| 1 | // SPDX-License-Identifier: GPL-2.0-or-later |
| 2 | /* MTD-based superblock management |
| 3 | * |
| 4 | * Copyright © 2001-2007 Red Hat, Inc. All Rights Reserved. |
| 5 | * Copyright © 2001-2010 David Woodhouse <dwmw2@infradead.org> |
| 6 | * |
| 7 | * Written by: David Howells <dhowells@redhat.com> |
| 8 | * David Woodhouse <dwmw2@infradead.org> |
| 9 | */ |
| 10 | |
| 11 | #include <linux/mtd/super.h> |
| 12 | #include <linux/namei.h> |
| 13 | #include <linux/export.h> |
| 14 | #include <linux/ctype.h> |
| 15 | #include <linux/slab.h> |
| 16 | #include <linux/major.h> |
| 17 | #include <linux/backing-dev.h> |
| 18 | #include <linux/blkdev.h> |
| 19 | #include <linux/fs_context.h> |
| 20 | #include "mtdcore.h" |
| 21 | |
| 22 | /* |
| 23 | * get a superblock on an MTD-backed filesystem |
| 24 | */ |
| 25 | static int mtd_get_sb(struct fs_context *fc, |
| 26 | struct mtd_info *mtd, |
| 27 | int (*fill_super)(struct super_block *, |
| 28 | struct fs_context *)) |
| 29 | { |
| 30 | struct super_block *sb; |
| 31 | int ret; |
| 32 | |
| 33 | sb = sget_dev(fc, MKDEV(MTD_BLOCK_MAJOR, mtd->index)); |
| 34 | if (IS_ERR(sb)) |
| 35 | return PTR_ERR(sb); |
| 36 | |
| 37 | if (sb->s_root) { |
| 38 | /* new mountpoint for an already mounted superblock */ |
| 39 | pr_debug("MTDSB: Device %d (\"%s\") is already mounted\n", |
| 40 | mtd->index, mtd->name); |
| 41 | put_mtd_device(mtd); |
| 42 | } else { |
| 43 | /* fresh new superblock */ |
| 44 | pr_debug("MTDSB: New superblock for device %d (\"%s\")\n", |
| 45 | mtd->index, mtd->name); |
| 46 | |
| 47 | /* |
| 48 | * Would usually have been set with @sb_lock held but in |
| 49 | * contrast to sb->s_bdev that's checked with only |
| 50 | * @sb_lock held, nothing checks sb->s_mtd without also |
| 51 | * holding sb->s_umount and we're holding sb->s_umount |
| 52 | * here. |
| 53 | */ |
| 54 | sb->s_mtd = mtd; |
| 55 | sb->s_bdi = bdi_get(mtd_bdi); |
| 56 | |
| 57 | ret = fill_super(sb, fc); |
| 58 | if (ret < 0) |
| 59 | goto error_sb; |
| 60 | |
| 61 | sb->s_flags |= SB_ACTIVE; |
| 62 | } |
| 63 | |
| 64 | BUG_ON(fc->root); |
| 65 | fc->root = dget(sb->s_root); |
| 66 | return 0; |
| 67 | |
| 68 | error_sb: |
| 69 | deactivate_locked_super(sb); |
| 70 | return ret; |
| 71 | } |
| 72 | |
| 73 | /* |
| 74 | * get a superblock on an MTD-backed filesystem by MTD device number |
| 75 | */ |
| 76 | static int mtd_get_sb_by_nr(struct fs_context *fc, int mtdnr, |
| 77 | int (*fill_super)(struct super_block *, |
| 78 | struct fs_context *)) |
| 79 | { |
| 80 | struct mtd_info *mtd; |
| 81 | |
| 82 | mtd = get_mtd_device(NULL, mtdnr); |
| 83 | if (IS_ERR(mtd)) { |
| 84 | errorf(fc, "MTDSB: Device #%u doesn't appear to exist\n", mtdnr); |
| 85 | return PTR_ERR(mtd); |
| 86 | } |
| 87 | |
| 88 | return mtd_get_sb(fc, mtd, fill_super); |
| 89 | } |
| 90 | |
| 91 | /** |
| 92 | * get_tree_mtd - Get a superblock based on a single MTD device |
