Re: [PATCH 5/9] block: add ability to flag write back caching on a device

[Jens Axboe]

On 03/30/2016 09:46 AM, Jens Axboe wrote:
> On 03/30/2016 09:42 AM, Christoph Hellwig wrote:
> > On Wed, Mar 30, 2016 at 09:07:53AM -0600, Jens Axboe wrote:
> > > Add an internal helper and flag for setting whether a queue has
> > > write back caching, or write through (or none). Add a sysfs file
> > > to show this as well, and make it changeable from user space.
> >
> > As per previous discussion:  I don't really care about the way how we
> > tell the block layer we have a writeback cache, but a NAK to having
> > each driver call two interfaces to convey the same information.
> >
> > Please just look at q->flush_flag & REQ_FLUSH for now, and then
> > improvem the interface if you don't like it (I don't particularly like
> > it, but not to the point that I'm motivated enough to fix it :))
>
> That's fine, I don't mind making that change, just didn't do it for this
> version. I prefer if we change the cache flagging to be the primary way
> to signal it, it's more intuitive than REQ_FLUSH.
>
> It'll be in the next version.

Conversion series in here now:

http://git.kernel.dk/cgit/linux-block/log/?h=wb-buf-throttle

--
Jens Axboe