Re: [PATCH 2/4] block: use the same failfast bits for bio and request
From: Tejun Heo
Date: Wed Jul 08 2009 - 20:45:55 EST
Hello, Boaz.
Boaz Harrosh wrote:
> Thanks for doing this, it has been neglected for a long time.
> However, it will happen again, I don't like these implicit matches
> which are not enforced, They get to drift away. There are several ways
> to make sure two sets of enums stay in sync. (I'll have a try at it
> tomorrow. if you want).
They don't share the exact same set of bits, so it's a bit blurry but
yeah it would be better if the bits are defined in more systematic
way.
>> @@ -142,37 +142,40 @@ struct bio {
>> *
>> * bit 0 -- data direction
>> * If not set, bio is a read from device. If set, it's a write to device.
>> - * bit 1 -- rw-ahead when set
>> - * bit 2 -- barrier
>> + * bit 1 -- fail fast device errors
>> + * bit 2 -- fail fast transport errors
>> + * bit 3 -- fail fast driver errors
>> + * bit 4 -- rw-ahead when set
>> + * bit 5 -- barrier
>
> Please kill all these evil bit 1, bit 2 ,bit n comments. The ways we
> invent to torture ourselfs...
>
> Just move all the comments to the enums declarations below. And be done
> with it, also for the next time.
Heh... I agree too. Unless ABI is fixed, this type of comments are
often painful. Care to submit a patch. This series is already in
block#for-next.
>> #define bio_rw_flagged(bio, flag) ((bio)->bi_rw & (1 << (flag)))
>>
>
> I wish there was also an helper to set these bits. it gives me an heart attack
> every time I need to:
> bio->bi_rw &= ~(1 << BIO_RW);
What's more disturbing to me is the different between RQ and BIO
flags. __REQ_* are bit positions, REQ_* are masks while BIO_* are bit
positions. Sadly it seems it's already too late to change that. I
personally an not a big fan of simple accessors or flags defined as
bit positions. They seem to obscure things without much benefit.
Thanks.
--
tejun
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