iget: stop HPPFS from using iget() and read_inode()

Stop the HPPFS filesystem from using iget() and read_inode().  Provide an
hppfs_iget(), and call that instead of iget().  hppfs_iget() then uses
iget_locked() directly and returns a proper error code instead of an inode in
the event of an error.

hppfs_fill_sb_common() returns any error incurred when getting the root inode
instead of EINVAL.

Note that the contents of hppfs_kern.c need to be examined:

 (*) The HPPFS inode retains a pointer to the proc dentry it is shadowing, but
     whilst it does appear to retain a reference to it, it doesn't appear to
     destroy the reference if the inode goes away.

 (*) hppfs_iget() should perhaps subsume init_inode() and hppfs_read_inode().

 (*) It would appear that all hppfs inodes are the same inode because iget()
     was being called with inode number 0, which forms the lookup key.
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/hppfs/hppfs_kern.c

@@ -155,6 +155,20 @@ static void hppfs_read_inode(struct inode *ino)
 	ino->i_blocks = proc_ino->i_blocks;
 }
 
+static struct inode *hppfs_iget(struct super_block *sb)
+{
+	struct inode *inode;
+
+	inode = iget_locked(sb, 0);
+	if (!inode)
+		return ERR_PTR(-ENOMEM);
+	if (inode->i_state & I_NEW) {
+		hppfs_read_inode(inode);
+		unlock_new_inode(inode);
+	}
+	return inode;
+}
+
 static struct dentry *hppfs_lookup(struct inode *ino, struct dentry *dentry,
                                   struct nameidata *nd)
 {
@@ -190,9 +204,11 @@ static struct dentry *hppfs_lookup(struct inode *ino, struct dentry *dentry,
 	if(IS_ERR(proc_dentry))
 		return(proc_dentry);
 
-	inode = iget(ino->i_sb, 0);
-	if(inode == NULL)
+	inode = hppfs_iget(ino->i_sb);
+	if (IS_ERR(inode)) {
+		err = PTR_ERR(inode);
 		goto out_dput;
+	}
 
 	err = init_inode(inode, proc_dentry);
 	if(err)
@@ -652,7 +668,6 @@ static void hppfs_destroy_inode(struct inode *inode)
 static const struct super_operations hppfs_sbops = {
 	.alloc_inode	= hppfs_alloc_inode,
 	.destroy_inode	= hppfs_destroy_inode,
-	.read_inode	= hppfs_read_inode,
 	.delete_inode	= hppfs_delete_inode,
 	.statfs		= hppfs_statfs,
 };
@@ -745,9 +760,11 @@ static int hppfs_fill_super(struct super_block *sb, void *d, int silent)
 	sb->s_magic = HPPFS_SUPER_MAGIC;
 	sb->s_op = &hppfs_sbops;
 
-	root_inode = iget(sb, 0);
-	if(root_inode == NULL)
+	root_inode = hppfs_iget(sb);
+	if (IS_ERR(root_inode)) {
+		err = PTR_ERR(root_inode);
 		goto out;
+	}
 
 	err = init_inode(root_inode, proc_sb->s_root);
 	if(err)