linux-kernel - [PATCH] befs: add NFS export support

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Message-Id: <20161105124235.22731-1-luisbg@osg.samsung.com>
Date:   Sat,  5 Nov 2016 12:42:35 +0000
From:   Luis de Bethencourt <luisbg@....samsung.com>
To:     linux-kernel@...r.kernel.org
Cc:     akpm@...ux-foundation.org, viro@...iv.linux.org.uk,
        salah.triki@....org, javier@....samsung.com,
        Luis de Bethencourt <luisbg@....samsung.com>
Subject: [PATCH] befs: add NFS export support

Implement mandatory export_operations, so it is possible to export befs via
nfs.

Signed-off-by: Luis de Bethencourt <luisbg@....samsung.com>
---

Hi,

NFS exporting is a very useful feature. I implement here fh_to_dentry because
it is the mandatory member of struct export_operations, and fh_to_parent since
it is easy once you have the previous one and recommended [0].

I can't trigger a call for get_parent, so not adding that one yet.

With this befs via NFS becomes available.

Thanks,
Luis


[0] Documentation/filesystems/nfs/Exporting


 fs/befs/linuxvfs.c | 38 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 38 insertions(+)

diff --git a/fs/befs/linuxvfs.c b/fs/befs/linuxvfs.c
index 8e4e18e..6ff7d01 100644
--- a/fs/befs/linuxvfs.c
+++ b/fs/befs/linuxvfs.c
@@ -18,6 +18,7 @@
 #include <linux/parser.h>
 #include <linux/namei.h>
 #include <linux/sched.h>
+#include <linux/exportfs.h>
 
 #include "befs.h"
 #include "btree.h"
@@ -52,6 +53,10 @@ static void befs_put_super(struct super_block *);
 static int befs_remount(struct super_block *, int *, char *);
 static int befs_statfs(struct dentry *, struct kstatfs *);
 static int parse_options(char *, struct befs_mount_options *);
+static struct dentry *befs_fh_to_dentry(struct super_block *sb,
+				struct fid *fid, int fh_len, int fh_type);
+static struct dentry *befs_fh_to_parent(struct super_block *sb,
+				struct fid *fid, int fh_len, int fh_type);
 
 static const struct super_operations befs_sops = {
 	.alloc_inode	= befs_alloc_inode,	/* allocate a new inode */
@@ -84,6 +89,11 @@ static const struct address_space_operations befs_symlink_aops = {
 	.readpage	= befs_symlink_readpage,
 };
 
+static const struct export_operations befs_export_operations = {
+	.fh_to_dentry	= befs_fh_to_dentry,
+	.fh_to_parent	= befs_fh_to_parent,
+};
+
 /* 
  * Called by generic_file_read() to read a page of data
  * 
@@ -629,6 +639,33 @@ befs_nls2utf(struct super_block *sb, const char *in,
 	return -EILSEQ;
 }
 
+static struct inode *befs_nfs_get_inode(struct super_block *sb, uint64_t ino,
+					 uint32_t generation)
+{
+	/* No need to handle i_generation */
+	return befs_iget(sb, ino);
+}
+
+/*
+ * Map a NFS file handle to a corresponding dentry
+ */
+static struct dentry *befs_fh_to_dentry(struct super_block *sb,
+				struct fid *fid, int fh_len, int fh_type)
+{
+	return generic_fh_to_dentry(sb, fid, fh_len, fh_type,
+				    befs_nfs_get_inode);
+}
+
+/*
+ * Find the parent for a file specified by NFS handle
+ */
+static struct dentry *befs_fh_to_parent(struct super_block *sb,
+				struct fid *fid, int fh_len, int fh_type)
+{
+	return generic_fh_to_parent(sb, fid, fh_len, fh_type,
+				    befs_nfs_get_inode);
+}
+
 enum {
 	Opt_uid, Opt_gid, Opt_charset, Opt_debug, Opt_err,
 };
@@ -829,6 +866,7 @@ befs_fill_super(struct super_block *sb, void *data, int silent)
 	/* Set real blocksize of fs */
 	sb_set_blocksize(sb, (ulong) befs_sb->block_size);
 	sb->s_op = &befs_sops;
+	sb->s_export_op = &befs_export_operations;
 	root = befs_iget(sb, iaddr2blockno(sb, &(befs_sb->root_dir)));
 	if (IS_ERR(root)) {
 		ret = PTR_ERR(root);
-- 
2.10.2