fs/anon_inode: Introduce a new lib function anon_inode_getfile_private()

Introduce a new lib function anon_inode_getfile_private(), it creates a new file
instance by hooking it up to an anonymous inode, and a dentry that describe the
"class" of the file, similar to anon_inode_getfile(), but each file holds a
single inode. Furthermore, anyone who wants to create a private anon file will
benefit from this change.

Signed-off-by: Gu Zheng <guz.fnst@cn.fujitsu.com>
Signed-off-by: Benjamin LaHaise <bcrl@kvack.org>

2 files changed, 69 insertions, 0 deletions

diff --git a/fs/anon_inodes.c b/fs/anon_inodes.c
index 47a65df8c871..85c961849953 100644
--- a/fs/anon_inodes.c
+++ b/fs/anon_inodes.c
@@ -109,6 +109,72 @@ static struct file_system_type anon_inode_fs_type = {
 };
 
 /**
+ * anon_inode_getfile_private - creates a new file instance by hooking it up to an
+ *                      anonymous inode, and a dentry that describe the "class"
+ *                      of the file
+ *
+ * @name:    [in]    name of the "class" of the new file
+ * @fops:    [in]    file operations for the new file
+ * @priv:    [in]    private data for the new file (will be file's private_data)
+ * @flags:   [in]    flags
+ *
+ *
+ * Similar to anon_inode_getfile, but each file holds a single inode.
+ *
+ */
+struct file *anon_inode_getfile_private(const char *name,
+                                        const struct file_operations *fops,
+                                        void *priv, int flags)
+{
+        struct qstr this;
+        struct path path;
+        struct file *file;
+        struct inode *inode;
+
+        if (fops->owner && !try_module_get(fops->owner))
+                return ERR_PTR(-ENOENT);
+
+        inode = anon_inode_mkinode(anon_inode_mnt->mnt_sb);
+        if (IS_ERR(inode)) {
+                file = ERR_PTR(-ENOMEM);
+                goto err_module;
+        }
+
+        /*
+         * Link the inode to a directory entry by creating a unique name
+         * using the inode sequence number.
+         */
+        file = ERR_PTR(-ENOMEM);
+        this.name = name;
+        this.len = strlen(name);
+        this.hash = 0;
+        path.dentry = d_alloc_pseudo(anon_inode_mnt->mnt_sb, &this);
+        if (!path.dentry)
+                goto err_module;
+
+        path.mnt = mntget(anon_inode_mnt);
+
+        d_instantiate(path.dentry, inode);
+
+        file = alloc_file(&path, OPEN_FMODE(flags), fops);
+        if (IS_ERR(file))
+                goto err_dput;
+
+        file->f_mapping = inode->i_mapping;
+        file->f_flags = flags & (O_ACCMODE | O_NONBLOCK);
+        file->private_data = priv;
+
+        return file;
+
+err_dput:
+        path_put(&path);
+err_module:
+        module_put(fops->owner);
+        return file;
+}
+EXPORT_SYMBOL_GPL(anon_inode_getfile_private);
+
+/**
  * anon_inode_getfile - creates a new file instance by hooking it up to an
  *                      anonymous inode, and a dentry that describe the "class"
  *                      of the file
diff --git a/include/linux/anon_inodes.h b/include/linux/anon_inodes.h
index 8013a45242fe..cf573c22b81e 100644
--- a/include/linux/anon_inodes.h
+++ b/include/linux/anon_inodes.h
@@ -13,6 +13,9 @@ struct file_operations;
 struct file *anon_inode_getfile(const char *name,
                                 const struct file_operations *fops,
                                 void *priv, int flags);
+struct file *anon_inode_getfile_private(const char *name,
+                                const struct file_operations *fops,
+                                void *priv, int flags);
 int anon_inode_getfd(const char *name, const struct file_operations *fops,
                      void *priv, int flags);