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

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

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

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

 (*) hostfs_iget() should perhaps subsume init_inode() and hostfs_read_inode().

 (*) It would appear that all hostfs inodes are the same inode because iget()
     was being called with inode number 0 - which forms the lookup key.

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: David Howells <dhowells@redhat.com>
Cc: Jeff Dike <jdike@addtoit.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/hostfs/hostfs_kern.c

@@ -202,7 +202,7 @@ static char *follow_link(char *link)
 	return ERR_PTR(n);
 }
 
-static int read_inode(struct inode *ino)
+static int hostfs_read_inode(struct inode *ino)
 {
 	char *name;
 	int err = 0;
@@ -233,6 +233,25 @@ static int read_inode(struct inode *ino)
 	return err;
 }
 
+static struct inode *hostfs_iget(struct super_block *sb)
+{
+	struct inode *inode;
+	long ret;
+
+	inode = iget_locked(sb, 0);
+	if (!inode)
+		return ERR_PTR(-ENOMEM);
+	if (inode->i_state & I_NEW) {
+		ret = hostfs_read_inode(inode);
+		if (ret < 0) {
+			iget_failed(inode);
+			return ERR_PTR(ret);
+		}
+		unlock_new_inode(inode);
+	}
+	return inode;
+}
+
 int hostfs_statfs(struct dentry *dentry, struct kstatfs *sf)
 {
 	/*
@@ -303,17 +322,11 @@ static void hostfs_destroy_inode(struct inode *inode)
 	kfree(HOSTFS_I(inode));
 }
 
-static void hostfs_read_inode(struct inode *inode)
-{
-	read_inode(inode);
-}
-
 static const struct super_operations hostfs_sbops = {
 	.alloc_inode	= hostfs_alloc_inode,
 	.drop_inode	= generic_delete_inode,
 	.delete_inode   = hostfs_delete_inode,
 	.destroy_inode	= hostfs_destroy_inode,
-	.read_inode	= hostfs_read_inode,
 	.statfs		= hostfs_statfs,
 };
 
@@ -571,10 +584,11 @@ int hostfs_create(struct inode *dir, struct dentry *dentry, int mode,
 	char *name;
 	int error, fd;
 
-	error = -ENOMEM;
-	inode = iget(dir->i_sb, 0);
-	if (inode == NULL)
+	inode = hostfs_iget(dir->i_sb);
+	if (IS_ERR(inode)) {
+		error = PTR_ERR(inode);
 		goto out;
+	}
 
 	error = init_inode(inode, dentry);
 	if (error)
@@ -615,10 +629,11 @@ struct dentry *hostfs_lookup(struct inode *ino, struct dentry *dentry,
 	char *name;
 	int err;
 
-	err = -ENOMEM;
-	inode = iget(ino->i_sb, 0);
-	if (inode == NULL)
+	inode = hostfs_iget(ino->i_sb);
+	if (IS_ERR(inode)) {
+		err = PTR_ERR(inode);
 		goto out;
+	}
 
 	err = init_inode(inode, dentry);
 	if (err)
@@ -736,11 +751,13 @@ int hostfs_mknod(struct inode *dir, struct dentry *dentry, int mode, dev_t dev)
 {
 	struct inode *inode;
 	char *name;
-	int err = -ENOMEM;
+	int err;
 
-	inode = iget(dir->i_sb, 0);
-	if (inode == NULL)
+	inode = hostfs_iget(dir->i_sb);
+	if (IS_ERR(inode)) {
+		err = PTR_ERR(inode);
 		goto out;
+	}
 
 	err = init_inode(inode, dentry);
 	if (err)
@@ -952,9 +969,11 @@ static int hostfs_fill_sb_common(struct super_block *sb, void *d, int silent)
 
 	sprintf(host_root_path, "%s/%s", root_ino, req_root);
 
-	root_inode = iget(sb, 0);
-	if (root_inode == NULL)
+	root_inode = hostfs_iget(sb);
+	if (IS_ERR(root_inode)) {
+		err = PTR_ERR(root_inode);
 		goto out_free;
+	}
 
 	err = init_inode(root_inode, NULL);
 	if (err)
@@ -972,7 +991,7 @@ static int hostfs_fill_sb_common(struct super_block *sb, void *d, int silent)
 	if (sb->s_root == NULL)
 		goto out_put;
 
-	err = read_inode(root_inode);
+	err = hostfs_read_inode(root_inode);
 	if (err) {
 		/* No iput in this case because the dput does that for us */
 		dput(sb->s_root);