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From: Jens Axboe <[email protected]>
To: Ammar Faizi <[email protected]>,
	Pavel Begunkov <[email protected]>
Cc: io-uring Mailing List <[email protected]>,
	Bedirhan KURT <[email protected]>,
	Louvian Lyndal <[email protected]>
Subject: Re: [PATCH v5 liburing 0/3] Implement the kernel style return value
Date: Sun, 3 Oct 2021 09:59:14 -0600	[thread overview]
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>

On 10/3/21 9:34 AM, Ammar Faizi wrote:
> Hi Jens,
> 
> This is the v5 of the kernel style return value implementation for
> liburing.
> 
> The main purpose of these changes is to make it possible to remove
> the dependency of `errno` variable in the liburing C sources. If we
> can land this on liburing, we will start working on adding support
> build liburing without libc.
> 
> Currently, we expose these functions to userland:
>   1) `__sys_io_uring_register`
>   2) `__sys_io_uring_setup`
>   3) `__sys_io_uring_enter2`
>   4) `__sys_io_uring_enter`
> 
> The tests in `test/io_uring_{enter,register,setup}.c` are the examples
> of it. Since the userland needs to check the `errno` value to use them
> properly, this means those functions always depend on libc. So we
> cannot change their behavior. Don't touch them all, this ensures the
> changes only affect liburing internal and no visible functionality
> changes for the users.
> 
> Then we introduce new functions with the same name (with extra
> underscore as prefix, 4 underscores):
>   1) `____sys_io_uring_register`
>   2) `____sys_io_uring_setup`
>   3) `____sys_io_uring_enter2`
>   4) `____sys_io_uring_enter`
> 
> These functions do not use `errno` variable *on the caller*, they use
> the kernel style return value (return a negative value of error code
> when errors).
> 
> These functions are defined as `static inline` in `src/syscall.h`.
> They are just a wrapper to make sure liburing internal sources do not
> touch `errno` variable from C files directly. We need to make C files
> not to touch the `errno` variable to support build without libc.
> 
> To completely remove the `errno` variable dependency from liburing C
> files. We wrap all syscalls in a kernel style return value as well.
> 
> Currently we have 5 other syscalls in liburing. We wrapped all of
> them as these 5 functions:
>   1) `uring_mmap`
>   2) `uring_munmap`
>   3) `uring_madvise`
>   4) `uring_getrlimit`
>   5) `uring_setrlimit`
> 
> All of them are `static inline` and will return a negative value of
> error code in case error happens.
> 
> Extra new helpers:
>   1) `ERR_PTR()`
>   2) `PTR_ERR()`
>   3) `IS_ERR()`
> 
> These helpers are used to deal with syscalls that return a pointer.
> Currently only `uring_mmap()` that depends on these.

Thanks, let's give this a go. I've applied the 3 patches.

-- 
Jens Axboe


      parent reply	other threads:[~2021-10-03 15:59 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-10-03 15:34 [PATCH v5 liburing 0/3] Implement the kernel style return value Ammar Faizi
2021-10-03 15:34 ` [PATCH v5 liburing 1/3] src/syscall: Wrap `errno` for `__sys_io_uring_{register,setup,enter{2,}}` Ammar Faizi
2021-10-03 15:34 ` [PATCH v5 liburing 2/3] src/{queue,register,setup}: Don't use `__sys_io_uring*` Ammar Faizi
2021-10-03 15:34 ` [PATCH v5 liburing 3/3] Wrap all syscalls in a kernel style return value Ammar Faizi
2021-10-03 15:59 ` Jens Axboe [this message]

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