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/fs_context.h> 19 #include "mtdcore.h" 20 21 /* 22 * compare superblocks to see if they're equivalent 23 * - they are if the underlying MTD device is the same 24 */ 25 static int mtd_test_super(struct super_block *sb, struct fs_context *fc) 26 { 27 struct mtd_info *mtd = fc->sget_key; 28 29 if (sb->s_mtd == fc->sget_key) { 30 pr_debug("MTDSB: Match on device %d (\"%s\")\n", 31 mtd->index, mtd->name); 32 return 1; 33 } 34 35 pr_debug("MTDSB: No match, device %d (\"%s\"), device %d (\"%s\")\n", 36 sb->s_mtd->index, sb->s_mtd->name, mtd->index, mtd->name); 37 return 0; 38 } 39 40 /* 41 * mark the superblock by the MTD device it is using 42 * - set the device number to be the correct MTD block device for pesuperstence 43 * of NFS exports 44 */ 45 static int mtd_set_super(struct super_block *sb, struct fs_context *fc) 46 { 47 sb->s_mtd = fc->sget_key; 48 sb->s_dev = MKDEV(MTD_BLOCK_MAJOR, sb->s_mtd->index); 49 sb->s_bdi = bdi_get(mtd_bdi); 50 return 0; 51 } 52 53 /* 54 * get a superblock on an MTD-backed filesystem 55 */ 56 static int mtd_get_sb(struct fs_context *fc, 57 struct mtd_info *mtd, 58 int (*fill_super)(struct super_block *, 59 struct fs_context *)) 60 { 61 struct super_block *sb; 62 int ret; 63 64 fc->sget_key = mtd; 65 sb = sget_fc(fc, mtd_test_super, mtd_set_super); 66 if (IS_ERR(sb)) 67 return PTR_ERR(sb); 68 69 if (sb->s_root) { 70 /* new mountpoint for an already mounted superblock */ 71 pr_debug("MTDSB: Device %d (\"%s\") is already mounted\n", 72 mtd->index, mtd->name); 73 put_mtd_device(mtd); 74 } else { 75 /* fresh new superblock */ 76 pr_debug("MTDSB: New superblock for device %d (\"%s\")\n", 77 mtd->index, mtd->name); 78 79 ret = fill_super(sb, fc); 80 if (ret < 0) 81 goto error_sb; 82 83 sb->s_flags |= SB_ACTIVE; 84 } 85 86 BUG_ON(fc->root); 87 fc->root = dget(sb->s_root); 88 return 0; 89 90 error_sb: 91 deactivate_locked_super(sb); 92 return ret; 93 } 94 95 /* 96 * get a superblock on an MTD-backed filesystem by MTD device number 97 */ 98 static int mtd_get_sb_by_nr(struct fs_context *fc, int mtdnr, 99 int (*fill_super)(struct super_block *, 100 struct fs_context *)) 101 { 102 struct mtd_info *mtd; 103 104 mtd = get_mtd_device(NULL, mtdnr); 105 if (IS_ERR(mtd)) { 106 errorf(fc, "MTDSB: Device #%u doesn't appear to exist\n", mtdnr); 107 return PTR_ERR(mtd); 108 } 109 110 return mtd_get_sb(fc, mtd, fill_super); 111 } 112 113 /** 114 * get_tree_mtd - Get a superblock based on a single MTD device 115 * @fc: The filesystem context holding the parameters 116 * @fill_super: Helper to initialise a new superblock 117 */ 118 int get_tree_mtd(struct fs_context *fc, 119 int (*fill_super)(struct super_block *sb, 120 struct fs_context *fc)) 121 { 122 #ifdef CONFIG_BLOCK 123 struct block_device *bdev; 124 int ret, major; 125 #endif 126 int mtdnr; 127 128 if (!fc->source) 129 return invalf(fc, "No source specified"); 130 131 pr_debug("MTDSB: dev_name \"%s\"\n", fc->source); 132 133 /* the preferred way of mounting in future; especially when 134 * CONFIG_BLOCK=n - we specify the underlying MTD device by number or 135 * by name, so that we don't require block device support to be present 136 * in the kernel. 137 */ 138 if (fc->source[0] == 'm' && 139 fc->source[1] == 't' && 140 fc->source[2] == 'd') { 141 if (fc->source[3] == ':') { 142 struct mtd_info *mtd; 143 144 /* mount by MTD device name */ 145 pr_debug("MTDSB: mtd:%%s, name \"%s\"\n", 146 fc->source + 4); 147 148 mtd = get_mtd_device_nm(fc->source + 4); 149 if (!IS_ERR(mtd)) 150 return mtd_get_sb(fc, mtd, fill_super); 151 152 errorf(fc, "MTD: MTD device with name \"%s\" not found", 153 fc->source + 4); 154 155 } else if (isdigit(fc->source[3])) { 156 /* mount by MTD device number name */ 157 char *endptr; 158 159 mtdnr = simple_strtoul(fc->source + 3, &endptr, 0); 160 if (!