path: root/ANDROID_3.4.5/fs/yaffs2/yaffs_vfs.c

/*
 * YAFFS: Yet Another Flash File System. A NAND-flash specific file system.
 *
 * Copyright (C) 2002-2010 Aleph One Ltd.
 *   for Toby Churchill Ltd and Brightstar Engineering
 *
 * Created by Charles Manning <charles@aleph1.co.uk>
 * Acknowledgements:
 * Luc van OostenRyck for numerous patches.
 * Nick Bane for numerous patches.
 * Nick Bane for 2.5/2.6 integration.
 * Andras Toth for mknod rdev issue.
 * Michael Fischer for finding the problem with inode inconsistency.
 * Some code bodily lifted from JFFS
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */

/*
 *
 * This is the file system front-end to YAFFS that hooks it up to
 * the VFS.
 *
 * Special notes:
 * >> 2.4: sb->u.generic_sbp points to the struct yaffs_dev associated with
 *         this superblock
 * >> 2.6: sb->s_fs_info  points to the struct yaffs_dev associated with this
 *         superblock
 * >> inode->u.generic_ip points to the associated struct yaffs_obj.
 */

/*
 * NB There are two variants of Linux VFS glue code. This variant supports
 * a single version and should not include any multi-version code.
 */
#include <linux/version.h>

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/init.h>
#include <linux/fs.h>
#include <linux/proc_fs.h>
#include <linux/smp_lock.h>
#include <linux/pagemap.h>
#include <linux/mtd/mtd.h>
#include <linux/interrupt.h>
#include <linux/string.h>
#include <linux/ctype.h>
#include <linux/namei.h>
#include <linux/exportfs.h>
#include <linux/kthread.h>
#include <linux/delay.h>
#include <linux/freezer.h>

#include <asm/div64.h>

#include <linux/statfs.h>

#define UnlockPage(p) unlock_page(p)
#define Page_Uptodate(page)	test_bit(PG_uptodate, &(page)->flags)

#define yaffs_devname(sb, buf)	bdevname(sb->s_bdev, buf)

#define YPROC_ROOT  NULL

#define Y_INIT_TIMER(a)	init_timer_on_stack(a)

#define WRITE_SIZE_STR "writesize"
#define WRITE_SIZE(mtd) ((mtd)->writesize)

static uint32_t YCALCBLOCKS(uint64_t partition_size, uint32_t block_size)
{
	uint64_t result = partition_size;
	do_div(result, block_size);
	return (uint32_t) result;
}

#include <linux/uaccess.h>
#include <linux/mtd/mtd.h>

#include "yportenv.h"
#include "yaffs_trace.h"
#include "yaffs_guts.h"
#include "yaffs_attribs.h"

#include "yaffs_linux.h"

#include "yaffs_mtdif.h"
#include "yaffs_mtdif1.h"
#include "yaffs_mtdif2.h"

unsigned int yaffs_trace_mask = YAFFS_TRACE_BAD_BLOCKS | YAFFS_TRACE_ALWAYS;
unsigned int yaffs_wr_attempts = YAFFS_WR_ATTEMPTS;
unsigned int yaffs_auto_checkpoint = 1;
unsigned int yaffs_gc_control = 1;
unsigned int yaffs_bg_enable = 1;

/* Module Parameters */
module_param(yaffs_trace_mask, uint, 0644);
module_param(yaffs_wr_attempts, uint, 0644);
module_param(yaffs_auto_checkpoint, uint, 0644);
module_param(yaffs_gc_control, uint, 0644);
module_param(yaffs_bg_enable, uint, 0644);


#define yaffs_inode_to_obj_lv(iptr) ((iptr)->i_private)
#define yaffs_inode_to_obj(iptr) ((struct yaffs_obj *)(yaffs_inode_to_obj_lv(iptr)))
#define yaffs_dentry_to_obj(dptr) yaffs_inode_to_obj((dptr)->d_inode)
#define yaffs_super_to_dev(sb)	((struct yaffs_dev *)sb->s_fs_info)

#define update_dir_time(dir) do {\
			(dir)->i_ctime = (dir)->i_mtime = CURRENT_TIME; \
		} while(0)


static unsigned yaffs_gc_control_callback(struct yaffs_dev *dev)
{
	return yaffs_gc_control;
}

static void yaffs_gross_lock(struct yaffs_dev *dev)
{
	yaffs_trace(YAFFS_TRACE_LOCK, "yaffs locking %p", current);
	mutex_lock(&(yaffs_dev_to_lc(dev)->gross_lock));
	yaffs_trace(YAFFS_TRACE_LOCK, "yaffs locked %p", current);
}

static void yaffs_gross_unlock(struct yaffs_dev *dev)
{
	yaffs_trace(YAFFS_TRACE_LOCK, "yaffs unlocking %p", current);
	mutex_unlock(&(yaffs_dev_to_lc(dev)->gross_lock));
}

static void yaffs_fill_inode_from_obj(struct inode *inode,
				      struct yaffs_obj *obj);

static struct inode *yaffs_iget(struct super_block *sb, unsigned long ino)
{
	struct inode *inode;
	struct yaffs_obj *obj;
	struct yaffs_dev *dev = yaffs_super_to_dev(sb);

	yaffs_trace(YAFFS_TRACE_OS, "yaffs_iget for %lu", ino);

	inode = iget_locked(sb, ino);
	if (!inode)
		return ERR_PTR(-ENOMEM);
	if (!(inode->i_state & I_NEW))
		return inode;

	/* NB This is called as a side effect of other functions, but
	 * we had to release the lock to prevent deadlocks, so
	 * need to lock again.
	 */

	yaffs_gross_lock(dev);

	obj = yaffs_find_by_number(dev, inode->i_ino);

	yaffs_fill_inode_from_obj(inode, obj);

	yaffs_gross_unlock(dev);

	unlock_new_inode(inode);
	return inode;
}

struct inode *yaffs_get_inode(struct super_block *sb, int mode, int dev,
			      struct yaffs_obj *obj)
{
	struct inode *inode;

	if (!sb) {
		yaffs_trace(YAFFS_TRACE_OS,
			"yaffs_get_inode for NULL super_block!!");
		return NULL;

	}

	if (!obj) {
		yaffs_trace(YAFFS_TRACE_OS,
			"yaffs_get_inode for NULL object!!");
		return NULL;

	}

	yaffs_trace(YAFFS_TRACE_OS,
		"yaffs_get_inode for object %d",
		obj->obj_id);

	inode = yaffs_iget(sb, obj->obj_id);
	if (IS_ERR(inode))
		return NULL;

	/* NB Side effect: iget calls back to yaffs_read_inode(). */
	/* iget also increments the inode's i_count */
	/* NB You can't be holding gross_lock or deadlock will happen! */

	return inode;
}

static int yaffs_mknod(struct inode *dir, struct dentry *dentry, int mode,
		       dev_t rdev)
{
	struct inode *inode;

	struct yaffs_obj *obj = NULL;
	struct yaffs_dev *dev;

	struct yaffs_obj *parent = yaffs_inode_to_obj(dir);

	int error = -ENOSPC;
	uid_t uid = current->cred->fsuid;
	gid_t gid =
	    (dir->i_mode & S_ISGID) ? dir->i_gid : current->cred->fsgid;

	if ((dir->i_mode & S_ISGID) && S_ISDIR(mode))
		mode |= S_ISGID;

	if (parent) {
		yaffs_trace(YAFFS_TRACE_OS,
			"yaffs_mknod: parent object %d type %d",
			parent->obj_id, parent->variant_type);
	} else {
		yaffs_trace(YAFFS_TRACE_OS,
			"yaffs_mknod: could not get parent object");
		return -EPERM;
	}

	yaffs_trace(YAFFS_TRACE_OS,
		"yaffs_mknod: making oject for %s, mode %x dev %x",
		dentry->d_name.name, mode, rdev);

	dev = parent->my_dev;

	yaffs_gross_lock(dev);

	switch (mode & S_IFMT) {
	default:
		/* Special (socket, fifo, device...) */
		yaffs_trace(YAFFS_TRACE_OS, "yaffs_mknod: making special");
		obj =
		    yaffs_create_special(parent, dentry->d_name.name, mode, uid,
					 gid, old_encode_dev(rdev));
		break;
	case S_IFREG:		/* file          */
		yaffs_trace(YAFFS_TRACE_OS, "yaffs_mknod: making file");
		obj = yaffs_create_file(parent, dentry->d_name.name, mode, uid,
					gid);
		break;
	case S_IFDIR:		/* directory */
		yaffs_trace(YAFFS_TRACE_OS, "yaffs_mknod: making directory");
		obj = yaffs_create_dir(parent, dentry->d_name.name, mode,
				       uid, gid);
		break;
	case S_IFLNK:		/* symlink */
		yaffs_trace(YAFFS_TRACE_OS, "yaffs_mknod: making symlink");
		obj = NULL;	/* Do we ever get here? */
		break;
	}

	/* Can not call yaffs_get_inode() with gross lock held */
	yaffs_gross_unlock(dev);

	if (obj) {
		inode = yaffs_get_inode(dir->i_sb, mode, rdev, obj);
		d_instantiate(dentry, inode);
		update_dir_time(dir);
		yaffs_trace(YAFFS_TRACE_OS,
			"yaffs_mknod created object %d count = %d",
			obj->obj_id, atomic_read(&inode->i_count));
		error = 0;
		yaffs_fill_inode_from_obj(dir, parent);
	} else {
		yaffs_trace(YAFFS_TRACE_OS, "yaffs_mknod failed making object");
		error = -ENOMEM;
	}

	return error;
}

static int yaffs_mkdir(struct inode *dir, struct dentry *dentry, int mode)
{
	return yaffs_mknod(dir, dentry, mode | S_IFDIR, 0);
}

static int yaffs_create(struct inode *dir, struct dentry *dentry, int mode,
			struct nameidata *n)
{
	return yaffs_mknod(dir, dentry, mode | S_IFREG, 0);
}

static int yaffs_link(struct dentry *old_dentry, struct inode *dir,
		      struct dentry *dentry)
{
	struct inode *inode = old_dentry->d_inode;
	struct yaffs_obj *obj = NULL;
	struct yaffs_obj *link = NULL;
	struct yaffs_dev *dev;

	yaffs_trace(YAFFS_TRACE_OS, "yaffs_link");

	obj = yaffs_inode_to_obj(inode);
	dev = obj->my_dev;

	yaffs_gross_lock(dev);

	if (!S_ISDIR(inode->i_mode))	/* Don't link directories */
		link =
		    yaffs_link_obj(yaffs_inode_to_obj(dir), dentry->d_name.name,
				   obj);

	if (link) {
		old_dentry->d_inode->i_nlink = yaffs_get_obj_link_count(obj);
		d_instantiate(dentry, old_dentry->d_inode);
		atomic_inc(&old_dentry->d_inode->i_count);
		yaffs_trace(YAFFS_TRACE_OS,
			"yaffs_link link count %d i_count %d",
			old_dentry->d_inode->i_nlink,
			atomic_read(&old_dentry->d_inode->i_count));
	}

	yaffs_gross_unlock(dev);

	if (link) {
		update_dir_time(dir);
		return 0;
	}

	return -EPERM;
}

static int yaffs_symlink(struct inode *dir, struct dentry *dentry,
			 const char *symname)
{
	struct yaffs_obj *obj;
	struct yaffs_dev *dev;
	uid_t uid = current->cred->fsuid;
	gid_t gid =
	    (dir->i_mode & S_ISGID) ? dir->i_gid : current->cred->fsgid;

