btrfs-progs: inspect: make sure LOGICAL_INO_V2 args are zero-initialized

LOGICAL_INO v1 ignored the reserved fields, so they could be filled
with random stack garbage and have no effect.  LOGICAL_INO_V2 requires
all unused reserved bits to be set to zero, and returns EINVAL if they
are not, to guard against future kernel versions which may interpret
non-zero bit values.

Sometimes when 'btrfs ins log' runs, the stack garbage is zeros, so the
-o (ignore offsets) option for logical-resolve works.  Sometimes the
stack garbage is something else, and 'btrfs ins log -o' fails with
invalid argument.  This depends mostly on compiler version and build
environment details, so a binary typically either always works or never
works.

Fix by initializing logical-resolve's argument structure with a C99
compound literal zero.

Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Zygo Blaxell <ce3g8jdj@umail.furryterror.org>
Signed-off-by: David Sterba <dsterba@suse.com>

cmds/inspect.c

@@ -149,7 +149,7 @@ static int cmd_inspect_logical_resolve(const struct cmd_struct *cmd,
 	int verbose = 0;
 	int getpath = 1;
 	int bytes_left;
-	struct btrfs_ioctl_logical_ino_args loi;
+	struct btrfs_ioctl_logical_ino_args loi = { 0 };
 	struct btrfs_data_container *inodes;
 	u64 size = SZ_64K;
 	char full_path[PATH_MAX];