mtdsuper.c

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/* MTD-based superblock management
 *
 * Copyright © 2001-2007 Red Hat, Inc. All Rights Reserved.
 * Copyright © 2001-2010 David Woodhouse <[email protected]>
 *
 * Written by:  David Howells <[email protected]>
 *              David Woodhouse <[email protected]>
 *
 * 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>

/*
 * 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\")\n",
              mtd->index, mtd->name);
        return 1;
    }

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

/*
 * 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 = mtd->backing_dev_info;
    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\")\n",
          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\n",
          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\n", 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\"\n", 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\"\n",
                  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.\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 */
                pr_debug("MTDSB: mtd%%d, mtdnr %d\n",
                      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\n", ret);
        return ERR_PTR(ret);
    }
    pr_debug("MTDSB: lookup_bdev() returned 0\n");

    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\"\n",
               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);