Re: [PATCH v1 01/16] iomap: move async bio read logic into helper function

[Christoph Hellwig <hch@infradead.org>]

On Wed, Sep 03, 2025 at 01:16:59PM -0700, Darrick J. Wong wrote:
> On Fri, Aug 29, 2025 at 04:56:12PM -0700, Joanne Koong wrote:
> > Move the iomap_readpage_iter() async bio read logic into a separate
> > helper function. This is needed to make iomap read/readahead more
> > generically usable, especially for filesystems that do not require
> > CONFIG_BLOCK.
> > 
> > Rename iomap_read_folio_range() to iomap_read_folio_range_sync() to
> > diferentiate between the synchronous and asynchronous bio folio read
> > calls.
> 
> Hrmm.  Readahead is asynchronous, whereas reading in data as part of an
> unaligned write to a file must be synchronous.  How about naming it
> iomap_readahead_folio_range() ?
> 
> Oh wait, iomap_read_folio also calls iomap_readpage_iter, which uses the
> readahead paths to fill out a folio, but then waits for the folio lock
> to drop, which effectively makes it ... a synchronous user of
> asynchronous code.
> 
> Bleh, naming is hard.  Though the code splitting seems fine...

Maybe we can look at it from a different angle - the code split out
isn't really about async vs sync, but about actually using a bio
to read data from a block device.  Which is also kinda important
for what Joanne is trying to do.  So I'd encode that in the name,
e.g. iomap_read_folio_range_bio to mimici the naming used for
iomap_dio_bio_iter in the direct I/O code.