[PATCH 14/20] selftests: ublk: add utility to get block device metadata size

Caleb Sander Mateos
2025-12-17T05:35:16Z

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>
---
tools/testing/selftests/ublk/Makefile | 4 +--
tools/testing/selftests/ublk/metadata_size.c | 36 ++++++++++++++++++++
2 files changed, 38 insertions(+), 2 deletions(-)
create mode 100644 tools/testing/selftests/ublk/metadata_size.c

diff --git a/tools/testing/selftests/ublk/Makefile b/tools/testing/selftests/ublk/Makefile
index 837977b62417..0f6abb95c87a 100644
--- a/tools/testing/selftests/ublk/Makefile
+++ b/tools/testing/selftests/ublk/Makefile
@@ -46,14 +46,14 @@ TEST_PROGS += test_stress_03.sh
TEST_PROGS += test_stress_04.sh
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

include ../lib.mk

-$(TEST_GEN_PROGS_EXTENDED): kublk.c null.c file_backed.c common.c stripe.c \
+$(OUTPUT)/kublk: kublk.c null.c file_backed.c common.c stripe.c \
fault_inject.c

check:
shellcheck -x -f gcc *.sh
diff --git a/tools/testing/selftests/ublk/metadata_size.c b/tools/testing/selftests/ublk/metadata_size.c
new file mode 100644
index 000000000000..76ecddf04d25
--- /dev/null
+++ b/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;
+}
--
2.45.2