/* MTD-based superblock management
   *
   * Copyright © 2001-2007 Red Hat, Inc. All Rights Reserved.

   * Copyright © 2001-2010 David Woodhouse <dwmw2@infradead.org>
   *

   * Written by:  David Howells <dhowells@redhat.com>
   *              David Woodhouse <dwmw2@infradead.org>
   *
   * This program is free software; you can redistribute it and/or
   * modify it under the terms of the GNU General Public License
   * as published by the Free Software Foundation; either version
   * 2 of the License, or (at your option) any later version.
   */
  
  #include <linux/mtd/super.h>
  #include <linux/namei.h>

  #include <linux/export.h>

  #include <linux/ctype.h>

  #include <linux/slab.h>

  #include <linux/major.h>

  #include <linux/backing-dev.h>

  
  /*
   * compare superblocks to see if they're equivalent
   * - they are if the underlying MTD device is the same
   */
  static int get_sb_mtd_compare(struct super_block *sb, void *_mtd)
  {
  	struct mtd_info *mtd = _mtd;
  
  	if (sb->s_mtd == mtd) {

  		pr_debug("MTDSB: Match on device %d (\"%s\")
  ",

  		      mtd->index, mtd->name);
  		return 1;
  	}

  	pr_debug("MTDSB: No match, device %d (\"%s\"), device %d (\"%s\")
  ",

  	      sb->s_mtd->index, sb->s_mtd->name, mtd->index, mtd->name);
  	return 0;
  }

  extern struct backing_dev_info *mtd_bdi;

  /*
   * mark the superblock by the MTD device it is using
   * - set the device number to be the correct MTD block device for pesuperstence
   *   of NFS exports
   */
  static int get_sb_mtd_set(struct super_block *sb, void *_mtd)
  {
  	struct mtd_info *mtd = _mtd;
  
  	sb->s_mtd = mtd;
  	sb->s_dev = MKDEV(MTD_BLOCK_MAJOR, mtd->index);

  	sb->s_bdi = bdi_get(mtd_bdi);

  	return 0;
  }
  
  /*
   * get a superblock on an MTD-backed filesystem
   */

  static struct dentry *mount_mtd_aux(struct file_system_type *fs_type, int flags,

  			  const char *dev_name, void *data,
  			  struct mtd_info *mtd,

  			  int (*fill_super)(struct super_block *, void *, int))

  {
  	struct super_block *sb;
  	int ret;

  	sb = sget(fs_type, get_sb_mtd_compare, get_sb_mtd_set, flags, mtd);

  	if (IS_ERR(sb))
  		goto out_error;
  
  	if (sb->s_root)
  		goto already_mounted;
  
  	/* fresh new superblock */

  	pr_debug("MTDSB: New superblock for device %d (\"%s\")
  ",

  	      mtd->index, mtd->name);
  
  	ret = fill_super(sb, data, flags & MS_SILENT ? 1 : 0);
  	if (ret < 0) {

  		deactivate_locked_super(sb);

  		return ERR_PTR(ret);

  	}
  
  	/* go */
  	sb->s_flags |= MS_ACTIVE;

  	return dget(sb->s_root);

  
  	/* new mountpoint for an already mounted superblock */
  already_mounted:

  	pr_debug("MTDSB: Device %d (\"%s\") is already mounted
  ",

  	      mtd->index, mtd->name);

  	put_mtd_device(mtd);
  	return dget(sb->s_root);

  
  out_error:

  	put_mtd_device(mtd);

  	return ERR_CAST(sb);

  }
  
  /*
   * get a superblock on an MTD-backed filesystem by MTD device number
   */

  static struct dentry *mount_mtd_nr(struct file_system_type *fs_type, int flags,

  			 const char *dev_name, void *data, int mtdnr,

  			 int (*fill_super)(struct super_block *, void *, int))

