linux-kernel - Re: [PATCH 05/11] iomap: zero newly allocated mapped blocks

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Date:   Tue, 8 Oct 2019 09:08:37 +1100
From:   Dave Chinner <david@...morbit.com>
To:     Christoph Hellwig <hch@....de>
Cc:     "Darrick J . Wong" <darrick.wong@...cle.com>,
        Damien Le Moal <Damien.LeMoal@....com>,
        Andreas Gruenbacher <agruenba@...hat.com>,
        linux-xfs@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 05/11] iomap: zero newly allocated mapped blocks

On Tue, Oct 08, 2019 at 08:46:32AM +1100, Dave Chinner wrote:
> On Sun, Oct 06, 2019 at 05:46:02PM +0200, Christoph Hellwig wrote:
> > File systems like gfs2 don't support delayed allocations or unwritten
> > extents and thus allocate normal mapped blocks to fill holes.  To
> > cover the case of such file systems allocating new blocks to fill holes
> > also zero out mapped blocks with the new flag.
> > 
> > Signed-off-by: Christoph Hellwig <hch@....de>
> > Reviewed-by: Darrick J. Wong <darrick.wong@...cle.com>
> > Signed-off-by: Darrick J. Wong <darrick.wong@...cle.com>
> > ---
> >  fs/iomap/buffered-io.c | 12 ++++++++++--
> >  1 file changed, 10 insertions(+), 2 deletions(-)
> > 
> > diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
> > index 23cc308f971d..4132c0cccb0a 100644
> > --- a/fs/iomap/buffered-io.c
> > +++ b/fs/iomap/buffered-io.c
> > @@ -207,6 +207,14 @@ iomap_read_inline_data(struct inode *inode, struct page *page,
> >  	SetPageUptodate(page);
> >  }
> >  
> > +static inline bool iomap_block_needs_zeroing(struct inode *inode,
> > +		struct iomap *iomap, loff_t pos)
> > +{
> > +	return iomap->type != IOMAP_MAPPED ||
> > +		(iomap->flags & IOMAP_F_NEW) ||
> > +		pos >= i_size_read(inode);
> 
> This is a change of logic - why is the IOMAP_F_NEW check added here
> and what bug does it fix?

Sorry, brain-fart here - that's what this patch is adding, it's not
a pure factoring patch.... :/

Cheers,

Dave.
-- 
Dave Chinner
david@...morbit.com