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

From: Dave Kleikamp
Date: Fri Apr 20 2012 - 11:09:41 EST

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
also guarantees that previous writes make it to media before the current
write, so it looks like I need to add an explicit vfs_fsync() in the new
path (conditional on REQ_FLUSH of course).

Zach, thoughts?


> Thanks,
> Maxim
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