Fix mmap / libaio deadlock

Calling uiomove() in mappedread() under the page lock can result
in a deadlock if the user space page needs to be faulted in.

Resolve the issue by dropping the page lock before the uiomove().
The inode range lock protects against concurrent updates via
zfs_read() and zfs_write().

Reviewed-by: Albert Lee <[email protected]>
Reviewed-by: Chunwei Chen <[email protected]>
Signed-off-by: Brian Behlendorf <[email protected]>
Closes #7335 
Closes #7339 

4 files changed, 99 insertions, 0 deletions

diff --git a/tests/zfs-tests/cmd/Makefile.am b/tests/zfs-tests/cmd/Makefile.am
index bc19f184c..0673fcbf6 100644
--- a/tests/zfs-tests/cmd/Makefile.am
+++ b/tests/zfs-tests/cmd/Makefile.am
@@ -14,6 +14,7 @@ SUBDIRS = \
 	mkfiles \
 	mktree \
 	mmap_exec \
+	mmap_libaio \
 	mmapwrite \
 	nvlist_to_lua \
 	randfree_file \
diff --git a/tests/zfs-tests/cmd/mmap_libaio/.gitignore b/tests/zfs-tests/cmd/mmap_libaio/.gitignore
new file mode 100644
index 000000000..792c8d340
--- /dev/null
+++ b/tests/zfs-tests/cmd/mmap_libaio/.gitignore
@@ -0,0 +1 @@
+/mmap_libaio
diff --git a/tests/zfs-tests/cmd/mmap_libaio/Makefile.am b/tests/zfs-tests/cmd/mmap_libaio/Makefile.am
new file mode 100644
index 000000000..67d0f0ece
--- /dev/null
+++ b/tests/zfs-tests/cmd/mmap_libaio/Makefile.am
@@ -0,0 +1,9 @@
+include $(top_srcdir)/config/Rules.am
+
+pkgexecdir = $(datadir)/@PACKAGE@/zfs-tests/bin
+
+if WANT_MMAP_LIBAIO
+pkgexec_PROGRAMS = mmap_libaio
+mmap_libaio_SOURCES = mmap_libaio.c
+mmap_libaio_LDADD = $(LIBAIO)
+endif
diff --git a/tests/zfs-tests/cmd/mmap_libaio/mmap_libaio.c b/tests/zfs-tests/cmd/mmap_libaio/mmap_libaio.c
new file mode 100644
index 000000000..21119ebca
--- /dev/null
+++ b/tests/zfs-tests/cmd/mmap_libaio/mmap_libaio.c
@@ -0,0 +1,88 @@
+/*
+ * CDDL HEADER START
+ *
+ * The contents of this file are subject to the terms of the
+ * Common Development and Distribution License (the "License").
+ * You may not use this file except in compliance with the License.
+ *
+ * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
+ * or http://www.opensolaris.org/os/licensing.
+ * See the License for the specific language governing permissions
+ * and limitations under the License.
+ *
+ * When distributing Covered Code, include this CDDL HEADER in each
+ * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
+ * If applicable, add the following below this CDDL HEADER, with the
+ * fields enclosed by brackets "[]" replaced with your own identifying
+ * information: Portions Copyright [yyyy] [name of copyright owner]
+ *
+ * CDDL HEADER END
+ */
+
+/*
+ * Copyright 2018 Canonical.  All rights reserved.
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <sys/mman.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <libaio.h>
+#include <err.h>
+
+io_context_t io_ctx;
+
+static void
+do_sync_io(struct iocb *iocb)
+{
+	struct io_event event;
+	struct iocb *iocbs[] = { iocb };
+	struct timespec ts = { 30, 0 };
+
+	if (io_submit(io_ctx, 1, iocbs) != 1)
+		err(1, "io_submit failed");
+
+	if (io_getevents(io_ctx, 0, 1, &event, &ts) != 1)
+		err(1, "io_getevents failed");
+}
+
+int
+main(int argc, char **argv)
+{
+	char *buf;
+	int page_size = getpagesize();
+	int buf_size = strtol(argv[2], NULL, 0);
+	int rwfd;
+	struct iocb iocb;
+
+	if (io_queue_init(1024, &io_ctx))
+		err(1, "io_queue_init failed");
+
+	rwfd = open(argv[1], O_RDWR | O_CREAT, S_IRUSR | S_IWUSR);
+	if (rwfd < 0)
+		err(1, "open failed");
+
+	if (ftruncate(rwfd, buf_size) < 0)
+		err(1, "ftruncate failed");
+
+	buf = mmap(0, page_size, PROT_READ | PROT_WRITE, MAP_SHARED, rwfd, 0);
+	if (buf == MAP_FAILED)
+		err(1, "mmap failed");
+
+	(void) io_prep_pwrite(&iocb, rwfd, buf, buf_size, 0);
+	do_sync_io(&iocb);
+
+	(void) io_prep_pread(&iocb, rwfd, buf, buf_size, 0);
+	do_sync_io(&iocb);
+
+	if (close(rwfd))
+		err(1, "close failed");
+
+	if (io_queue_release(io_ctx) != 0)
+		err(1, "io_queue_release failed");
+
+	return (0);
+}