	yaffs_trace(YAFFS_TRACE_OS, "yaffs_symlink");

	dev = yaffs_inode_to_obj(dir)->my_dev;
	yaffs_gross_lock(dev);
	obj = yaffs_create_symlink(yaffs_inode_to_obj(dir), dentry->d_name.name,
				   S_IFLNK | S_IRWXUGO, uid, gid, symname);
	yaffs_gross_unlock(dev);

	if (obj) {
		struct inode *inode;

		inode = yaffs_get_inode(dir->i_sb, obj->yst_mode, 0, obj);
		d_instantiate(dentry, inode);
		update_dir_time(dir);
		yaffs_trace(YAFFS_TRACE_OS, "symlink created OK");
		return 0;
	} else {
		yaffs_trace(YAFFS_TRACE_OS, "symlink not created");
	}

	return -ENOMEM;
}

static struct dentry *yaffs_lookup(struct inode *dir, struct dentry *dentry,
				   struct nameidata *n)
{
	struct yaffs_obj *obj;
	struct inode *inode = NULL;

	struct yaffs_dev *dev = yaffs_inode_to_obj(dir)->my_dev;

	if (current != yaffs_dev_to_lc(dev)->readdir_process)
		yaffs_gross_lock(dev);

	yaffs_trace(YAFFS_TRACE_OS,
		"yaffs_lookup for %d:%s",
		yaffs_inode_to_obj(dir)->obj_id, dentry->d_name.name);

	obj = yaffs_find_by_name(yaffs_inode_to_obj(dir), dentry->d_name.name);

	obj = yaffs_get_equivalent_obj(obj);	/* in case it was a hardlink */

	/* Can't hold gross lock when calling yaffs_get_inode() */
	if (current != yaffs_dev_to_lc(dev)->readdir_process)
		yaffs_gross_unlock(dev);

	if (obj) {
		yaffs_trace(YAFFS_TRACE_OS,
			"yaffs_lookup found %d", obj->obj_id);

		inode = yaffs_get_inode(dir->i_sb, obj->yst_mode, 0, obj);

		if (inode) {
			yaffs_trace(YAFFS_TRACE_OS, "yaffs_loookup dentry");
			d_add(dentry, inode);
			/* return dentry; */
			return NULL;
		}

	} else {
		yaffs_trace(YAFFS_TRACE_OS, "yaffs_lookup not found");

	}

	d_add(dentry, inode);

	return NULL;
}

static int yaffs_unlink(struct inode *dir, struct dentry *dentry)
{
	int ret_val;

	struct yaffs_dev *dev;
	struct yaffs_obj *obj;

	yaffs_trace(YAFFS_TRACE_OS,
		"yaffs_unlink %d:%s",
		(int)(dir->i_ino), dentry->d_name.name);
	obj = yaffs_inode_to_obj(dir);
	dev = obj->my_dev;

	yaffs_gross_lock(dev);

	ret_val = yaffs_unlinker(obj, dentry->d_name.name);

	if (ret_val == YAFFS_OK) {
		dentry->d_inode->i_nlink--;
		dir->i_version++;
		yaffs_gross_unlock(dev);
		mark_inode_dirty(dentry->d_inode);
		update_dir_time(dir);
		return 0;
	}
	yaffs_gross_unlock(dev);
	return -ENOTEMPTY;
}

static int yaffs_sync_object(struct file *file, int datasync)
{

	struct yaffs_obj *obj;
	struct yaffs_dev *dev;
	struct dentry *dentry = file->f_path.dentry;

	obj = yaffs_dentry_to_obj(dentry);

	dev = obj->my_dev;

	yaffs_trace(YAFFS_TRACE_OS | YAFFS_TRACE_SYNC, "yaffs_sync_object");
	yaffs_gross_lock(dev);
	yaffs_flush_file(obj, 1, datasync);
	yaffs_gross_unlock(dev);
	return 0;
}
/*
 * The VFS layer already does all the dentry stuff for rename.
 *
 * NB: POSIX says you can rename an object over an old object of the same name
 */
static int yaffs_rename(struct inode *old_dir, struct dentry *old_dentry,
			struct inode *new_dir, struct dentry *new_dentry)
{
	struct yaffs_dev *dev;
	int ret_val = YAFFS_FAIL;
	struct yaffs_obj *target;

	yaffs_trace(YAFFS_TRACE_OS, "yaffs_rename");
	dev = yaffs_inode_to_obj(old_dir)->my_dev;

	yaffs_gross_lock(dev);

	/* Check if the target is an existing directory that is not empty. */
	target = yaffs_find_by_name(yaffs_inode_to_obj(new_dir),
				    new_dentry->d_name.name);

	if (target && target->variant_type == YAFFS_OBJECT_TYPE_DIRECTORY &&
	    !list_empty(&target->variant.dir_variant.children)) {

		yaffs_trace(YAFFS_TRACE_OS, "target is non-empty dir");

		ret_val = YAFFS_FAIL;
	} else {
		/* Now does unlinking internally using shadowing mechanism */
		yaffs_trace(YAFFS_TRACE_OS, "calling yaffs_rename_obj");

		ret_val = yaffs_rename_obj(yaffs_inode_to_obj(old_dir),
					   old_dentry->d_name.name,
					   yaffs_inode_to_obj(new_dir),
					   new_dentry->d_name.name);
	}
	yaffs_gross_unlock(dev);

	if (ret_val == YAFFS_OK) {
		if (target) {
			new_dentry->d_inode->i_nlink--;
			mark_inode_dirty(new_dentry->d_inode);
		}

		update_dir_time(old_dir);
		if (old_dir != new_dir)
			update_dir_time(new_dir);
		return 0;
	} else {
		return -ENOTEMPTY;
	}
}

static int yaffs_setattr(struct dentry *dentry, struct iattr *attr)
{
	struct inode *inode = dentry->d_inode;
	int error = 0;
	struct yaffs_dev *dev;

	yaffs_trace(YAFFS_TRACE_OS,
		"yaffs_setattr of object %d",
		yaffs_inode_to_obj(inode)->obj_id);

	/* Fail if a requested resize >= 2GB */
	if (attr->ia_valid & ATTR_SIZE && (attr->ia_size >> 31))
		error = -EINVAL;

	if (error == 0)
		error = inode_change_ok(inode, attr);
	if (error == 0) {
		int result;
		if (!error) {
			setattr_copy(inode, attr);
			yaffs_trace(YAFFS_TRACE_OS, "inode_setattr called");
			if (attr->ia_valid & ATTR_SIZE) {
				truncate_setsize(inode, attr->ia_size);
				inode->i_blocks = (inode->i_size + 511) >> 9;
			}
		}
		dev = yaffs_inode_to_obj(inode)->my_dev;
		if (attr->ia_valid & ATTR_SIZE) {
			yaffs_trace(YAFFS_TRACE_OS, "resize to %d(%x)",
					   (int)(attr->ia_size),
					   (int)(attr->ia_size));
		}
		yaffs_gross_lock(dev);
		result = yaffs_set_attribs(yaffs_inode_to_obj(inode), attr);
		if (result == YAFFS_OK) {
			error = 0;
		} else {
			error = -EPERM;
		}
		yaffs_gross_unlock(dev);

	}

	yaffs_trace(YAFFS_TRACE_OS, "yaffs_setattr done returning %d", error);

	return error;
}

#ifdef CONFIG_YAFFS_XATTR
static int yaffs_setxattr(struct dentry *dentry, const char *name,
		   const void *value, size_t size, int flags)
{
	struct inode *inode = dentry->d_inode;
	int error = 0;
	struct yaffs_dev *dev;
	struct yaffs_obj *obj = yaffs_inode_to_obj(inode);

	yaffs_trace(YAFFS_TRACE_OS, "yaffs_setxattr of object %d", obj->obj_id);

	if (error == 0) {
		int result;
		dev = obj->my_dev;
		yaffs_gross_lock(dev);
		result = yaffs_set_xattrib(obj, name, value, size, flags);
		if (result == YAFFS_OK)
			error = 0;
		else if (result < 0)
			error = result;
		yaffs_gross_unlock(dev);

	}
	yaffs_trace(YAFFS_TRACE_OS, "yaffs_setxattr done returning %d", error);

	return error;
}

static ssize_t yaffs_getxattr(struct dentry * dentry, const char *name, void *buff,
		       size_t size)
{
	struct inode *inode = dentry->d_inode;
	int error = 0;
	struct yaffs_dev *dev;
	struct yaffs_obj *obj = yaffs_inode_to_obj(inode);

	yaffs_trace(YAFFS_TRACE_OS,
		"yaffs_getxattr \"%s\" from object %d",
		name, obj->obj_id);

	if (error == 0) {
		dev = obj->my_dev;
		yaffs_gross_lock(dev);
		error = yaffs_get_xattrib(obj, name, buff, size);
		yaffs_gross_unlock(dev);

	}
	yaffs_trace(YAFFS_TRACE_OS, "yaffs_getxattr done returning %d", error);

	return error;
}

static int yaffs_removexattr(struct dentry *dentry, const char *name)
{
	struct inode *inode = dentry->d_inode;
	int error = 0;
	struct yaffs_dev *dev;
	struct yaffs_obj *obj = yaffs_inode_to_obj(inode);

	yaffs_trace(YAFFS_TRACE_OS,
		"yaffs_removexattr of object %d", obj->obj_id);

	if (error == 0) {
		int result;
		dev = obj->my_dev;
		yaffs_gross_lock(dev);
		result = yaffs_remove_xattrib(obj, name);
		if (result == YAFFS_OK)
			error = 0;
		else if (result < 0)
			error = result;
		yaffs_gross_unlock(dev);

	}
	yaffs_trace(YAFFS_TRACE_OS,
		"yaffs_removexattr done returning %d", error);

	return error;
}

static ssize_t yaffs_listxattr(struct dentry * dentry, char *buff, size_t size)
{
	struct inode *inode = dentry->d_inode;
	int error = 0;
	struct yaffs_dev *dev;
	struct yaffs_obj *obj = yaffs_inode_to_obj(inode);

	yaffs_trace(YAFFS_TRACE_OS,
		"yaffs_listxattr of object %d", obj->obj_id);

	if (error == 0) {
		dev = obj->my_dev;
		yaffs_gross_lock(dev);
		error = yaffs_list_xattrib(obj, buff, size);
		yaffs_gross_unlock(dev);

	}
	yaffs_trace(YAFFS_TRACE_OS,
		"yaffs_listxattr done returning %d", error);

	return error;
}

#endif

static const struct inode_operations yaffs_dir_inode_operations = {
	.create = yaffs_create,
	.lookup = yaffs_lookup,
	.link = yaffs_link,
	.unlink = yaffs_unlink,
	.symlink = yaffs_symlink,
	.mkdir = yaffs_mkdir,
	.rmdir = yaffs_unlink,
	.mknod = yaffs_mknod,
	.rename = yaffs_rename,
	.setattr = yaffs_setattr,
#ifdef CONFIG_YAFFS_XATTR
	.setxattr = yaffs_setxattr,
	.getxattr = yaffs_getxattr,
	.listxattr = yaffs_listxattr,
	.removexattr = yaffs_removexattr,
#endif
};
/*-----------------------------------------------------------------*/
/* Directory search context allows us to unlock access to yaffs during
 * filldir without causing problems with the directory being modified.
 * This is similar to the tried and tested mechanism used in yaffs direct.
 *
 * A search context iterates along a doubly linked list of siblings in the
 * directory. If the iterating object is deleted then this would corrupt
 * the list iteration, likely causing a crash. The search context avoids
 * this by using the remove_obj_fn to move the search context to the
 * next object before the object is deleted.
 *
 * Many readdirs (and thus seach conexts) may be alive simulateously so
 * each struct yaffs_dev has a list of these.
 *
 * A seach context lives for the duration of a readdir.
 *
 * All these functions must be called while yaffs is locked.
 */

struct yaffs_search_context {
	struct yaffs_dev *dev;
	struct yaffs_obj *dir_obj;
	struct yaffs_obj *next_return;
	struct list_head others;
};

