On Fri, Aug 27, 2021 at 06:49:22PM +0200, Andreas Gruenbacher wrote:
> In iomap_dio_rw, when iomap_apply returns an -EFAULT error and the
> IOMAP_DIO_PARTIAL flag is set, complete the request synchronously and
> return a partial result. This allows the caller to deal with the page
> fault and retry the remainder of the request.
>
> Signed-off-by: Andreas Gruenbacher <agruenba@xxxxxxxxxx>
Pretty straightforward.
Reviewed-by: Darrick J. Wong <djwong@xxxxxxxxxx>
--D
> ---
> fs/iomap/direct-io.c | 6 ++++++
> include/linux/iomap.h | 7 +++++++
> 2 files changed, 13 insertions(+)
>
> diff --git a/fs/iomap/direct-io.c b/fs/iomap/direct-io.c
> index 8054f5d6c273..ba88fe51b77a 100644
> --- a/fs/iomap/direct-io.c
> +++ b/fs/iomap/direct-io.c
> @@ -561,6 +561,12 @@ __iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
> ret = iomap_apply(inode, pos, count, iomap_flags, ops, dio,
> iomap_dio_actor);
> if (ret <= 0) {
> + if (ret == -EFAULT && dio->size &&
> + (dio_flags & IOMAP_DIO_PARTIAL)) {
> + wait_for_completion = true;
> + ret = 0;
> + }
> +
> /* magic error code to fall back to buffered I/O */
> if (ret == -ENOTBLK) {
> wait_for_completion = true;
> diff --git a/include/linux/iomap.h b/include/linux/iomap.h
> index 479c1da3e221..bcae4814b8e3 100644
> --- a/include/linux/iomap.h
> +++ b/include/linux/iomap.h
> @@ -267,6 +267,13 @@ struct iomap_dio_ops {
> */
> #define IOMAP_DIO_OVERWRITE_ONLY (1 << 1)
>
> +/*
> + * When a page fault occurs, return a partial synchronous result and allow
> + * the caller to retry the rest of the operation after dealing with the page
> + * fault.
> + */
> +#define IOMAP_DIO_PARTIAL (1 << 2)
> +
> ssize_t iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
> const struct iomap_ops *ops, const struct iomap_dio_ops *dops,
> unsigned int dio_flags);
> --
> 2.26.3
>
