Re: [PATCH] Block layer: separate out queue-oriented ioctls

From: Joerg Schilling
Date: Sun Feb 18 2007 - 13:30:29 EST

Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> wrote:

> > Alternatively the SG_GET_RESERVED_SIZE ioctl could be
> > modified to yield no more than max_sectors*512 .
> There should be one single ioctl which can be applied uniformly to all
> CD-type devices (in fact, to all devices using a request_queue) to learn
> max_sectors. This rules out using SG_GET_RESERVED_SIZE.

This has nothing to do with CD-type devices!
It is related to SCSI tansport.

> Furthermore, if you changed SG_GET_RESERVED_SIZE in this way you would
> only increase the confusion. The reserved size isn't directly related to
> the maximum allowed DMA length, and there's no point pretending it is.
> What if it turns out that the reserved size is smaller than max_sectors?
> Then you'd force user programs to do I/O in chunks that were smaller than
> necessary.

It would not increase confusion but reduce confusion because all
programs would later behave correctly without the need to change them.


EMail:joerg@xxxxxxxxxxxxxxxxxxxxxxxxxxx (home) Jörg Schilling D-13353 Berlin
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