/*
 * yaffs_new_search() creates a new search context, initialises it and
 * adds it to the device's search context list.
 *
 * Called at start of readdir.
 */
static struct yaffs_search_context *yaffs_new_search(struct yaffs_obj *dir)
{
	struct yaffs_dev *dev = dir->my_dev;
	struct yaffs_search_context *sc =
	    kmalloc(sizeof(struct yaffs_search_context), GFP_NOFS);
	if (sc) {
		sc->dir_obj = dir;
		sc->dev = dev;
		if (list_empty(&sc->dir_obj->variant.dir_variant.children))
			sc->next_return = NULL;
		else
			sc->next_return =
			    list_entry(dir->variant.dir_variant.children.next,
				       struct yaffs_obj, siblings);
		INIT_LIST_HEAD(&sc->others);
		list_add(&sc->others, &(yaffs_dev_to_lc(dev)->search_contexts));
	}
	return sc;
}

/*
 * yaffs_search_end() disposes of a search context and cleans up.
 */
static void yaffs_search_end(struct yaffs_search_context *sc)
{
	if (sc) {
		list_del(&sc->others);
		kfree(sc);
	}
}

/*
 * yaffs_search_advance() moves a search context to the next object.
 * Called when the search iterates or when an object removal causes
 * the search context to be moved to the next object.
 */
static void yaffs_search_advance(struct yaffs_search_context *sc)
{
	if (!sc)
		return;

	if (sc->next_return == NULL ||
	    list_empty(&sc->dir_obj->variant.dir_variant.children))
		sc->next_return = NULL;
	else {
		struct list_head *next = sc->next_return->siblings.next;

		if (next == &sc->dir_obj->variant.dir_variant.children)
			sc->next_return = NULL;	/* end of list */
		else
			sc->next_return =
			    list_entry(next, struct yaffs_obj, siblings);
	}
}

/*
 * yaffs_remove_obj_callback() is called when an object is unlinked.
 * We check open search contexts and advance any which are currently
 * on the object being iterated.
 */
static void yaffs_remove_obj_callback(struct yaffs_obj *obj)
{

	struct list_head *i;
	struct yaffs_search_context *sc;
	struct list_head *search_contexts =
	    &(yaffs_dev_to_lc(obj->my_dev)->search_contexts);

	/* Iterate through the directory search contexts.
	 * If any are currently on the object being removed, then advance
	 * the search context to the next object to prevent a hanging pointer.
	 */
	list_for_each(i, search_contexts) {
		if (i) {
			sc = list_entry(i, struct yaffs_search_context, others);
			if (sc->next_return == obj)
				yaffs_search_advance(sc);
		}
	}

}

static int yaffs_readdir(struct file *f, void *dirent, filldir_t filldir)
{
	struct yaffs_obj *obj;
	struct yaffs_dev *dev;
	struct yaffs_search_context *sc;
	struct inode *inode = f->f_dentry->d_inode;
	unsigned long offset, curoffs;
	struct yaffs_obj *l;
	int ret_val = 0;

	char name[YAFFS_MAX_NAME_LENGTH + 1];

	obj = yaffs_dentry_to_obj(f->f_dentry);
	dev = obj->my_dev;

	yaffs_gross_lock(dev);

	yaffs_dev_to_lc(dev)->readdir_process = current;

	offset = f->f_pos;

	sc = yaffs_new_search(obj);
	if (!sc) {
		ret_val = -ENOMEM;
		goto out;
	}

	yaffs_trace(YAFFS_TRACE_OS,
		"yaffs_readdir: starting at %d", (int)offset);

	if (offset == 0) {
		yaffs_trace(YAFFS_TRACE_OS,
			"yaffs_readdir: entry . ino %d",
			(int)inode->i_ino);
		yaffs_gross_unlock(dev);
		if (filldir(dirent, ".", 1, offset, inode->i_ino, DT_DIR) < 0) {
			yaffs_gross_lock(dev);
			goto out;
		}
		yaffs_gross_lock(dev);
		offset++;
		f->f_pos++;
	}
	if (offset == 1) {
		yaffs_trace(YAFFS_TRACE_OS,
			"yaffs_readdir: entry .. ino %d",
			(int)f->f_dentry->d_parent->d_inode->i_ino);
		yaffs_gross_unlock(dev);
		if (filldir(dirent, "..", 2, offset,
			    f->f_dentry->d_parent->d_inode->i_ino,
			    DT_DIR) < 0) {
			yaffs_gross_lock(dev);
			goto out;
		}
		yaffs_gross_lock(dev);
		offset++;
		f->f_pos++;
	}

	curoffs = 1;

	/* If the directory has changed since the open or last call to
	   readdir, rewind to after the 2 canned entries. */
	if (f->f_version != inode->i_version) {
		offset = 2;
		f->f_pos = offset;
		f->f_version = inode->i_version;
	}

	while (sc->next_return) {
		curoffs++;
		l = sc->next_return;
		if (curoffs >= offset) {
			int this_inode = yaffs_get_obj_inode(l);
			int this_type = yaffs_get_obj_type(l);

			yaffs_get_obj_name(l, name, YAFFS_MAX_NAME_LENGTH + 1);
			yaffs_trace(YAFFS_TRACE_OS,
				"yaffs_readdir: %s inode %d",
				name, yaffs_get_obj_inode(l));

			yaffs_gross_unlock(dev);

			if (filldir(dirent,
				    name,
				    strlen(name),
				    offset, this_inode, this_type) < 0) {
				yaffs_gross_lock(dev);
				goto out;
			}

			yaffs_gross_lock(dev);

			offset++;
			f->f_pos++;
		}
		yaffs_search_advance(sc);
	}

out:
	yaffs_search_end(sc);
	yaffs_dev_to_lc(dev)->readdir_process = NULL;
	yaffs_gross_unlock(dev);

	return ret_val;
}

static const struct file_operations yaffs_dir_operations = {
	.read = generic_read_dir,
	.readdir = yaffs_readdir,
	.fsync = yaffs_sync_object,
	.llseek = generic_file_llseek,
};



static int yaffs_file_flush(struct file *file, fl_owner_t id)
{
	struct yaffs_obj *obj = yaffs_dentry_to_obj(file->f_dentry);

	struct yaffs_dev *dev = obj->my_dev;

	yaffs_trace(YAFFS_TRACE_OS,
	  	"yaffs_file_flush object %d (%s)",
		obj->obj_id, obj->dirty ? "dirty" : "clean");

	yaffs_gross_lock(dev);

	yaffs_flush_file(obj, 1, 0);

	yaffs_gross_unlock(dev);

	return 0;
}

static const struct file_operations yaffs_file_operations = {
	.read = do_sync_read,
	.write = do_sync_write,
	.aio_read = generic_file_aio_read,
	.aio_write = generic_file_aio_write,
	.mmap = generic_file_mmap,
	.flush = yaffs_file_flush,
	.fsync = yaffs_sync_object,
	.splice_read = generic_file_splice_read,
	.splice_write = generic_file_splice_write,
	.llseek = generic_file_llseek,
};


/* ExportFS support */
static struct inode *yaffs2_nfs_get_inode(struct super_block *sb, uint64_t ino,
					  uint32_t generation)
{
	return yaffs_iget(sb, ino);
}

static struct dentry *yaffs2_fh_to_dentry(struct super_block *sb,
					  struct fid *fid, int fh_len,
					  int fh_type)
{
	return generic_fh_to_dentry(sb, fid, fh_len, fh_type,
				    yaffs2_nfs_get_inode);
}

static struct dentry *yaffs2_fh_to_parent(struct super_block *sb,
					  struct fid *fid, int fh_len,
					  int fh_type)
{
	return generic_fh_to_parent(sb, fid, fh_len, fh_type,
				    yaffs2_nfs_get_inode);
}

struct dentry *yaffs2_get_parent(struct dentry *dentry)
{

	struct super_block *sb = dentry->d_inode->i_sb;
	struct dentry *parent = ERR_PTR(-ENOENT);
	struct inode *inode;
	unsigned long parent_ino;
	struct yaffs_obj *d_obj;
	struct yaffs_obj *parent_obj;

	d_obj = yaffs_inode_to_obj(dentry->d_inode);

	if (d_obj) {
		parent_obj = d_obj->parent;
		if (parent_obj) {
			parent_ino = yaffs_get_obj_inode(parent_obj);
			inode = yaffs_iget(sb, parent_ino);

			if (IS_ERR(inode)) {
				parent = ERR_CAST(inode);
			} else {
				parent = d_obtain_alias(inode);
				if (!IS_ERR(parent)) {
					parent = ERR_PTR(-ENOMEM);
					iput(inode);
				}
			}
		}
	}

	return parent;
}

/* Just declare a zero structure as a NULL value implies
 * using the default functions of exportfs.
 */

static struct export_operations yaffs_export_ops = {
	.fh_to_dentry = yaffs2_fh_to_dentry,
	.fh_to_parent = yaffs2_fh_to_parent,
	.get_parent = yaffs2_get_parent,
};


/*-----------------------------------------------------------------*/

static int yaffs_readlink(struct dentry *dentry, char __user * buffer,
			  int buflen)
{
	unsigned char *alias;
	int ret;

	struct yaffs_dev *dev = yaffs_dentry_to_obj(dentry)->my_dev;

	yaffs_gross_lock(dev);

	alias = yaffs_get_symlink_alias(yaffs_dentry_to_obj(dentry));

	yaffs_gross_unlock(dev);

	if (!alias)
		return -ENOMEM;

	ret = vfs_readlink(dentry, buffer, buflen, alias);
	kfree(alias);
	return ret;
}

static void *yaffs_follow_link(struct dentry *dentry, struct nameidata *nd)
{
	unsigned char *alias;
	void *ret;
	struct yaffs_dev *dev = yaffs_dentry_to_obj(dentry)->my_dev;

	yaffs_gross_lock(dev);

	alias = yaffs_get_symlink_alias(yaffs_dentry_to_obj(dentry));
	yaffs_gross_unlock(dev);

	if (!alias) {
		ret = ERR_PTR(-ENOMEM);
		goto out;
	}

	nd_set_link(nd, alias);
	ret = (void *)alias;
out:
	return ret;
}

void yaffs_put_link(struct dentry *dentry, struct nameidata *nd, void *alias)
{
	kfree(alias);
}


static void yaffs_unstitch_obj(struct inode *inode, struct yaffs_obj *obj)
{
	/* Clear the association between the inode and
	 * the struct yaffs_obj.
	 */
	obj->my_inode = NULL;
	yaffs_inode_to_obj_lv(inode) = NULL;

	/* If the object freeing was deferred, then the real
	 * free happens now.
	 * This should fix the inode inconsistency problem.
	 */
	yaffs_handle_defered_free(obj);
}

