v0.7 statx compile fail with kernels before 4.10

[zenfey]

Hi, PR #95 will include <linux/stat.h> to deal with earlier systems with undefined STATX_TYPE, it seems old versions kernel headers before 4.10 do not contain definition of STATX in this header file.

On my centos 7 machine with kernel version 3.10 LTS, the compile error occured on line 442 of uring_stubs.c, prompting "invalid application of 'sizeof' to incomplete type 'struct statx'".

Elrepo is an option for me to update system kernel to mainline version (>5.1) so to support syscalls of statx and io_uring at all on centos7, but I'm afraid this may get things into totally mess.

Could some additional macros be added so as to bypass statx compilation, thx : )

[talex5]

Happy to accept a PR for that, if you can find something that works!

[avsm]

Why are you compiling io_uring on such an old kernel? It won't reliably work with anything older than 5.11, and preferably 6.1.

[talex5]

I assume it's for programs that depend on eio_main, which uses eio_linux if the running kernel is new enough (so you still need to be able to compile it). Perhaps we just need an OS version constraint in eio_main's dependency to fix that?

[zenfey]

Why are you compiling io_uring on such an old kernel? It won't reliably work with anything older than 5.11, and preferably 6.1.

Some vendor provided libraries have dependency on specified version of libssl. I tried to compile install this libssl form source on machines with Rocky 9 and openSUSE 15 both have kernel version higher than 5.11 but still have linking problems.

I've got no idea why procedures with eio with uring(<=0.6) can run on a kernel that doesn't support liburing. Timer, net, fiber and green threads all work in a good state. The benchmark of flow.copy is also significant. I guess some constraint can bypass liburing when meeting async io on old machines? Could someone explain, thanks: )

[chris-armstrong]

Not sure if this is of any help, but I'm trying to compile iouring on a ~5.10 series kernel, and found I needed to make this change to get it to compile (the system I'm targeting is Amazon Linux 2, which uses an old kernel version, but is still maintained, as it used in AWS Lambda provided runtimes).

[talex5]

I've got no idea why procedures with eio with uring(<=0.6) can run on a kernel that doesn't support liburing.

It checks the kernel version at runtime and switches to eio_posix if it's too old.

I've added an opam constraint to ignore eio_linux on centos 7:

ocaml-multicore/eio#638

[zenfey]

I've got no idea why procedures with eio with uring(<=0.6) can run on a kernel that doesn't support liburing.

It checks the kernel version at runtime and switches to eio_posix if it's too old.

I've added an opam constraint to ignore eio_linux on centos 7:

ocaml-multicore/eio#638

I'v just opam upgraded packages and uring 0.8 is certainly failed to compile on centos7, while eio comes to version 0.13 successfully. cheers 👍