[Cbe-oss-dev] [PATCH] ps3rom: sector size should be 512 bytes

[Geert Uytterhoeven]

On Thu, 31 Jan 2008, Nicholas A. Bellinger wrote:
> On Thu, 2008-01-31 at 11:53 -0600, James Bottomley wrote:
> > On Thu, 2008-01-31 at 09:28 -0800, Nicholas A. Bellinger wrote:
> > > The problem case is a SCSI Target Mode engine that receives a 2048 Byte
> > > single sector ATAPI READ_10 request from the storage fabric, and uses
> > > scsi_execute_async() (the only option >= 2.6.18) to issue said request
> > > to the underlying struct scsi_device.  Because the underlying bio code
> > > assumes 512 byte only sectors, the check in __bio_add_page() incorrectly
> > > determines that max_sectors (max_sectors has to be low, as with 32 from
> > > ps3rom.c) has been exceeded, and fails the request back up the stack.
> > 
> > OK, so this is a totally separate issue from the one you actually posted
> > it as a patch to fix?
> > 
> > the queue max_sectors parameter is also counted in the block internal of
> > 512 byte sectors.  If you set it to 32 that means you were only
> > expecting 16k of transfers per command maximum.  If that's not right,
> > then set the limit correctly.
> > 
> > In short, and to repeat: almost every internal size counter to block is
> > in units of 512 byte sectors ... that includes capacity, maximum etc ...
> > 
> 
> Ok, after reading your followup with Geert I see that this looks like a
> bug in ps3rom.c assuming 2048 byte sectors to calculate .max_sectors
> (which was originally set to 32 as I mentioned).  Using the setting
> BOUNCE_SIZE << 9 where BOUNCE_SIZE is the request size in bytes looks
> like this will solve the issue.  My misunderstanding was
> that .max_sectors was allowed to be calcuated in non 512 byte sectors,
> so please disregard my patch.
> 
> Geert, .max_sectors for ps3rom.c using 512 byte sectors ends up being
> 128, yes.?

Yes.

With kind regards,

Geert Uytterhoeven
Software Architect

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