/* yaffs_evict_inode combines into one operation what was previously done in
 * yaffs_clear_inode() and yaffs_delete_inode()
 *
 */
static void yaffs_evict_inode(struct inode *inode)
{
	struct yaffs_obj *obj;
	struct yaffs_dev *dev;
	int deleteme = 0;

	obj = yaffs_inode_to_obj(inode);

	yaffs_trace(YAFFS_TRACE_OS,
		"yaffs_evict_inode: ino %d, count %d %s",
		(int)inode->i_ino,
		atomic_read(&inode->i_count),
		obj ? "object exists" : "null object");

	if (!inode->i_nlink && !is_bad_inode(inode))
		deleteme = 1;
	truncate_inode_pages(&inode->i_data, 0);
	end_writeback(inode);

	if (deleteme && obj) {
		dev = obj->my_dev;
		yaffs_gross_lock(dev);
		yaffs_del_obj(obj);
		yaffs_gross_unlock(dev);
	}
	if (obj) {
		dev = obj->my_dev;
		yaffs_gross_lock(dev);
		yaffs_unstitch_obj(inode, obj);
		yaffs_gross_unlock(dev);
	}

}

static void yaffs_touch_super(struct yaffs_dev *dev)
{
	struct super_block *sb = yaffs_dev_to_lc(dev)->super;

	yaffs_trace(YAFFS_TRACE_OS, "yaffs_touch_super() sb = %p", sb);
	if (sb)
		sb->s_dirt = 1;
}

static int yaffs_readpage_nolock(struct file *f, struct page *pg)
{
	/* Lifted from jffs2 */

	struct yaffs_obj *obj;
	unsigned char *pg_buf;
	int ret;

	struct yaffs_dev *dev;

	yaffs_trace(YAFFS_TRACE_OS,
		"yaffs_readpage_nolock at %08x, size %08x",
		(unsigned)(pg->index << PAGE_CACHE_SHIFT),
		(unsigned)PAGE_CACHE_SIZE);

	obj = yaffs_dentry_to_obj(f->f_dentry);

	dev = obj->my_dev;

	BUG_ON(!PageLocked(pg));

	pg_buf = kmap(pg);
	/* FIXME: Can kmap fail? */

	yaffs_gross_lock(dev);

	ret = yaffs_file_rd(obj, pg_buf,
			    pg->index << PAGE_CACHE_SHIFT, PAGE_CACHE_SIZE);

	yaffs_gross_unlock(dev);

	if (ret >= 0)
		ret = 0;

	if (ret) {
		ClearPageUptodate(pg);
		SetPageError(pg);
	} else {
		SetPageUptodate(pg);
		ClearPageError(pg);
	}

	flush_dcache_page(pg);
	kunmap(pg);

	yaffs_trace(YAFFS_TRACE_OS, "yaffs_readpage_nolock done");
	return ret;
}

static int yaffs_readpage_unlock(struct file *f, struct page *pg)
{
	int ret = yaffs_readpage_nolock(f, pg);
	UnlockPage(pg);
	return ret;
}

static int yaffs_readpage(struct file *f, struct page *pg)
{
	int ret;

	yaffs_trace(YAFFS_TRACE_OS, "yaffs_readpage");
	ret = yaffs_readpage_unlock(f, pg);
	yaffs_trace(YAFFS_TRACE_OS, "yaffs_readpage done");
	return ret;
}

/* writepage inspired by/stolen from smbfs */

static int yaffs_writepage(struct page *page, struct writeback_control *wbc)
{
	struct yaffs_dev *dev;
	struct address_space *mapping = page->mapping;
	struct inode *inode;
	unsigned long end_index;
	char *buffer;
	struct yaffs_obj *obj;
	int n_written = 0;
	unsigned n_bytes;
	loff_t i_size;

	if (!mapping)
		BUG();
	inode = mapping->host;
	if (!inode)
		BUG();
	i_size = i_size_read(inode);

	end_index = i_size >> PAGE_CACHE_SHIFT;

	if (page->index < end_index)
		n_bytes = PAGE_CACHE_SIZE;
	else {
		n_bytes = i_size & (PAGE_CACHE_SIZE - 1);

		if (page->index > end_index || !n_bytes) {
			yaffs_trace(YAFFS_TRACE_OS,
				"yaffs_writepage at %08x, inode size = %08x!!!",
				(unsigned)(page->index << PAGE_CACHE_SHIFT),
				(unsigned)inode->i_size);
			yaffs_trace(YAFFS_TRACE_OS,
			  "                -> don't care!!");

			zero_user_segment(page, 0, PAGE_CACHE_SIZE);
			set_page_writeback(page);
			unlock_page(page);
			end_page_writeback(page);
			return 0;
		}
	}

	if (n_bytes != PAGE_CACHE_SIZE)
		zero_user_segment(page, n_bytes, PAGE_CACHE_SIZE);

	get_page(page);

	buffer = kmap(page);

	obj = yaffs_inode_to_obj(inode);
	dev = obj->my_dev;
	yaffs_gross_lock(dev);

	yaffs_trace(YAFFS_TRACE_OS,
		"yaffs_writepage at %08x, size %08x",
		(unsigned)(page->index << PAGE_CACHE_SHIFT), n_bytes);
	yaffs_trace(YAFFS_TRACE_OS,
		"writepag0: obj = %05x, ino = %05x",
		(int)obj->variant.file_variant.file_size, (int)inode->i_size);

	n_written = yaffs_wr_file(obj, buffer,
				  page->index << PAGE_CACHE_SHIFT, n_bytes, 0);

	yaffs_touch_super(dev);

	yaffs_trace(YAFFS_TRACE_OS,
		"writepag1: obj = %05x, ino = %05x",
		(int)obj->variant.file_variant.file_size, (int)inode->i_size);

	yaffs_gross_unlock(dev);

	kunmap(page);
	set_page_writeback(page);
	unlock_page(page);
	end_page_writeback(page);
	put_page(page);

	return (n_written == n_bytes) ? 0 : -ENOSPC;
}

/* Space holding and freeing is done to ensure we have space available for 
 * write_begin/end.
 * For now we just assume few parallel writes and check against a small
 * number.
 * Todo: need to do this with a counter to handle parallel reads better.
 */

static ssize_t yaffs_hold_space(struct file *f)
{
	struct yaffs_obj *obj;
	struct yaffs_dev *dev;

	int n_free_chunks;

	obj = yaffs_dentry_to_obj(f->f_dentry);

	dev = obj->my_dev;

	yaffs_gross_lock(dev);

	n_free_chunks = yaffs_get_n_free_chunks(dev);

	yaffs_gross_unlock(dev);

	return (n_free_chunks > 20) ? 1 : 0;
}

static void yaffs_release_space(struct file *f)
{
	struct yaffs_obj *obj;
	struct yaffs_dev *dev;

	obj = yaffs_dentry_to_obj(f->f_dentry);

	dev = obj->my_dev;

	yaffs_gross_lock(dev);

	yaffs_gross_unlock(dev);
}

static int yaffs_write_begin(struct file *filp, struct address_space *mapping,
			     loff_t pos, unsigned len, unsigned flags,
			     struct page **pagep, void **fsdata)
{
	struct page *pg = NULL;
	pgoff_t index = pos >> PAGE_CACHE_SHIFT;

	int ret = 0;
	int space_held = 0;

	/* Get a page */
	pg = grab_cache_page_write_begin(mapping, index, flags);

	*pagep = pg;
	if (!pg) {
		ret = -ENOMEM;
		goto out;
	}
	yaffs_trace(YAFFS_TRACE_OS,
		"start yaffs_write_begin index %d(%x) uptodate %d",
		(int)index, (int)index, Page_Uptodate(pg) ? 1 : 0);

	/* Get fs space */
	space_held = yaffs_hold_space(filp);

	if (!space_held) {
		ret = -ENOSPC;
		goto out;
	}

	/* Update page if required */

	if (!Page_Uptodate(pg))
		ret = yaffs_readpage_nolock(filp, pg);

	if (ret)
		goto out;

	/* Happy path return */
	yaffs_trace(YAFFS_TRACE_OS, "end yaffs_write_begin - ok");

	return 0;

out:
	yaffs_trace(YAFFS_TRACE_OS,
		"end yaffs_write_begin fail returning %d", ret);
	if (space_held)
		yaffs_release_space(filp);
	if (pg) {
		unlock_page(pg);
		page_cache_release(pg);
	}
	return ret;
}

static ssize_t yaffs_file_write(struct file *f, const char *buf, size_t n,
				loff_t * pos)
{
	struct yaffs_obj *obj;
	int n_written, ipos;
	struct inode *inode;
	struct yaffs_dev *dev;

	obj = yaffs_dentry_to_obj(f->f_dentry);

	dev = obj->my_dev;

	yaffs_gross_lock(dev);

	inode = f->f_dentry->d_inode;

	if (!S_ISBLK(inode->i_mode) && f->f_flags & O_APPEND)
		ipos = inode->i_size;
	else
		ipos = *pos;

	if (!obj)
		yaffs_trace(YAFFS_TRACE_OS,
			"yaffs_file_write: hey obj is null!");
	else
		yaffs_trace(YAFFS_TRACE_OS,
			"yaffs_file_write about to write writing %u(%x) bytes to object %d at %d(%x)",
			(unsigned)n, (unsigned)n, obj->obj_id, ipos, ipos);

	n_written = yaffs_wr_file(obj, buf, ipos, n, 0);

	yaffs_touch_super(dev);

	yaffs_trace(YAFFS_TRACE_OS,
		"yaffs_file_write: %d(%x) bytes written",
		(unsigned)n, (unsigned)n);

	if (n_written > 0) {
		ipos += n_written;
		*pos = ipos;
		if (ipos > inode->i_size) {
			inode->i_size = ipos;
			inode->i_blocks = (ipos + 511) >> 9;

			yaffs_trace(YAFFS_TRACE_OS,
				"yaffs_file_write size updated to %d bytes, %d blocks",
				ipos, (int)(inode->i_blocks));
		}

	}
	yaffs_gross_unlock(dev);
	return (n_written == 0) && (n > 0) ? -ENOSPC : n_written;
}

static int yaffs_write_end(struct file *filp, struct address_space *mapping,
			   loff_t pos, unsigned len, unsigned copied,
			   struct page *pg, void *fsdadata)
{
	int ret = 0;
	void *addr, *kva;
	uint32_t offset_into_page = pos & (PAGE_CACHE_SIZE - 1);

	kva = kmap(pg);
	addr = kva + offset_into_page;

	yaffs_trace(YAFFS_TRACE_OS,
		"yaffs_write_end addr %p pos %x n_bytes %d",
		addr, (unsigned)pos, copied);

	ret = yaffs_file_write(filp, addr, copied, &pos);

	if (ret != copied) {
		yaffs_trace(YAFFS_TRACE_OS,
			"yaffs_write_end not same size ret %d  copied %d",
			ret, copied);
		SetPageError(pg);
	}

	kunmap(pg);

	yaffs_release_space(filp);
	unlock_page(pg);
	page_cache_release(pg);
	return ret;
}

static int yaffs_statfs(struct dentry *dentry, struct kstatfs *buf)
{
	struct yaffs_dev *dev = yaffs_dentry_to_obj(dentry)->my_dev;
	struct super_block *sb = dentry->d_sb;

	yaffs_trace(YAFFS_TRACE_OS, "yaffs_statfs");

	yaffs_gross_lock(dev);

	buf->f_type = YAFFS_MAGIC;
	buf->f_bsize = sb->s_blocksize;
	buf->f_namelen = 255;

	if (dev->data_bytes_per_chunk & (dev->data_bytes_per_chunk - 1)) {
		/* Do this if chunk size is not a power of 2 */

		uint64_t bytes_in_dev;
		uint64_t bytes_free;

		bytes_in_dev =
		    ((uint64_t)
		     ((dev->param.end_block - dev->param.start_block +
		       1))) * ((uint64_t) (dev->param.chunks_per_block *
					   dev->data_bytes_per_chunk));

		do_div(bytes_in_dev, sb->s_blocksize);	/* bytes_in_dev becomes the number of blocks */
		buf->f_blocks = bytes_in_dev;

		bytes_free = ((uint64_t) (yaffs_get_n_free_chunks(dev))) *
		    ((uint64_t) (dev->data_bytes_per_chunk));

		do_div(bytes_free, sb->s_blocksize);

		buf->f_bfree = bytes_free;

