Re: [PATCH] mkfs: Remove messages printed when blocksize < physical sectorsize

[Dave Chinner <david@fromorbit.com>]

On Tue, Sep 05, 2017 at 09:00:26AM -0600, Jens Axboe wrote:
> On 09/05/2017 01:37 AM, Chandan Rajendra wrote:
> > On Tuesday, September 5, 2017 12:12:08 PM IST Omar Sandoval wrote:
> >> On Mon, Sep 04, 2017 at 11:31:39PM -0700, Christoph Hellwig wrote:
> >>> On Tue, Sep 05, 2017 at 11:14:42AM +0530, Chandan Rajendra wrote:
> >>>> Linux kernel commit 6c6b6f28b3335fd85ec833ee0005d9c9dca6c003 (loop: set
> >>>> physical block size to PAGE_SIZE) now sets PAGE_SIZE as the default
> >>>> physical sector size of loop devices. On ppc64, this causes loop devices
> >>>> to have 64k as the physical sector size.
> >>>
> >>> Eek.  We'll need to revert the loop change ASAP!
> >>
> >> Most annoying patch series ever. It hasn't made it to Linus' tree yet,
> >> right? We can revert (although the later change depends on that), fold
> >> in a fix, or apply a fix on top of it, whatever Jens prefers.
> >>
> >>
> > 
> > My bad. 6c6b6f28b3335fd85ec833ee0005d9c9dca6c003 is the commit id from 
> > Linux-next. I don't see this commit in Linus's git tree.
> 
> Right, it's only queued up, and scheduled for the 2nd part of the
> block changes for 4.14. It should have been PAGE_CACHE_SIZE, but
> we don't have that anymore...

But PAGE_CACHE_SIZE was equal to PAGE_SIZE, so that would have been
wrong, too.

I just don't see why this is necessary, given that buffered IO
through the upper filesystem will already be doing page
sized/aligned IO where possible (because that's what the page cache
does!). And for direct IO the loop device should just export the
underlying host filesystem logical/physical sector sizes, which
should be optimal for the backing storage to begin with.

Someone want to enlighten me as to what problem is being solved
here?

Cheers,

Dave.
-- 
Dave Chinner
david@fromorbit.com