On Wed, 15 Aug 2007 11:19:43 -0400 (EDT), Alan Stern <[EMAIL PROTECTED]> wrote:

> And that's not even taking into account the fact that
> sd_read_capcity(), together with everything else under
> sd_revalidate_disk(), gets called twice in a row during device
> scanning.  (What's the reason for that, anyway?)

I think this is an oldish problem in the block layer, which started
around 2.6.9. Right about that time Al Viro did something to make the
opens sane, and required ioctl to do opens right. This in turn busted
DASD on s390, and even floppies. The symptom was that after a media
change, first open would fail. This was fixed back in some 2.6.12
or so, I do not remember exactly, but the price was the redundant
call to revalidate the media.

IIRC the issue is open-from-within open, which is needed to check
partitions. Application opens sda1, and this in turn opens sda.
Something like that.

-- Pete
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