shmem.c

ARM 嵌入式 系统 设计与实例开发 实验教材 二源码

	return shmem_mknod(dir, dentry, mode | S_IFREG, 0);
}

/*
 * Link a file..
 */
static int shmem_link(struct dentry *old_dentry, struct inode * dir, struct dentry * dentry)
{
	struct inode *inode = old_dentry->d_inode;

	if (S_ISDIR(inode->i_mode))
		return -EPERM;

	inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
	inode->i_nlink++;
	atomic_inc(&inode->i_count);	/* New dentry reference */
	dget(dentry);		/* Extra pinning count for the created dentry */
	d_instantiate(dentry, inode);
	return 0;
}

static inline int shmem_positive(struct dentry *dentry)
{
	return dentry->d_inode && !d_unhashed(dentry);
}

/*
 * Check that a directory is empty (this works
 * for regular files too, they'll just always be
 * considered empty..).
 *
 * Note that an empty directory can still have
 * children, they just all have to be negative..
 */
static int shmem_empty(struct dentry *dentry)
{
	struct list_head *list;

	spin_lock(&dcache_lock);
	list = dentry->d_subdirs.next;

	while (list != &dentry->d_subdirs) {
		struct dentry *de = list_entry(list, struct dentry, d_child);

		if (shmem_positive(de)) {
			spin_unlock(&dcache_lock);
			return 0;
		}
		list = list->next;
	}
	spin_unlock(&dcache_lock);
	return 1;
}

static int shmem_unlink(struct inode * dir, struct dentry *dentry)
{
	struct inode *inode = dentry->d_inode;
	inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
	inode->i_nlink--;
	dput(dentry);	/* Undo the count from "create" - this does all the work */
	return 0;
}

static int shmem_rmdir(struct inode * dir, struct dentry *dentry)
{
	if (!shmem_empty(dentry))
		return -ENOTEMPTY;

	dir->i_nlink--;
	return shmem_unlink(dir, dentry);
}

/*
 * The VFS layer already does all the dentry stuff for rename,
 * we just have to decrement the usage count for the target if
 * it exists so that the VFS layer correctly free's it when it
 * gets overwritten.
 */
static int shmem_rename(struct inode * old_dir, struct dentry *old_dentry, struct inode * new_dir,struct dentry *new_dentry)
{
	int error = -ENOTEMPTY;

	if (shmem_empty(new_dentry)) {
		struct inode *inode = new_dentry->d_inode;
		if (inode) {
			inode->i_ctime = CURRENT_TIME;
			inode->i_nlink--;
			dput(new_dentry);
		}
		error = 0;
		old_dentry->d_inode->i_ctime = old_dir->i_ctime = old_dir->i_mtime = CURRENT_TIME;
	}
	return error;
}

static int shmem_symlink(struct inode * dir, struct dentry *dentry, const char * symname)
{
	int error;
	int len;
	struct inode *inode;
	struct page *page;
	char *kaddr;
	struct shmem_inode_info * info;

	error = shmem_mknod(dir, dentry, S_IFLNK | S_IRWXUGO, 0);
	if (error)
		return error;

	len = strlen(symname) + 1;
	if (len > PAGE_CACHE_SIZE)
		return -ENAMETOOLONG;
		
	inode = dentry->d_inode;
	info = SHMEM_I(inode);
	inode->i_size = len-1;
	if (len <= sizeof(struct shmem_inode_info)) {
		/* do it inline */
		memcpy(info, symname, len);
		inode->i_op = &shmem_symlink_inline_operations;
	} else {
		spin_lock (&shmem_ilock);
		list_add (&info->list, &shmem_inodes);
		spin_unlock (&shmem_ilock);
		down(&info->sem);
		page = shmem_getpage_locked(info, inode, 0);
		if (IS_ERR(page)) {
			up(&info->sem);
			return PTR_ERR(page);
		}
		kaddr = kmap(page);
		memcpy(kaddr, symname, len);
		kunmap(page);
		SetPageDirty(page);
		UnlockPage(page);
		page_cache_release(page);
		up(&info->sem);
		inode->i_op = &shmem_symlink_inode_operations;
	}
	dir->i_ctime = dir->i_mtime = CURRENT_TIME;
	return 0;
}

static int shmem_readlink_inline(struct dentry *dentry, char *buffer, int buflen)
{
	return vfs_readlink(dentry,buffer,buflen, (const char *)SHMEM_I(dentry->d_inode));
}

static int shmem_follow_link_inline(struct dentry *dentry, struct nameidata *nd)
{
	return vfs_follow_link(nd, (const char *)SHMEM_I(dentry->d_inode));
}

static int shmem_readlink(struct dentry *dentry, char *buffer, int buflen)
{
	struct page * page;
	int res = shmem_getpage(dentry->d_inode, 0, &page);

	if (res)
		return res;

	res = vfs_readlink(dentry,buffer,buflen, kmap(page));
	kunmap(page);
	page_cache_release(page);
	return res;
}

