linux-ext4 - Re: [PATCH 4/5] dax: use sb_issue_zerout instead of calling dax_clear

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Date:	Fri, 1 Apr 2016 19:17:52 +0000
From:	"Verma, Vishal L" <vishal.l.verma@...el.com>
To:	"jack@...e.cz" <jack@...e.cz>
CC:	"linux-block@...r.kernel.org" <linux-block@...r.kernel.org>,
	"xfs@....sgi.com" <xfs@....sgi.com>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"viro@...iv.linux.org.uk" <viro@...iv.linux.org.uk>,
	"Williams, Dan J" <dan.j.williams@...el.com>,
	"axboe@...com" <axboe@...com>,
	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
	"linux-nvdimm@...ts.01.org" <linux-nvdimm@...ts.01.org>,
	"linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
	"ross.zwisler@...ux.intel.com" <ross.zwisler@...ux.intel.com>,
	"linux-ext4@...r.kernel.org" <linux-ext4@...r.kernel.org>,
	"Wilcox, Matthew R" <matthew.r.wilcox@...el.com>,
	"david@...morbit.com" <david@...morbit.com>
Subject: Re: [PATCH 4/5] dax: use sb_issue_zerout instead of calling
 dax_clear_sectors

On Wed, 2016-03-30 at 09:49 +0200, Jan Kara wrote:
> On Tue 29-03-16 18:57:16, Verma, Vishal L wrote:
> > 
> > On Mon, 2016-03-28 at 16:34 -0700, Dan Williams wrote:
> > 
> > <>
> > 
> > > 
> > > Seems kind of sad to fail the fault due to a bad block when we
> > > were
> > > going to zero it anyway, right?  I'm not seeing a compelling
> > > reason to
> > > keep any zeroing in fs/dax.c.
> > Agreed - but how do we do this? clear_pmem needs to be able to clear
> > an
> > arbitrary number of bytes, but to go through the driver, we'd need
> > to
> > send down a bio? If only the driver had an rw_bytes like interface
> > that
> > could be used by anyone... :)
> Actually, my patches for page fault locking remove zeroing from
> dax_insert_mapping() and __dax_pmd_fault() - the zeroing now happens
> from
> the filesystem only and the zeroing in those two functions is just a
> dead
> code...

That should make things easier! Do you have a tree I could merge in to
get this? (WIP is ok as we know that my series will depend on yours..)
or, if you can distill out that patch on a 4.6-rc1 base, I could carry
it in my series too (your v2's 3/10 doesn't apply on 4.6-rc1..)

Thanks,
	-Vishal