fs/libfs.c - SHIFTPHONES/android_kernel_shift_sdm845 - Gitiles

 /*
  *	fs/libfs.c
  *	Library for filesystems writers.
  */

 #include <linux/module.h>
 #include <linux/pagemap.h>
 #include <linux/mount.h>
 #include <linux/vfs.h>
 #include <linux/mutex.h>

 #include <asm/uaccess.h>

 int simple_getattr(struct vfsmount *mnt, struct dentry *dentry,
 		   struct kstat *stat)
 {
 	struct inode *inode = dentry->d_inode;
 	generic_fillattr(inode, stat);
 	stat->blocks = inode->i_mapping->nrpages << (PAGE_CACHE_SHIFT - 9);
 	return 0;
 }

 int simple_statfs(struct dentry *dentry, struct kstatfs *buf)
 {
 	buf->f_type = dentry->d_sb->s_magic;
 	buf->f_bsize = PAGE_CACHE_SIZE;
 	buf->f_namelen = NAME_MAX;
 	return 0;
 }

 /*
  * Retaining negative dentries for an in-memory filesystem just wastes
  * memory and lookup time: arrange for them to be deleted immediately.
  */
 static int simple_delete_dentry(struct dentry *dentry)
 {
 	return 1;
 }

 /*
  * Lookup the data. This is trivial - if the dentry didn't already
  * exist, we know it is negative.  Set d_op to delete negative dentries.
  */
 struct dentry *simple_lookup(struct inode *dir, struct dentry *dentry, struct nameidata *nd)
 {
 	static struct dentry_operations simple_dentry_operations = {
 		.d_delete = simple_delete_dentry,
 	};

 	if (dentry->d_name.len > NAME_MAX)
 		return ERR_PTR(-ENAMETOOLONG);
 	dentry->d_op = &simple_dentry_operations;
 	d_add(dentry, NULL);
 	return NULL;
 }

 int simple_sync_file(struct file * file, struct dentry *dentry, int datasync)
 {
 	return 0;
 }

 int dcache_dir_open(struct inode *inode, struct file *file)
 {
 	static struct qstr cursor_name = {.len = 1, .name = "."};

 	file->private_data = d_alloc(file->f_dentry, &cursor_name);

 	return file->private_data ? 0 : -ENOMEM;
 }

 int dcache_dir_close(struct inode *inode, struct file *file)
 {
 	dput(file->private_data);
 	return 0;
 }

 loff_t dcache_dir_lseek(struct file *file, loff_t offset, int origin)
 {
 	mutex_lock(&file->f_dentry->d_inode->i_mutex);
 	switch (origin) {
 		case 1:
 			offset += file->f_pos;
 		case 0:
 			if (offset >= 0)
 				break;
 		default:
 			mutex_unlock(&file->f_dentry->d_inode->i_mutex);
 			return -EINVAL;
 	}
 	if (offset != file->f_pos) {
 		file->f_pos = offset;
 		if (file->f_pos >= 2) {
 			struct list_head *p;
 			struct dentry *cursor = file->private_data;
 			loff_t n = file->f_pos - 2;

 			spin_lock(&dcache_lock);
 			list_del(&cursor->d_u.d_child);
 			p = file->f_dentry->d_subdirs.next;
 			while (n && p != &file->f_dentry->d_subdirs) {
 				struct dentry *next;
 				next = list_entry(p, struct dentry, d_u.d_child);
 				if (!d_unhashed(next) && next->d_inode)
 					n--;
 				p = p->next;
 			}
 			list_add_tail(&cursor->d_u.d_child, p);
 			spin_unlock(&dcache_lock);
 		}
 	}
 	mutex_unlock(&file->f_dentry->d_inode->i_mutex);
 	return offset;
 }

 /* Relationship between i_mode and the DT_xxx types */
 static inline unsigned char dt_type(struct inode *inode)
 {
 	return (inode->i_mode >> 12) & 15;
 }

 /*
  * Directory is locked and all positive dentries in it are safe, since
  * for ramfs-type trees they can't go away without unlink() or rmdir(),
  * both impossible due to the lock on directory.
  */

 int dcache_readdir(struct file * filp, void * dirent, filldir_t filldir)
 {
 	struct dentry *dentry = filp->f_dentry;
 	struct dentry *cursor = filp->private_data;
 	struct list_head *p, *q = &cursor->d_u.d_child;
 	ino_t ino;
 	int i = filp->f_pos;

 	switch (i) {
 		case 0:
 			ino = dentry->d_inode->i_ino;
 			if (filldir(dirent, ".", 1, i, ino, DT_DIR) < 0)
 				break;
 			filp->f_pos++;
 			i++;
 			/* fallthrough */
 		case 1:
 			ino = parent_ino(dentry);
 			if (filldir(dirent, "..", 2, i, ino, DT_DIR) < 0)
 				break;
 			filp->f_pos++;
 			i++;
 			/* fallthrough */
 		default:
 			spin_lock(&dcache_lock);
 			if (filp->f_pos == 2)
 				list_move(q, &dentry->d_subdirs);

