[PATCH 3/4] nfs: don't mangle i_version on NFS

["J. Bruce Fields" <bfields@redhat.com>]

From: "J. Bruce Fields" <bfields@redhat.com>

The i_version on NFS has pretty much opaque to the client, so we don't
want to give the low bit any special interpretation.

Define a new FS_PRIVATE_I_VERSION flag for filesystems that manage the
i_version on their own.

Signed-off-by: J. Bruce Fields <bfields@redhat.com>
---
 fs/nfs/export.c          | 1 +
 include/linux/exportfs.h | 1 +
 include/linux/iversion.h | 4 ++++
 3 files changed, 6 insertions(+)

diff --git a/fs/nfs/export.c b/fs/nfs/export.c
index 3430d6891e89..c2eb915a54ca 100644
--- a/fs/nfs/export.c
+++ b/fs/nfs/export.c
@@ -171,4 +171,5 @@ const struct export_operations nfs_export_ops = {
 	.encode_fh = nfs_encode_fh,
 	.fh_to_dentry = nfs_fh_to_dentry,
 	.get_parent = nfs_get_parent,
+	.fetch_iversion = inode_peek_iversion_raw,
 };
diff --git a/include/linux/exportfs.h b/include/linux/exportfs.h
index 3ceb72b67a7a..6000121a201f 100644
--- a/include/linux/exportfs.h
+++ b/include/linux/exportfs.h
@@ -213,6 +213,7 @@ struct export_operations {
 			  bool write, u32 *device_generation);
 	int (*commit_blocks)(struct inode *inode, struct iomap *iomaps,
 			     int nr_iomaps, struct iattr *iattr);
+	u64 (*fetch_iversion)(const struct inode *);
 };
 
 extern int exportfs_encode_inode_fh(struct inode *inode, struct fid *fid,
diff --git a/include/linux/iversion.h b/include/linux/iversion.h
index 2917ef990d43..481b3debf6bb 100644
--- a/include/linux/iversion.h
+++ b/include/linux/iversion.h
@@ -3,6 +3,7 @@
 #define _LINUX_IVERSION_H
 
 #include <linux/fs.h>
+#include <linux/exportfs.h>
 
 /*
  * The inode->i_version field:
@@ -306,6 +307,9 @@ inode_query_iversion(struct inode *inode)
 {
 	u64 cur, old, new;
 
+	if (inode->i_sb->s_export_op->fetch_iversion)
+		return inode->i_sb->s_export_op->fetch_iversion(inode);
+
 	cur = inode_peek_iversion_raw(inode);
 	for (;;) {
 		/* If flag is already set, then no need to swap */
-- 
2.28.0