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

[Christoph Hellwig]

On Tue, Jun 25, 2019 at 08:13:57AM -0700, Darrick J. Wong wrote:
> > 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?

The core code doesn't decide when to overwrite it, that ->map_blocks
method does that based on a few factors (including the data_seq/cow_seq
counters that are entirely inside xfs).