Re: [PATCH 04/12] xfs: initialize ioma->flags in xfs_bmbt_to_iomap

[Darrick J. Wong]

On Tue, Jun 25, 2019 at 12:07:01PM +0200, Christoph Hellwig wrote:
> On Mon, Jun 24, 2019 at 07:57:07AM -0700, Darrick J. Wong wrote:
> > On Mon, Jun 24, 2019 at 07:52:45AM +0200, Christoph Hellwig wrote:
> > > Currently we don't overwrite the flags field in the iomap in
> > > xfs_bmbt_to_iomap.  This works fine with 0-initialized iomaps on stack,
> > > but is harmful once we want to be able to reuse an iomap in the
> > > writeback code.
> > 
> > Is that going to affect all the other iomap users, or is xfs the only
> > one that assumes zero-initialized iomaps being passed into
> > ->iomap_begin?
> 
> This doesn't affect any existing user as they all get a zeroed iomap
> passed from the caller in iomap.c.  It affects the writeback code
> once it uses struct iomap as it overwrites a previously used iomap.

Then shouldn't this new writeback code zero the iomap before calling
back into the filesystem, just to maintain consistent behavior?

--D