Re: [PATCH 10/14] iomap: free the bio before completing the dio

[Christoph Hellwig <hch@lst.de>]

On Wed, Jan 14, 2026 at 02:55:54PM -0800, Darrick J. Wong wrote:
> On Wed, Jan 14, 2026 at 08:41:08AM +0100, Christoph Hellwig wrote:
> > There are good arguments for processing the user completions ASAP vs.
> > freeing resources ASAP, but freeing the bio first here removes potential
> > use after free hazards when checking flags, and will simplify the
> > upcoming bounce buffer support.
> > 
> > Signed-off-by: Christoph Hellwig <hch@lst.de>
> > ---
> >  fs/iomap/direct-io.c | 15 +++++++--------
> >  1 file changed, 7 insertions(+), 8 deletions(-)
> > 
> > diff --git a/fs/iomap/direct-io.c b/fs/iomap/direct-io.c
> > index bf59241a090b..6f7036e72b23 100644
> > --- a/fs/iomap/direct-io.c
> > +++ b/fs/iomap/direct-io.c
> > @@ -213,7 +213,13 @@ static void iomap_dio_done(struct iomap_dio *dio)
> >  static void __iomap_dio_bio_end_io(struct bio *bio, bool inline_completion)
> >  {
> >  	struct iomap_dio *dio = bio->bi_private;
> > -	bool should_dirty = (dio->flags & IOMAP_DIO_DIRTY);
> > +
> > +	if (dio->flags & IOMAP_DIO_DIRTY) {
> > +		bio_check_pages_dirty(bio);
> > +	} else {
> > +		bio_release_pages(bio, false);
> > +		bio_put(bio);
> > +	}
> 
> /me wonders if we ought to set bio = NULL to make "thou shalt not touch
> bio" here explicit?  Otherwise seems it seems fine to me to make this
> change.

I guess we could do that (and could have done it before for the dio).
The compiler will optimize it away, but maybe that's a hint to the
user.  The compilers with the toned down warnings flags decided on by
the chief pinhead will be useless either way.