On Sat, Mar 28, 2020 at 01:50:12AM +0900, Johannes Thumshirn wrote:
> Synchronous direct I/O to a sequential write only zone can be issued using
> the new REQ_OP_ZONE_APPEND request operation. As dispatching multiple
> BIOs can potentially result in reordering, we cannot support asynchronous
> IO via this interface.
We trivially can if the write size is smaller than the supported zone
append size. We could slightly less trivially by chaining a new
submission after the first bio completes.
> +static void zonefs_zone_append_bio_endio(struct bio *bio)
> +{
> + struct task_struct *waiter = bio->bi_private;
> +
> + WRITE_ONCE(bio->bi_private, NULL);
> + blk_wake_io_task(waiter);
> +
> + bio_release_pages(bio, false);
> + bio_put(bio);
> +}
> +
> +static ssize_t zonefs_file_dio_append(struct kiocb *iocb, struct iov_iter *from)
> +{
> + struct inode *inode = file_inode(iocb->ki_filp);
> + struct zonefs_inode_info *zi = ZONEFS_I(inode);
> + struct block_device *bdev = inode->i_sb->s_bdev;
> + ssize_t ret = 0;
> + ssize_t size;
> + struct bio *bio;
> + unsigned max;
> + int nr_pages;
> + blk_qc_t qc;
> +
> + nr_pages = iov_iter_npages(from, BIO_MAX_PAGES);
> + if (!nr_pages)
> + return 0;
> +
> + max = queue_max_zone_append_sectors(bdev_get_queue(bdev)) << 9;
> + max = ALIGN_DOWN(max, inode->i_sb->s_blocksize);
> + iov_iter_truncate(from, max);
> +
> + bio = bio_alloc_bioset(GFP_NOFS, nr_pages, &fs_bio_set);
> + if (!bio)
> + return -ENOMEM;
> +
> + bio_set_dev(bio, bdev);
> + bio->bi_iter.bi_sector = zi->i_zsector;
> + bio->bi_write_hint = iocb->ki_hint;
> + bio->bi_private = current;
> + bio->bi_end_io = zonefs_zone_append_bio_endio;
> + bio->bi_ioprio = iocb->ki_ioprio;
> + bio->bi_opf = REQ_OP_ZONE_APPEND | REQ_SYNC | REQ_IDLE;
> + if (iocb->ki_flags & IOCB_DSYNC)
> + bio->bi_opf |= REQ_FUA;
> +
> + ret = bio_iov_iter_get_pages(bio, from);
> + if (unlikely(ret)) {
> + bio->bi_status = BLK_STS_IOERR;
> + bio_endio(bio);
> + return ret;
> + }
> + size = bio->bi_iter.bi_size;
> + task_io_account_write(ret);
> +
> + if (iocb->ki_flags & IOCB_HIPRI)
> + bio_set_polled(bio, iocb);
> +
> + bio_get(bio);
> + qc = submit_bio(bio);
> + for (;;) {
> + set_current_state(TASK_UNINTERRUPTIBLE);
> + if (!READ_ONCE(bio->bi_private))
> + break;
> + if (!(iocb->ki_flags & IOCB_HIPRI) ||
> + !blk_poll(bdev_get_queue(bdev), qc, true))
> + io_schedule();
> + }
> + __set_current_state(TASK_RUNNING);
> +
> + if (unlikely(bio->bi_status))
> + ret = blk_status_to_errno(bio->bi_status);
> +
> + bio_put(bio);
> +
> + zonefs_file_write_dio_end_io(iocb, size, ret, 0);
> + if (ret >= 0) {
> + iocb->ki_pos += size;
> + return size;
> + }
> +
> + return ret;
This looks like no one waits for I/O completion? Also it looks
like it silently causes a short write, which probably needs to be
documented..
