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    SubjectRe: [PATCH v4] drivers/block/mtip32xx: Adding new driver mtip32xx
    On Tue, Sep 13, 2011 at 5:49 AM, Christoph Hellwig <hch@infradead.org> wrote:
    > Btw, there is another _huge_ issue with the driver, and that is the
    > lack of any internal queueing.  Remember the make_request interface is
    > an extremly thin layer (or rather the lack of it) below the filesystem.
    >
    > So for example if eh_active is non-zero you return -EBUSY to the
    > filesystems.  That's an error code it a) doesn't recognize and b)
    > couldn't handle even if it did.  Similarly mtip_hw_get_scatterlist
    > simply blocks if no tag is currently available instead of queueing
    > it up.

    Just out of curiosity, why is blocking on no-tag-available a bad
    thing? How is it any different than the blocking that will occur when
    a request queue is full? When the hardware queue depth is bigger than
    that of a request queue, what extra benefit does queuing give?
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