--- /dev/null
+/*
+ * fs/anon_inodes.c
+ *
+ * Copyright (C) 2007 Davide Libenzi <davidel@xmailserver.org>
+ *
+ * Thanks to Arnd Bergmann for code review and suggestions.
+ * More changes for Thomas Gleixner suggestions.
+ *
+ */
+
+#include <linux/cred.h>
+#include <linux/file.h>
+#include <linux/poll.h>
+#include <linux/sched.h>
+#include <linux/init.h>
+#include <linux/fs.h>
+#include <linux/mount.h>
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/magic.h>
+#include <linux/anon_inodes.h>
+
+#include <asm/uaccess.h>
+
+static struct vfsmount *anon_inode_mnt __read_mostly;
+static struct inode *anon_inode_inode;
+
+/*
+ * anon_inodefs_dname() is called from d_path().
+ */
+static char *anon_inodefs_dname(struct dentry *dentry, char *buffer, int buflen)
+{
+ return dynamic_dname(dentry, buffer, buflen, "anon_inode:%s",
+ dentry->d_name.name);
+}
+
+static const struct dentry_operations anon_inodefs_dentry_operations = {
+ .d_dname = anon_inodefs_dname,
+};
+
+static struct dentry *anon_inodefs_mount(struct file_system_type *fs_type,
+ int flags, const char *dev_name, void *data)
+{
+ return mount_pseudo(fs_type, "anon_inode:", NULL,
+ &anon_inodefs_dentry_operations, ANON_INODE_FS_MAGIC);
+}
+
+static struct file_system_type anon_inode_fs_type = {
+ .name = "anon_inodefs",
+ .mount = anon_inodefs_mount,
+ .kill_sb = kill_anon_super,
+};
+
+/**
+ * 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
+ *
+ * @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
+ *
+ * Creates a new file by hooking it on a single inode. This is useful for files
+ * that do not need to have a full-fledged inode in order to operate correctly.
+ * All the files created with anon_inode_getfile() will share a single inode,
+ * hence saving memory and avoiding code duplication for the file/inode/dentry
+ * setup. Returns the newly created file* or an error pointer.
+ */
+struct file *anon_inode_getfile(const char *name,
+ const struct file_operations *fops,
+ void *priv, int flags)
+{
+ struct qstr this;
+ struct path path;
+ struct file *file;
+
+ if (IS_ERR(anon_inode_inode))
+ return ERR_PTR(-ENODEV);
+
+ if (fops->owner && !try_module_get(fops->owner))
+ return ERR_PTR(-ENOENT);
+
+ /*
+ * 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);
+ /*
+ * We know the anon_inode inode count is always greater than zero,
+ * so ihold() is safe.
+ */
+ ihold(anon_inode_inode);
+
+ d_instantiate(path.dentry, anon_inode_inode);
+
+ file = alloc_file(&path, OPEN_FMODE(flags), fops);
+ if (IS_ERR(file))
+ goto err_dput;
+ file->f_mapping = anon_inode_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);
+
+/**
+ * anon_inode_getfd - 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
+ *
+ * Creates a new file by hooking it on a single inode. This is useful for files
+ * that do not need to have a full-fledged inode in order to operate correctly.
+ * All the files created with anon_inode_getfd() will share a single inode,
+ * hence saving memory and avoiding code duplication for the file/inode/dentry
+ * setup. Returns new descriptor or an error code.
+ */
+int anon_inode_getfd(const char *name, const struct file_operations *fops,
+ void *priv, int flags)
+{
+ int error, fd;
+ struct file *file;
+
+ error = get_unused_fd_flags(flags);
+ if (error < 0)
+ return error;
+ fd = error;
+
+ file = anon_inode_getfile(name, fops, priv, flags);
+ if (IS_ERR(file)) {
+ error = PTR_ERR(file);
+ goto err_put_unused_fd;
+ }
+ fd_install(fd, file);
+
+ return fd;
+
+err_put_unused_fd:
+ put_unused_fd(fd);
+ return error;
+}
+EXPORT_SYMBOL_GPL(anon_inode_getfd);
+
+static int __init anon_inode_init(void)
+{
+ anon_inode_mnt = kern_mount(&anon_inode_fs_type);
+ if (IS_ERR(anon_inode_mnt))
+ panic("anon_inode_init() kernel mount failed (%ld)\n", PTR_ERR(anon_inode_mnt));
+
+ anon_inode_inode = alloc_anon_inode(anon_inode_mnt->mnt_sb);
+ if (IS_ERR(anon_inode_inode))
+ panic("anon_inode_init() inode allocation failed (%ld)\n", PTR_ERR(anon_inode_inode));
+
+ return 0;
+}
+
+fs_initcall(anon_inode_init);
+
Code Review / kvmfornfv.git / blobdiff