 			for (p=q->next; p != &dentry->d_subdirs; p=p->next) {
 				struct dentry *next;
 				next = list_entry(p, struct dentry, d_u.d_child);
 				if (d_unhashed(next) || !next->d_inode)
 					continue;

 				spin_unlock(&dcache_lock);
 				if (filldir(dirent, next->d_name.name, next->d_name.len, filp->f_pos, next->d_inode->i_ino, dt_type(next->d_inode)) < 0)
 					return 0;
 				spin_lock(&dcache_lock);
 				/* next is still alive */
 				list_move(q, p);
 				p = q;
 				filp->f_pos++;
 			}
 			spin_unlock(&dcache_lock);
 	}
 	return 0;
 }

 ssize_t generic_read_dir(struct file *filp, char __user *buf, size_t siz, loff_t *ppos)
 {
 	return -EISDIR;
 }

 const struct file_operations simple_dir_operations = {
 	.open		= dcache_dir_open,
 	.release	= dcache_dir_close,
 	.llseek		= dcache_dir_lseek,
 	.read		= generic_read_dir,
 	.readdir	= dcache_readdir,
 	.fsync		= simple_sync_file,
 };

 struct inode_operations simple_dir_inode_operations = {
 	.lookup		= simple_lookup,
 };

 /*
  * Common helper for pseudo-filesystems (sockfs, pipefs, bdev - stuff that
  * will never be mountable)
  */
 int get_sb_pseudo(struct file_system_type *fs_type, char *name,
 	struct super_operations *ops, unsigned long magic,
 	struct vfsmount *mnt)
 {
 	struct super_block *s = sget(fs_type, NULL, set_anon_super, NULL);
 	static struct super_operations default_ops = {.statfs = simple_statfs};
 	struct dentry *dentry;
 	struct inode *root;
 	struct qstr d_name = {.name = name, .len = strlen(name)};

 	if (IS_ERR(s))
 		return PTR_ERR(s);

 	s->s_flags = MS_NOUSER;
 	s->s_maxbytes = ~0ULL;
 	s->s_blocksize = 1024;
 	s->s_blocksize_bits = 10;
 	s->s_magic = magic;
 	s->s_op = ops ? ops : &default_ops;
 	s->s_time_gran = 1;
 	root = new_inode(s);
 	if (!root)
 		goto Enomem;
 	root->i_mode = S_IFDIR | S_IRUSR | S_IWUSR;
 	root->i_uid = root->i_gid = 0;
 	root->i_atime = root->i_mtime = root->i_ctime = CURRENT_TIME;
 	dentry = d_alloc(NULL, &d_name);
 	if (!dentry) {
 		iput(root);
 		goto Enomem;
 	}
 	dentry->d_sb = s;
 	dentry->d_parent = dentry;
 	d_instantiate(dentry, root);
 	s->s_root = dentry;
 	s->s_flags |= MS_ACTIVE;
 	return simple_set_mnt(mnt, s);

 Enomem:
 	up_write(&s->s_umount);
 	deactivate_super(s);
 	return -ENOMEM;
 }

 int simple_link(struct dentry *old_dentry, struct inode *dir, struct dentry *dentry)
 {
 	struct inode *inode = old_dentry->d_inode;

 	inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
 	inode->i_nlink++;
 	atomic_inc(&inode->i_count);
 	dget(dentry);
 	d_instantiate(dentry, inode);
 	return 0;
 }

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

 int simple_empty(struct dentry *dentry)
 {
 	struct dentry *child;
 	int ret = 0;

 	spin_lock(&dcache_lock);
 	list_for_each_entry(child, &dentry->d_subdirs, d_u.d_child)
 		if (simple_positive(child))
 			goto out;
 	ret = 1;
 out:
 	spin_unlock(&dcache_lock);
 	return ret;
 }

 int simple_unlink(struct inode *dir, struct dentry *dentry)
 {
 	struct inode *inode = dentry->d_inode;

 	inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
 	drop_nlink(inode);
 	dput(dentry);
 	return 0;
 }

 int simple_rmdir(struct inode *dir, struct dentry *dentry)
 {
 	if (!simple_empty(dentry))
 		return -ENOTEMPTY;

 	drop_nlink(dentry->d_inode);
 	simple_unlink(dir, dentry);
 	drop_nlink(dir);
 	return 0;
 }

 int simple_rename(struct inode *old_dir, struct dentry *old_dentry,
 		struct inode *new_dir, struct dentry *new_dentry)
 {
 	struct inode *inode = old_dentry->d_inode;
 	int they_are_dirs = S_ISDIR(old_dentry->d_inode->i_mode);

 	if (!simple_empty(new_dentry))
 		return -ENOTEMPTY;

 	if (new_dentry->d_inode) {
 		simple_unlink(new_dir, new_dentry);
 		if (they_are_dirs)
 			drop_nlink(old_dir);
 	} else if (they_are_dirs) {
 		drop_nlink(old_dir);
 		new_dir->i_nlink++;
 	}

 	old_dir->i_ctime = old_dir->i_mtime = new_dir->i_ctime =
 		new_dir->i_mtime = inode->i_ctime = CURRENT_TIME;

