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

[Joerg Schilling]

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.

Jörg

-- 
 EMail:joerg@xxxxxxxxxxxxxxxxxxxxxxxxxxx (home) Jörg Schilling D-13353 Berlin
       js@xxxxxxxxxxxxxxx                (uni)  
       schilling@xxxxxxxxxxxxxxxxxxx     (work) Blog: http://schily.blogspot.com/
 URL:  http://cdrecord.berlios.de/old/private/ ftp://ftp.berlios.de/pub/schily
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/