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

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Message-ID: <20191007214632.GA16973@dread.disaster.area>
Date:   Tue, 8 Oct 2019 08:46:32 +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 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?

Cheers,

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