 	return 0;
 }

 int simple_readpage(struct file *file, struct page *page)
 {
 	clear_highpage(page);
 	flush_dcache_page(page);
 	SetPageUptodate(page);
 	unlock_page(page);
 	return 0;
 }

 int simple_prepare_write(struct file *file, struct page *page,
 			unsigned from, unsigned to)
 {
 	if (!PageUptodate(page)) {
 		if (to - from != PAGE_CACHE_SIZE) {
 			void *kaddr = kmap_atomic(page, KM_USER0);
 			memset(kaddr, 0, from);
 			memset(kaddr + to, 0, PAGE_CACHE_SIZE - to);
 			flush_dcache_page(page);
 			kunmap_atomic(kaddr, KM_USER0);
 		}
 		SetPageUptodate(page);
 	}
 	return 0;
 }

 int simple_commit_write(struct file *file, struct page *page,
 			unsigned offset, unsigned to)
 {
 	struct inode *inode = page->mapping->host;
 	loff_t pos = ((loff_t)page->index << PAGE_CACHE_SHIFT) + to;

 	/*
 	 * No need to use i_size_read() here, the i_size
 	 * cannot change under us because we hold the i_mutex.
 	 */
 	if (pos > inode->i_size)
 		i_size_write(inode, pos);
 	set_page_dirty(page);
 	return 0;
 }

 int simple_fill_super(struct super_block *s, int magic, struct tree_descr *files)
 {
 	static struct super_operations s_ops = {.statfs = simple_statfs};
 	struct inode *inode;
 	struct dentry *root;
 	struct dentry *dentry;
 	int i;

 	s->s_blocksize = PAGE_CACHE_SIZE;
 	s->s_blocksize_bits = PAGE_CACHE_SHIFT;
 	s->s_magic = magic;
 	s->s_op = &s_ops;
 	s->s_time_gran = 1;

 	inode = new_inode(s);
 	if (!inode)
 		return -ENOMEM;
 	inode->i_mode = S_IFDIR | 0755;
 	inode->i_uid = inode->i_gid = 0;
 	inode->i_blocks = 0;
 	inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
 	inode->i_op = &simple_dir_inode_operations;
 	inode->i_fop = &simple_dir_operations;
 	inode->i_nlink = 2;
 	root = d_alloc_root(inode);
 	if (!root) {
 		iput(inode);
 		return -ENOMEM;
 	}
 	for (i = 0; !files->name || files->name[0]; i++, files++) {
 		if (!files->name)
 			continue;
 		dentry = d_alloc_name(root, files->name);
 		if (!dentry)
 			goto out;
 		inode = new_inode(s);
 		if (!inode)
 			goto out;
 		inode->i_mode = S_IFREG | files->mode;
 		inode->i_uid = inode->i_gid = 0;
 		inode->i_blocks = 0;
 		inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
 		inode->i_fop = files->ops;
 		inode->i_ino = i;
 		d_add(dentry, inode);
 	}
 	s->s_root = root;
 	return 0;
 out:
 	d_genocide(root);
 	dput(root);
 	return -ENOMEM;
 }

 static DEFINE_SPINLOCK(pin_fs_lock);

 int simple_pin_fs(struct file_system_type *type, struct vfsmount **mount, int *count)
 {
 	struct vfsmount *mnt = NULL;
 	spin_lock(&pin_fs_lock);
 	if (unlikely(!*mount)) {
 		spin_unlock(&pin_fs_lock);
 		mnt = vfs_kern_mount(type, 0, type->name, NULL);
 		if (IS_ERR(mnt))
 			return PTR_ERR(mnt);
 		spin_lock(&pin_fs_lock);
 		if (!*mount)
 			*mount = mnt;
 	}
 	mntget(*mount);
 	++*count;
 	spin_unlock(&pin_fs_lock);
 	mntput(mnt);
 	return 0;
 }

 void simple_release_fs(struct vfsmount **mount, int *count)
 {
 	struct vfsmount *mnt;
 	spin_lock(&pin_fs_lock);
 	mnt = *mount;
 	if (!--*count)
 		*mount = NULL;
 	spin_unlock(&pin_fs_lock);
 	mntput(mnt);
 }

 ssize_t simple_read_from_buffer(void __user *to, size_t count, loff_t *ppos,
 				const void *from, size_t available)
 {
 	loff_t pos = *ppos;
 	if (pos < 0)
 		return -EINVAL;
 	if (pos >= available)
 		return 0;
 	if (count > available - pos)
 		count = available - pos;
 	if (copy_to_user(to, from + pos, count))
 		return -EFAULT;
 	*ppos = pos + count;
 	return count;
 }

 /*
  * Transaction based IO.
  * The file expects a single write which triggers the transaction, and then
  * possibly a read which collects the result - which is stored in a
  * file-local buffer.
  */
 char *simple_transaction_get(struct file *file, const char __user *buf, size_t size)
 {
 	struct simple_transaction_argresp *ar;
 	static DEFINE_SPINLOCK(simple_transaction_lock);

 	if (size > SIMPLE_TRANSACTION_LIMIT - 1)
 		return ERR_PTR(-EFBIG);

 	ar = (struct simple_transaction_argresp *)get_zeroed_page(GFP_KERNEL);
 	if (!ar)
 		return ERR_PTR(-ENOMEM);

 	spin_lock(&simple_transaction_lock);

