Re: [PATCH, RFC] Don't do page stablization if !CONFIG_BLKDEV_INTEGRITY

Chris Mason
2012-03-09T01:02:07Z

On Thu, Mar 08, 2012 at 04:41:48PM -0500, Ted Ts'o wrote:
> On Thu, Mar 08, 2012 at 04:38:08PM -0500, Chris Mason wrote:
> > Btrfs currently does this, and the DIF code is by definition right
> > before the write. The pages really only get set writeback when they are
> > being sent in flight, so the waiting being done by the stable pages
> > patch is file_write or page_mkwrite being polite and waiting for the IO
> > to finish before changing the page.
>
> Right before submission to the bio layer? Or right before the device
> driver sends the request to the host bus adapter? I was thinking of
> the latter....

blktrace can probably give us numbers for how big that wait is, but
hopefully it is very small. If it is too big, you can always bump
nr_requests.

Btrfs crcs before submit_bio, not sure when the dif code does it.

-chris