pr);
 	if (rc >= 0 && ctl->lowprobe_superblocks)
-		rc = lowprobe_superblocks(pr);
+		rc = lowprobe_superblocks(pr, ctl);
 	if (rc < 0)
 		goto done;
 
@@ -661,6 +664,7 @@ int main(int argc, char **argv)
 	static const struct option longopts[] = {
 		{ "cache-file",	      required_argument, NULL, 'c' },
 		{ "no-encoding",      no_argument,	 NULL, 'd' },
+		{ "no-part-details",  no_argument,       NULL, 'D' },
 		{ "garbage-collect",  no_argument,	 NULL, 'g' },
 		{ "output",	      required_argument, NULL, 'o' },
 		{ "list-filesystems", no_argument,	 NULL, 'k' },
@@ -694,7 +698,7 @@ int main(int argc, char **argv)
 	strutils_set_exitcode(BLKID_EXIT_OTHER);
 
 	while ((c = getopt_long (argc, argv,
-			    "c:dghilL:n:ko:O:ps:S:t:u:U:w:Vv", longopts, NULL)) != -1) {
+			    "c:DdghilL:n:ko:O:ps:S:t:u:U:w:Vv", longopts, NULL)) != -1) {
 
 		err_exclusive_options(c, NULL, excl, excl_st);
 
@@ -705,6 +709,9 @@ int main(int argc, char **argv)
 		case 'd':
 			ctl.raw_chars = 1;
 			break;
+		case 'D':
+			ctl.no_part_details = 1;
+			break;
 		case 'L':
 			ctl.eval = 1;
 			search_value = xstrdup(optarg);