btrfs: fail if fstrim_range->start == U64_MAX

We've always been failing generic/260 because it's testing things we
actually don't care about and thus won't fail for.  However we probably
should fail for fstrim_range->start == U64_MAX since we clearly can't
trim anything past that.  This in combination with an update to
generic/260 will allow us to pass this test properly.

Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/extent-tree.c

@@ -6051,6 +6051,9 @@ int btrfs_trim_fs(struct btrfs_fs_info *fs_info, struct fstrim_range *range)
 	int dev_ret = 0;
 	int ret = 0;
 
+	if (range->start == U64_MAX)
+		return -EINVAL;
+
 	/*
 	 * Check range overflow if range->len is set.
 	 * The default range->len is U64_MAX.