[Cluster-devel] [RFC v6 08/10] iomap/xfs: Eliminate the iomap_valid handler

[Christoph Hellwig <hch@infradead.org>]

On Sun, Jan 15, 2023 at 09:29:58AM -0800, Darrick J. Wong wrote:
> I don't have any objections to pulling everything except patches 8 and
> 10 for testing this week. 

That would be great.  I now have a series to return the ERR_PTR
from __filemap_get_folio which will cause a minor conflict, but
I think that's easy enough for Linux to handle.

> 
> 1. Does zonefs need to revalidate mappings?  The mappings are 1:1 so I
> don't think it does, but OTOH zone pointer management might complicate
> that.

Adding Damien.

> 2. How about porting the writeback iomap validation to use this
> mechanism?  (I suspect Dave might already be working on this...)

What is "this mechanism"?  Do you mean the here removed ->iomap_valid
?   writeback calls into ->map_blocks for every block while under the
folio lock, so the validation can (and for XFS currently is) done
in that.  Moving it out into a separate method with extra indirect
functiona call overhead and interactions between the methods seems
like a retrograde step to me.

> 2. Do we need to revalidate mappings for directio writes?  I think the
> answer is no (for xfs) because the ->iomap_begin call will allocate
> whatever blocks are needed and truncate/punch/reflink block on the
> iolock while the directio writes are pending, so you'll never end up
> with a stale mapping.

Yes.