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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>, Matthew Wilcox <willy@infradead.org>,
	cluster-devel@redhat.com, linux-fsdevel@vger.kernel.org,
	linux-kernel@vger.kernel.org, ocfs2-devel@oss.oracle.com,
	Andreas Gruenbacher <agruenba@redhat.com>
Subject: [PATCH v4 6/8] iomap: Support restarting direct I/O requests after user copy failures
Date: Sat, 24 Jul 2021 21:34:47 +0200	[thread overview]
Message-ID: <20210724193449.361667-7-agruenba@redhat.com> (raw)
In-Reply-To: <20210724193449.361667-1-agruenba@redhat.com>

In iomap_dio_rw, when iomap_apply returns an -EFAULT error, complete the
request synchronously.  Either return a partial result (when the
IOMAP_DIO_FAULT_RETRY flag is set and the caller is thus prepared to handle
partial results), or reset the iterator to the start to allow a restart.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
---
 fs/iomap/direct-io.c  | 13 +++++++++++++
 include/linux/iomap.h |  7 +++++++
 2 files changed, 20 insertions(+)

diff --git a/fs/iomap/direct-io.c b/fs/iomap/direct-io.c
index 51831ce93f6e..1ba825bab08b 100644
--- a/fs/iomap/direct-io.c
+++ b/fs/iomap/direct-io.c
@@ -565,6 +565,19 @@ __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) {
+				/*
+				 * Finish synchronously and revert the iterator
+				 * when failing the request to allow a retry.
+				 */
+				wait_for_completion = true;
+				if (dio->size &&
+				    (dio_flags & IOMAP_DIO_FAULT_RETRY))
+					ret = 0;
+				else
+					iov_iter_revert(iter, dio->size);
+			}
+
 			/* 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 8aea35f1a003..9dbba9f7c945 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_FAULT_RETRY		(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, size_t done_before);
-- 
2.26.3


  parent reply	other threads:[~2021-07-24 19:35 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-24 19:34 [PATCH v4 0/8] gfs2: Fix mmap + page fault deadlocks Andreas Gruenbacher
2021-07-24 19:34 ` [PATCH v4 1/8] iov_iter: Introduce iov_iter_fault_in_writeable helper Andreas Gruenbacher
2021-07-24 19:52   ` Linus Torvalds
2021-07-24 20:24     ` Al Viro
2021-07-24 20:37       ` Linus Torvalds
2021-07-24 21:38       ` Andreas Gruenbacher
2021-07-24 21:57         ` Al Viro
2021-07-24 22:06           ` Andreas Gruenbacher
2021-07-24 23:39             ` Al Viro
2021-07-27  9:30     ` David Laight
2021-07-27 11:13       ` Andreas Gruenbacher
2021-07-27 17:51         ` Linus Torvalds
2021-07-24 19:34 ` [PATCH v4 2/8] gfs2: Add wrapper for iomap_file_buffered_write Andreas Gruenbacher
2021-07-24 19:34 ` [PATCH v4 3/8] gfs2: Fix mmap + page fault deadlocks for buffered I/O Andreas Gruenbacher
2021-07-24 19:34 ` [PATCH v4 4/8] iomap: Fix iomap_dio_rw return value for user copies Andreas Gruenbacher
2021-07-24 19:34 ` [PATCH v4 5/8] iomap: Add done_before argument to iomap_dio_rw Andreas Gruenbacher
2021-07-24 19:34 ` Andreas Gruenbacher [this message]
2021-07-24 19:34 ` [PATCH v4 7/8] iov_iter: Introduce noio flag to disable page faults Andreas Gruenbacher
2021-07-24 19:34 ` [PATCH v4 8/8] gfs2: Fix mmap + page fault deadlocks for direct I/O Andreas Gruenbacher

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