 	/* only one write allowed per open */
 	if (file->private_data) {
 		spin_unlock(&simple_transaction_lock);
 		free_page((unsigned long)ar);
 		return ERR_PTR(-EBUSY);
 	}

 	file->private_data = ar;

 	spin_unlock(&simple_transaction_lock);

 	if (copy_from_user(ar->data, buf, size))
 		return ERR_PTR(-EFAULT);

 	return ar->data;
 }

 ssize_t simple_transaction_read(struct file *file, char __user *buf, size_t size, loff_t *pos)
 {
 	struct simple_transaction_argresp *ar = file->private_data;

 	if (!ar)
 		return 0;
 	return simple_read_from_buffer(buf, size, pos, ar->data, ar->size);
 }

 int simple_transaction_release(struct inode *inode, struct file *file)
 {
 	free_page((unsigned long)file->private_data);
 	return 0;
 }

 /* Simple attribute files */

 struct simple_attr {
 	u64 (*get)(void *);
 	void (*set)(void *, u64);
 	char get_buf[24];	/* enough to store a u64 and "\n\0" */
 	char set_buf[24];
 	void *data;
 	const char *fmt;	/* format for read operation */
 	struct mutex mutex;	/* protects access to these buffers */
 };

 /* simple_attr_open is called by an actual attribute open file operation
  * to set the attribute specific access operations. */
 int simple_attr_open(struct inode *inode, struct file *file,
 		     u64 (*get)(void *), void (*set)(void *, u64),
 		     const char *fmt)
 {
 	struct simple_attr *attr;

 	attr = kmalloc(sizeof(*attr), GFP_KERNEL);
 	if (!attr)
 		return -ENOMEM;

 	attr->get = get;
 	attr->set = set;
 	attr->data = inode->i_private;
 	attr->fmt = fmt;
 	mutex_init(&attr->mutex);

 	file->private_data = attr;

 	return nonseekable_open(inode, file);
 }

 int simple_attr_close(struct inode *inode, struct file *file)
 {
 	kfree(file->private_data);
 	return 0;
 }

 /* read from the buffer that is filled with the get function */
 ssize_t simple_attr_read(struct file *file, char __user *buf,
 			 size_t len, loff_t *ppos)
 {
 	struct simple_attr *attr;
 	size_t size;
 	ssize_t ret;

 	attr = file->private_data;

 	if (!attr->get)
 		return -EACCES;

 	mutex_lock(&attr->mutex);
 	if (*ppos) /* continued read */
 		size = strlen(attr->get_buf);
 	else	  /* first read */
 		size = scnprintf(attr->get_buf, sizeof(attr->get_buf),
 				 attr->fmt,
 				 (unsigned long long)attr->get(attr->data));

 	ret = simple_read_from_buffer(buf, len, ppos, attr->get_buf, size);
 	mutex_unlock(&attr->mutex);
 	return ret;
 }

 /* interpret the buffer as a number to call the set function with */
 ssize_t simple_attr_write(struct file *file, const char __user *buf,
 			  size_t len, loff_t *ppos)
 {
 	struct simple_attr *attr;
 	u64 val;
 	size_t size;
 	ssize_t ret;

 	attr = file->private_data;

 	if (!attr->set)
 		return -EACCES;

 	mutex_lock(&attr->mutex);
 	ret = -EFAULT;
 	size = min(sizeof(attr->set_buf) - 1, len);
 	if (copy_from_user(attr->set_buf, buf, size))
 		goto out;

 	ret = len; /* claim we got the whole input */
 	attr->set_buf[size] = '\0';
 	val = simple_strtol(attr->set_buf, NULL, 0);
 	attr->set(attr->data, val);
 out:
 	mutex_unlock(&attr->mutex);
 	return ret;
 }

 EXPORT_SYMBOL(dcache_dir_close);
 EXPORT_SYMBOL(dcache_dir_lseek);
 EXPORT_SYMBOL(dcache_dir_open);
 EXPORT_SYMBOL(dcache_readdir);
 EXPORT_SYMBOL(generic_read_dir);
 EXPORT_SYMBOL(get_sb_pseudo);
 EXPORT_SYMBOL(simple_commit_write);
 EXPORT_SYMBOL(simple_dir_inode_operations);
 EXPORT_SYMBOL(simple_dir_operations);
 EXPORT_SYMBOL(simple_empty);
 EXPORT_SYMBOL(d_alloc_name);
 EXPORT_SYMBOL(simple_fill_super);
 EXPORT_SYMBOL(simple_getattr);
 EXPORT_SYMBOL(simple_link);
 EXPORT_SYMBOL(simple_lookup);
 EXPORT_SYMBOL(simple_pin_fs);
 EXPORT_SYMBOL(simple_prepare_write);
 EXPORT_SYMBOL(simple_readpage);
 EXPORT_SYMBOL(simple_release_fs);
 EXPORT_SYMBOL(simple_rename);
 EXPORT_SYMBOL(simple_rmdir);
 EXPORT_SYMBOL(simple_statfs);
 EXPORT_SYMBOL(simple_sync_file);
 EXPORT_SYMBOL(simple_unlink);
 EXPORT_SYMBOL(simple_read_from_buffer);
 EXPORT_SYMBOL(simple_transaction_get);
 EXPORT_SYMBOL(simple_transaction_read);
 EXPORT_SYMBOL(simple_transaction_release);
 EXPORT_SYMBOL_GPL(simple_attr_open);
 EXPORT_SYMBOL_GPL(simple_attr_close);
 EXPORT_SYMBOL_GPL(simple_attr_read);
 EXPORT_SYMBOL_GPL(simple_attr_write);
	/*
	* fs/libfs.c
	* Library for filesystems writers.
	*/

