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From: Andreas Gruenbacher <agruenba@redhat.com>
To: Linus Torvalds <torvalds@linux-foundation.org>,
	Alexander Viro <viro@zeniv.linux.org.uk>,
	Christoph Hellwig <hch@infradead.org>,
	"Darrick J. Wong" <djwong@kernel.org>
Cc: Jan Kara <jack@suse.cz>,
	Andreas Gruenbacher <agruenba@redhat.com>,
	linux-kernel@vger.kernel.org, cluster-devel@redhat.com,
	linux-fsdevel@vger.kernel.org, ocfs2-devel@oss.oracle.com
Subject: [Ocfs2-devel] [PATCH v6 14/19] iomap: Support partial direct I/O on user copy failures
Date: Thu, 19 Aug 2021 21:40:57 +0200	[thread overview]
Message-ID: <20210819194102.1491495-15-agruenba@redhat.com> (raw)
In-Reply-To: <20210819194102.1491495-1-agruenba@redhat.com>

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>
---
 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


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  parent reply	other threads:[~2021-08-19 19:42 UTC|newest]

Thread overview: 33+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-19 19:40 [Ocfs2-devel] [PATCH v6 00/19] gfs2: Fix mmap + page fault deadlocks Andreas Gruenbacher
2021-08-19 19:40 ` [Ocfs2-devel] [PATCH v6 01/19] iov_iter: Fix iov_iter_get_pages{, _alloc} page fault return value Andreas Gruenbacher
2021-08-19 19:40 ` [Ocfs2-devel] [PATCH v6 02/19] powerpc/kvm: Fix kvm_use_magic_page Andreas Gruenbacher
2021-08-19 19:40 ` [Ocfs2-devel] [PATCH v6 03/19] Turn fault_in_pages_{readable, writeable} into fault_in_{readable, writeable} Andreas Gruenbacher
2021-08-19 19:40 ` [Ocfs2-devel] [PATCH v6 04/19] Turn iov_iter_fault_in_readable into fault_in_iov_iter_readable Andreas Gruenbacher
2021-08-19 19:40 ` [Ocfs2-devel] [PATCH v6 05/19] iov_iter: Introduce fault_in_iov_iter_writeable Andreas Gruenbacher
2021-08-19 19:40 ` [Ocfs2-devel] [PATCH v6 06/19] gfs2: Add wrapper for iomap_file_buffered_write Andreas Gruenbacher
2021-08-19 19:40 ` [Ocfs2-devel] [PATCH v6 07/19] gfs2: Clean up function may_grant Andreas Gruenbacher
2021-08-19 19:40 ` [Ocfs2-devel] [PATCH v6 08/19] gfs2: Eliminate vestigial HIF_FIRST Andreas Gruenbacher
2021-08-19 19:40 ` [Ocfs2-devel] [PATCH v6 09/19] gfs2: Remove redundant check from gfs2_glock_dq Andreas Gruenbacher
2021-08-19 19:40 ` [Ocfs2-devel] [PATCH v6 10/19] gfs2: Introduce flag for glock holder auto-demotion Andreas Gruenbacher
2021-08-20  9:35   ` [Ocfs2-devel] [Cluster-devel] " Steven Whitehouse
2021-08-20 13:11     ` Bob Peterson
2021-08-20 13:41       ` Steven Whitehouse
2021-08-20 15:22       ` Andreas Gruenbacher
2021-08-23  8:14         ` Steven Whitehouse
2021-08-23 15:18           ` Andreas Gruenbacher
2021-08-23 16:05             ` Matthew Wilcox
2021-08-23 16:36               ` Bob Peterson
2021-08-23 19:12               ` Andreas Gruenbacher
2021-08-24  7:59             ` Steven Whitehouse
2021-08-20 13:17     ` Andreas Gruenbacher
2021-08-20 13:47       ` Steven Whitehouse
2021-08-20 14:43         ` Andreas Grünbacher
2021-08-19 19:40 ` [Ocfs2-devel] [PATCH v6 11/19] gfs2: Move the inode glock locking to gfs2_file_buffered_write Andreas Gruenbacher
2021-08-19 19:40 ` [Ocfs2-devel] [PATCH v6 12/19] gfs2: Fix mmap + page fault deadlocks for buffered I/O Andreas Gruenbacher
2021-08-19 19:40 ` [Ocfs2-devel] [PATCH v6 13/19] iomap: Fix iomap_dio_rw return value for user copies Andreas Gruenbacher
2021-08-19 19:40 ` Andreas Gruenbacher [this message]
2021-08-19 19:40 ` [Ocfs2-devel] [PATCH v6 15/19] iomap: Add done_before argument to iomap_dio_rw Andreas Gruenbacher
2021-08-19 19:40 ` [Ocfs2-devel] [PATCH v6 16/19] gup: Introduce FOLL_NOFAULT flag to disable page faults Andreas Gruenbacher
2021-08-19 19:41 ` [Ocfs2-devel] [PATCH v6 17/19] iov_iter: Introduce nofault " Andreas Gruenbacher
2021-08-19 19:41 ` [Ocfs2-devel] [PATCH v6 18/19] gfs2: Fix mmap + page fault deadlocks for direct I/O Andreas Gruenbacher
2021-08-19 19:41 ` [Ocfs2-devel] [PATCH v6 19/19] gfs2: Eliminate ip->i_gh Andreas Gruenbacher

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