Re: [RFC PATCH v2 15/21] loop: use aio to perform io on the underlyingfile

From: Dave Kleikamp
Date: Fri Apr 20 2012 - 12:14:33 EST

On 04/20/2012 10:20 AM, Jeff Moyer wrote:
> Dave Kleikamp <dave.kleikamp@xxxxxxxxxx> writes:
>> On 04/20/2012 09:48 AM, Maxim V. Patlasov wrote:
>>> On 03/30/2012 07:43 PM, Dave Kleikamp wrote:
>>>> From: Zach Brown<zab@xxxxxxxxx>
>>>> This uses the new kernel aio interface to process loopback IO by
>>>> submitting concurrent direct aio. Previously loop's IO was serialized
>>>> by synchronous processing in a thread.
>>> The patch ignores REQ_FLUSH bit of bi_rw. Is it simply overlook?
>> Good question. Since the loop device is sending only direct IO requests,
>> it shouldn't be necessary to explicitly flush page cache, but REQ_FLUSH
> REQ_FLUSH isn't about the page cache, it's about flushing the volatile
> disk write cache. You need to handle that.

Yeah, and looking again at this code, I need to handle REQ_DISCARD as well.

> Cheers,
> Jeff
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