Re: [PATCH v7 15/19] iomap: Support partial direct I/O on user copy failures
From: "Darrick J. Wong" <djwong@kernel.org>
Date: 2021-09-03 18:54:35
Also in:
lkml, ocfs2-devel
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@redhat.com>
Pretty straightforward. Reviewed-by: Darrick J. Wong <djwong@kernel.org> --D
quoted hunk ↗ jump to hunk
--- 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