Re: [PATCH v1 1/1] iomap: don't mark folio uptodate if read IO has bytes pending

["Darrick J. Wong" <djwong@kernel.org>]

On Thu, Feb 19, 2026 at 04:23:23AM +0000, Matthew Wilcox wrote:
> On Wed, Feb 18, 2026 at 06:45:34PM -0800, Darrick J. Wong wrote:
> > On Wed, Feb 18, 2026 at 04:39:11PM -0800, Joanne Koong wrote:
> > > If a folio has ifs metadata attached to it and the folio is partially
> > > read in through an async IO helper with the rest of it then being read
> > > in through post-EOF zeroing or as inline data, and the helper
> > > successfully finishes the read first, then post-EOF zeroing / reading
> > > inline will mark the folio as uptodate in iomap_set_range_uptodate().
> > > 
> > > This is a problem because when the read completion path later calls
> > > iomap_read_end(), it will call folio_end_read(), which sets the uptodate
> > > bit using XOR semantics. Calling folio_end_read() on a folio that was
> > > already marked uptodate clears the uptodate bit.
> > 
> > Aha, I wondered if that xor thing was going to come back to bite us.
> 
> This isn't "the xor thing has come back to bite us".  This is "the iomap
> code is now too complicated and I cannot figure out how to explain to
> Joanne that there's really a simple way to do this".
> 
> I'm going to have to set aside my current projects and redo the iomap
> readahead/read_folio code myself, aren't I?

Well you could try explaining to me what that simpler way is?

/me gets the sense he's missing a discussion somewhere...

--D