From a5a87e5b451ded2c7d65c0a53ee3e9e4f32c11f9 Mon Sep 17 00:00:00 2001
From: Rich Ercolani <rincebrain@gmail.com>
Date: Fri, 14 Jan 2022 05:07:33 -0500
Subject: [PATCH] Linux 5.16 compat: Added mapping for
 iov_iter_fault_in_readable

Linux decided to rename this for some reason. At some point, we
should probably invert this mapping, but for now...

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Coleman Kane <ckane@colemankane.org>
Signed-off-by: Rich Ercolani <rincebrain@gmail.com>
Closes #12975
(cherry picked from commit 299fbf75ecf302e790908d8098a8cd215125a6b5)
Signed-off-by: Jonathon Fernyhough <jonathon@m2x.dev>
---
 config/kernel-add-disk.m4      |  1 -
 config/kernel-vfs-iov_iter.m4  | 22 ++++++++++++++++++++--
 include/os/linux/spl/sys/uio.h |  4 ++++
 3 files changed, 24 insertions(+), 3 deletions(-)

diff --git a/config/kernel-add-disk.m4 b/config/kernel-add-disk.m4
index 3bc40f1e7d21..5d1779eb4328 100644
--- a/config/kernel-add-disk.m4
+++ b/config/kernel-add-disk.m4
@@ -13,7 +13,6 @@ AC_DEFUN([ZFS_AC_KERNEL_SRC_ADD_DISK], [
 	])
 
 ])
-
 AC_DEFUN([ZFS_AC_KERNEL_ADD_DISK], [
 	AC_MSG_CHECKING([whether add_disk() returns int])
 	ZFS_LINUX_TEST_RESULT([add_disk_ret],
diff --git a/config/kernel-vfs-iov_iter.m4 b/config/kernel-vfs-iov_iter.m4
index ecdda939f1cf..57f78745a24b 100644
--- a/config/kernel-vfs-iov_iter.m4
+++ b/config/kernel-vfs-iov_iter.m4
@@ -41,6 +41,17 @@ AC_DEFUN([ZFS_AC_KERNEL_SRC_VFS_IOV_ITER], [
 		error = iov_iter_fault_in_readable(&iter, size);
 	])
 
+	ZFS_LINUX_TEST_SRC([fault_in_iov_iter_readable], [
+		#include <linux/fs.h>
+		#include <linux/uio.h>
+	],[
+		struct iov_iter iter = { 0 };
+		size_t size = 512;
+		int error __attribute__ ((unused));
+
+		error = fault_in_iov_iter_readable(&iter, size);
+	])
+
 	ZFS_LINUX_TEST_SRC([iov_iter_count], [
 		#include <linux/fs.h>
 		#include <linux/uio.h>
@@ -123,8 +134,15 @@ AC_DEFUN([ZFS_AC_KERNEL_VFS_IOV_ITER], [
 		AC_DEFINE(HAVE_IOV_ITER_FAULT_IN_READABLE, 1,
 		    [iov_iter_fault_in_readable() is available])
 	],[
-		AC_MSG_RESULT(no)
-		enable_vfs_iov_iter="no"
+		AC_MSG_CHECKING([whether fault_in_iov_iter_readable() is available])
+		ZFS_LINUX_TEST_RESULT([fault_in_iov_iter_readable], [
+			AC_MSG_RESULT(yes)
+			AC_DEFINE(HAVE_FAULT_IN_IOV_ITER_READABLE, 1,
+			    [fault_in_iov_iter_readable() is available])
+		],[
+			AC_MSG_RESULT(no)
+			enable_vfs_iov_iter="no"
+		])
 	])
 
 	AC_MSG_CHECKING([whether iov_iter_count() is available])
diff --git a/include/os/linux/spl/sys/uio.h b/include/os/linux/spl/sys/uio.h
index 66af2b0b534c..439eec986236 100644
--- a/include/os/linux/spl/sys/uio.h
+++ b/include/os/linux/spl/sys/uio.h
@@ -34,6 +34,10 @@
 #include <asm/uaccess.h>
 #include <sys/types.h>
 
+#if defined(HAVE_VFS_IOV_ITER) && defined(HAVE_FAULT_IN_IOV_ITER_READABLE)
+#define	iov_iter_fault_in_readable(a, b)	fault_in_iov_iter_readable(a, b)
+#endif
+
 typedef struct iovec iovec_t;
 
 typedef enum zfs_uio_rw {