Re: [PATCH 10/13] iomap: use a function pointer for dio submits

[Goldwyn Rodrigues <RGoldwyn@suse.com>]

On Fri, 2019-08-02 at 17:21 -0700,  Darrick J. Wong  wrote:
> On Fri, Aug 02, 2019 at 05:00:45PM -0500, Goldwyn Rodrigues wrote:
> > From: Goldwyn Rodrigues <rgoldwyn@suse.com>
> > 
> > This helps filesystems to perform tasks on the bio while
> > submitting for I/O. Since btrfs requires the position
> > we are working on, pass pos to iomap_dio_submit_bio()
> 
> What /does/ btrfs_submit_direct do, anyway?  Looks like it's a custom
> submission function that ... does something related to setting
> checksums?  And, uh, RAID?

Yes and yes.

> 
> > The correct place for submit_io() is not page_ops. Would it
> > better to rename the structure to something like iomap_io_ops
> > or put it directly under struct iomap?
> 
> Seeing as the ->iomap_begin handler knows if the requested op is a
> buffered write or a direct write, what if we just declare a union of
> ops?
> 
> e.g.
> 
> struct iomap_page_ops;
> struct iomap_directio_ops;
> 
> struct iomap {
> 	<usual stuff>
> 	union {
> 		const struct iomap_page_ops *page_ops;
> 		const struct iomap_directio_ops *directio_ops;
> 	};
> };

Yes, that looks good. Thanks. I will incorporate it.

> 
> --D
> 
> > Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.com>
> > ---
> >  fs/iomap/direct-io.c  | 16 +++++++++++-----
> >  include/linux/iomap.h |  1 +
> >  2 files changed, 12 insertions(+), 5 deletions(-)
> > 
> > diff --git a/fs/iomap/direct-io.c b/fs/iomap/direct-io.c
> > index 5279029c7a3c..a802e66bf11f 100644
> > --- a/fs/iomap/direct-io.c
> > +++ b/fs/iomap/direct-io.c
> > @@ -59,7 +59,7 @@ int iomap_dio_iopoll(struct kiocb *kiocb, bool
> > spin)
> >  EXPORT_SYMBOL_GPL(iomap_dio_iopoll);
> >  
> >  static void iomap_dio_submit_bio(struct iomap_dio *dio, struct
> > iomap *iomap,
> > -		struct bio *bio)
> > +		struct bio *bio, loff_t pos)
> >  {
> >  	atomic_inc(&dio->ref);
> >  
> > @@ -67,7 +67,13 @@ static void iomap_dio_submit_bio(struct
> > iomap_dio *dio, struct iomap *iomap,
> >  		bio_set_polled(bio, dio->iocb);
> >  
> >  	dio->submit.last_queue = bdev_get_queue(iomap->bdev);
> > -	dio->submit.cookie = submit_bio(bio);
> > +	if (iomap->page_ops && iomap->page_ops->submit_io) {
> > +		iomap->page_ops->submit_io(bio, file_inode(dio-
> > >iocb->ki_filp),
> > +				pos);
> > +		dio->submit.cookie = BLK_QC_T_NONE;
> > +	} else {
> > +		dio->submit.cookie = submit_bio(bio);
> > +	}
> >  }
> >  
> >  static ssize_t iomap_dio_complete(struct iomap_dio *dio)
> > @@ -195,7 +201,7 @@ iomap_dio_zero(struct iomap_dio *dio, struct
> > iomap *iomap, loff_t pos,
> >  	get_page(page);
> >  	__bio_add_page(bio, page, len, 0);
> >  	bio_set_op_attrs(bio, REQ_OP_WRITE, flags);
> > -	iomap_dio_submit_bio(dio, iomap, bio);
> > +	iomap_dio_submit_bio(dio, iomap, bio, pos);
> >  }
> >  
> >  static loff_t
> > @@ -301,11 +307,11 @@ iomap_dio_bio_actor(struct inode *inode,
> > loff_t pos, loff_t length,
> >  		iov_iter_advance(dio->submit.iter, n);
> >  
> >  		dio->size += n;
> > -		pos += n;
> >  		copied += n;
> >  
> >  		nr_pages = iov_iter_npages(&iter, BIO_MAX_PAGES);
> > -		iomap_dio_submit_bio(dio, iomap, bio);
> > +		iomap_dio_submit_bio(dio, iomap, bio, pos);
> > +		pos += n;
> >  	} while (nr_pages);
> >  
> >  	/*
> > diff --git a/include/linux/iomap.h b/include/linux/iomap.h
> > index 5b2055e8ca8a..6617e4b6fb6d 100644
> > --- a/include/linux/iomap.h
> > +++ b/include/linux/iomap.h
> > @@ -92,6 +92,7 @@ struct iomap_page_ops {
> >  			struct iomap *iomap);
> >  	void (*page_done)(struct inode *inode, loff_t pos,
> > unsigned copied,
> >  			struct page *page, struct iomap *iomap);
> > +	dio_submit_t 		*submit_io;
> >  };
> >  
> >  /*
> > -- 
> > 2.16.4
> > 
> 
>