Re: [PATCH blktests] create a test for direct io offsets

[Christoph Hellwig <hch@infradead.org>]

> +static void init_kernel_version()
> +{
> +	struct utsname buffer;
> +	char *major_version_str;
> +	char *minor_version_str;
> +	if (uname(&buffer) != 0)
> +		err(errno, "uname");
> +
> +	major_version_str = strtok(buffer.release, ".");
> +	minor_version_str = strtok(NULL, ".");
> +
> +	kernel_major = strtol(major_version_str, NULL, 0);
> +	kernel_minor = strtol(minor_version_str, NULL, 0);
> +}

Testing for specific kernel versions is probably going to fall
flat when this stuff gets backported..  I just realize that maybe
we just need a statx / fsxattr flag to report that this is supported
to make everyones life easier?  statx probably won't make Christian
happy, but now that the fsxattr stuff is in common code that seems
like an easy enough option to rush into 6.18 still.

I.e., we should find a way to remove all the need to find the kernel
version, mount point and bdev from mountpoint.  Especially as the
latter won't work for multi-device configurations like btrfs or
the XFS rtdev.  My rule of thumb for new I/O path features is that
the application should be able to discover everything it needs just
using the FD used for I/O as that is a huge differenciator for
usability.