--- /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/file.h>
+#include <linux/poll.h>
+#include <linux/slab.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;
+static const struct file_operations anon_inode_fops;
+
+static int anon_inodefs_get_sb(struct file_system_type *fs_type, int flags,
+ const char *dev_name, void *data,
+ struct vfsmount *mnt)
+{
+ return get_sb_pseudo(fs_type, "anon_inode:", NULL, ANON_INODE_FS_MAGIC,
+ mnt);
+}
+
+static int anon_inodefs_delete_dentry(struct dentry *dentry)
+{
+ /*
+ * We faked vfs to believe the dentry was hashed when we created it.
+ * Now we restore the flag so that dput() will work correctly.
+ */
+ dentry->d_flags |= DCACHE_UNHASHED;
+ return 1;
+}
+
+static struct file_system_type anon_inode_fs_type = {
+ .name = "anon_inodefs",
+ .get_sb = anon_inodefs_get_sb,
+ .kill_sb = kill_anon_super,
+};
+static struct dentry_operations anon_inodefs_dentry_operations = {
+ .d_delete = anon_inodefs_delete_dentry,
+};
+
+/**
+ * anon_inode_getfd - creates a new file instance by hooking it up to and
+ * anonymous inode, and a dentry that describe the "class"
+ * of the file
+ *
+ * @pfd: [out] pointer to the file descriptor
+ * @dpinode: [out] pointer to the inode
+ * @pfile: [out] pointer to the file struct
+ * @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)
+ *
+ * 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, by
+ * hence saving memory and avoiding code duplication for the file/inode/dentry
+ * setup.
+ */
+int anon_inode_getfd(int *pfd, struct inode **pinode, struct file **pfile,
+ const char *name, const struct file_operations *fops,
+ void *priv)
+{
+ struct qstr this;
+ struct dentry *dentry;
+ struct inode *inode;
+ struct file *file;
+ int error, fd;
+
+ if (IS_ERR(anon_inode_inode))
+ return -ENODEV;
+ file = get_empty_filp();
+ if (!file)
+ return -ENFILE;
+
+ inode = igrab(anon_inode_inode);
+ if (IS_ERR(inode)) {
+ error = PTR_ERR(inode);
+ goto err_put_filp;
+ }
+
+ error = get_unused_fd();
+ if (error < 0)
+ goto err_iput;
+ fd = error;
+
+ /*
+ * Link the inode to a directory entry by creating a unique name
+ * using the inode sequence number.
+ */
+ error = -ENOMEM;
+ this.name = name;
+ this.len = strlen(name);
+ this.hash = 0;
+ dentry = d_alloc(anon_inode_mnt->mnt_sb->s_root, &this);
+ if (!dentry)
+ goto err_put_unused_fd;
+ dentry->d_op = &anon_inodefs_dentry_operations;
+ /* Do not publish this dentry inside the global dentry hash table */
+ dentry->d_flags &= ~DCACHE_UNHASHED;
+ d_instantiate(dentry, inode);
+
+ file->f_path.mnt = mntget(anon_inode_mnt);
+ file->f_path.dentry = dentry;
+ file->f_mapping = inode->i_mapping;
+
+ file->f_pos = 0;
+ file->f_flags = O_RDWR;
+ file->f_op = fops;
+ file->f_mode = FMODE_READ | FMODE_WRITE;
+ file->f_version = 0;
+ file->private_data = priv;
+
+ fd_install(fd, file);
+
+ *pfd = fd;
+ *pinode = inode;
+ *pfile = file;
+ return 0;
+
+err_put_unused_fd:
+ put_unused_fd(fd);
+err_iput:
+ iput(inode);
+err_put_filp:
+ put_filp(file);
+ return error;
+}
+
+/*
+ * A single inode exist for all anon_inode files. Contrary to pipes,
+ * anon_inode inodes has no per-instance data associated, so we can avoid
+ * the allocation of multiple of them.
+ */
+static struct inode *anon_inode_mkinode(void)
+{
+ struct inode *inode = new_inode(anon_inode_mnt->mnt_sb);
+
+ if (!inode)
+ return ERR_PTR(-ENOMEM);
+
+ inode->i_fop = &anon_inode_fops;
+
+ /*
+ * Mark the inode dirty from the very beginning,
+ * that way it will never be moved to the dirty
+ * list because mark_inode_dirty() will think
+ * that it already _is_ on the dirty list.
+ */
+ inode->i_state = I_DIRTY;
+ inode->i_mode = S_IRUSR | S_IWUSR;
+ inode->i_uid = current->fsuid;
+ inode->i_gid = current->fsgid;
+ inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
+ return inode;
+}
+
+static int __init anon_inode_init(void)
+{
+ int error;
+
+ error = register_filesystem(&anon_inode_fs_type);
+ if (error)
+ goto err_exit;
+ anon_inode_mnt = kern_mount(&anon_inode_fs_type);
+ if (IS_ERR(anon_inode_mnt)) {
+ error = PTR_ERR(anon_inode_mnt);
+ goto err_unregister_filesystem;
+ }
+ anon_inode_inode = anon_inode_mkinode();
+ if (IS_ERR(anon_inode_inode)) {
+ error = PTR_ERR(anon_inode_inode);
+ goto err_mntput;
+ }
+
+ return 0;
+
+err_mntput:
+ mntput(anon_inode_mnt);
+err_unregister_filesystem:
+ unregister_filesystem(&anon_inode_fs_type);
+err_exit:
+ panic(KERN_ERR "anon_inode_init() failed (%d)\n", error);
+}
+
+fs_initcall(anon_inode_init);
+
projects / kernel / kernel-generic.git / commitdiff