	} else if (sb->s_blocksize > dev->data_bytes_per_chunk) {

		buf->f_blocks =
		    (dev->param.end_block - dev->param.start_block + 1) *
		    dev->param.chunks_per_block /
		    (sb->s_blocksize / dev->data_bytes_per_chunk);
		buf->f_bfree =
		    yaffs_get_n_free_chunks(dev) /
		    (sb->s_blocksize / dev->data_bytes_per_chunk);
	} else {
		buf->f_blocks =
		    (dev->param.end_block - dev->param.start_block + 1) *
		    dev->param.chunks_per_block *
		    (dev->data_bytes_per_chunk / sb->s_blocksize);

		buf->f_bfree =
		    yaffs_get_n_free_chunks(dev) *
		    (dev->data_bytes_per_chunk / sb->s_blocksize);
	}

	buf->f_files = 0;
	buf->f_ffree = 0;
	buf->f_bavail = buf->f_bfree;

	yaffs_gross_unlock(dev);
	return 0;
}

static void yaffs_flush_inodes(struct super_block *sb)
{
	struct inode *iptr;
	struct yaffs_obj *obj;

	list_for_each_entry(iptr, &sb->s_inodes, i_sb_list) {
		obj = yaffs_inode_to_obj(iptr);
		if (obj) {
			yaffs_trace(YAFFS_TRACE_OS,
				"flushing obj %d", obj->obj_id);
			yaffs_flush_file(obj, 1, 0);
		}
	}
}

static void yaffs_flush_super(struct super_block *sb, int do_checkpoint)
{
	struct yaffs_dev *dev = yaffs_super_to_dev(sb);
	if (!dev)
		return;

	yaffs_flush_inodes(sb);
	yaffs_update_dirty_dirs(dev);
	yaffs_flush_whole_cache(dev);
	if (do_checkpoint)
		yaffs_checkpoint_save(dev);
}

static unsigned yaffs_bg_gc_urgency(struct yaffs_dev *dev)
{
	unsigned erased_chunks =
	    dev->n_erased_blocks * dev->param.chunks_per_block;
	struct yaffs_linux_context *context = yaffs_dev_to_lc(dev);
	unsigned scattered = 0;	/* Free chunks not in an erased block */

	if (erased_chunks < dev->n_free_chunks)
		scattered = (dev->n_free_chunks - erased_chunks);

	if (!context->bg_running)
		return 0;
	else if (scattered < (dev->param.chunks_per_block * 2))
		return 0;
	else if (erased_chunks > dev->n_free_chunks / 2)
		return 0;
	else if (erased_chunks > dev->n_free_chunks / 4)
		return 1;
	else
		return 2;
}

static int yaffs_do_sync_fs(struct super_block *sb, int request_checkpoint)
{

	struct yaffs_dev *dev = yaffs_super_to_dev(sb);
	unsigned int oneshot_checkpoint = (yaffs_auto_checkpoint & 4);
	unsigned gc_urgent = yaffs_bg_gc_urgency(dev);
	int do_checkpoint;

	yaffs_trace(YAFFS_TRACE_OS | YAFFS_TRACE_SYNC | YAFFS_TRACE_BACKGROUND,
		"yaffs_do_sync_fs: gc-urgency %d %s %s%s",
		gc_urgent,
		sb->s_dirt ? "dirty" : "clean",
		request_checkpoint ? "checkpoint requested" : "no checkpoint",
		oneshot_checkpoint ? " one-shot" : "");

	yaffs_gross_lock(dev);
	do_checkpoint = ((request_checkpoint && !gc_urgent) ||
			 oneshot_checkpoint) && !dev->is_checkpointed;

	if (sb->s_dirt || do_checkpoint) {
		yaffs_flush_super(sb, !dev->is_checkpointed && do_checkpoint);
		sb->s_dirt = 0;
		if (oneshot_checkpoint)
			yaffs_auto_checkpoint &= ~4;
	}
	yaffs_gross_unlock(dev);

	return 0;
}

/*
 * yaffs background thread functions .
 * yaffs_bg_thread_fn() the thread function
 * yaffs_bg_start() launches the background thread.
 * yaffs_bg_stop() cleans up the background thread.
 *
 * NB: 
 * The thread should only run after the yaffs is initialised
 * The thread should be stopped before yaffs is unmounted.
 * The thread should not do any writing while the fs is in read only.
 */

void yaffs_background_waker(unsigned long data)
{
	wake_up_process((struct task_struct *)data);
}

static int yaffs_bg_thread_fn(void *data)
{
	struct yaffs_dev *dev = (struct yaffs_dev *)data;
	struct yaffs_linux_context *context = yaffs_dev_to_lc(dev);
	unsigned long now = jiffies;
	unsigned long next_dir_update = now;
	unsigned long next_gc = now;
	unsigned long expires;
	unsigned int urgency;

	int gc_result;
	struct timer_list timer;

	yaffs_trace(YAFFS_TRACE_BACKGROUND,
		"yaffs_background starting for dev %p", (void *)dev);

	set_freezable();
	while (context->bg_running) {
		yaffs_trace(YAFFS_TRACE_BACKGROUND, "yaffs_background");

		if (kthread_should_stop())
			break;

		if (try_to_freeze())
			continue;

		yaffs_gross_lock(dev);

		now = jiffies;

		if (time_after(now, next_dir_update) && yaffs_bg_enable) {
			yaffs_update_dirty_dirs(dev);
			next_dir_update = now + HZ;
		}

		if (time_after(now, next_gc) && yaffs_bg_enable) {
			if (!dev->is_checkpointed) {
				urgency = yaffs_bg_gc_urgency(dev);
				gc_result = yaffs_bg_gc(dev, urgency);
				if (urgency > 1)
					next_gc = now + HZ / 20 + 1;
				else if (urgency > 0)
					next_gc = now + HZ / 10 + 1;
				else
					next_gc = now + HZ * 2;
			} else	{
			        /*
				 * gc not running so set to next_dir_update
				 * to cut down on wake ups
				 */
				next_gc = next_dir_update;
                        }
		}
		yaffs_gross_unlock(dev);
		expires = next_dir_update;
		if (time_before(next_gc, expires))
			expires = next_gc;
		if (time_before(expires, now))
			expires = now + HZ;

		Y_INIT_TIMER(&timer);
		timer.expires = expires + 1;
		timer.data = (unsigned long)current;
		timer.function = yaffs_background_waker;

		set_current_state(TASK_INTERRUPTIBLE);
		add_timer(&timer);
		schedule();
		del_timer_sync(&timer);
	}

	return 0;
}

static int yaffs_bg_start(struct yaffs_dev *dev)
{
	int retval = 0;
	struct yaffs_linux_context *context = yaffs_dev_to_lc(dev);

	if (dev->read_only)
		return -1;

	context->bg_running = 1;

	context->bg_thread = kthread_run(yaffs_bg_thread_fn,
					 (void *)dev, "yaffs-bg-%d",
					 context->mount_id);

	if (IS_ERR(context->bg_thread)) {
		retval = PTR_ERR(context->bg_thread);
		context->bg_thread = NULL;
		context->bg_running = 0;
	}
	return retval;
}

static void yaffs_bg_stop(struct yaffs_dev *dev)
{
	struct yaffs_linux_context *ctxt = yaffs_dev_to_lc(dev);

	ctxt->bg_running = 0;

	if (ctxt->bg_thread) {
		kthread_stop(ctxt->bg_thread);
		ctxt->bg_thread = NULL;
	}
}

static void yaffs_write_super(struct super_block *sb)
{
	unsigned request_checkpoint = (yaffs_auto_checkpoint >= 2);

	yaffs_trace(YAFFS_TRACE_OS | YAFFS_TRACE_SYNC | YAFFS_TRACE_BACKGROUND,
		"yaffs_write_super%s",
		request_checkpoint ? " checkpt" : "");

	yaffs_do_sync_fs(sb, request_checkpoint);

}

static int yaffs_sync_fs(struct super_block *sb, int wait)
{
	unsigned request_checkpoint = (yaffs_auto_checkpoint >= 1);

	yaffs_trace(YAFFS_TRACE_OS | YAFFS_TRACE_SYNC,
		"yaffs_sync_fs%s", request_checkpoint ? " checkpt" : "");

	yaffs_do_sync_fs(sb, request_checkpoint);

	return 0;
}


static LIST_HEAD(yaffs_context_list);
struct mutex yaffs_context_lock;



struct yaffs_options {
	int inband_tags;
	int skip_checkpoint_read;
	int skip_checkpoint_write;
	int no_cache;
	int tags_ecc_on;
	int tags_ecc_overridden;
	int lazy_loading_enabled;
	int lazy_loading_overridden;
	int empty_lost_and_found;
	int empty_lost_and_found_overridden;
};

#define MAX_OPT_LEN 30
static int yaffs_parse_options(struct yaffs_options *options,
			       const char *options_str)
{
	char cur_opt[MAX_OPT_LEN + 1];
	int p;
	int error = 0;

	/* Parse through the options which is a comma seperated list */

	while (options_str && *options_str && !error) {
		memset(cur_opt, 0, MAX_OPT_LEN + 1);
		p = 0;

		while (*options_str == ',')
			options_str++;

		while (*options_str && *options_str != ',') {
			if (p < MAX_OPT_LEN) {
				cur_opt[p] = *options_str;
				p++;
			}
			options_str++;
		}

		if (!strcmp(cur_opt, "inband-tags")) {
			options->inband_tags = 1;
		} else if (!strcmp(cur_opt, "tags-ecc-off")) {
			options->tags_ecc_on = 0;
			options->tags_ecc_overridden = 1;
		} else if (!strcmp(cur_opt, "tags-ecc-on")) {
			options->tags_ecc_on = 1;
			options->tags_ecc_overridden = 1;
		} else if (!strcmp(cur_opt, "lazy-loading-off")) {
			options->lazy_loading_enabled = 0;
			options->lazy_loading_overridden = 1;
		} else if (!strcmp(cur_opt, "lazy-loading-on")) {
			options->lazy_loading_enabled = 1;
			options->lazy_loading_overridden = 1;
		} else if (!strcmp(cur_opt, "empty-lost-and-found-off")) {
			options->empty_lost_and_found = 0;
			options->empty_lost_and_found_overridden = 1;
		} else if (!strcmp(cur_opt, "empty-lost-and-found-on")) {
			options->empty_lost_and_found = 1;
			options->empty_lost_and_found_overridden = 1;
		} else if (!strcmp(cur_opt, "no-cache")) {
			options->no_cache = 1;
		} else if (!strcmp(cur_opt, "no-checkpoint-read")) {
			options->skip_checkpoint_read = 1;
		} else if (!strcmp(cur_opt, "no-checkpoint-write")) {
			options->skip_checkpoint_write = 1;
		} else if (!strcmp(cur_opt, "no-checkpoint")) {
			options->skip_checkpoint_read = 1;
			options->skip_checkpoint_write = 1;
		} else {
			printk(KERN_INFO "yaffs: Bad mount option \"%s\"\n",
			       cur_opt);
			error = 1;
		}
	}

	return error;
}

static struct address_space_operations yaffs_file_address_operations = {
	.readpage = yaffs_readpage,
	.writepage = yaffs_writepage,
	.write_begin = yaffs_write_begin,
	.write_end = yaffs_write_end,
};



static const struct inode_operations yaffs_file_inode_operations = {
	.setattr = yaffs_setattr,
#ifdef CONFIG_YAFFS_XATTR
	.setxattr = yaffs_setxattr,
	.getxattr = yaffs_getxattr,
	.listxattr = yaffs_listxattr,
	.removexattr = yaffs_removexattr,
#endif
};

static const struct inode_operations yaffs_symlink_inode_operations = {
	.readlink = yaffs_readlink,
	.follow_link = yaffs_follow_link,
	.put_link = yaffs_put_link,
	.setattr = yaffs_setattr,
#ifdef CONFIG_YAFFS_XATTR
	.setxattr = yaffs_setxattr,
	.getxattr = yaffs_getxattr,
	.listxattr = yaffs_listxattr,
	.removexattr = yaffs_removexattr,
#endif
};

static void yaffs_fill_inode_from_obj(struct inode *inode,
				      struct yaffs_obj *obj)
{
	if (inode && obj) {

