Commit 97308f8b authored by Andreas Gruenbacher's avatar Andreas Gruenbacher
Browse files

iomap: Support partial direct I/O on user copy failures 



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: default avatarAndreas Gruenbacher <agruenba@redhat.com>
Reviewed-by: default avatarDarrick J. Wong <djwong@kernel.org>
parent 42c498c1

fs/iomap/direct-io.c

+6 −0
Original line number Diff line number Diff line
@@ -581,6 +581,12 @@ __iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter, 
	if (iov_iter_rw(iter) == READ && iomi.pos >= dio->i_size)

		iov_iter_revert(iter, iomi.pos - dio->i_size);



	if (ret == -EFAULT && dio->size && (dio_flags & IOMAP_DIO_PARTIAL)) {

		if (!(iocb->ki_flags & IOCB_NOWAIT))

			wait_for_completion = true;

		ret = 0;

	}



	/* magic error code to fall back to buffered I/O */

	if (ret == -ENOTBLK) {

		wait_for_completion = true;

include/linux/iomap.h

+7 −0
Original line number Diff line number Diff line
@@ -330,6 +330,13 @@ 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);