	#include <linux/module.h>
	#include <linux/pagemap.h>
	#include <linux/mount.h>
	#include <linux/vfs.h>
	#include <linux/mutex.h>

	#include <asm/uaccess.h>

	int simple_getattr(struct vfsmount mnt, struct dentry dentry,
	struct kstat *stat)
	{
	struct inode *inode = dentry->d_inode;
	generic_fillattr(inode, stat);
	stat->blocks = inode->i_mapping->nrpages << (PAGE_CACHE_SHIFT - 9);
	return 0;
	}

	int simple_statfs(struct dentry dentry, struct kstatfs buf)
	{
	buf->f_type = dentry->d_sb->s_magic;
	buf->f_bsize = PAGE_CACHE_SIZE;
	buf->f_namelen = NAME_MAX;
	return 0;
	}

	/*
	* Retaining negative dentries for an in-memory filesystem just wastes
	* memory and lookup time: arrange for them to be deleted immediately.
	*/
	static int simple_delete_dentry(struct dentry *dentry)
	{
	return 1;
	}

	/*
	* Lookup the data. This is trivial - if the dentry didn't already
	* exist, we know it is negative. Set d_op to delete negative dentries.
	*/
	struct dentry simple_lookup(struct inode dir, struct dentry dentry, struct nameidata nd)
	{
	static struct dentry_operations simple_dentry_operations = {
	.d_delete = simple_delete_dentry,
	};

	if (dentry->d_name.len > NAME_MAX)
	return ERR_PTR(-ENAMETOOLONG);
	dentry->d_op = &simple_dentry_operations;
	d_add(dentry, NULL);
	return NULL;
	}

	int simple_sync_file(struct file * file, struct dentry *dentry, int datasync)
	{
	return 0;
	}

	int dcache_dir_open(struct inode inode, struct file file)
	{
	static struct qstr cursor_name = {.len = 1, .name = "."};

	file->private_data = d_alloc(file->f_dentry, &cursor_name);

	return file->private_data ? 0 : -ENOMEM;
	}

	int dcache_dir_close(struct inode inode, struct file file)
	{
	dput(file->private_data);
	return 0;
	}

	loff_t dcache_dir_lseek(struct file *file, loff_t offset, int origin)
	{
	mutex_lock(&file->f_dentry->d_inode->i_mutex);
	switch (origin) {
	case 1:
	offset += file->f_pos;
	case 0:
	if (offset >= 0)
	break;
	default:
	mutex_unlock(&file->f_dentry->d_inode->i_mutex);
	return -EINVAL;
	}
	if (offset != file->f_pos) {
	file->f_pos = offset;
	if (file->f_pos >= 2) {
	struct list_head *p;
	struct dentry *cursor = file->private_data;
	loff_t n = file->f_pos - 2;

	spin_lock(&dcache_lock);
	list_del(&cursor->d_u.d_child);
	p = file->f_dentry->d_subdirs.next;
	while (n && p != &file->f_dentry->d_subdirs) {
	struct dentry *next;
	next = list_entry(p, struct dentry, d_u.d_child);
	if (!d_unhashed(next) && next->d_inode)
	n--;
	p = p->next;
	}
	list_add_tail(&cursor->d_u.d_child, p);
	spin_unlock(&dcache_lock);
	}
	}
	mutex_unlock(&file->f_dentry->d_inode->i_mutex);
	return offset;
	}

	/* Relationship between i_mode and the DT_xxx types */
	static inline unsigned char dt_type(struct inode *inode)
	{
	return (inode->i_mode >> 12) & 15;
	}

	/*
	* Directory is locked and all positive dentries in it are safe, since
	* for ramfs-type trees they can't go away without unlink() or rmdir(),
	* both impossible due to the lock on directory.
	*/

	int dcache_readdir(struct file * filp, void * dirent, filldir_t filldir)
	{
	struct dentry *dentry = filp->f_dentry;
	struct dentry *cursor = filp->private_data;
	struct list_head p, q = &cursor->d_u.d_child;
	ino_t ino;
	int i = filp->f_pos;

	switch (i) {
	case 0:
	ino = dentry->d_inode->i_ino;
	if (filldir(dirent, ".", 1, i, ino, DT_DIR) < 0)
	break;
	filp->f_pos++;
	i++;
	/* fallthrough */
	case 1:
	ino = parent_ino(dentry);
	if (filldir(dirent, "..", 2, i, ino, DT_DIR) < 0)
	break;
	filp->f_pos++;
	i++;
	/* fallthrough */
	default:
	spin_lock(&dcache_lock);
	if (filp->f_pos == 2)
	list_move(q, &dentry->d_subdirs);