		/* Check mode against the variant type and attempt to repair if broken. */
		u32 mode = obj->yst_mode;
		switch (obj->variant_type) {
		case YAFFS_OBJECT_TYPE_FILE:
			if (!S_ISREG(mode)) {
				obj->yst_mode &= ~S_IFMT;
				obj->yst_mode |= S_IFREG;
			}

			break;
		case YAFFS_OBJECT_TYPE_SYMLINK:
			if (!S_ISLNK(mode)) {
				obj->yst_mode &= ~S_IFMT;
				obj->yst_mode |= S_IFLNK;
			}

			break;
		case YAFFS_OBJECT_TYPE_DIRECTORY:
			if (!S_ISDIR(mode)) {
				obj->yst_mode &= ~S_IFMT;
				obj->yst_mode |= S_IFDIR;
			}

			break;
		case YAFFS_OBJECT_TYPE_UNKNOWN:
		case YAFFS_OBJECT_TYPE_HARDLINK:
		case YAFFS_OBJECT_TYPE_SPECIAL:
		default:
			/* TODO? */
			break;
		}

		inode->i_flags |= S_NOATIME;

		inode->i_ino = obj->obj_id;
		inode->i_mode = obj->yst_mode;
		inode->i_uid = obj->yst_uid;
		inode->i_gid = obj->yst_gid;

		inode->i_rdev = old_decode_dev(obj->yst_rdev);

		inode->i_atime.tv_sec = (time_t) (obj->yst_atime);
		inode->i_atime.tv_nsec = 0;
		inode->i_mtime.tv_sec = (time_t) obj->yst_mtime;
		inode->i_mtime.tv_nsec = 0;
		inode->i_ctime.tv_sec = (time_t) obj->yst_ctime;
		inode->i_ctime.tv_nsec = 0;
		inode->i_size = yaffs_get_obj_length(obj);
		inode->i_blocks = (inode->i_size + 511) >> 9;

		inode->i_nlink = yaffs_get_obj_link_count(obj);

		yaffs_trace(YAFFS_TRACE_OS,
			"yaffs_fill_inode mode %x uid %d gid %d size %d count %d",
			inode->i_mode, inode->i_uid, inode->i_gid,
			(int)inode->i_size, atomic_read(&inode->i_count));

		switch (obj->yst_mode & S_IFMT) {
		default:	/* fifo, device or socket */
			init_special_inode(inode, obj->yst_mode,
					   old_decode_dev(obj->yst_rdev));
			break;
		case S_IFREG:	/* file */
			inode->i_op = &yaffs_file_inode_operations;
			inode->i_fop = &yaffs_file_operations;
			inode->i_mapping->a_ops =
			    &yaffs_file_address_operations;
			break;
		case S_IFDIR:	/* directory */
			inode->i_op = &yaffs_dir_inode_operations;
			inode->i_fop = &yaffs_dir_operations;
			break;
		case S_IFLNK:	/* symlink */
			inode->i_op = &yaffs_symlink_inode_operations;
			break;
		}

		yaffs_inode_to_obj_lv(inode) = obj;

		obj->my_inode = inode;

	} else {
		yaffs_trace(YAFFS_TRACE_OS,
			"yaffs_fill_inode invalid parameters");
	}
}

static void yaffs_put_super(struct super_block *sb)
{
	struct yaffs_dev *dev = yaffs_super_to_dev(sb);

	yaffs_trace(YAFFS_TRACE_OS, "yaffs_put_super");

	yaffs_trace(YAFFS_TRACE_OS | YAFFS_TRACE_BACKGROUND,
		"Shutting down yaffs background thread");
	yaffs_bg_stop(dev);
	yaffs_trace(YAFFS_TRACE_OS | YAFFS_TRACE_BACKGROUND,
		"yaffs background thread shut down");

	yaffs_gross_lock(dev);

	yaffs_flush_super(sb, 1);

	if (yaffs_dev_to_lc(dev)->put_super_fn)
		yaffs_dev_to_lc(dev)->put_super_fn(sb);

	yaffs_deinitialise(dev);

	yaffs_gross_unlock(dev);
	mutex_lock(&yaffs_context_lock);
	list_del_init(&(yaffs_dev_to_lc(dev)->context_list));
	mutex_unlock(&yaffs_context_lock);

	if (yaffs_dev_to_lc(dev)->spare_buffer) {
		kfree(yaffs_dev_to_lc(dev)->spare_buffer);
		yaffs_dev_to_lc(dev)->spare_buffer = NULL;
	}

	kfree(dev);
}

static void yaffs_mtd_put_super(struct super_block *sb)
{
	struct mtd_info *mtd = yaffs_dev_to_mtd(yaffs_super_to_dev(sb));

	if (mtd->sync)
		mtd->sync(mtd);

	put_mtd_device(mtd);
}

static const struct super_operations yaffs_super_ops = {
	.statfs = yaffs_statfs,
	.put_super = yaffs_put_super,
	.evict_inode = yaffs_evict_inode,
	.sync_fs = yaffs_sync_fs,
	.write_super = yaffs_write_super,
};

static struct super_block *yaffs_internal_read_super(int yaffs_version,
						     struct super_block *sb,
						     void *data, int silent)
{
	int n_blocks;
	struct inode *inode = NULL;
	struct dentry *root;
	struct yaffs_dev *dev = 0;
	char devname_buf[BDEVNAME_SIZE + 1];
	struct mtd_info *mtd;
	int err;
	char *data_str = (char *)data;
	struct yaffs_linux_context *context = NULL;
	struct yaffs_param *param;

	int read_only = 0;

	struct yaffs_options options;

	unsigned mount_id;
	int found;
	struct yaffs_linux_context *context_iterator;
	struct list_head *l;

	sb->s_magic = YAFFS_MAGIC;
	sb->s_op = &yaffs_super_ops;
	sb->s_flags |= MS_NOATIME;

	read_only = ((sb->s_flags & MS_RDONLY) != 0);

	sb->s_export_op = &yaffs_export_ops;

	if (!sb)
		printk(KERN_INFO "yaffs: sb is NULL\n");
	else if (!sb->s_dev)
		printk(KERN_INFO "yaffs: sb->s_dev is NULL\n");
	else if (!yaffs_devname(sb, devname_buf))
		printk(KERN_INFO "yaffs: devname is NULL\n");
	else
		printk(KERN_INFO "yaffs: dev is %d name is \"%s\" %s\n",
		       sb->s_dev,
		       yaffs_devname(sb, devname_buf), read_only ? "ro" : "rw");

	if (!data_str)
		data_str = "";

	printk(KERN_INFO "yaffs: passed flags \"%s\"\n", data_str);

	memset(&options, 0, sizeof(options));

	if (yaffs_parse_options(&options, data_str)) {
		/* Option parsing failed */
		return NULL;
	}

	sb->s_blocksize = PAGE_CACHE_SIZE;
	sb->s_blocksize_bits = PAGE_CACHE_SHIFT;

	yaffs_trace(YAFFS_TRACE_OS,
		"yaffs_read_super: Using yaffs%d", yaffs_version);
	yaffs_trace(YAFFS_TRACE_OS,
		"yaffs_read_super: block size %d", (int)(sb->s_blocksize));

	yaffs_trace(YAFFS_TRACE_ALWAYS,
		"Attempting MTD mount of %u.%u,\"%s\"",
		MAJOR(sb->s_dev), MINOR(sb->s_dev),
		yaffs_devname(sb, devname_buf));

	/* Check it's an mtd device..... */
	if (MAJOR(sb->s_dev) != MTD_BLOCK_MAJOR)
		return NULL;	/* This isn't an mtd device */

	/* Get the device */
	mtd = get_mtd_device(NULL, MINOR(sb->s_dev));
	if (!mtd) {
		yaffs_trace(YAFFS_TRACE_ALWAYS,
			"MTD device #%u doesn't appear to exist",
			MINOR(sb->s_dev));
		return NULL;
	}
	/* Check it's NAND */
	if (mtd->type != MTD_NANDFLASH) {
		yaffs_trace(YAFFS_TRACE_ALWAYS,
			"MTD device is not NAND it's type %d",
			mtd->type);
		return NULL;
	}

	yaffs_trace(YAFFS_TRACE_OS, " erase %p", mtd->erase);
	yaffs_trace(YAFFS_TRACE_OS, " read %p", mtd->read);
	yaffs_trace(YAFFS_TRACE_OS, " write %p", mtd->write);
	yaffs_trace(YAFFS_TRACE_OS, " readoob %p", mtd->read_oob);
	yaffs_trace(YAFFS_TRACE_OS, " writeoob %p", mtd->write_oob);
	yaffs_trace(YAFFS_TRACE_OS, " block_isbad %p", mtd->block_isbad);
	yaffs_trace(YAFFS_TRACE_OS, " block_markbad %p", mtd->block_markbad);
	yaffs_trace(YAFFS_TRACE_OS, " %s %d", WRITE_SIZE_STR, WRITE_SIZE(mtd));
	yaffs_trace(YAFFS_TRACE_OS, " oobsize %d", mtd->oobsize);
	yaffs_trace(YAFFS_TRACE_OS, " erasesize %d", mtd->erasesize);
	yaffs_trace(YAFFS_TRACE_OS, " size %lld", mtd->size);

#ifdef CONFIG_YAFFS_AUTO_YAFFS2

	if (yaffs_version == 1 && WRITE_SIZE(mtd) >= 2048) {
		yaffs_trace(YAFFS_TRACE_ALWAYS, "auto selecting yaffs2");
		yaffs_version = 2;
	}

	/* Added NCB 26/5/2006 for completeness */
	if (yaffs_version == 2 && !options.inband_tags
	    && WRITE_SIZE(mtd) == 512) {
		yaffs_trace(YAFFS_TRACE_ALWAYS, "auto selecting yaffs1");
		yaffs_version = 1;
	}
#endif

	if (yaffs_version == 2) {
		/* Check for version 2 style functions */
		if (!mtd->erase ||
		    !mtd->block_isbad ||
		    !mtd->block_markbad ||
		    !mtd->read ||
		    !mtd->write || !mtd->read_oob || !mtd->write_oob) {
			yaffs_trace(YAFFS_TRACE_ALWAYS,
				"MTD device does not support required functions");
			return NULL;
		}

		if ((WRITE_SIZE(mtd) < YAFFS_MIN_YAFFS2_CHUNK_SIZE ||
		     mtd->oobsize < YAFFS_MIN_YAFFS2_SPARE_SIZE) &&
		    !options.inband_tags) {
			yaffs_trace(YAFFS_TRACE_ALWAYS,
				"MTD device does not have the right page sizes");
			return NULL;
		}
	} else {
		/* Check for V1 style functions */
		if (!mtd->erase ||
		    !mtd->read ||
		    !mtd->write || !mtd->read_oob || !mtd->write_oob) {
			yaffs_trace(YAFFS_TRACE_ALWAYS,
				"MTD device does not support required functions");
			return NULL;
		}

		if (WRITE_SIZE(mtd) < YAFFS_BYTES_PER_CHUNK ||
		    mtd->oobsize != YAFFS_BYTES_PER_SPARE) {
			yaffs_trace(YAFFS_TRACE_ALWAYS,
				"MTD device does not support have the right page sizes");
			return NULL;
		}
	}

