Re: [PATCH] fs: Return EOPNOTSUPP if block layer does not support REQ_NOWAIT

[Goldwyn Rodrigues <rgoldwyn@suse.de>]

On 19:08 22/07, Avi Kivity wrote:
> 
> On 13/12/2018 13.53, Goldwyn Rodrigues wrote:
> > For AIO+DIO with RWF_NOWAIT, if the block layer does not support REQ_NOWAIT,
> > it returns EIO. Return EOPNOTSUPP to represent the correct error code.
> > 
> > Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.com>
> > ---
> >   fs/direct-io.c | 11 +++++++----
> >   1 file changed, 7 insertions(+), 4 deletions(-)
> > 
> > diff --git a/fs/direct-io.c b/fs/direct-io.c
> > index 41a0e97252ae..77adf33916b8 100644
> > --- a/fs/direct-io.c
> > +++ b/fs/direct-io.c
> > @@ -542,10 +542,13 @@ static blk_status_t dio_bio_complete(struct dio *dio, struct bio *bio)
> >   	blk_status_t err = bio->bi_status;
> >   	if (err) {
> > -		if (err == BLK_STS_AGAIN && (bio->bi_opf & REQ_NOWAIT))
> > -			dio->io_error = -EAGAIN;
> > -		else
> > -			dio->io_error = -EIO;
> > +		dio->io_error = -EIO;
> > +		if (bio->bi_opf & REQ_NOWAIT) {
> > +			if (err == BLK_STS_AGAIN)
> > +				dio->io_error = -EAGAIN;
> > +			else if (err == BLK_STS_NOTSUPP)
> > +				dio->io_error = -EOPNOTSUPP;
> > +		}
> >   	}
> >   	if (dio->is_async && dio->op == REQ_OP_READ && dio->should_dirty) {
> 
> 
> In the end, did this or some alternative get applied? I'd like to enable
> RWF_NOWAIT support, but EIO scares me and my application.
> 

No, it was not. There were lot of objections to return error from the
block layer for a filesystem nowait request.

-- 
Goldwyn