	for (p=q->next; p != &dentry->d_subdirs; p=p->next) {
	struct dentry *next;
	next = list_entry(p, struct dentry, d_u.d_child);
	if (d_unhashed(next) \|\| !next->d_inode)
	continue;

	spin_unlock(&dcache_lock);
	if (filldir(dirent, next->d_name.name, next->d_name.len, filp->f_pos, next->d_inode->i_ino, dt_type(next->d_inode)) < 0)
	return 0;
	spin_lock(&dcache_lock);
	/* next is still alive */
	list_move(q, p);
	p = q;
	filp->f_pos++;
	}
	spin_unlock(&dcache_lock);
	}
	return 0;
	}

	ssize_t generic_read_dir(struct file filp, char __user buf, size_t siz, loff_t *ppos)
	{
	return -EISDIR;
	}

	const struct file_operations simple_dir_operations = {
	.open = dcache_dir_open,
	.release = dcache_dir_close,
	.llseek = dcache_dir_lseek,
	.read = generic_read_dir,
	.readdir = dcache_readdir,
	.fsync = simple_sync_file,
	};

	struct inode_operations simple_dir_inode_operations = {
	.lookup = simple_lookup,
	};

	/*
	* Common helper for pseudo-filesystems (sockfs, pipefs, bdev - stuff that
	* will never be mountable)
	*/
	int get_sb_pseudo(struct file_system_type fs_type, char name,
	struct super_operations *ops, unsigned long magic,
	struct vfsmount *mnt)
	{
	struct super_block *s = sget(fs_type, NULL, set_anon_super, NULL);
	static struct super_operations default_ops = {.statfs = simple_statfs};
	struct dentry *dentry;
	struct inode *root;
	struct qstr d_name = {.name = name, .len = strlen(name)};

	if (IS_ERR(s))
	return PTR_ERR(s);

	s->s_flags = MS_NOUSER;
	s->s_maxbytes = ~0ULL;
	s->s_blocksize = 1024;
	s->s_blocksize_bits = 10;
	s->s_magic = magic;
	s->s_op = ops ? ops : &default_ops;
	s->s_time_gran = 1;
	root = new_inode(s);
	if (!root)
	goto Enomem;
	root->i_mode = S_IFDIR \| S_IRUSR \| S_IWUSR;
	root->i_uid = root->i_gid = 0;
	root->i_atime = root->i_mtime = root->i_ctime = CURRENT_TIME;
	dentry = d_alloc(NULL, &d_name);
	if (!dentry) {
	iput(root);
	goto Enomem;
	}
	dentry->d_sb = s;
	dentry->d_parent = dentry;
	d_instantiate(dentry, root);
	s->s_root = dentry;
	s->s_flags \|= MS_ACTIVE;
	return simple_set_mnt(mnt, s);

	Enomem:
	up_write(&s->s_umount);
	deactivate_super(s);
	return -ENOMEM;
	}

	int simple_link(struct dentry old_dentry, struct inode dir, struct dentry *dentry)
	{
	struct inode *inode = old_dentry->d_inode;

	inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
	inode->i_nlink++;
	atomic_inc(&inode->i_count);
	dget(dentry);
	d_instantiate(dentry, inode);
	return 0;
	}

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

	int simple_empty(struct dentry *dentry)
	{
	struct dentry *child;
	int ret = 0;

	spin_lock(&dcache_lock);
	list_for_each_entry(child, &dentry->d_subdirs, d_u.d_child)
	if (simple_positive(child))
	goto out;
	ret = 1;
	out:
	spin_unlock(&dcache_lock);
	return ret;
	}

	int simple_unlink(struct inode dir, struct dentry dentry)
	{
	struct inode *inode = dentry->d_inode;

	inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
	drop_nlink(inode);
	dput(dentry);
	return 0;
	}

	int simple_rmdir(struct inode dir, struct dentry dentry)
	{
	if (!simple_empty(dentry))
	return -ENOTEMPTY;

	drop_nlink(dentry->d_inode);
	simple_unlink(dir, dentry);
	drop_nlink(dir);
	return 0;
	}

	int simple_rename(struct inode old_dir, struct dentry old_dentry,
	struct inode new_dir, struct dentry new_dentry)
	{
	struct inode *inode = old_dentry->d_inode;
	int they_are_dirs = S_ISDIR(old_dentry->d_inode->i_mode);

	if (!simple_empty(new_dentry))
	return -ENOTEMPTY;

	if (new_dentry->d_inode) {
	simple_unlink(new_dir, new_dentry);
	if (they_are_dirs)
	drop_nlink(old_dir);
	} else if (they_are_dirs) {
	drop_nlink(old_dir);
	new_dir->i_nlink++;
	}

	old_dir->i_ctime = old_dir->i_mtime = new_dir->i_ctime =
	new_dir->i_mtime = inode->i_ctime = CURRENT_TIME;

