knfsd: exportfs: add procedural interface for NFSD

Currently NFSD calls directly into filesystems through the export_operations
structure.  I plan to change this interface in various ways in later patches,
and want to avoid the export of the default operations to NFSD, so this patch
adds two simple exportfs_encode_fh/exportfs_decode_fh helpers for NFSD to call
instead of poking into exportfs guts.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/exportfs/expfs.c

@@ -3,6 +3,7 @@
 #include <linux/fs.h>
 #include <linux/file.h>
 #include <linux/module.h>
+#include <linux/mount.h>
 #include <linux/namei.h>
 
 struct export_operations export_op_default;
@@ -468,6 +469,26 @@ static struct dentry *export_decode_fh(struct super_block *sb, __u32 *fh, int fh
 				   acceptable, context);
 }
 
+int exportfs_encode_fh(struct dentry *dentry, __u32 *fh, int *max_len,
+		int connectable)
+{
+	struct export_operations *nop = dentry->d_sb->s_export_op;
+
+	return CALL(nop, encode_fh)(dentry, fh, max_len, connectable);
+}
+EXPORT_SYMBOL_GPL(exportfs_encode_fh);
+
+struct dentry *exportfs_decode_fh(struct vfsmount *mnt, __u32 *fh, int fh_len,
+		int fileid_type, int (*acceptable)(void *, struct dentry *),
+		void *context)
+{
+	struct export_operations *nop = mnt->mnt_sb->s_export_op;
+
+	return CALL(nop, decode_fh)(mnt->mnt_sb, fh, fh_len, fileid_type,
+			acceptable, context);
+}
+EXPORT_SYMBOL_GPL(exportfs_decode_fh);
+
 struct export_operations export_op_default = {
 	.decode_fh	= export_decode_fh,
 	.encode_fh	= export_encode_fh,
@@ -477,7 +498,6 @@ struct export_operations export_op_default = {
 	.get_dentry	= get_dentry,
 };
 
-EXPORT_SYMBOL(export_op_default);
 EXPORT_SYMBOL(find_exported_dentry);
 
 MODULE_LICENSE("GPL");

fs/nfsd/nfsfh.c

@@ -28,10 +28,6 @@
 static int nfsd_nr_verified;
 static int nfsd_nr_put;
 
-extern struct export_operations export_op_default;
-
-#define	CALL(ops,fun) ((ops->fun)?(ops->fun):export_op_default.fun)
-
 /*
  * our acceptability function.
  * if NOSUBTREECHECK, accept anything
@@ -212,10 +208,8 @@ fh_verify(struct svc_rqst *rqstp, struct svc_fh *fhp, int type, int access)
 		if (fileid_type == 0)
 			dentry = dget(exp->ex_dentry);
 		else {
-			struct export_operations *nop = exp->ex_mnt->mnt_sb->s_export_op;
-			dentry = CALL(nop,decode_fh)(exp->ex_mnt->mnt_sb,
-						     datap, data_left,
-						     fileid_type,
+			dentry = exportfs_decode_fh(exp->ex_mnt, datap,
+					data_left, fileid_type,
 					nfsd_acceptable, exp);
 		}
 		if (dentry == NULL)
@@ -287,15 +281,13 @@ fh_verify(struct svc_rqst *rqstp, struct svc_fh *fhp, int type, int access)
 static inline int _fh_update(struct dentry *dentry, struct svc_export *exp,
 			     __u32 *datap, int *maxsize)
 {
-	struct export_operations *nop = exp->ex_mnt->mnt_sb->s_export_op;
-
 	if (dentry == exp->ex_dentry) {
 		*maxsize = 0;
 		return 0;
 	}
 
-	return CALL(nop,encode_fh)(dentry, datap, maxsize,
-			  !(exp->ex_flags&NFSEXP_NOSUBTREECHECK));
+	return exportfs_encode_fh(dentry, datap, maxsize,
+			  !(exp->ex_flags & NFSEXP_NOSUBTREECHECK));
 }
 
 /*

include/linux/exportfs.h

@@ -5,6 +5,7 @@
 
 struct dentry;
 struct super_block;
+struct vfsmount;
 
 
 /**
@@ -116,4 +117,10 @@ extern struct dentry *find_exported_dentry(struct super_block *sb, void *obj,
 	void *parent, int (*acceptable)(void *context, struct dentry *de),
 	void *context);
 
+extern int exportfs_encode_fh(struct dentry *dentry, __u32 *fh, int *max_len,
+	int connectable);
+extern struct dentry *exportfs_decode_fh(struct vfsmount *mnt, __u32 *fh,
+	int fh_len, int fileid_type, int (*acceptable)(void *, struct dentry *),
+	void *context);
+
 #endif /* LINUX_EXPORTFS_H */