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    SubjectRe: [RFC PATCH v2 15/21] loop: use aio to perform io on the underlying file


    On 04/20/2012 10:20 AM, Jeff Moyer wrote:
    > Dave Kleikamp <dave.kleikamp@oracle.com> 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@zabbo.net>
    >>>>
    >>>> 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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