	/* OK, so if we got here, we have an MTD that's NAND and looks
	 * like it has the right capabilities
	 * Set the struct yaffs_dev up for mtd
	 */

	if (!read_only && !(mtd->flags & MTD_WRITEABLE)) {
		read_only = 1;
		printk(KERN_INFO
		       "yaffs: mtd is read only, setting superblock read only");
		sb->s_flags |= MS_RDONLY;
	}

	dev = kmalloc(sizeof(struct yaffs_dev), GFP_KERNEL);
	context = kmalloc(sizeof(struct yaffs_linux_context), GFP_KERNEL);

	if (!dev || !context) {
		if (dev)
			kfree(dev);
		if (context)
			kfree(context);
		dev = NULL;
		context = NULL;
	}

	if (!dev) {
		/* Deep shit could not allocate device structure */
		yaffs_trace(YAFFS_TRACE_ALWAYS,
			"yaffs_read_super failed trying to allocate yaffs_dev");
		return NULL;
	}
	memset(dev, 0, sizeof(struct yaffs_dev));
	param = &(dev->param);

	memset(context, 0, sizeof(struct yaffs_linux_context));
	dev->os_context = context;
	INIT_LIST_HEAD(&(context->context_list));
	context->dev = dev;
	context->super = sb;

	dev->read_only = read_only;

	sb->s_fs_info = dev;

	dev->driver_context = mtd;
	param->name = mtd->name;

	/* Set up the memory size parameters.... */

	n_blocks =
	    YCALCBLOCKS(mtd->size,
			(YAFFS_CHUNKS_PER_BLOCK * YAFFS_BYTES_PER_CHUNK));

	param->start_block = 0;
	param->end_block = n_blocks - 1;
	param->chunks_per_block = YAFFS_CHUNKS_PER_BLOCK;
	param->total_bytes_per_chunk = YAFFS_BYTES_PER_CHUNK;
	param->n_reserved_blocks = 5;
	param->n_caches = (options.no_cache) ? 0 : 10;
	param->inband_tags = options.inband_tags;

#ifdef CONFIG_YAFFS_DISABLE_LAZY_LOAD
	param->disable_lazy_load = 1;
#endif
#ifdef CONFIG_YAFFS_XATTR
	param->enable_xattr = 1;
#endif
	if (options.lazy_loading_overridden)
		param->disable_lazy_load = !options.lazy_loading_enabled;

#ifdef CONFIG_YAFFS_DISABLE_TAGS_ECC
	param->no_tags_ecc = 1;
#endif

#ifdef CONFIG_YAFFS_DISABLE_BACKGROUND
#else
	param->defered_dir_update = 1;
#endif

	if (options.tags_ecc_overridden)
		param->no_tags_ecc = !options.tags_ecc_on;

#ifdef CONFIG_YAFFS_EMPTY_LOST_AND_FOUND
	param->empty_lost_n_found = 1;
#endif

#ifdef CONFIG_YAFFS_DISABLE_BLOCK_REFRESHING
	param->refresh_period = 0;
#else
	param->refresh_period = 500;
#endif

#ifdef CONFIG_YAFFS_ALWAYS_CHECK_CHUNK_ERASED
	param->always_check_erased = 1;
#endif

	if (options.empty_lost_and_found_overridden)
		param->empty_lost_n_found = options.empty_lost_and_found;

	/* ... and the functions. */
	if (yaffs_version == 2) {
		param->write_chunk_tags_fn = nandmtd2_write_chunk_tags;
		param->read_chunk_tags_fn = nandmtd2_read_chunk_tags;
		param->bad_block_fn = nandmtd2_mark_block_bad;
		param->query_block_fn = nandmtd2_query_block;
		yaffs_dev_to_lc(dev)->spare_buffer = 
		                kmalloc(mtd->oobsize, GFP_NOFS);
		param->is_yaffs2 = 1;
		param->total_bytes_per_chunk = mtd->writesize;
		param->chunks_per_block = mtd->erasesize / mtd->writesize;
		n_blocks = YCALCBLOCKS(mtd->size, mtd->erasesize);

		param->start_block = 0;
		param->end_block = n_blocks - 1;
	} else {
		/* use the MTD interface in yaffs_mtdif1.c */
		param->write_chunk_tags_fn = nandmtd1_write_chunk_tags;
		param->read_chunk_tags_fn = nandmtd1_read_chunk_tags;
		param->bad_block_fn = nandmtd1_mark_block_bad;
		param->query_block_fn = nandmtd1_query_block;
		param->is_yaffs2 = 0;
	}
	/* ... and common functions */
	param->erase_fn = nandmtd_erase_block;
	param->initialise_flash_fn = nandmtd_initialise;

	yaffs_dev_to_lc(dev)->put_super_fn = yaffs_mtd_put_super;

	param->sb_dirty_fn = yaffs_touch_super;
	param->gc_control = yaffs_gc_control_callback;

	yaffs_dev_to_lc(dev)->super = sb;

#ifndef CONFIG_YAFFS_DOES_ECC
	param->use_nand_ecc = 1;
#endif

	param->skip_checkpt_rd = options.skip_checkpoint_read;
	param->skip_checkpt_wr = options.skip_checkpoint_write;

	mutex_lock(&yaffs_context_lock);
	/* Get a mount id */
	found = 0;
	for (mount_id = 0; !found; mount_id++) {
		found = 1;
		list_for_each(l, &yaffs_context_list) {
			context_iterator =
			    list_entry(l, struct yaffs_linux_context,
				       context_list);
			if (context_iterator->mount_id == mount_id)
				found = 0;
		}
	}
	context->mount_id = mount_id;

	list_add_tail(&(yaffs_dev_to_lc(dev)->context_list),
		      &yaffs_context_list);
	mutex_unlock(&yaffs_context_lock);

	/* Directory search handling... */
	INIT_LIST_HEAD(&(yaffs_dev_to_lc(dev)->search_contexts));
	param->remove_obj_fn = yaffs_remove_obj_callback;

	mutex_init(&(yaffs_dev_to_lc(dev)->gross_lock));

	yaffs_gross_lock(dev);

	err = yaffs_guts_initialise(dev);

	yaffs_trace(YAFFS_TRACE_OS,
		"yaffs_read_super: guts initialised %s",
		(err == YAFFS_OK) ? "OK" : "FAILED");

	if (err == YAFFS_OK)
		yaffs_bg_start(dev);

	if (!context->bg_thread)
		param->defered_dir_update = 0;

	/* Release lock before yaffs_get_inode() */
	yaffs_gross_unlock(dev);

	/* Create root inode */
	if (err == YAFFS_OK)
		inode = yaffs_get_inode(sb, S_IFDIR | 0755, 0, yaffs_root(dev));

	if (!inode)
		return NULL;

	inode->i_op = &yaffs_dir_inode_operations;
	inode->i_fop = &yaffs_dir_operations;

	yaffs_trace(YAFFS_TRACE_OS, "yaffs_read_super: got root inode");

	root = d_alloc_root(inode);

	yaffs_trace(YAFFS_TRACE_OS, "yaffs_read_super: d_alloc_root done");

	if (!root) {
		iput(inode);
		return NULL;
	}
	sb->s_root = root;
	sb->s_dirt = !dev->is_checkpointed;
	yaffs_trace(YAFFS_TRACE_ALWAYS,
		"yaffs_read_super: is_checkpointed %d",
		dev->is_checkpointed);

	yaffs_trace(YAFFS_TRACE_OS, "yaffs_read_super: done");
	return sb;
}

static int yaffs_internal_read_super_mtd(struct super_block *sb, void *data,
					 int silent)
{
	return yaffs_internal_read_super(1, sb, data, silent) ? 0 : -EINVAL;
}

static int yaffs_read_super(struct file_system_type *fs,
			    int flags, const char *dev_name,
			    void *data, struct vfsmount *mnt)
{

	return get_sb_bdev(fs, flags, dev_name, data,
			   yaffs_internal_read_super_mtd, mnt);
}

static struct file_system_type yaffs_fs_type = {
	.owner = THIS_MODULE,
	.name = "yaffs",
	.get_sb = yaffs_read_super,
	.kill_sb = kill_block_super,
	.fs_flags = FS_REQUIRES_DEV,
};

#ifdef CONFIG_YAFFS_YAFFS2

static int yaffs2_internal_read_super_mtd(struct super_block *sb, void *data,
					  int silent)
{
	return yaffs_internal_read_super(2, sb, data, silent) ? 0 : -EINVAL;
}

static int yaffs2_read_super(struct file_system_type *fs,
			     int flags, const char *dev_name, void *data,
			     struct vfsmount *mnt)
{
	return get_sb_bdev(fs, flags, dev_name, data,
			   yaffs2_internal_read_super_mtd, mnt);
}

static struct file_system_type yaffs2_fs_type = {
	.owner = THIS_MODULE,
	.name = "yaffs2",
	.get_sb = yaffs2_read_super,
	.kill_sb = kill_block_super,
	.fs_flags = FS_REQUIRES_DEV,
};
#endif /* CONFIG_YAFFS_YAFFS2 */

static struct proc_dir_entry *my_proc_entry;

static char *yaffs_dump_dev_part0(char *buf, struct yaffs_dev *dev)
{
	struct yaffs_param *param = &dev->param;
	buf += sprintf(buf, "start_block........... %d\n", param->start_block);
	buf += sprintf(buf, "end_block............. %d\n", param->end_block);
	buf += sprintf(buf, "total_bytes_per_chunk. %d\n",
			param->total_bytes_per_chunk);
	buf += sprintf(buf, "use_nand_ecc.......... %d\n",
			param->use_nand_ecc);
	buf += sprintf(buf, "no_tags_ecc........... %d\n", param->no_tags_ecc);
	buf += sprintf(buf, "is_yaffs2............. %d\n", param->is_yaffs2);
	buf += sprintf(buf, "inband_tags........... %d\n", param->inband_tags);
	buf += sprintf(buf, "empty_lost_n_found.... %d\n",
			param->empty_lost_n_found);
	buf += sprintf(buf, "disable_lazy_load..... %d\n",
			param->disable_lazy_load);
	buf += sprintf(buf, "refresh_period........ %d\n",
			param->refresh_period);
	buf += sprintf(buf, "n_caches.............. %d\n", param->n_caches);
	buf += sprintf(buf, "n_reserved_blocks..... %d\n",
			param->n_reserved_blocks);
	buf += sprintf(buf, "always_check_erased... %d\n",
			param->always_check_erased);

