// SPDX-License-Identifier: GPL-2.0-or-later
/* 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>
 */

#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>
#include <linux/fs_context.h>
#include "mtdcore.h"

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

        if (sb->s_mtd == fc->sget_key) {
                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 mtd_set_super(struct super_block *sb, struct fs_context *fc)
{
        sb->s_mtd = fc->sget_key;
        sb->s_dev = MKDEV(MTD_BLOCK_MAJOR, sb->s_mtd->index);
        sb->s_bdi = bdi_get(mtd_bdi);
        return 0;
}

/*
 * get a superblock on an MTD-backed filesystem
 */
static int mtd_get_sb(struct fs_context *fc,
                      struct mtd_info *mtd,
                      int (*fill_super)(struct super_block *,
                                        struct fs_context *))
{
        struct super_block *sb;
        int ret;

        fc->sget_key = mtd;
        sb = sget_fc(fc, mtd_test_super, mtd_set_super);
        if (IS_ERR(sb))
                return PTR_ERR(sb);

        if (sb->s_root) {
                /* new mountpoint for an already mounted superblock */
                pr_debug("MTDSB: Device %d (\"%s\") is already mounted\n",
                         mtd->index, mtd->name);
                put_mtd_device(mtd);
        } else {
                /* fresh new superblock */
                pr_debug("MTDSB: New superblock for device %d (\"%s\")\n",
                         mtd->index, mtd->name);

                ret = fill_super(sb, fc);
                if (ret < 0)
                        goto error_sb;

                sb->s_flags |= SB_ACTIVE;
        }

        BUG_ON(fc->root);
        fc->root = dget(sb->s_root);
        return 0;

error_sb:
        deactivate_locked_super(sb);
        return ret;
}

/*
 * get a superblock on an MTD-backed filesystem by MTD device number
 */
static int mtd_get_sb_by_nr(struct fs_context *fc, int mtdnr,
                            int (*fill_super)(struct super_block *,
                                              struct fs_context *))
{
        struct mtd_info *mtd;

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

        return mtd_get_sb(fc, mtd, fill_super);
}

/**
 * get_tree_mtd - Get a superblock based on a single MTD device
 * @fc: The filesystem context holding the parameters
 * @fill_super: Helper to initialise a new superblock
 */
int get_tree_mtd(struct fs_context *fc,
              int (*fill_super)(struct super_block *sb,
                                struct fs_context *fc))
{
#ifdef CONFIG_BLOCK
        dev_t dev;
        int ret;
#endif
        int mtdnr;

        if (!fc->source)
                return invalf(fc, "No source specified");

        pr_debug("MTDSB: dev_name \"%s\"\n", fc->source);

        /* 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 (fc->source[0] == 'm' &&
            fc->source[1] == 't' &&
            fc->source[2] == 'd') {
                if (fc->source[3] == ':') {
                        struct mtd_info *mtd;

                        /* mount by MTD device name */
                        pr_debug("MTDSB: mtd:%%s, name \"%s\"\n",
                                 fc->source + 4);

                        mtd = get_mtd_device_nm(fc->source + 4);
                        if (!IS_ERR(mtd))
                                return mtd_get_sb(fc, mtd, fill_super);

                        errorf(fc, "MTD: MTD device with name \"%s\" not found",
                               fc->source + 4);

                } else if (isdigit(fc->source[3])) {
                        /* mount by MTD device number name */
                        char *endptr;

                        mtdnr = simple_strtoul(fc->source + 3, &endptr, 0);
                        if (!*endptr) {
                                /* It was a valid number */
                                pr_debug("MTDSB: mtd%%d, mtdnr %d\n", mtdnr);
                                return mtd_get_sb_by_nr(fc, 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
         */
        ret = lookup_bdev(fc->source, &dev);
        if (ret) {
                errorf(fc, "MTD: Couldn't look up '%s': %d", fc->source, ret);
                return ret;
        }
        pr_debug("MTDSB: lookup_bdev() returned 0\n");

        if (MAJOR(dev) == MTD_BLOCK_MAJOR)
                return mtd_get_sb_by_nr(fc, MINOR(dev), fill_super);

#endif /* CONFIG_BLOCK */

        if (!(fc->sb_flags & SB_SILENT))
                errorf(fc, "MTD: Attempt to mount non-MTD device \"%s\"",
                       fc->source);
        return -EINVAL;
}
EXPORT_SYMBOL_GPL(get_tree_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);