[PATCH v4 9/9] loop: Add LOOP_CONFIGURE ioctl

[Denys Vlasenko]

> +config LOOP_CONFIGURE
> +       bool "always uses LOOP_CONFIGURE, kernel version >= 5.8"
> +
> +config NO_LOOP_CONFIGURE
> +       bool "never uses LOOP_CONFIGURE, kernel version < 5.8"
> +
> +config TRY_LOOP_CONFIGURE
> +       bool "try LOOP_CONFIGURE, kernel version is unknown"

The descriptions need improvement.

> +static int set_loop_configure(int ffd, int lfd, const bb_loop_info *loopinfo)
> +{
> +       int rc;
> +       struct loop_config config;
> +
> +       memset(&config, 0, sizeof(config));
> +       config.fd = ffd;
> +       memcpy(&config.info, loopinfo, sizeof(config.info));

This copying of the struct can be eliminated, a-la:

+#if ENABLE_TRY_LOOP_CONFIGURE || ENABLE_LOOP_CONFIGURE
+       struct loop_config lconfig;
+# define loopinfo lconfig.info
+#else
        bb_loop_info loopinfo;
+#endif

I reworked and applied it. Please try current git.