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RE: [PATCH v2 3/5] dax: improve documentation for fsync/msync

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---
Robert Elliott, HPE Persistent Memory


> -----Original Message-----
> From: Linux-nvdimm [mailto:linux-nvdimm-bounces@lists.01.org] On Behalf Of
> Ross Zwisler
> Sent: Friday, January 22, 2016 9:58 AM
> To: Jan Kara <jack@suse.cz>
> Cc: Andrew Morton <akpm@linux-foundation.org>; linux-nvdimm@lists.01.org;
> Dave Chinner <david@fromorbit.com>; linux-kernel@vger.kernel.org;
> Alexander Viro <viro@zeniv.linux.org.uk>; Jan Kara <jack@suse.com>; linux-
> fsdevel@vger.kernel.org
> Subject: Re: [PATCH v2 3/5] dax: improve documentation for fsync/msync
> 
> On Fri, Jan 22, 2016 at 04:01:29PM +0100, Jan Kara wrote:
> > On Thu 21-01-16 10:46:02, Ross Zwisler wrote:
...
> > > diff --git a/fs/dax.c b/fs/dax.c
> > > index d589113..55ae394 100644
> > > --- a/fs/dax.c
> > > +++ b/fs/dax.c
> > > @@ -350,6 +350,13 @@ static int dax_radix_entry(struct address_space
> *mapping, pgoff_t index,
> > >
> > >  		if (!pmd_entry || type == RADIX_DAX_PMD)
> > >  			goto dirty;
> > > +
> > > +		/*
> > > +		 * We only insert dirty PMD entries into the radix tree.  This
> > > +		 * means we don't need to worry about removing a dirty PTE
> > > +		 * entry and inserting a clean PMD entry, thus reducing the
> > > +		 * range we would flush with a follow-up fsync/msync call.
> > > +		 */
> >
> > May be acompany this with:
> >
> > 		WARN_ON(pmd_entry && !dirty);
> >
> > somewhere in dax_radix_entry()?
> 
> Sure, I'll add one.

If this is something that could trigger due to I/O traffic, please
use WARN_ONCE rather than WARN_ON to avoid the risk of swamping
the serial output.

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[PATCH v2 0/5] DAX fsync/msync fixes Ross Zwisler <ross.zwisler@linux.intel.com> - 2016-01-21 18:50 +0100
  [PATCH v2 4/5] dax: fix PMD handling for fsync/msync Ross Zwisler <ross.zwisler@linux.intel.com> - 2016-01-21 18:50 +0100
    Re: [PATCH v2 4/5] dax: fix PMD handling for fsync/msync Jan Kara <jack@suse.cz> - 2016-01-22 16:20 +0100
      Re: [PATCH v2 4/5] dax: fix PMD handling for fsync/msync Ross Zwisler <ross.zwisler@linux.intel.com> - 2016-01-22 17:10 +0100
  [PATCH v2 3/5] dax: improve documentation for fsync/msync Ross Zwisler <ross.zwisler@linux.intel.com> - 2016-01-21 18:50 +0100
    Re: [PATCH v2 3/5] dax: improve documentation for fsync/msync Jan Kara <jack@suse.cz> - 2016-01-22 16:10 +0100
      Re: [PATCH v2 3/5] dax: improve documentation for fsync/msync Ross Zwisler <ross.zwisler@linux.intel.com> - 2016-01-22 17:00 +0100
        RE: [PATCH v2 3/5] dax: improve documentation for fsync/msync "Elliott, Robert (Persistent Memory)" <elliott@hpe.com> - 2016-01-22 17:20 +0100
  [PATCH v2 2/5] dax: clear TOWRITE flag after flush is complete Ross Zwisler <ross.zwisler@linux.intel.com> - 2016-01-21 18:50 +0100
    Re: [PATCH v2 2/5] dax: clear TOWRITE flag after flush is complete Jan Kara <jack@suse.cz> - 2016-01-22 16:00 +0100
  [PATCH v2 1/5] dax: never rely on bh.b_dev being set by get_block() Ross Zwisler <ross.zwisler@linux.intel.com> - 2016-01-21 18:50 +0100
    Re: [PATCH v2 1/5] dax: never rely on bh.b_dev being set by  get_block() Jan Kara <jack@suse.cz> - 2016-01-22 16:00 +0100
  [PATCH v2 5/5] dax: fix clearing of holes in __dax_pmd_fault() Ross Zwisler <ross.zwisler@linux.intel.com> - 2016-01-21 18:50 +0100
    Re: [PATCH v2 5/5] dax: fix clearing of holes in __dax_pmd_fault() Jan Kara <jack@suse.cz> - 2016-01-22 16:40 +0100
      Re: [PATCH v2 5/5] dax: fix clearing of holes in __dax_pmd_fault() Ross Zwisler <ross.zwisler@linux.intel.com> - 2016-01-22 17:20 +0100
        Re: [PATCH v2 5/5] dax: fix clearing of holes in __dax_pmd_fault() Jan Kara <jack@suse.cz> - 2016-01-25 15:50 +0100

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