Re: [PATCH v1 2/8] iomap: add IOMAP_IN_MEM iomap type

[Christoph Hellwig <hch@infradead.org>]

On Mon, Jun 09, 2025 at 02:45:34PM -0700, Joanne Koong wrote:
> IOMAP_INLINE is the closest in idea to what I'm looking for in that
> it's completely independent from block io, but it falls short in a few
> ways (described in the reply to Darrick in [1]). In terms of
> implementation logic, IOMAP_MAPPED fits great but that's tied in idea
> to mapped blocks and we'd be unable to make certain assertions (eg if
> the iomap type doesn't use bios, the caller must provide
> ->read_folio_sync() and ->writeback_folio() callbacks).

Well, IFF we end up with both my proposals those two are the clean
abstractions between the generic and block-level code and everyone
is using them.  Let's see how that plays out.  I'd rather have a strong
abstraction like that if we can and not add new types for what is
essentially the same.

Btw, for zoned XFS, IOMAP_MAPPED also doesn't have a block number
assigned yet and only actually does the I/O in the submit_ioend method.