[Cluster-devel] [PATCH v2 2/3] GFS2: Implement iomap for block_map

[Christoph Hellwig <hch@infradead.org>]

> > > That wasn't quite what I was getting at... we have two sets of
> > > flags. IOMAP_ZERO, IOMAP_WRITE and IOMAP_REPORT form one set that
> > > are passed as an argument to ->iomap_begin() and ->iomap_end()

They actually are the type of operation we perform, so maybe we should
rename them to "op" or similar.

> For GFS2 then we want to use the IOMAP_* flags as they are at the moment,
> but for the function that maps back from iomap to gfs2_block_map() we'd need
> to add a IOMAP_F_ZEROED or something like that from which to set the
> BH_zeronew() flag, which is used as both a request and result flag for the
> zeroing operation. That flag would very likely go away in due course when
> the final iomap migration is done for GFS2, so would just be a temporary
> thing in the mean time.

That would be the existing IOMAP_F_NEW I guess?

> I also wondered whether it would be possible to write a generic
> implementation of SEEK_HOLE/SEEK_END for iomap supporting filesystems at the
> VFS level. That would get GFS2 support for those two operations and be a
> nice clean up too. I've added an item on our todo list for that, but it may
> be a little while before we get around to it,

Yes, that should be doable.  Would be great if you could look at it,
otherwise I'll add it to my todo list.