/* 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\")\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;
}

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\")\n",
              mtd->index, mtd->name);

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

        /* go */
        sb->s_flags |= SB_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 & SB_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);