On 18/01/2020 01:49, Jens Axboe wrote:
> On 1/17/20 3:41 PM, Pavel Begunkov wrote:
>> *lost the cover-letter, but here we go*
>>
>> The main idea is to optimise code like the following by directly
>> copying sqe flags:
>>
>> if (sqe_flags & IOSQE_IO_HARDLINK)
>> req->flags |= REQ_F_HARDLINK;
>>
>> The first patch is a minor cleanup, and the second one do the
>> trick. No functional changes.
>>
>> The other thing to consider is whether to use such flags as
>> REQ_F_LINK = IOSQE_IO_LINK, or directly use IOSQE_IO_LINK instead.
>
> I think we should keep the names separate. I think it looks fine, though
> I do wish that we could just have both in an enum and not have to do
> weird naming. We sometimes do:
>
> enum {
> __REQ_F_FOO
> };
>
> #define REQ_F_FOO (1U << __REQ_F_FOO)
>
I thought it will be too bulky as it needs retyping the same name many times.
Though, it solves numbering problem and is less error-prone indeed. Let me to
play with it a bit.
BTW, there is another issue from development perspective -- it's harder to find
from where a flag is came. E.g. search for REQ_F_FOO won't give you a place,
where it was set. SQE_INHERITED_FLAGS is close in the code to its usage exactly
for this reason.
> and with that we could have things Just Work in terms of numbering, if
> we keep the overlapped values at the start. Would need IOSQE_* to also
> use an enum, ala:
>
> enum {
> __IOSQE_FIXED_FILE,
> __IOSQE_IO_DRAIN,
> ...
> };
>
I tried to not modify the userspace header. Wouldn't it be better to add _BIT
postfix instead of the underscores?
> and then do
>
> #define IOSQE_FIXED_FILE (1U << __IOSQE_FIXED_FILE)
>
> and have the __REQ enum start with
>
> enum {
> __REQ_F_FIXED_FILE = __IOSQE_FIXED_FILE,
> __REQ_F_IO_DRAIN = __IOSQE_IO_DRAIN,
> ...
> __REQ_F_LINK_NEXT,
> __REQ_F_FAIL_LINK,
> ...
> };
>
--
Pavel Begunkov
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