| 93 | * @fc: The filesystem context holding the parameters |
| 94 | * @fill_super: Helper to initialise a new superblock |
| 95 | */ |
| 96 | int get_tree_mtd(struct fs_context *fc, |
| 97 | int (*fill_super)(struct super_block *sb, |
| 98 | struct fs_context *fc)) |
| 99 | { |
| 100 | #ifdef CONFIG_BLOCK |
| 101 | dev_t dev; |
| 102 | int ret; |
| 103 | #endif |
| 104 | int mtdnr; |
| 105 | |
| 106 | if (!fc->source) |
| 107 | return invalf(fc, "No source specified"); |
| 108 | |
| 109 | pr_debug("MTDSB: dev_name \"%s\"\n", fc->source); |
| 110 | |
| 111 | /* the preferred way of mounting in future; especially when |
| 112 | * CONFIG_BLOCK=n - we specify the underlying MTD device by number or |
| 113 | * by name, so that we don't require block device support to be present |
| 114 | * in the kernel. |
| 115 | */ |
| 116 | if (fc->source[0] == 'm' && |
| 117 | fc->source[1] == 't' && |
| 118 | fc->source[2] == 'd') { |
| 119 | if (fc->source[3] == ':') { |
| 120 | struct mtd_info *mtd; |
| 121 | |
| 122 | /* mount by MTD device name */ |
| 123 | pr_debug("MTDSB: mtd:%%s, name \"%s\"\n", |
| 124 | fc->source + 4); |
| 125 | |
| 126 | mtd = get_mtd_device_nm(fc->source + 4); |
| 127 | if (!IS_ERR(mtd)) |
| 128 | return mtd_get_sb(fc, mtd, fill_super); |
| 129 | |
| 130 | errorf(fc, "MTD: MTD device with name \"%s\" not found", |
| 131 | fc->source + 4); |
| 132 | |
| 133 | } else if (isdigit(fc->source[3])) { |
| 134 | /* mount by MTD device number name */ |
| 135 | char *endptr; |
| 136 | |
| 137 | mtdnr = simple_strtoul(fc->source + 3, &endptr, 0); |
| 138 | if (!*endptr) { |
| 139 | /* It was a valid number */ |
| 140 | pr_debug("MTDSB: mtd%%d, mtdnr %d\n", mtdnr); |
| 141 | return mtd_get_sb_by_nr(fc, mtdnr, fill_super); |
| 142 | } |
| 143 | } |
| 144 | } |
| 145 | |
| 146 | #ifdef CONFIG_BLOCK |
| 147 | /* try the old way - the hack where we allowed users to mount |
| 148 | * /dev/mtdblock$(n) but didn't actually _use_ the blockdev |
| 149 | */ |
| 150 | ret = lookup_bdev(fc->source, &dev); |
| 151 | if (ret) { |
| 152 | errorf(fc, "MTD: Couldn't look up '%s': %d", fc->source, ret); |
| 153 | return ret; |
| 154 | } |
| 155 | pr_debug("MTDSB: lookup_bdev() returned 0\n"); |
| 156 | |
| 157 | if (MAJOR(dev) == MTD_BLOCK_MAJOR) |
| 158 | return mtd_get_sb_by_nr(fc, MINOR(dev), fill_super); |
| 159 | |
| 160 | #endif /* CONFIG_BLOCK */ |
| 161 | |
| 162 | if (!(fc->sb_flags & SB_SILENT)) |
| 163 | errorf(fc, "MTD: Attempt to mount non-MTD device \"%s\"", |
| 164 | fc->source); |
| 165 | return -EINVAL; |
| 166 | } |
| 167 | EXPORT_SYMBOL_GPL(get_tree_mtd); |
| 168 | |
| 169 | /* |
| 170 | * destroy an MTD-based superblock |
| 171 | */ |
| 172 | void kill_mtd_super(struct super_block *sb) |
| 173 | { |
| 174 | generic_shutdown_super(sb); |
| 175 | put_mtd_device(sb->s_mtd); |
| 176 | sb->s_mtd = NULL; |
| 177 | } |
| 178 | |
| 179 | EXPORT_SYMBOL_GPL(kill_mtd_super); |