1 files changed, 122 insertions, 0 deletions
diff --git a/mm/tiny-shmem.c b/mm/tiny-shmem.c
new file mode 100644
index 000000000000..c13a2161bca2
--- /dev/null
+++ b/mm/tiny-shmem.c
@@ -0,0 +1,122 @@
+/*
+ * tiny-shmem.c: simple shmemfs and tmpfs using ramfs code
+ *
+ * Matt Mackall <mpm@selenic.com> January, 2004
+ * derived from mm/shmem.c and fs/ramfs/inode.c
+ *
+ * This is intended for small system where the benefits of the full
+ * shmem code (swap-backed and resource-limited) are outweighed by
+ * their complexity. On systems without swap this code should be
+ * effectively equivalent, but much lighter weight.
+ */
+
+#include <linux/fs.h>
+#include <linux/init.h>
+#include <linux/devfs_fs_kernel.h>
+#include <linux/vfs.h>
+#include <linux/mount.h>
+#include <linux/file.h>
+#include <linux/mm.h>
+#include <linux/module.h>
+#include <linux/swap.h>
+#include <linux/ramfs.h>
+
+static struct file_system_type tmpfs_fs_type = {
+	.name		= "tmpfs",
+	.get_sb		= ramfs_get_sb,
+	.kill_sb	= kill_litter_super,
+};
+
+static struct vfsmount *shm_mnt;
+
+static int __init init_tmpfs(void)
+{
+	register_filesystem(&tmpfs_fs_type);
+#ifdef CONFIG_TMPFS
+	devfs_mk_dir("shm");
+#endif
+	shm_mnt = kern_mount(&tmpfs_fs_type);
+	return 0;
+}
+module_init(init_tmpfs)
+
+/*
+ * shmem_file_setup - get an unlinked file living in tmpfs
+ *
+ * @name: name for dentry (to be seen in /proc/<pid>/maps
+ * @size: size to be set for the file
+ *
+ */
+struct file *shmem_file_setup(char *name, loff_t size, unsigned long flags)
+{
+	int error;
+	struct file *file;
+	struct inode *inode;
+	struct dentry *dentry, *root;
+	struct qstr this;
+
+	if (IS_ERR(shm_mnt))
+		return (void *)shm_mnt;
+
+	error = -ENOMEM;
+	this.name = name;
+	this.len = strlen(name);
+	this.hash = 0; /* will go */
+	root = shm_mnt->mnt_root;
+	dentry = d_alloc(root, &this);
+	if (!dentry)
+		goto put_memory;
+
+	error = -ENFILE;
+	file = get_empty_filp();
+	if (!file)
+		goto put_dentry;
+
+	error = -ENOSPC;
+	inode = ramfs_get_inode(root->d_sb, S_IFREG | S_IRWXUGO, 0);
+	if (!inode)
+		goto close_file;
+
+	d_instantiate(dentry, inode);
+	inode->i_size = size;
+	inode->i_nlink = 0;	/* It is unlinked */
+	file->f_vfsmnt = mntget(shm_mnt);
+	file->f_dentry = dentry;
+	file->f_mapping = inode->i_mapping;
+	file->f_op = &ramfs_file_operations;
+	file->f_mode = FMODE_WRITE | FMODE_READ;
+	return file;
+
+close_file:
+	put_filp(file);
+put_dentry:
+	dput(dentry);
+put_memory:
+	return ERR_PTR(error);
+}
+
+/*
+ * shmem_zero_setup - setup a shared anonymous mapping
+ *
+ * @vma: the vma to be mmapped is prepared by do_mmap_pgoff
+ */
+int shmem_zero_setup(struct vm_area_struct *vma)
+{
+	struct file *file;
+	loff_t size = vma->vm_end - vma->vm_start;
+
+	file = shmem_file_setup("dev/zero", size, vma->vm_flags);
+	if (IS_ERR(file))
+		return PTR_ERR(file);
+
+	if (vma->vm_file)
+		fput(vma->vm_file);
+	vma->vm_file = file;
+	vma->vm_ops = &generic_file_vm_ops;
+	return 0;
+}
+
+int shmem_unuse(swp_entry_t entry, struct page *page)
+{
+	return 0;
+}