LXR RHEL4/mm/tiny-shmem.c

   1/*
   2 * tiny-shmem.c: simple shmemfs and tmpfs using ramfs code
   3 *
   4 * Matt Mackall <mpm@selenic.com> January, 2004
   5 * derived from mm/shmem.c and fs/ramfs/inode.c
   6 *
   7 * This is intended for small system where the benefits of the full
   8 * shmem code (swap-backed and resource-limited) are outweighed by
   9 * their complexity. On systems without swap this code should be
  10 * effectively equivalent, but much lighter weight.
  11 */
  12
  13#include <linux/fs.h>
  14#include <linux/init.h>
  15#include <linux/devfs_fs_kernel.h>
  16#include <linux/vfs.h>
  17#include <linux/mount.h>
  18#include <linux/file.h>
  19#include <linux/mm.h>
  20#include <linux/module.h>
  21#include <linux/swap.h>
  22#include <linux/ramfs.h>
  23
  24static struct file_system_type tmpfs_fs_type = {
  25        .name           = "tmpfs",
  26        .get_sb         = ramfs_get_sb,
  27        .kill_sb        = kill_litter_super,
  28};
  29
  30static struct vfsmount *shm_mnt;
  31
  32static int __init init_tmpfs(void)
  33{
  34        register_filesystem(&tmpfs_fs_type);
  35#ifdef CONFIG_TMPFS
  36        devfs_mk_dir("shm");
  37#endif
  38        shm_mnt = kern_mount(&tmpfs_fs_type);
  39        return 0;
  40}
  41module_init(init_tmpfs)
  42
  43/*
  44 * shmem_file_setup - get an unlinked file living in tmpfs
  45 *
  46 * @name: name for dentry (to be seen in /proc/<pid>/maps
  47 * @size: size to be set for the file
  48 *
  49 */
  50struct file *shmem_file_setup(char *name, loff_t size, unsigned long flags)
  51{
  52        int error;
  53        struct file *file;
  54        struct inode *inode;
  55        struct dentry *dentry, *root;
  56        struct qstr this;
  57
  58        if (IS_ERR(shm_mnt))
  59                return (void *)shm_mnt;
  60
  61        error = -ENOMEM;
  62        this.name = name;
  63        this.len = strlen(name);
  64        this.hash = 0; /* will go */
  65        root = shm_mnt->mnt_root;
  66        dentry = d_alloc(root, &this);
  67        if (!dentry)
  68                goto put_memory;
  69
  70        error = -ENFILE;
  71        file = get_empty_filp();
  72        if (!file)
  73                goto put_dentry;
  74
  75        error = -ENOSPC;
  76        inode = ramfs_get_inode(root->d_sb, S_IFREG | S_IRWXUGO, 0);
  77        if (!inode)
  78                goto close_file;
  79
  80        d_instantiate(dentry, inode);
  81        inode->i_size = size;
  82        inode->i_nlink = 0;     /* It is unlinked */
  83        file->f_vfsmnt = mntget(shm_mnt);
  84        file->f_dentry = dentry;
  85        file->f_mapping = inode->i_mapping;
  86        file->f_op = &ramfs_file_operations;
  87        file->f_mode = FMODE_WRITE | FMODE_READ;
  88        return file;
  89
  90close_file:
  91        put_filp(file);
  92put_dentry:
  93        dput(dentry);
  94put_memory:
  95        return ERR_PTR(error);
  96}
  97
  98/*
  99 * shmem_zero_setup - setup a shared anonymous mapping
 100 *
 101 * @vma: the vma to be mmapped is prepared by do_mmap_pgoff
 102 */
 103int shmem_zero_setup(struct vm_area_struct *vma)
 104{
 105        struct file *file;
 106        loff_t size = vma->vm_end - vma->vm_start;
 107
 108        file = shmem_file_setup("dev/zero", size, vma->vm_flags);
 109        if (IS_ERR(file))
 110                return PTR_ERR(file);
 111
 112        if (vma->vm_file)
 113                fput(vma->vm_file);
 114        vma->vm_file = file;
 115        vma->vm_ops = &generic_file_vm_ops;
 116        return 0;
 117}
 118
 119int shmem_unuse(swp_entry_t entry, struct page *page)
 120{
 121        return 0;
 122}
 123