[PATCH] Add basic export support to HFS+.

["Diego Elio 'Flameeyes' Pettenò" <flameeyes@gmail.com>]

From: Diego E. 'Flameeyes' Pettenò <flameeyes@gmail.com>

The functions' skeleton is taken from ext2/super.c and seems to work
fine for R/W access to HFS+ non-journaled case-sensitive filesystems.

It's probably slow and has a lot of space for improvement but it's
still better than having no hope to export HFS+ filesystems.

Signed-off-by: Diego E. 'Flameeyes' Pettenò <flameeyes@gmail.com>
---

 fs/hfsplus/super.c |   49 +++++++++++++++++++++++++++++++++++++++++++++++++
 1 files changed, 49 insertions(+), 0 deletions(-)

diff --git a/fs/hfsplus/super.c b/fs/hfsplus/super.c
index eb74531..45b48cc 100644
--- a/fs/hfsplus/super.c
+++ b/fs/hfsplus/super.c
@@ -11,6 +11,7 @@
 #include <linux/init.h>
 #include <linux/pagemap.h>
 #include <linux/fs.h>
+#include <linux/exportfs.h>
 #include <linux/slab.h>
 #include <linux/vfs.h>
 #include <linux/nls.h>
@@ -281,6 +282,53 @@ static const struct super_operations hfsplus_sops = {
 	.show_options	= hfsplus_show_options,
 };
 
+static struct inode *hfsplus_export_get_inode(struct super_block *sb,
+					      u64 ino, u32 generation)
+{
+	struct inode *inode;
+
+	if (ino < HFSPLUS_FIRSTUSER_CNID && ino != HFSPLUS_ROOT_CNID)
+		return ERR_PTR(-ESTALE);
+
+	/* iget isn't really right if the inode is currently unallocated!!
+	 */
+	inode = hfsplus_iget(sb, ino);
+	if (IS_ERR(inode))
+		return ERR_CAST(inode);
+	if (generation && inode->i_generation != generation) {
+		/* we didn't find the right inode.. */
+		iput(inode);
+		return ERR_PTR(-ESTALE);
+	}
+	return inode;
+}
+
+static struct dentry *hfsplus_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,
+				    hfsplus_export_get_inode);
+}
+
+static struct dentry *hfsplus_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,
+				    hfsplus_export_get_inode);
+}
+
+/* Yes, most of these are left as NULL!!
+ * A NULL value implies the default, which (hopefully) works with
+ * hfs+-like file systems, but can be improved upon.
+ * Currently only fh_to_dentry is required.
+ */
+static const struct export_operations hfsplus_export_ops = {
+	.fh_to_dentry = hfsplus_fh_to_dentry,
+	.fh_to_parent = hfsplus_fh_to_parent,
+};
+
 static int hfsplus_fill_super(struct super_block *sb, void *data, int silent)
 {
 	struct hfsplus_vh *vhdr;
@@ -345,6 +393,7 @@ static int hfsplus_fill_super(struct super_block *sb, void *data, int silent)
 
 	/* Set up operations so we can load metadata */
 	sb->s_op = &hfsplus_sops;
+	sb->s_export_op = &hfsplus_export_ops;
 	sb->s_maxbytes = MAX_LFS_FILESIZE;
 
 	if (!(vhdr->attributes & cpu_to_be32(HFSPLUS_VOL_UNMNT))) {