btrfs-progs: provide fail safe for BTRFS_IOC_GET_FSLABEL ioctl

Old kernels before 3.9 do not provide ioctl BTRFS_IOC_GET_FSLABEL.
So we need to provide a fail safe logic for btrfs-progs running
on those kernel.

In this patch when get_label_mounted() fails on the old kernel
it will fail back to the old method and uses get_label_unmounted(),
where it will read from the disk directly.

Signed-off-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: David Sterba <dsterba@suse.com>

1 files changed, 1 insertions, 0 deletions

diff --git a/utils.h b/utils.h
index dce0a47c..93e1de6b 100644
--- a/utils.h
+++ b/utils.h
@@ -164,6 +164,7 @@ u64 btrfs_device_size(int fd, struct stat *st);
 #define strncpy_null(dest, src) __strncpy__null(dest, src, sizeof(dest))
 int test_dev_for_mkfs(char *file, int force_overwrite);
 int get_label_mounted(const char *mount_path, char *labelp);
+int get_label_unmounted(const char *dev, char *label);
 int test_num_disk_vs_raid(u64 metadata_profile, u64 data_profile,
 	u64 dev_cnt, int mixed);
 int group_profile_max_safe_loss(u64 flags);