Re: [RFC PATCH 0/7] Non-blockling buffered fs read (page cache only)

[Milosz Tanski]

I'll send out the next RFC with 2 syscalls and magic position values.
I'm waiting for Jeff to chime in on the v2 patchset before I send out
the next one.

On Mon, Sep 22, 2014 at 12:42 PM, Christoph Hellwig <hch@xxxxxxxxxxxxx> wrote:
> On Mon, Sep 22, 2014 at 12:32:02PM -0400, Milosz Tanski wrote:
>> I spent some time thinking about multi-position scatter/gather in
>> context of this over the weekend. The non-blocking case seams easy,
>> the implementation I purposed needs an extra loop. Where this gets
>> hairy is making the non-trivial blocking case work well (as in have
>> concurrent requests for each of the ranges) in the filesystem code. If
>> that's the road we're going to go down I have a gut feeling we're
>> going to get stuck in the same spot(s) as the other non-blocking
>> buffered r/w attempts from the past.
>
> The other thing sis that we have a basically ready, easy to use
> implementation of flagged I/O (my name for the new syscalls), while
> S/G I/O will take forever to discuss and is the natual vehicle for
> other extensions like T10 DIX.
>
> I'd like to suggest you consolidate your syscalls down from 4 to 2
> as suggestes by overloading the negative offset argument, giving
> us two more syscalls slows for S/G once it's ready.  Note that
> a sync S/G syscalls should of course also support these flags, although
> I suspect the primary use cases for S/G I/O would be through the aio
> machinery.



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Milosz Tanski
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