selftests: ublk: add utility to get block device metadata size

Some block device integrity parameters are available in sysfs, but
others are only accessible using the FS_IOC_GETLBMD_CAP ioctl. Add a
metadata_size utility program to print out the logical block metadata
size, PI offset, and PI size within the metadata. Example output:
$ metadata_size /dev/ublkb0
metadata_size: 64
pi_offset: 56
pi_tuple_size: 8

Signed-off-by: Caleb Sander Mateos <csander@purestorage.com>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Author: calebsander

tools/testing/selftests/ublk/Makefile

@@ -49,12 +49,13 @@ TEST_PROGS += test_stress_05.sh
 TEST_PROGS += test_stress_06.sh
 TEST_PROGS += test_stress_07.sh
 
-TEST_GEN_PROGS_EXTENDED = kublk
+TEST_GEN_PROGS_EXTENDED = kublk metadata_size
+STANDALONE_UTILS := metadata_size.c
 
 LOCAL_HDRS += $(wildcard *.h)
 include ../lib.mk
 
-$(TEST_GEN_PROGS_EXTENDED): $(wildcard *.c)
+$(OUTPUT)/kublk: $(filter-out $(STANDALONE_UTILS),$(wildcard *.c))
 
 check:
 	shellcheck -x -f gcc *.sh

tools/testing/selftests/ublk/metadata_size.c

@@ -0,0 +1,36 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <fcntl.h>
+#include <linux/fs.h>
+#include <stdio.h>
+#include <sys/ioctl.h>
+
+int main(int argc, char **argv)
+{
+	struct logical_block_metadata_cap cap = {};
+	const char *filename;
+	int fd;
+	int result;
+
+	if (argc != 2) {
+		fprintf(stderr, "Usage: %s BLOCK_DEVICE\n", argv[0]);
+		return 1;
+	}
+
+	filename = argv[1];
+	fd = open(filename, O_RDONLY);
+	if (fd < 0) {
+		perror(filename);
+		return 1;
+	}
+
+	result = ioctl(fd, FS_IOC_GETLBMD_CAP, &cap);
+	if (result < 0) {
+		perror("ioctl");
+		return 1;
+	}
+
+	printf("metadata_size: %u\n", cap.lbmd_size);
+	printf("pi_offset: %u\n", cap.lbmd_pi_offset);
+	printf("pi_tuple_size: %u\n", cap.lbmd_pi_size);
+	return 0;
+}