On Thu, Dec 12, 2024 at 08:29:36AM -0500, Brian Foster wrote:
> > + bool should_dirty = (dio->flags & IOMAP_DIO_DIRTY);
> > + struct kiocb *iocb = dio->iocb;
> > + u32 vec_count = ioend->io_bio.bi_vcnt;
> > +
> > + if (ioend->io_error)
> > + iomap_dio_set_error(dio, ioend->io_error);
> > +
> > + if (atomic_dec_and_test(&dio->ref)) {
> > + struct inode *inode = file_inode(iocb->ki_filp);
> > +
> > + if (dio->wait_for_completion) {
> > + struct task_struct *waiter = dio->submit.waiter;
> > +
> > + WRITE_ONCE(dio->submit.waiter, NULL);
> > + blk_wake_io_task(waiter);
> > + } else if (!inode->i_mapping->nrpages) {
> > + WRITE_ONCE(iocb->private, NULL);
> > +
> > + /*
> > + * We must never invalidate pages from this thread to
> > + * avoid deadlocks with buffered I/O completions.
> > + * Tough luck if you hit the tiny race with someone
> > + * dirtying the range now.
> > + */
> > + dio->flags |= IOMAP_DIO_NO_INVALIDATE;
> > + iomap_dio_complete_work(&dio->aio.work);
> > + } else {
> > + INIT_WORK(&dio->aio.work, iomap_dio_complete_work);
> > + queue_work(inode->i_sb->s_dio_done_wq, &dio->aio.work);
> > + }
> > + }
> > +
> > + if (should_dirty) {
> > + bio_check_pages_dirty(&ioend->io_bio);
> > + } else {
> > + bio_release_pages(&ioend->io_bio, false);
> > + bio_put(&ioend->io_bio);
> > + }
> > +
>
> Not that it matters all that much, but I'm a little curious about the
> reasoning for using vec_count here. AFAICS this correlates to per-folio
> writeback completions for buffered I/O, but that doesn't seem to apply
> to direct I/O. Is there a reason to have the caller throttle based on
> vec_counts, or are we just pulling some non-zero value for consistency
> sake?
So direct I/O also iterates over all folios for the bio, to unpin,
and in case of reads dirty all of them.
I wanted to plug something useful into cond_resched condition in the
caller. Now number of bvecs isn't the number of folios as we can
physically merge outside the folio context, but I think this is about
as goot as it gets without changing the block code to return the
number of folios processed from __bio_release_pages and
bio_check_pages_dirty.
