Messages in this thread |  | | Date | Mon, 19 Feb 2007 22:48:08 -0500 (EST) | From | Alan Stern <> | Subject | Re: [PATCH] Block layer: separate out queue-oriented ioctls |
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On Mon, 19 Feb 2007, Douglas Gilbert wrote:
> Alan, > The SG_GET_RESERVED_SIZE ioctl is also defined in > the block layer, see block/scsi_ioctl.c .
Ah, I didn't know that. (Or more likely, I used to know and have since forgotten.) Thanks for pointing it out.
> I suspect it is just a kludge to fool cdrecord that it > is talking to a sg device. [One of many kludges in the > block SG_IO ioctl implementation to that end.] > So perhaps the block layer versions of SG_SET_RESERVED_SIZE > and SG_GET_RESERVED_SIZE need to be similarly capped.
Yes. In fact one of them already is, but the other should be too.
> Actually I think that I would default SG_GET_RESERVED_SIZE to > request_queue->max_sectors * 512 in the block layer > implementation (as there is no "reserve buffer" associated > with a block device).
Okay.
Come to think of it, the reserved_size value used when a new sg device is created should also be capped at max_sectors * 512. Agreed? I can't see any reason for ever having a larger buffer -- it would be impossible to make use of the extra space.
Alan Stern
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