	return buf;
}

static char *yaffs_dump_dev_part1(char *buf, struct yaffs_dev *dev)
{
	buf +=
	    sprintf(buf, "data_bytes_per_chunk.. %d\n",
		    dev->data_bytes_per_chunk);
	buf += sprintf(buf, "chunk_grp_bits........ %d\n", dev->chunk_grp_bits);
	buf += sprintf(buf, "chunk_grp_size........ %d\n", dev->chunk_grp_size);
	buf +=
	    sprintf(buf, "n_erased_blocks....... %d\n", dev->n_erased_blocks);
	buf +=
	    sprintf(buf, "blocks_in_checkpt..... %d\n", dev->blocks_in_checkpt);
	buf += sprintf(buf, "\n");
	buf += sprintf(buf, "n_tnodes.............. %d\n", dev->n_tnodes);
	buf += sprintf(buf, "n_obj................. %d\n", dev->n_obj);
	buf += sprintf(buf, "n_free_chunks......... %d\n", dev->n_free_chunks);
	buf += sprintf(buf, "\n");
	buf += sprintf(buf, "n_page_writes......... %u\n", dev->n_page_writes);
	buf += sprintf(buf, "n_page_reads.......... %u\n", dev->n_page_reads);
	buf += sprintf(buf, "n_erasures............ %u\n", dev->n_erasures);
	buf += sprintf(buf, "n_gc_copies........... %u\n", dev->n_gc_copies);
	buf += sprintf(buf, "all_gcs............... %u\n", dev->all_gcs);
	buf +=
	    sprintf(buf, "passive_gc_count...... %u\n", dev->passive_gc_count);
	buf +=
	    sprintf(buf, "oldest_dirty_gc_count. %u\n",
		    dev->oldest_dirty_gc_count);
	buf += sprintf(buf, "n_gc_blocks........... %u\n", dev->n_gc_blocks);
	buf += sprintf(buf, "bg_gcs................ %u\n", dev->bg_gcs);
	buf +=
	    sprintf(buf, "n_retired_writes...... %u\n", dev->n_retired_writes);
	buf +=
	    sprintf(buf, "n_retired_blocks...... %u\n", dev->n_retired_blocks);
	buf += sprintf(buf, "n_ecc_fixed........... %u\n", dev->n_ecc_fixed);
	buf += sprintf(buf, "n_ecc_unfixed......... %u\n", dev->n_ecc_unfixed);
	buf +=
	    sprintf(buf, "n_tags_ecc_fixed...... %u\n", dev->n_tags_ecc_fixed);
	buf +=
	    sprintf(buf, "n_tags_ecc_unfixed.... %u\n",
		    dev->n_tags_ecc_unfixed);
	buf += sprintf(buf, "cache_hits............ %u\n", dev->cache_hits);
	buf +=
	    sprintf(buf, "n_deleted_files....... %u\n", dev->n_deleted_files);
	buf +=
	    sprintf(buf, "n_unlinked_files...... %u\n", dev->n_unlinked_files);
	buf += sprintf(buf, "refresh_count......... %u\n", dev->refresh_count);
	buf += sprintf(buf, "n_bg_deletions........ %u\n", dev->n_bg_deletions);

	return buf;
}

static int yaffs_proc_read(char *page,
			   char **start,
			   off_t offset, int count, int *eof, void *data)
{
	struct list_head *item;
	char *buf = page;
	int step = offset;
	int n = 0;

	/* Get proc_file_read() to step 'offset' by one on each sucessive call.
	 * We use 'offset' (*ppos) to indicate where we are in dev_list.
	 * This also assumes the user has posted a read buffer large
	 * enough to hold the complete output; but that's life in /proc.
	 */

	*(int *)start = 1;

	/* Print header first */
	if (step == 0)
		buf += sprintf(buf, "YAFFS built:" __DATE__ " " __TIME__ "\n");
	else if (step == 1)
		buf += sprintf(buf, "\n");
	else {
		step -= 2;

		mutex_lock(&yaffs_context_lock);

		/* Locate and print the Nth entry.  Order N-squared but N is small. */
		list_for_each(item, &yaffs_context_list) {
			struct yaffs_linux_context *dc =
			    list_entry(item, struct yaffs_linux_context,
				       context_list);
			struct yaffs_dev *dev = dc->dev;

			if (n < (step & ~1)) {
				n += 2;
				continue;
			}
			if ((step & 1) == 0) {
				buf +=
				    sprintf(buf, "\nDevice %d \"%s\"\n", n,
					    dev->param.name);
				buf = yaffs_dump_dev_part0(buf, dev);
			} else {
				buf = yaffs_dump_dev_part1(buf, dev);
                        }

			break;
		}
		mutex_unlock(&yaffs_context_lock);
	}

	return buf - page < count ? buf - page : count;
}


/**
 * Set the verbosity of the warnings and error messages.
 *
 * Note that the names can only be a..z or _ with the current code.
 */

static struct {
	char *mask_name;
	unsigned mask_bitfield;
} mask_flags[] = {
	{"allocate", YAFFS_TRACE_ALLOCATE}, 
	{"always", YAFFS_TRACE_ALWAYS},
	{"background", YAFFS_TRACE_BACKGROUND},
	{"bad_blocks", YAFFS_TRACE_BAD_BLOCKS},
	{"buffers", YAFFS_TRACE_BUFFERS},
	{"bug", YAFFS_TRACE_BUG},
	{"checkpt", YAFFS_TRACE_CHECKPOINT},
	{"deletion", YAFFS_TRACE_DELETION},
	{"erase", YAFFS_TRACE_ERASE},
	{"error", YAFFS_TRACE_ERROR},
	{"gc_detail", YAFFS_TRACE_GC_DETAIL},
	{"gc", YAFFS_TRACE_GC},
	{"lock", YAFFS_TRACE_LOCK},
	{"mtd", YAFFS_TRACE_MTD},
	{"nandaccess", YAFFS_TRACE_NANDACCESS},
	{"os", YAFFS_TRACE_OS},
	{"scan_debug", YAFFS_TRACE_SCAN_DEBUG},
	{"scan", YAFFS_TRACE_SCAN},
	{"mount", YAFFS_TRACE_MOUNT},
	{"tracing", YAFFS_TRACE_TRACING},
	{"sync", YAFFS_TRACE_SYNC},
	{"write", YAFFS_TRACE_WRITE},
	{"verify", YAFFS_TRACE_VERIFY},
	{"verify_nand", YAFFS_TRACE_VERIFY_NAND},
	{"verify_full", YAFFS_TRACE_VERIFY_FULL},
	{"verify_all", YAFFS_TRACE_VERIFY_ALL},
	{"all", 0xffffffff},
	{"none", 0},
	{NULL, 0},
};

#define MAX_MASK_NAME_LENGTH 40
static int yaffs_proc_write_trace_options(struct file *file, const char *buf,
					  unsigned long count, void *data)
{
	unsigned rg = 0, mask_bitfield;
	char *end;
	char *mask_name;
	const char *x;
	char substring[MAX_MASK_NAME_LENGTH + 1];
	int i;
	int done = 0;
	int add, len = 0;
	int pos = 0;

	rg = yaffs_trace_mask;

	while (!done && (pos < count)) {
		done = 1;
		while ((pos < count) && isspace(buf[pos]))
			pos++;

		switch (buf[pos]) {
		case '+':
		case '-':
		case '=':
			add = buf[pos];
			pos++;
			break;

		default:
			add = ' ';
			break;
		}
		mask_name = NULL;

		mask_bitfield = simple_strtoul(buf + pos, &end, 0);

		if (end > buf + pos) {
			mask_name = "numeral";
			len = end - (buf + pos);
			pos += len;
			done = 0;
		} else {
			for (x = buf + pos, i = 0;
			     (*x == '_' || (*x >= 'a' && *x <= 'z')) &&
			     i < MAX_MASK_NAME_LENGTH; x++, i++, pos++)
				substring[i] = *x;
			substring[i] = '\0';

			for (i = 0; mask_flags[i].mask_name != NULL; i++) {
				if (strcmp(substring, mask_flags[i].mask_name)
				    == 0) {
					mask_name = mask_flags[i].mask_name;
					mask_bitfield =
					    mask_flags[i].mask_bitfield;
					done = 0;
					break;
				}
			}
		}

		if (mask_name != NULL) {
			done = 0;
			switch (add) {
			case '-':
				rg &= ~mask_bitfield;
				break;
			case '+':
				rg |= mask_bitfield;
				break;
			case '=':
				rg = mask_bitfield;
				break;
			default:
				rg |= mask_bitfield;
				break;
			}
		}
	}

	yaffs_trace_mask = rg | YAFFS_TRACE_ALWAYS;

	printk(KERN_DEBUG "new trace = 0x%08X\n", yaffs_trace_mask);

	if (rg & YAFFS_TRACE_ALWAYS) {
		for (i = 0; mask_flags[i].mask_name != NULL; i++) {
			char flag;
			flag = ((rg & mask_flags[i].mask_bitfield) ==
				mask_flags[i].mask_bitfield) ? '+' : '-';
			printk(KERN_DEBUG "%c%s\n", flag,
			       mask_flags[i].mask_name);
		}
	}

	return count;
}

static int yaffs_proc_write(struct file *file, const char *buf,
			    unsigned long count, void *data)
{
	return yaffs_proc_write_trace_options(file, buf, count, data);
}

/* Stuff to handle installation of file systems */
struct file_system_to_install {
	struct file_system_type *fst;
	int installed;
};

static struct file_system_to_install fs_to_install[] = {
	{&yaffs_fs_type, 0},
	{&yaffs2_fs_type, 0},
	{NULL, 0}
};

static int __init init_yaffs_fs(void)
{
	int error = 0;
	struct file_system_to_install *fsinst;

	yaffs_trace(YAFFS_TRACE_ALWAYS,
		"yaffs built " __DATE__ " " __TIME__ " Installing.");

#ifdef CONFIG_YAFFS_ALWAYS_CHECK_CHUNK_ERASED
	yaffs_trace(YAFFS_TRACE_ALWAYS,
		"\n\nYAFFS-WARNING CONFIG_YAFFS_ALWAYS_CHECK_CHUNK_ERASED selected.\n\n\n");
#endif

	mutex_init(&yaffs_context_lock);

	/* Install the proc_fs entries */
	my_proc_entry = create_proc_entry("yaffs",
					  S_IRUGO | S_IFREG, YPROC_ROOT);

	if (my_proc_entry) {
		my_proc_entry->write_proc = yaffs_proc_write;
		my_proc_entry->read_proc = yaffs_proc_read;
		my_proc_entry->data = NULL;
	} else {
		return -ENOMEM;
        }


	/* Now add the file system entries */

	fsinst = fs_to_install;

	while (fsinst->fst && !error) {
		error = register_filesystem(fsinst->fst);
		if (!error)
			fsinst->installed = 1;
		fsinst++;
	}

	/* Any errors? uninstall  */
	if (error) {
		fsinst = fs_to_install;

		while (fsinst->fst) {
			if (fsinst->installed) {
				unregister_filesystem(fsinst->fst);
				fsinst->installed = 0;
			}
			fsinst++;
		}
	}

	return error;
}

static void __exit exit_yaffs_fs(void)
{

	struct file_system_to_install *fsinst;

	yaffs_trace(YAFFS_TRACE_ALWAYS,
		"yaffs built " __DATE__ " " __TIME__ " removing.");

	remove_proc_entry("yaffs", YPROC_ROOT);

	fsinst = fs_to_install;

	while (fsinst->fst) {
		if (fsinst->installed) {
			unregister_filesystem(fsinst->fst);
			fsinst->installed = 0;
		}
		fsinst++;
	}
}

module_init(init_yaffs_fs)
    module_exit(exit_yaffs_fs)

    MODULE_DESCRIPTION("YAFFS2 - a NAND specific flash file system");
MODULE_AUTHOR("Charles Manning, Aleph One Ltd., 2002-2010");
MODULE_LICENSE("GPL");