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/*

 * 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

 *

 */

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 = -ENOSPC;

        inode = ramfs_get_inode(root->d_sb, S_IFREG | S_IRWXUGO, 0);

        if (!inode)

                goto put_dentry;

        d_instantiate(dentry, inode);

        error = -ENFILE;

        file = alloc_file(shm_mnt, dentry, FMODE_WRITE | FMODE_READ,

                        &ramfs_file_operations);

        if (!file)

                goto put_dentry;

        inode->i_nlink = 0;      /* It is unlinked */

        /* notify everyone as to the change of file size */

        error = do_truncate(dentry, size, 0, file);

        if (error < 0)

                goto close_file;

        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;

}

#if 0

int shmem_mmap(struct file *file, struct vm_area_struct *vma)

{

        file_accessed(file);

#ifndef CONFIG_MMU

        return ramfs_nommu_mmap(file, vma);

#else

        return 0;

#endif

}

#endif  /*  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