Re: [PATCH 3/5] fs: sys_ringbuffer

Thomas Gleixner
2024-06-23T22:13:44Z

Kent!

On Sun, Jun 02 2024 at 20:33, Kent Overstreet wrote:
> +/*
> + * ringbuffer_ptrs - head and tail pointers for a ringbuffer, mappped to
> + * userspace:
> + */
> +struct ringbuffer_ptrs {

The naming is confusing. ringbuffer_ctrl or something like that would be
more clear because it's more than just the pointers, which are in fact
positions. You have size, mask ... too, no?

> + /*
> + * We use u32s because this type is shared between the kernel and
> + * userspace - ulong/size_t won't work here, we might be 32bit userland
> + * and 64 bit kernel, and u64 would be preferable (reduced probability
> + * of ABA) but not all architectures can atomically read/write to a u64;
> + * we need to avoid torn reads/writes.

union rbmagic {
u64 __val64;
struct {
// TOOTIRED: Add big/little endian voodoo
u32 __val32;
u32 __unused;
};
};

Plus a bunch of accessors which depend on BITS_PER_LONG, no?

Thanks,

tglx