Re: [PATCH v1 0/5] io_uring: add xattr support

Stefan Metzmacher
2021-12-01T12:19:13Z

Hi Stefan,

> On 11/29/21 5:08 PM, Clay Harris wrote:
>> On Mon, Nov 29 2021 at 14:12:52 -0800, Stefan Roesch quoth thus:
>>
>>> This adds the xattr support to io_uring. The intent is to have a more
>>> complete support for file operations in io_uring.
>>>
>>> This change adds support for the following functions to io_uring:
>>> - fgetxattr
>>> - fsetxattr
>>> - getxattr
>>> - setxattr
>>
>> You may wish to consider the following.
>>
>> Patching for these functions makes for an excellent opportunity
>> to provide a better interface. Rather than implement fXetattr
>> at all, you could enable io_uring to use functions like:
>>
>> int Xetxattr(int dfd, const char *path, const char *name,
>> [const] void *value, size_t size, int flags);
>>
>> Not only does this simplify the io_uring interface down to two
>> functions, but modernizes and fixes a deficit in usability.
>> In terms of io_uring, this is just changing internal interfaces.
>>
>> Although unnecessary for io_uring, it would be nice to at least
>> consider what parts of this code could be leveraged for future
>> Xetxattr2 syscalls.
>
> Clay,
>
> while we can reduce the number of calls to 2, providing 4 calls will
> ease the adoption of the interface.
>
> If you look at the userspace interface in liburing, you can see the
> following function signature:
>
> static inline void io_uring_prep_fgetxattr(struct io_uring_sqe *sqe,
> int fd,
> const char *name,
> const char *value,
> size_t len)
>
> This is very similar to what you proposed.

What's with lsetxattr and lgetxattr, why are they missing.

I'd assume that even 6 helper functions in liburing would be able
to use just 2 low level iouring opcodes.

*listxattr is also missing, are there plans for them?

metze