	return 0;
	}

	int simple_readpage(struct file file, struct page page)
	{
	clear_highpage(page);
	flush_dcache_page(page);
	SetPageUptodate(page);
	unlock_page(page);
	return 0;
	}

	int simple_prepare_write(struct file file, struct page page,
	unsigned from, unsigned to)
	{
	if (!PageUptodate(page)) {
	if (to - from != PAGE_CACHE_SIZE) {
	void *kaddr = kmap_atomic(page, KM_USER0);
	memset(kaddr, 0, from);
	memset(kaddr + to, 0, PAGE_CACHE_SIZE - to);
	flush_dcache_page(page);
	kunmap_atomic(kaddr, KM_USER0);
	}
	SetPageUptodate(page);
	}
	return 0;
	}

	int simple_commit_write(struct file file, struct page page,
	unsigned offset, unsigned to)
	{
	struct inode *inode = page->mapping->host;
	loff_t pos = ((loff_t)page->index << PAGE_CACHE_SHIFT) + to;

	/*
	* No need to use i_size_read() here, the i_size
	* cannot change under us because we hold the i_mutex.
	*/
	if (pos > inode->i_size)
	i_size_write(inode, pos);
	set_page_dirty(page);
	return 0;
	}

	int simple_fill_super(struct super_block s, int magic, struct tree_descr files)
	{
	static struct super_operations s_ops = {.statfs = simple_statfs};
	struct inode *inode;
	struct dentry *root;
	struct dentry *dentry;
	int i;

	s->s_blocksize = PAGE_CACHE_SIZE;
	s->s_blocksize_bits = PAGE_CACHE_SHIFT;
	s->s_magic = magic;
	s->s_op = &s_ops;
	s->s_time_gran = 1;

	inode = new_inode(s);
	if (!inode)
	return -ENOMEM;
	inode->i_mode = S_IFDIR \| 0755;
	inode->i_uid = inode->i_gid = 0;
	inode->i_blocks = 0;
	inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
	inode->i_op = &simple_dir_inode_operations;
	inode->i_fop = &simple_dir_operations;
	inode->i_nlink = 2;
	root = d_alloc_root(inode);
	if (!root) {
	iput(inode);
	return -ENOMEM;
	}
	for (i = 0; !files->name \|\| files->name[0]; i++, files++) {
	if (!files->name)
	continue;
	dentry = d_alloc_name(root, files->name);
	if (!dentry)
	goto out;
	inode = new_inode(s);
	if (!inode)
	goto out;
	inode->i_mode = S_IFREG \| files->mode;
	inode->i_uid = inode->i_gid = 0;
	inode->i_blocks = 0;
	inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
	inode->i_fop = files->ops;
	inode->i_ino = i;
	d_add(dentry, inode);
	}
	s->s_root = root;
	return 0;
	out:
	d_genocide(root);
	dput(root);
	return -ENOMEM;
	}

	static DEFINE_SPINLOCK(pin_fs_lock);

	int simple_pin_fs(struct file_system_type type, struct vfsmount mount, int count)
	{
	struct vfsmount *mnt = NULL;
	spin_lock(&pin_fs_lock);
	if (unlikely(!*mount)) {
	spin_unlock(&pin_fs_lock);
	mnt = vfs_kern_mount(type, 0, type->name, NULL);
	if (IS_ERR(mnt))
	return PTR_ERR(mnt);
	spin_lock(&pin_fs_lock);
	if (!*mount)
	*mount = mnt;
	}
	mntget(*mount);
	++*count;
	spin_unlock(&pin_fs_lock);
	mntput(mnt);
	return 0;
	}

	void simple_release_fs(struct vfsmount *mount, int count)
	{
	struct vfsmount *mnt;
	spin_lock(&pin_fs_lock);
	mnt = *mount;
	if (!--*count)
	*mount = NULL;
	spin_unlock(&pin_fs_lock);
	mntput(mnt);
	}

	ssize_t simple_read_from_buffer(void __user to, size_t count, loff_t ppos,
	const void *from, size_t available)
	{
	loff_t pos = *ppos;
	if (pos < 0)
	return -EINVAL;
	if (pos >= available)
	return 0;
	if (count > available - pos)
	count = available - pos;
	if (copy_to_user(to, from + pos, count))
	return -EFAULT;
	*ppos = pos + count;
	return count;
	}

	/*
	* Transaction based IO.
	* The file expects a single write which triggers the transaction, and then
	* possibly a read which collects the result - which is stored in a
	* file-local buffer.
	*/
	char simple_transaction_get(struct file file, const char __user *buf, size_t size)
	{
	struct simple_transaction_argresp *ar;
	static DEFINE_SPINLOCK(simple_transaction_lock);

	if (size > SIMPLE_TRANSACTION_LIMIT - 1)
	return ERR_PTR(-EFBIG);

	ar = (struct simple_transaction_argresp *)get_zeroed_page(GFP_KERNEL);
	if (!ar)
	return ERR_PTR(-ENOMEM);

	spin_lock(&simple_transaction_lock);

