root/mm/tiny-shmem.c

DEFINITIONS

1. init_tmpfs
2. module_init
3. shmem_zero_setup
4. shmem_unuse
5. shmem_get_unmapped_area

/*
 * 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/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)
{
        BUG_ON(register_filesystem(&tmpfs_fs_type) != 0);

        shm_mnt = kern_mount(&tmpfs_fs_type);
        BUG_ON(IS_ERR(shm_mnt));

        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
 * @flags: vm_flags
 */
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 */
        init_file(file, shm_mnt, dentry, FMODE_WRITE | FMODE_READ,
                        &ramfs_file_operations);

#ifndef CONFIG_MMU
        error = ramfs_nommu_expand_for_mapping(inode, size);
        if (error)
                goto close_file;
#endif
        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;
}

#ifndef CONFIG_MMU
unsigned long shmem_get_unmapped_area(struct file *file,
                                      unsigned long addr,
                                      unsigned long len,
                                      unsigned long pgoff,
                                      unsigned long flags)
{
        return ramfs_nommu_get_unmapped_area(file, addr, len, pgoff, flags);
}
#endif