Re: Linux 2.6.29

Hugh Dickins
2009-03-26T14:51:11Z

On Thu, 26 Mar 2009, Jens Axboe wrote:
> On Wed, Mar 25 2009, Hugh Dickins wrote:
> >
> > Tangential question, but am I right in thinking that BIO_RW_BARRIER
> > similarly bars across all partitions, whereas its WRITE_BARRIER and
> > DISCARD_BARRIER users would actually prefer it to apply to just one?
>
> All the barriers refer to just that range which the barrier itself
> references.

Ah, thank you: then I had a fundamental misunderstanding of them,
and need to go away and work that out some more.

Though I didn't read it before asking, doesn't the I/O Barriers section
of Documentation/block/biodoc.txt give a very different impression?

> The problem with the full device flushes is implementation
> on the hardware side, since we can't do small range flushes. So it's not
> as-designed, but rather the best we can do...

Right, that part of it I did get.

Hugh