Re: [PATCH 14/17] iomap: make buffered writes work with RWF_UNCACHED

[Christoph Hellwig]

On Wed, Dec 11, 2024 at 10:26:41PM -0800, Darrick J. Wong wrote:
> > iomap.flags and the IOMAP_F_* namespace is used to communicate flags
> > from the file system to the iomap core, so this looks wrong.
> 
> Not entirely true -- IOMAP_F_SIZE_CHANGED is used to communicate state
> from iomap to gfs2, and IOMAP_F_STALE is set/checked only by the iomap
> core.  iomap.h even says as much.

Indeed, some of the non-initial additions already broke this.  And now
that you mentioned it I ran into that before because it was in the way
of some further constifycation I attempted in fs/iomap/.

> Though given that there's a 4-byte gap in struct iomap between flags and
> the bdev pointer (at least on 64-bit) maybe we should make a separate
> field for these iomap state bits?

Probably.  Preferably in a way that isn't too painful for Jens, though.