mtdsuper.c 5.53 KB
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/* MTD-based superblock management
 *
 * Copyright © 2001-2007 Red Hat, Inc. All Rights Reserved.
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 * Copyright © 2001-2010 David Woodhouse <dwmw2@infradead.org>
 *
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 * 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>
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#include <linux/export.h>
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#include <linux/ctype.h>
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#include <linux/slab.h>
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#include <linux/major.h>
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#include <linux/backing-dev.h>
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/*
 * 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) {
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		pr_debug("MTDSB: Match on device %d (\"%s\")\n",
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		      mtd->index, mtd->name);
		return 1;
	}

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	pr_debug("MTDSB: No match, device %d (\"%s\"), device %d (\"%s\")\n",
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	      sb->s_mtd->index, sb->s_mtd->name, mtd->index, mtd->name);
	return 0;
}

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extern struct backing_dev_info *mtd_bdi;

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/*
 * 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);
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	sb->s_bdi = bdi_get(mtd_bdi);

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	return 0;
}

/*
 * get a superblock on an MTD-backed filesystem
 */
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static struct dentry *mount_mtd_aux(struct file_system_type *fs_type, int flags,
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			  const char *dev_name, void *data,
			  struct mtd_info *mtd,
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			  int (*fill_super)(struct super_block *, void *, int))
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{
	struct super_block *sb;
	int ret;

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	sb = sget(fs_type, get_sb_mtd_compare, get_sb_mtd_set, flags, mtd);
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	if (IS_ERR(sb))
		goto out_error;

	if (sb->s_root)
		goto already_mounted;

	/* fresh new superblock */
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	pr_debug("MTDSB: New superblock for device %d (\"%s\")\n",
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	      mtd->index, mtd->name);

	ret = fill_super(sb, data, flags & MS_SILENT ? 1 : 0);
	if (ret < 0) {
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		deactivate_locked_super(sb);
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		return ERR_PTR(ret);
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	}

	/* go */
	sb->s_flags |= MS_ACTIVE;
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	return dget(sb->s_root);
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	/* new mountpoint for an already mounted superblock */
already_mounted:
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	pr_debug("MTDSB: Device %d (\"%s\") is already mounted\n",
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	      mtd->index, mtd->name);
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	put_mtd_device(mtd);
	return dget(sb->s_root);
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out_error:
	put_mtd_device(mtd);
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	return ERR_CAST(sb);
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}

/*
 * get a superblock on an MTD-backed filesystem by MTD device number
 */
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static struct dentry *mount_mtd_nr(struct file_system_type *fs_type, int flags,
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			 const char *dev_name, void *data, int mtdnr,
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			 int (*fill_super)(struct super_block *, void *, int))
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{
	struct mtd_info *mtd;

	mtd = get_mtd_device(NULL, mtdnr);
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	if (IS_ERR(mtd)) {
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		pr_debug("MTDSB: Device #%u doesn't appear to exist\n", mtdnr);
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		return ERR_CAST(mtd);
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	}

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

/*
 * set up an MTD-based superblock
 */
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struct dentry *mount_mtd(struct file_system_type *fs_type, int flags,
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	       const char *dev_name, void *data,
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	       int (*fill_super)(struct super_block *, void *, int))
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{
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#ifdef CONFIG_BLOCK
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	struct block_device *bdev;
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	int ret, major;
#endif
	int mtdnr;
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	if (!dev_name)
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		return ERR_PTR(-EINVAL);
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	pr_debug("MTDSB: dev_name \"%s\"\n", dev_name);
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	/* 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 */
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			pr_debug("MTDSB: mtd:%%s, name \"%s\"\n",
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			      dev_name + 4);

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			mtd = get_mtd_device_nm(dev_name + 4);
			if (!IS_ERR(mtd))
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				return mount_mtd_aux(
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					fs_type, flags,
					dev_name, data, mtd,
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					fill_super);
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			printk(KERN_NOTICE "MTD:"
			       " MTD device with name \"%s\" not found.\n",
			       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 */
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				pr_debug("MTDSB: mtd%%d, mtdnr %d\n",
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				      mtdnr);
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				return mount_mtd_nr(fs_type, flags,
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						     dev_name, data,
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						     mtdnr, fill_super);
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			}
		}
	}

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#ifdef CONFIG_BLOCK
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	/* try the old way - the hack where we allowed users to mount
	 * /dev/mtdblock$(n) but didn't actually _use_ the blockdev
	 */
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	bdev = lookup_bdev(dev_name);
	if (IS_ERR(bdev)) {
		ret = PTR_ERR(bdev);
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		pr_debug("MTDSB: lookup_bdev() returned %d\n", ret);
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		return ERR_PTR(ret);
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	}
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	pr_debug("MTDSB: lookup_bdev() returned 0\n");
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	ret = -EINVAL;
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	major = MAJOR(bdev->bd_dev);
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	mtdnr = MINOR(bdev->bd_dev);
	bdput(bdev);
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	if (major != MTD_BLOCK_MAJOR)
		goto not_an_MTD_device;

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	return mount_mtd_nr(fs_type, flags, dev_name, data, mtdnr, fill_super);
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not_an_MTD_device:
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#endif /* CONFIG_BLOCK */

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

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EXPORT_SYMBOL_GPL(mount_mtd);
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/*
 * 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);