static int shmem_follow_link(struct dentry *dentry, struct nameidata *nd)
{
	struct page * page;
	int res = shmem_getpage(dentry->d_inode, 0, &page);
	if (res)
		return res;

	res = vfs_follow_link(nd, kmap(page));
	kunmap(page);
	page_cache_release(page);
	return res;
}

static struct inode_operations shmem_symlink_inline_operations = {
	readlink:	shmem_readlink_inline,
	follow_link:	shmem_follow_link_inline,
};

static struct inode_operations shmem_symlink_inode_operations = {
	truncate:	shmem_truncate,
	readlink:	shmem_readlink,
	follow_link:	shmem_follow_link,
};

static int shmem_parse_options(char *options, int *mode, uid_t *uid, gid_t *gid, unsigned long * blocks, unsigned long *inodes)
{
	char *this_char, *value, *rest;

	this_char = NULL;
	if ( options )
		this_char = strtok(options,",");
	for ( ; this_char; this_char = strtok(NULL,",")) {
		if ((value = strchr(this_char,'=')) != NULL) {
			*value++ = 0;
		} else {
			printk(KERN_ERR 
			    "tmpfs: No value for mount option '%s'\n", 
			    this_char);
			return 1;
		}

		if (!strcmp(this_char,"size")) {
			unsigned long long size;
			size = memparse(value,&rest);
			if (*rest)
				goto bad_val;
			*blocks = size >> PAGE_CACHE_SHIFT;
		} else if (!strcmp(this_char,"nr_blocks")) {
			*blocks = memparse(value,&rest);
			if (*rest)
				goto bad_val;
		} else if (!strcmp(this_char,"nr_inodes")) {
			*inodes = memparse(value,&rest);
			if (*rest)
				goto bad_val;
		} else if (!strcmp(this_char,"mode")) {
			if (!mode)
				continue;
			*mode = simple_strtoul(value,&rest,8);
			if (*rest)
				goto bad_val;
		} else if (!strcmp(this_char,"uid")) {
			if (!uid)
				continue;
			*uid = simple_strtoul(value,&rest,0);
			if (*rest)
				goto bad_val;
		} else if (!strcmp(this_char,"gid")) {
			if (!gid)
				continue;
			*gid = simple_strtoul(value,&rest,0);
			if (*rest)
				goto bad_val;
		} else {
			printk(KERN_ERR "tmpfs: Bad mount option %s\n",
			       this_char);
			return 1;
		}
	}
	return 0;

bad_val:
	printk(KERN_ERR "tmpfs: Bad value '%s' for mount option '%s'\n", 
	       value, this_char);
	return 1;

}

static int shmem_remount_fs (struct super_block *sb, int *flags, char *data)
{
	struct shmem_sb_info *sbinfo = &sb->u.shmem_sb;
	unsigned long max_blocks = sbinfo->max_blocks;
	unsigned long max_inodes = sbinfo->max_inodes;

	if (shmem_parse_options (data, NULL, NULL, NULL, &max_blocks, &max_inodes))
		return -EINVAL;
	return shmem_set_size(sbinfo, max_blocks, max_inodes);
}

int shmem_sync_file(struct file * file, struct dentry *dentry, int datasync)
{
	return 0;
}
#endif

static struct super_block *shmem_read_super(struct super_block * sb, void * data, int silent)
{
	struct inode * inode;
	struct dentry * root;
	unsigned long blocks, inodes;
	int mode   = S_IRWXUGO | S_ISVTX;
	uid_t uid = current->fsuid;
	gid_t gid = current->fsgid;
	struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
	struct sysinfo si;

	/*
	 * Per default we only allow half of the physical ram per
	 * tmpfs instance
	 */
	si_meminfo(&si);
	blocks = inodes = si.totalram / 2;

#ifdef CONFIG_TMPFS
	if (shmem_parse_options (data, &mode, &uid, &gid, &blocks, &inodes))
		return NULL;
#endif

	spin_lock_init (&sbinfo->stat_lock);
	sbinfo->max_blocks = blocks;
	sbinfo->free_blocks = blocks;
	sbinfo->max_inodes = inodes;
	sbinfo->free_inodes = inodes;
	sb->s_maxbytes = (unsigned long long) SHMEM_MAX_BLOCKS << PAGE_CACHE_SHIFT;
	sb->s_blocksize = PAGE_CACHE_SIZE;
	sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
	sb->s_magic = TMPFS_MAGIC;
	sb->s_op = &shmem_ops;
	inode = shmem_get_inode(sb, S_IFDIR | mode, 0);
	if (!inode)
		return NULL;

	inode->i_uid = uid;
	inode->i_gid = gid;
	root = d_alloc_root(inode);
	if (!root) {
		iput(inode);
		return NULL;
	}
	sb->s_root = root;
	return sb;
}



static struct address_space_operations shmem_aops = {
	writepage:	shmem_writepage,
};

