LXR linux/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/vfs.h>
  16#include <linux/mount.h>
  17#include <linux/file.h>
  18#include <linux/mm.h>
  19#include <linux/module.h>
  20#include <linux/swap.h>
  21#include <linux/ramfs.h>
  22
  23static struct file_system_type tmpfs_fs_type = {
  24        .name           = "tmpfs",
  25        .get_sb         = ramfs_get_sb,
  26        .kill_sb        = kill_litter_super,
  27};
  28
  29static struct vfsmount *shm_mnt;
  30
  31static int __init init_tmpfs(void)
  32{
  33        BUG_ON(register_filesystem(&tmpfs_fs_type) != 0);
  34
  35        shm_mnt = kern_mount(&tmpfs_fs_type);
  36        BUG_ON(IS_ERR(shm_mnt));
  37
  38        return 0;
  39}
  40module_init(init_tmpfs)
  41
  42/*
  43 * shmem_file_setup - get an unlinked file living in tmpfs
  44 *
  45 * @name: name for dentry (to be seen in /proc/<pid>/maps
  46 * @size: size to be set for the file
  47 *
  48 */
  49struct file *shmem_file_setup(char *name, loff_t size, unsigned long flags)
  50{
  51        int error;
  52        struct file *file;
  53        struct inode *inode;
  54        struct dentry *dentry, *root;
  55        struct qstr this;
  56
  57        if (IS_ERR(shm_mnt))
  58                return (void *)shm_mnt;
  59
  60        error = -ENOMEM;
  61        this.name = name;
  62        this.len = strlen(name);
  63        this.hash = 0; /* will go */
  64        root = shm_mnt->mnt_root;
  65        dentry = d_alloc(root, &this);
  66        if (!dentry)
  67                goto put_memory;
  68
  69        error = -ENFILE;
  70        file = get_empty_filp();
  71        if (!file)
  72                goto put_dentry;
  73
  74        error = -ENOSPC;
  75        inode = ramfs_get_inode(root->d_sb, S_IFREG | S_IRWXUGO, 0);
  76        if (!inode)
  77                goto close_file;
  78
  79        d_instantiate(dentry, inode);
  80        inode->i_nlink = 0;     /* It is unlinked */
  81
  82        file->f_path.mnt = mntget(shm_mnt);
  83        file->f_path.dentry = dentry;
  84        file->f_mapping = inode->i_mapping;
  85        file->f_op = &ramfs_file_operations;
  86        file->f_mode = FMODE_WRITE | FMODE_READ;
  87
  88        /* notify everyone as to the change of file size */
  89        error = do_truncate(dentry, size, 0, file);
  90        if (error < 0)
  91                goto close_file;
  92
  93        return file;
  94
  95close_file:
  96        put_filp(file);
  97put_dentry:
  98        dput(dentry);
  99put_memory:
 100        return ERR_PTR(error);
 101}
 102
 103/*
 104 * shmem_zero_setup - setup a shared anonymous mapping
 105 *
 106 * @vma: the vma to be mmapped is prepared by do_mmap_pgoff
 107 */
 108int shmem_zero_setup(struct vm_area_struct *vma)
 109{
 110        struct file *file;
 111        loff_t size = vma->vm_end - vma->vm_start;
 112
 113        file = shmem_file_setup("dev/zero", size, vma->vm_flags);
 114        if (IS_ERR(file))
 115                return PTR_ERR(file);
 116
 117        if (vma->vm_file)
 118                fput(vma->vm_file);
 119        vma->vm_file = file;
 120        vma->vm_ops = &generic_file_vm_ops;
 121        return 0;
 122}
 123
 124int shmem_unuse(swp_entry_t entry, struct page *page)
 125{
 126        return 0;
 127}
 128
 129#if 0
 130int shmem_mmap(struct file *file, struct vm_area_struct *vma)
 131{
 132        file_accessed(file);
 133#ifndef CONFIG_MMU
 134        return ramfs_nommu_mmap(file, vma);
 135#else
 136        return 0;
 137#endif
 138}
 139#endif  /*  0  */
 140
 141#ifndef CONFIG_MMU
 142unsigned long shmem_get_unmapped_area(struct file *file,
 143                                      unsigned long addr,
 144                                      unsigned long len,
 145                                      unsigned long pgoff,
 146                                      unsigned long flags)
 147{
 148        return ramfs_nommu_get_unmapped_area(file, addr, len, pgoff, flags);
 149}
 150#endif
 151