[linux.git] / mm / tiny-shmem.c

/*
 * tiny-shmem.c: simple shmemfs and tmpfs using ramfs code
 *
 * Matt Mackall <[email protected]> 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);

#ifdef CONFIG_TMPFS
	devfs_mk_dir("shm");
#endif
	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_size = size;
	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;
	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;
}
Commit	Line	Data
1da177e4 LT	1	/*
	2	* tiny-shmem.c: simple shmemfs and tmpfs using ramfs code
	3	*
	4	* Matt Mackall <[email protected]> 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
	24	static struct file_system_type tmpfs_fs_type = {
	25	.name = "tmpfs",
	26	.get_sb = ramfs_get_sb,
	27	.kill_sb = kill_litter_super,
	28	};
	29
	30	static struct vfsmount *shm_mnt;
	31
	32	static int __init init_tmpfs(void)
	33	{
5d57bd39 MM	34	BUG_ON(register_filesystem(&tmpfs_fs_type) != 0);
5d57bd39 MM	35
1da177e4 LT	36	#ifdef CONFIG_TMPFS
	37	devfs_mk_dir("shm");
	38	#endif
	39	shm_mnt = kern_mount(&tmpfs_fs_type);
5d57bd39 MM	40	BUG_ON(IS_ERR(shm_mnt));
5d57bd39 MM	41
1da177e4 LT	42	return 0;
	43	}
	44	module_init(init_tmpfs)
	45
	46	/*
	47	* shmem_file_setup - get an unlinked file living in tmpfs
	48	*
	49	* @name: name for dentry (to be seen in /proc/<pid>/maps
	50	* @size: size to be set for the file
	51	*
	52	*/
	53	struct file shmem_file_setup(char name, loff_t size, unsigned long flags)
	54	{
	55	int error;
	56	struct file *file;
	57	struct inode *inode;
	58	struct dentry dentry, root;
	59	struct qstr this;
	60
	61	if (IS_ERR(shm_mnt))
	62	return (void *)shm_mnt;
	63
	64	error = -ENOMEM;
	65	this.name = name;
	66	this.len = strlen(name);
	67	this.hash = 0; /* will go */
	68	root = shm_mnt->mnt_root;
	69	dentry = d_alloc(root, &this);
	70	if (!dentry)
	71	goto put_memory;
	72
	73	error = -ENFILE;
	74	file = get_empty_filp();
	75	if (!file)
	76	goto put_dentry;
	77
	78	error = -ENOSPC;
	79	inode = ramfs_get_inode(root->d_sb, S_IFREG \| S_IRWXUGO, 0);
	80	if (!inode)
	81	goto close_file;
	82
	83	d_instantiate(dentry, inode);
	84	inode->i_size = size;
	85	inode->i_nlink = 0; /* It is unlinked */
	86	file->f_vfsmnt = mntget(shm_mnt);
	87	file->f_dentry = dentry;
	88	file->f_mapping = inode->i_mapping;
	89	file->f_op = &ramfs_file_operations;
	90	file->f_mode = FMODE_WRITE \| FMODE_READ;
	91	return file;
	92
	93	close_file:
	94	put_filp(file);
	95	put_dentry:
	96	dput(dentry);
	97	put_memory:
	98	return ERR_PTR(error);
	99	}
	100
	101	/*
	102	* shmem_zero_setup - setup a shared anonymous mapping
	103	*
	104	* @vma: the vma to be mmapped is prepared by do_mmap_pgoff
	105	*/
106	int shmem_zero_setup(struct vm_area_struct *vma)
107	{
108	struct file *file;
109	loff_t size = vma->vm_end - vma->vm_start;
110
111	file = shmem_file_setup("dev/zero", size, vma->vm_flags);
112	if (IS_ERR(file))
113	return PTR_ERR(file);
114
115	if (vma->vm_file)
116	fput(vma->vm_file);
117	vma->vm_file = file;
118	vma->vm_ops = &generic_file_vm_ops;
119	return 0;
120	}
121
122	int shmem_unuse(swp_entry_t entry, struct page *page)
123	{
124	return 0;
125	}