Re: Re: Hardsector size support in 2.4 and 2.5

Re: Re: Hardsector size support in 2.4 and 2.5

[Mark Peloquin]

Martin Dalecki wrote:
> > I was wondering if 2.5 will *really* support different hard sector
> > sizes. Today the hardsect array in the kernel seems to serve
> > little purpose. Drivers fill it in, but then what? It does not appear
> > to be used in any io path computations as illustrated by code
> > in submit_bh and generic_make_request which use a few
> > hardcoded shifts by 9 when dealing with sector sizes.
> >
> > Is the hardsect array on the way *in* or the way *out* of the
> > kernel? Will 2.5 take the real hardsector value into account?
> > Or can we expect everything to be handled in 512 byte
> > multiples  (as we do today)?

> It is on it's way out, since:

That is good, then the code should be less confusing.

> 1. Most hardware sec sizes are obscelny lower that the minimal logical
> sizes those days (512 ver. 4096 page size),
> so the tuning there doesn't matter.

> 2. All of it is "tuning", which can be handled generically on higher
> levels. (Like setting FS blocksize....)

> 3. The hard limits are handled on device driver level anyway (best
> example here are the odd fs block sizes for iso9660 filesystem).

So any block device, can always expect to receive buffer heads
whose b_rsector value represents the offset from the beginning
of that device in 512 byte multiples? And this will continue
to hold true in 2.5 as well?

Re: [Evms-devel] Re: Re: Hardsector size support in 2.4 and 2.5

[Christoph Hellwig]

On Mon, Nov 12, 2001 at 02:05:19PM -0600, Mark Peloquin wrote:
> So any block device, can always expect to receive buffer heads
> whose b_rsector value represents the offset from the beginning
> of that device in 512 byte multiples? And this will continue
> to hold true in 2.5 as well?

There is a good chance that no 2.5 block driver will ever see a buffer_head,
take a look at http://www.kernel.org/pub/linux/kernel/people/axboe/v2.5/ for
details.

	Christoph

-- 
Of course it doesn't work. We've performed a software upgrade.

Re: [Evms-devel] Re: Re: Hardsector size support in 2.4 and 2.5

[Jens Axboe]

On Mon, Nov 12 2001, Christoph Hellwig wrote:
> On Mon, Nov 12, 2001 at 02:05:19PM -0600, Mark Peloquin wrote:
> > So any block device, can always expect to receive buffer heads
> > whose b_rsector value represents the offset from the beginning
> > of that device in 512 byte multiples? And this will continue
> > to hold true in 2.5 as well?
> 
> There is a good chance that no 2.5 block driver will ever see a buffer_head,
> take a look at http://www.kernel.org/pub/linux/kernel/people/axboe/v2.5/ for
> details.

To expand on the specific point -- in 2.5, what will change is that
b_rsector (or equiv field, bi_sector in bio) will be offset from the
beginning of the disk, not the beginning of the partition. This moves
toe partion remaps out of the driver itself.

-- 
Jens Axboe