static struct file_operations shmem_file_operations = {
	mmap:	shmem_mmap,
#ifdef CONFIG_TMPFS
	read:	shmem_file_read,
	write:	shmem_file_write,
	fsync:	shmem_sync_file,
#endif
};

static struct inode_operations shmem_inode_operations = {
	truncate:	shmem_truncate,
};

static struct file_operations shmem_dir_operations = {
	read:		generic_read_dir,
	readdir:	dcache_readdir,
#ifdef CONFIG_TMPFS
	fsync:		shmem_sync_file,
#endif
};

static struct inode_operations shmem_dir_inode_operations = {
#ifdef CONFIG_TMPFS
	create:		shmem_create,
	lookup:		shmem_lookup,
	link:		shmem_link,
	unlink:		shmem_unlink,
	symlink:	shmem_symlink,
	mkdir:		shmem_mkdir,
	rmdir:		shmem_rmdir,
	mknod:		shmem_mknod,
	rename:		shmem_rename,
#endif
};

static struct super_operations shmem_ops = {
#ifdef CONFIG_TMPFS
	statfs:		shmem_statfs,
	remount_fs:	shmem_remount_fs,
#endif
	delete_inode:	shmem_delete_inode,
	put_inode:	force_delete,	
};

static struct vm_operations_struct shmem_vm_ops = {
	nopage:	shmem_nopage,
};

#ifdef CONFIG_TMPFS
/* type "shm" will be tagged obsolete in 2.5 */
static DECLARE_FSTYPE(shmem_fs_type, "shm", shmem_read_super, FS_LITTER);
static DECLARE_FSTYPE(tmpfs_fs_type, "tmpfs", shmem_read_super, FS_LITTER);
#else
static DECLARE_FSTYPE(tmpfs_fs_type, "tmpfs", shmem_read_super, FS_LITTER|FS_NOMOUNT);
#endif
static struct vfsmount *shm_mnt;

static int __init init_shmem_fs(void)
{
	int error;
	struct vfsmount * res;

	if ((error = register_filesystem(&tmpfs_fs_type))) {
		printk (KERN_ERR "Could not register tmpfs\n");
		return error;
	}
#ifdef CONFIG_TMPFS
	if ((error = register_filesystem(&shmem_fs_type))) {
		printk (KERN_ERR "Could not register shm fs\n");
		return error;
	}
	devfs_mk_dir (NULL, "shm", NULL);
#endif
	res = kern_mount(&tmpfs_fs_type);
	if (IS_ERR (res)) {
		printk (KERN_ERR "could not kern_mount tmpfs\n");
		unregister_filesystem(&tmpfs_fs_type);
		return PTR_ERR(res);
	}
	shm_mnt = res;

	/* The internal instance should not do size checking */
	if ((error = shmem_set_size(SHMEM_SB(res->mnt_sb), ULONG_MAX, ULONG_MAX)))
		printk (KERN_ERR "could not set limits on internal tmpfs\n");

	return 0;
}

static void __exit exit_shmem_fs(void)
{
#ifdef CONFIG_TMPFS
	unregister_filesystem(&shmem_fs_type);
#endif
	unregister_filesystem(&tmpfs_fs_type);
	mntput(shm_mnt);
}

module_init(init_shmem_fs)
module_exit(exit_shmem_fs)

/*
 * shmem_file_setup - get an unlinked file living in shmem fs
 *
 * @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)
{
	int error;
	struct file *file;
	struct inode * inode;
	struct dentry *dentry, *root;
	struct qstr this;
	int vm_enough_memory(long pages);

	if (size > (unsigned long long) SHMEM_MAX_BLOCKS << PAGE_CACHE_SHIFT)
		return ERR_PTR(-EINVAL);

	if (!vm_enough_memory((size) >> PAGE_CACHE_SHIFT))
		return ERR_PTR(-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)
		return ERR_PTR(-ENOMEM);

	error = -ENFILE;
	file = get_empty_filp();
	if (!file)
		goto put_dentry;

	error = -ENOSPC;
	inode = shmem_get_inode(root->d_sb, S_IFREG | S_IRWXUGO, 0);
	if (!inode) 
		goto close_file;

	d_instantiate(dentry, inode);
	dentry->d_inode->i_size = size;
	shmem_truncate(inode);
	file->f_vfsmnt = mntget(shm_mnt);
	file->f_dentry = dentry;
	file->f_op = &shmem_file_operations;
	file->f_mode = FMODE_WRITE | FMODE_READ;
	inode->i_nlink = 0;	/* It is unlinked */
	return(file);

close_file:
	put_filp(file);
put_dentry:
	dput (dentry);
	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);
	if (IS_ERR(file))
		return PTR_ERR(file);

	if (vma->vm_file)
		fput (vma->vm_file);
	vma->vm_file = file;
	vma->vm_ops = &shmem_vm_ops;
	return 0;
}

EXPORT_SYMBOL(shmem_file_setup);