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    SubjectRe: [PATCH] block: export SSD/non-rotational queue flag through sysfs
    On Mon, 5 Jan 2009, Sitsofe Wheeler wrote:
    > Kay Sievers wrote:
    > > On Mon, Jan 5, 2009 at 19:54, Jens Axboe <jens.axboe@oracle.com> wrote:
    > > > On Mon, Jan 05 2009, Bartlomiej Zolnierkiewicz wrote:
    > >
    > > > > +static struct queue_sysfs_entry queue_nonrot_entry = {
    > > > > + .attr = {.name = "nonrot", .mode = S_IRUGO | S_IWUSR },
    > > > > + .show = queue_nonrot_show,
    > > > > + .store = queue_nonrot_store,
    > > > > +};
    > > > > +
    > > > Lets please use a better name for export reasons, non-rotational is a
    > > > lot better. Nobody will know what nonrot means :-)
    > >
    > > What's that negation good for? Can't we just have "rotational", like
    > > we have "removable" and not "non-removable"? :)
    >
    > How about cheapseek? fastrandom? flash? ssd? However the internal flag is
    > called QUEUE_FLAG_NONROT so it kind of makes sense just to leave it as
    > nonrot...

    Many thanks to Bart (and Alan) for this patch:
    just what I'd been hoping for when I wrote (25 Nov)
    But how to get my SD card, accessed by USB card reader, reported as NONROT?

    However, may I join Kai in protesting the negative boolean flag?
    I've never quite recovered from CONFIG_SCHED_NO_NO_OMIT_FRAME_POINTER;
    and while this is obviously nowhere near the same league, I'd much
    rather stay well away.

    I don't like the "nonrot" or "rotational" at all myself: though you
    may be able to advance convincing arguments why it's not accidental,
    isn't the rotationality pretty much incidental to whether the seeks
    are cheap? I imagine a long bar loaded with data, which zips back
    and forth through the reader: nothing rotational, but expensive seeks.
    (I had been going to propose magnetic tape, but the rotation of the
    spools muddies that argument.)

    When doing the swap patch, though I toed the line with SWP_NONROT
    for quite a while (I do dislike using different names for the same
    notion at different levels), I couldn't stomach it in the end, and
    went for SWP_SOLIDSTATE.

    But I particularly like Sitsofe's "cheapseek". Is that is an accurate
    representation of how the I/O schedulers treat it? then please can we
    name the user-visible sysfs file accordingly?

    The kernel-internal name is much less important, though I'd be pretty
    happy to have CHEAPSEEK instead of NONROT throughout there too.

    Oh, another problem with NONROT: flash rots a lot sooner than disk,
    doesn't it?

    Hugh


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