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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/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)
{
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 = -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_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;
/* 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;
}
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
}
#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
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