On Tue, 2018-11-20 at 10:19 -0700, Jens Axboe wrote:
> Add an iomap implementation of fops->iopoll() and wire it up for
> XFS.
>
> Signed-off-by: Jens Axboe <ax...@kernel.dk>
> ---
> fs/iomap.c | 50 +++++++++++++++++++++++++++++--------------
> fs/xfs/xfs_file.c | 1 +
> include/linux/iomap.h | 1 +
> 3 files changed, 36 insertions(+), 16 deletions(-)
>
> diff --git a/fs/iomap.c b/fs/iomap.c
> index 74c1f37f0fd6..faf96198f99a 100644
> --- a/fs/iomap.c
> +++ b/fs/iomap.c
> @@ -1419,14 +1419,14 @@ struct iomap_dio {
> unsigned flags;
> int error;
> bool wait_for_completion;
> + blk_qc_t cookie;
> + struct request_queue *last_queue;
>
> union {
> /* used during submission and for synchronous completion: */
> struct {
> struct iov_iter *iter;
> struct task_struct *waiter;
> - struct request_queue *last_queue;
> - blk_qc_t cookie;
> } submit;
>
> /* used for aio completion: */
> @@ -1436,6 +1436,30 @@ struct iomap_dio {
> };
> };
>
> +int iomap_dio_iopoll(struct kiocb *kiocb, bool spin)
> +{
> + struct iomap_dio *dio = kiocb->private;
> + struct request_queue *q = READ_ONCE(dio->last_queue);
> +
> + if (!q || dio->cookie == BLK_QC_T_NONE)
> + return 0;
> + return blk_poll(q, READ_ONCE(dio->cookie), spin);
How about:
blk_qc_t cookie = READ_ONCE(dio->cookie);
if (!q || cookie == BLK_QC_T_NONE)
return 0;
return blk_poll(q, cookie, spin);
Is there a chance the dio->cookie in the if () condition
will be stale?
>
> +}
> +EXPORT_SYMBOL_GPL(iomap_dio_iopoll);
> +
> +static void iomap_dio_submit_bio(struct iomap_dio *dio, struct iomap *iomap,
> + struct bio *bio)
> +{
> + atomic_inc(&dio->ref);
> +
> + /*
> + * iomap_dio_iopoll can race with us. A non-zero last_queue marks that
> + * we are ready to poll.
> + */
> + WRITE_ONCE(dio->cookie, submit_bio(bio));
> + WRITE_ONCE(dio->last_queue, bdev_get_queue(iomap->bdev));
> +}
> +
> static ssize_t iomap_dio_complete(struct iomap_dio *dio)
> {
> struct kiocb *iocb = dio->iocb;
> @@ -1548,7 +1572,7 @@ static void iomap_dio_bio_end_io(struct bio *bio)
> }
> }
>
> -static blk_qc_t
> +static void
> iomap_dio_zero(struct iomap_dio *dio, struct iomap *iomap, loff_t pos,
> unsigned len)
> {
> @@ -1568,9 +1592,7 @@ 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);
> -
> - atomic_inc(&dio->ref);
> - return submit_bio(bio);
> + iomap_dio_submit_bio(dio, iomap, bio);
> }
>
> static loff_t
> @@ -1676,11 +1698,7 @@ iomap_dio_bio_actor(struct inode *inode, loff_t pos,
> loff_t length,
> copied += n;
>
> nr_pages = iov_iter_npages(&iter, BIO_MAX_PAGES);
> -
> - atomic_inc(&dio->ref);
> -
> - dio->submit.last_queue = bdev_get_queue(iomap->bdev);
> - dio->submit.cookie = submit_bio(bio);
> + iomap_dio_submit_bio(dio, iomap, bio);
> } while (nr_pages);
>
> if (need_zeroout) {
> @@ -1782,6 +1800,7 @@ iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
> dio = kmalloc(sizeof(*dio), GFP_KERNEL);
> if (!dio)
> return -ENOMEM;
> + iocb->private = dio;
>
> dio->iocb = iocb;
> atomic_set(&dio->ref, 1);
> @@ -1791,11 +1810,11 @@ iomap_dio_rw(struct kiocb *iocb, struct iov_iter
> *iter,
> dio->error = 0;
> dio->flags = 0;
> dio->wait_for_completion = is_sync_kiocb(iocb);
> + dio->cookie = BLK_QC_T_NONE;
> + dio->last_queue = NULL;
>
> dio->submit.iter = iter;
> dio->submit.waiter = current;
> - dio->submit.cookie = BLK_QC_T_NONE;
> - dio->submit.last_queue = NULL;
>
> if (iov_iter_rw(iter) == READ) {
> if (pos >= dio->i_size)
> @@ -1894,9 +1913,8 @@ iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
> break;
>
> if (!(iocb->ki_flags & IOCB_HIPRI) ||
> - !dio->submit.last_queue ||
> - !blk_poll(dio->submit.last_queue,
> - dio->submit.cookie, true))
> + !dio->last_queue ||
> + !blk_poll(dio->last_queue, dio->cookie, true))
> io_schedule();
> }
> __set_current_state(TASK_RUNNING);
> diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
> index 53c9ab8fb777..603e705781a4 100644
> --- a/fs/xfs/xfs_file.c
> +++ b/fs/xfs/xfs_file.c
> @@ -1203,6 +1203,7 @@ const struct file_operations xfs_file_operations = {
> .write_iter = xfs_file_write_iter,
> .splice_read = generic_file_splice_read,
> .splice_write = iter_file_splice_write,
> + .iopoll = iomap_dio_iopoll,
> .unlocked_ioctl = xfs_file_ioctl,
> #ifdef CONFIG_COMPAT
> .compat_ioctl = xfs_file_compat_ioctl,
> diff --git a/include/linux/iomap.h b/include/linux/iomap.h
> index 9a4258154b25..0fefb5455bda 100644
> --- a/include/linux/iomap.h
> +++ b/include/linux/iomap.h
> @@ -162,6 +162,7 @@ typedef int (iomap_dio_end_io_t)(struct kiocb *iocb,
> ssize_t ret,
> unsigned flags);
> ssize_t iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
> const struct iomap_ops *ops, iomap_dio_end_io_t end_io);
> +int iomap_dio_iopoll(struct kiocb *kiocb, bool spin);
>
> #ifdef CONFIG_SWAP
> struct file;
