From 393b44c7112854fc11dc97885a87f666780cc9fe Mon Sep 17 00:00:00 2001
From: Cyril Plisko <cyril.plisko@mountall.com>
Date: Sun, 16 Sep 2012 09:03:04 +0300
Subject: [PATCH] Implement .commit_metadata hook for NFS export

In order to implement synchronous NFS metadata semantics ZFS
needs to provide the .commit_metadata hook.  All it takes there
is to make sure changes are committed to ZIL.  Fortunately
zfs_fsync() does just that, so simply calling it from
zpl_commit_metadata() does the trick.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #969
---
 config/kernel-commit-metadata.m4 | 23 +++++++++++++++++++++++
 config/kernel.m4                 |  1 +
 module/zfs/zpl_export.c          | 22 +++++++++++++++++++++-
 3 files changed, 45 insertions(+), 1 deletion(-)
 create mode 100644 config/kernel-commit-metadata.m4

diff --git a/config/kernel-commit-metadata.m4 b/config/kernel-commit-metadata.m4
new file mode 100644
index 000000000..b66a16fd2
--- /dev/null
+++ b/config/kernel-commit-metadata.m4
@@ -0,0 +1,23 @@
+dnl #
+dnl # 2.6.33 API change
+dnl # Added eops->commit_metadata() callback to allow the underlying
+dnl # filesystem to determine the most efficient way to commit the inode.
+dnl # Prior to this the nfs server would issue an explicit fsync().
+dnl #
+AC_DEFUN([ZFS_AC_KERNEL_COMMIT_METADATA], [
+	AC_MSG_CHECKING([whether eops->commit_metadata() exists])
+	ZFS_LINUX_TRY_COMPILE([
+		#include <linux/exportfs.h>
+		int commit_metadata(struct inode *inode) { return 0; }
+		static struct export_operations eops __attribute__ ((unused))={
+			.commit_metadata = commit_metadata,
+		};
+	],[
+	],[
+		AC_MSG_RESULT(yes)
+		AC_DEFINE(HAVE_COMMIT_METADATA, 1,
+		          [eops->commit_metadata() exists])
+	],[
+		AC_MSG_RESULT(no)
+	])
+])
diff --git a/config/kernel.m4 b/config/kernel.m4
index d10c6e628..262dc7fcb 100644
--- a/config/kernel.m4
+++ b/config/kernel.m4
@@ -53,6 +53,7 @@ AC_DEFUN([ZFS_AC_CONFIG_KERNEL], [
 	ZFS_AC_KERNEL_CREATE_UMODE_T
 	ZFS_AC_KERNEL_AUTOMOUNT
 	ZFS_AC_KERNEL_ENCODE_FH_WITH_INODE
+	ZFS_AC_KERNEL_COMMIT_METADATA
 	ZFS_AC_KERNEL_CLEAR_INODE
 	ZFS_AC_KERNEL_INSERT_INODE_LOCKED
 	ZFS_AC_KERNEL_D_MAKE_ROOT
diff --git a/module/zfs/zpl_export.c b/module/zfs/zpl_export.c
index 395c5584c..94625e13c 100644
--- a/module/zfs/zpl_export.c
+++ b/module/zfs/zpl_export.c
@@ -20,6 +20,7 @@
  */
 /*
  * Copyright (c) 2011 Gunnar Beutner
+ * Copyright (c) 2012 Cyril Plisko. All rights reserved.
  */
 
 
@@ -121,8 +122,27 @@ zpl_get_parent(struct dentry *child)
 	return zpl_dentry_obtain_alias(ip);
 }
 
+#ifdef HAVE_COMMIT_METADATA
+static int
+zpl_commit_metadata(struct inode *inode)
+{
+	cred_t *cr = CRED();
+	int error;
+
+	crhold(cr);
+	error = -zfs_fsync(inode, 0, cr);
+	crfree(cr);
+	ASSERT3S(error, <=, 0);
+
+	return error;
+}
+#endif /* HAVE_COMMIT_METADATA */
+
 const struct export_operations zpl_export_operations = {
 	.encode_fh	= zpl_encode_fh,
 	.fh_to_dentry	= zpl_fh_to_dentry,
-	.get_parent	= zpl_get_parent
+	.get_parent	= zpl_get_parent,
+#ifdef HAVE_COMMIT_METADATA
+	.commit_metadata= zpl_commit_metadata,
+#endif /* HAVE_COMMIT_METADATA */
 };