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    SubjectRe: [PATCH] block: Force sector and nr_sects to device alignment and granularity.
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    Frank Mayhar <fmayhar@google.com> writes:

    > On Wed, 2014-03-12 at 14:20 -0400, Jeff Moyer wrote:
    >> but you managed to read my mind well enough. The question is how high
    >> up the stack do you put the logic for this? Is it worth it to duplicate
    >> the checks in the OS that are already done on the device? I don't
    >> know. Martin, do you have an opinion on this?
    >
    > Well, my opinion (and I suspect that Ted agrees with me to at least some
    > extent) is that this is where it should be, i.e. in the block layer, in
    > the place that already knows about and deals with alignment and
    > granularity. Sure, you could leave it to the device itself but it seems
    > reasonable to take care of this here for two reasons: First, doing this
    > means that if a TRIM is issued it will be successful and the intent of

    No, TRIM is advisory, even for well-formed TRIMs. I guess you could
    alter the definition of successful and have a correct statement there.

    > the discard will be at least partly satisfied. Second, we're already
    > doing most of the computations and making decisions based on the
    > alignment and granularity anyway, so the overhead is pretty negligible
    > (and if the discard size goes to zero we short-circuit the process and
    > never go to the device at all).

    Sure, there's no sense getting information from the device and not using
    it. I guess you've talked me into it.

    Cheers,
    Jeff


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