  {
  	struct mtd_info *mtd;
  
  	mtd = get_mtd_device(NULL, mtdnr);

  	if (IS_ERR(mtd)) {

  		pr_debug("MTDSB: Device #%u doesn't appear to exist
  ", mtdnr);

  		return ERR_CAST(mtd);

  	}

  	return mount_mtd_aux(fs_type, flags, dev_name, data, mtd, fill_super);

  }
  
  /*
   * set up an MTD-based superblock
   */

  struct dentry *mount_mtd(struct file_system_type *fs_type, int flags,

  	       const char *dev_name, void *data,

  	       int (*fill_super)(struct super_block *, void *, int))

  {

  #ifdef CONFIG_BLOCK

  	struct block_device *bdev;

  	int ret, major;
  #endif
  	int mtdnr;

  
  	if (!dev_name)

  		return ERR_PTR(-EINVAL);

  	pr_debug("MTDSB: dev_name \"%s\"
  ", dev_name);

  
  	/* the preferred way of mounting in future; especially when
  	 * CONFIG_BLOCK=n - we specify the underlying MTD device by number or
  	 * by name, so that we don't require block device support to be present
  	 * in the kernel. */
  	if (dev_name[0] == 'm' && dev_name[1] == 't' && dev_name[2] == 'd') {
  		if (dev_name[3] == ':') {
  			struct mtd_info *mtd;
  
  			/* mount by MTD device name */

  			pr_debug("MTDSB: mtd:%%s, name \"%s\"
  ",

  			      dev_name + 4);

  			mtd = get_mtd_device_nm(dev_name + 4);
  			if (!IS_ERR(mtd))

  				return mount_mtd_aux(

  					fs_type, flags,
  					dev_name, data, mtd,

  					fill_super);

  
  			printk(KERN_NOTICE "MTD:"
  			       " MTD device with name \"%s\" not found.
  ",
  			       dev_name + 4);
  
  		} else if (isdigit(dev_name[3])) {
  			/* mount by MTD device number name */
  			char *endptr;
  
  			mtdnr = simple_strtoul(dev_name + 3, &endptr, 0);
  			if (!*endptr) {
  				/* It was a valid number */

  				pr_debug("MTDSB: mtd%%d, mtdnr %d
  ",

  				      mtdnr);

  				return mount_mtd_nr(fs_type, flags,

  						     dev_name, data,

  						     mtdnr, fill_super);

  			}
  		}
  	}

  #ifdef CONFIG_BLOCK

  	/* try the old way - the hack where we allowed users to mount
  	 * /dev/mtdblock$(n) but didn't actually _use_ the blockdev
  	 */

  	bdev = lookup_bdev(dev_name);
  	if (IS_ERR(bdev)) {
  		ret = PTR_ERR(bdev);

  		pr_debug("MTDSB: lookup_bdev() returned %d
  ", ret);

  		return ERR_PTR(ret);

  	}

  	pr_debug("MTDSB: lookup_bdev() returned 0
  ");

  	ret = -EINVAL;

  	major = MAJOR(bdev->bd_dev);

  	mtdnr = MINOR(bdev->bd_dev);
  	bdput(bdev);

  	if (major != MTD_BLOCK_MAJOR)
  		goto not_an_MTD_device;

  	return mount_mtd_nr(fs_type, flags, dev_name, data, mtdnr, fill_super);

  
  not_an_MTD_device:

  #endif /* CONFIG_BLOCK */

  	if (!(flags & MS_SILENT))
  		printk(KERN_NOTICE
  		       "MTD: Attempt to mount non-MTD device \"%s\"
  ",
  		       dev_name);

  	return ERR_PTR(-EINVAL);

  }

  EXPORT_SYMBOL_GPL(mount_mtd);

  
  /*
   * destroy an MTD-based superblock
   */
  void kill_mtd_super(struct super_block *sb)
  {
  	generic_shutdown_super(sb);
  	put_mtd_device(sb->s_mtd);
  	sb->s_mtd = NULL;
  }
  
  EXPORT_SYMBOL_GPL(kill_mtd_super);