	/* only one write allowed per open */
	if (file->private_data) {
	spin_unlock(&simple_transaction_lock);
	free_page((unsigned long)ar);
	return ERR_PTR(-EBUSY);
	}

	file->private_data = ar;

	spin_unlock(&simple_transaction_lock);

	if (copy_from_user(ar->data, buf, size))
	return ERR_PTR(-EFAULT);

	return ar->data;
	}

	ssize_t simple_transaction_read(struct file file, char __user buf, size_t size, loff_t *pos)
	{
	struct simple_transaction_argresp *ar = file->private_data;

	if (!ar)
	return 0;
	return simple_read_from_buffer(buf, size, pos, ar->data, ar->size);
	}

	int simple_transaction_release(struct inode inode, struct file file)
	{
	free_page((unsigned long)file->private_data);
	return 0;
	}

	/* Simple attribute files */

	struct simple_attr {
	u64 (get)(void );
	void (set)(void , u64);
	char get_buf[24]; /* enough to store a u64 and "\n\0" */
	char set_buf[24];
	void *data;
	const char fmt; / format for read operation */
	struct mutex mutex; /* protects access to these buffers */
	};

	/* simple_attr_open is called by an actual attribute open file operation
	* to set the attribute specific access operations. */
	int simple_attr_open(struct inode inode, struct file file,
	u64 (get)(void ), void (set)(void , u64),
	const char *fmt)
	{
	struct simple_attr *attr;

	attr = kmalloc(sizeof(*attr), GFP_KERNEL);
	if (!attr)
	return -ENOMEM;

	attr->get = get;
	attr->set = set;
	attr->data = inode->i_private;
	attr->fmt = fmt;
	mutex_init(&attr->mutex);

	file->private_data = attr;

	return nonseekable_open(inode, file);
	}

	int simple_attr_close(struct inode inode, struct file file)
	{
	kfree(file->private_data);
	return 0;
	}

	/* read from the buffer that is filled with the get function */
	ssize_t simple_attr_read(struct file file, char __user buf,
	size_t len, loff_t *ppos)
	{
	struct simple_attr *attr;
	size_t size;
	ssize_t ret;

	attr = file->private_data;

	if (!attr->get)
	return -EACCES;

	mutex_lock(&attr->mutex);
	if (ppos) / continued read */
	size = strlen(attr->get_buf);
	else /* first read */
	size = scnprintf(attr->get_buf, sizeof(attr->get_buf),
	attr->fmt,
	(unsigned long long)attr->get(attr->data));

	ret = simple_read_from_buffer(buf, len, ppos, attr->get_buf, size);
	mutex_unlock(&attr->mutex);
	return ret;
	}

	/* interpret the buffer as a number to call the set function with */
	ssize_t simple_attr_write(struct file file, const char __user buf,
	size_t len, loff_t *ppos)
	{
	struct simple_attr *attr;
	u64 val;
	size_t size;
	ssize_t ret;

	attr = file->private_data;

	if (!attr->set)
	return -EACCES;

	mutex_lock(&attr->mutex);
	ret = -EFAULT;
	size = min(sizeof(attr->set_buf) - 1, len);
	if (copy_from_user(attr->set_buf, buf, size))
	goto out;

	ret = len; /* claim we got the whole input */
	attr->set_buf[size] = '\0';
	val = simple_strtol(attr->set_buf, NULL, 0);
	attr->set(attr->data, val);
	out:
	mutex_unlock(&attr->mutex);
	return ret;
	}

	EXPORT_SYMBOL(dcache_dir_close);
	EXPORT_SYMBOL(dcache_dir_lseek);
	EXPORT_SYMBOL(dcache_dir_open);
	EXPORT_SYMBOL(dcache_readdir);
	EXPORT_SYMBOL(generic_read_dir);
	EXPORT_SYMBOL(get_sb_pseudo);
	EXPORT_SYMBOL(simple_commit_write);
	EXPORT_SYMBOL(simple_dir_inode_operations);
	EXPORT_SYMBOL(simple_dir_operations);
	EXPORT_SYMBOL(simple_empty);
	EXPORT_SYMBOL(d_alloc_name);
	EXPORT_SYMBOL(simple_fill_super);
	EXPORT_SYMBOL(simple_getattr);
	EXPORT_SYMBOL(simple_link);
	EXPORT_SYMBOL(simple_lookup);
	EXPORT_SYMBOL(simple_pin_fs);
	EXPORT_SYMBOL(simple_prepare_write);
	EXPORT_SYMBOL(simple_readpage);
	EXPORT_SYMBOL(simple_release_fs);
	EXPORT_SYMBOL(simple_rename);
	EXPORT_SYMBOL(simple_rmdir);
	EXPORT_SYMBOL(simple_statfs);
	EXPORT_SYMBOL(simple_sync_file);
	EXPORT_SYMBOL(simple_unlink);
	EXPORT_SYMBOL(simple_read_from_buffer);
	EXPORT_SYMBOL(simple_transaction_get);
	EXPORT_SYMBOL(simple_transaction_read);
	EXPORT_SYMBOL(simple_transaction_release);
	EXPORT_SYMBOL_GPL(simple_attr_open);
	EXPORT_SYMBOL_GPL(simple_attr_close);
	EXPORT_SYMBOL_GPL(simple_attr_read);
	EXPORT_SYMBOL_GPL(simple_attr_write);