*endptr) { 161 /* It was a valid number */ 162 pr_debug("MTDSB: mtd%%d, mtdnr %d\n", mtdnr); 163 return mtd_get_sb_by_nr(fc, mtdnr, fill_super); 164 } 165 } 166 } 167 168 #ifdef CONFIG_BLOCK 169 /* try the old way - the hack where we allowed users to mount 170 * /dev/mtdblock$(n) but didn't actually _use_ the blockdev 171 */ 172 bdev = lookup_bdev(fc->source); 173 if (IS_ERR(bdev)) { 174 ret = PTR_ERR(bdev); 175 errorf(fc, "MTD: Couldn't look up '%s': %d", fc->source, ret); 176 return ret; 177 } 178 pr_debug("MTDSB: lookup_bdev() returned 0\n"); 179 180 major = MAJOR(bdev->bd_dev); 181 mtdnr = MINOR(bdev->bd_dev); 182 bdput(bdev); 183 184 if (major == MTD_BLOCK_MAJOR) 185 return mtd_get_sb_by_nr(fc, mtdnr, fill_super); 186 187 #endif /* CONFIG_BLOCK */ 188 189 if (!(fc->sb_flags & SB_SILENT)) 190 errorf(fc, "MTD: Attempt to mount non-MTD device \"%s\"", 191 fc->source); 192 return -EINVAL; 193 } 194 EXPORT_SYMBOL_GPL(get_tree_mtd); 195 196 /* 197 * compare superblocks to see if they're equivalent 198 * - they are if the underlying MTD device is the same 199 */ 200 static int get_sb_mtd_compare(struct super_block *sb, void *_mtd) 201 { 202 struct mtd_info *mtd = _mtd; 203 204 if (sb->s_mtd == mtd) { 205 pr_debug("MTDSB: Match on device %d (\"%s\")\n", 206 mtd->index, mtd->name); 207 return 1; 208 } 209 210 pr_debug("MTDSB: No match, device %d (\"%s\"), device %d (\"%s\")\n", 211 sb->s_mtd->index, sb->s_mtd->name, mtd->index, mtd->name); 212 return 0; 213 } 214 215 /* 216 * mark the superblock by the MTD device it is using 217 * - set the device number to be the correct MTD block device for pesuperstence 218 * of NFS exports 219 */ 220 static int get_sb_mtd_set(struct super_block *sb, void *_mtd) 221 { 222 struct mtd_info *mtd = _mtd; 223 224 sb->s_mtd = mtd; 225 sb->s_dev = MKDEV(MTD_BLOCK_MAJOR, mtd->index); 226 sb->s_bdi = bdi_get(mtd_bdi); 227 228 return 0; 229 } 230 231 /* 232 * get a superblock on an MTD-backed filesystem 233 */ 234 static struct dentry *mount_mtd_aux(struct file_system_type *fs_type, int flags, 235 const char *dev_name, void *data, 236 struct mtd_info *mtd, 237 int (*fill_super)(struct super_block *, void *, int)) 238 { 239 struct super_block *sb; 240 int ret; 241 242 sb = sget(fs_type, get_sb_mtd_compare, get_sb_mtd_set, flags, mtd); 243 if (IS_ERR(sb)) 244 goto out_error; 245 246 if (sb->s_root) 247 goto already_mounted; 248 249 /* fresh new superblock */ 250 pr_debug("MTDSB: New superblock for device %d (\"%s\")\n", 251 mtd->index, mtd->name); 252 253 ret = fill_super(sb, data, flags & SB_SILENT ? 1 : 0); 254 if (ret < 0) { 255 deactivate_locked_super(sb); 256 return ERR_PTR(ret); 257 } 258 259 /* go */ 260 sb->s_flags |= SB_ACTIVE; 261 return dget(sb->s_root); 262 263 /* new mountpoint for an already mounted superblock */ 264 already_mounted: 265 pr_debug("MTDSB: Device %d (\"%s\") is already mounted\n", 266 mtd->index, mtd->name); 267 put_mtd_device(mtd); 268 return dget(sb->s_root); 269 270 out_error: 271 put_mtd_device(mtd); 272 return ERR_CAST(sb); 273 } 274 275 /* 276 * get a superblock on an MTD-backed filesystem by MTD device number 277 */ 278 static struct dentry *mount_mtd_nr(struct file_system_type *fs_type, int flags, 279 const char *dev_name, void *data, int mtdnr, 280 int (*fill_super)(struct super_block *, void *, int)) 281 { 282 struct mtd_info *mtd; 283 284 mtd = get_mtd_device(NULL, mtdnr); 285 if (IS_ERR(mtd)) { 286 pr_debug("MTDSB: Device #%u doesn't appear to exist\n", mtdnr); 287 return ERR_CAST(mtd); 288 } 289 290 return mount_mtd_aux(fs_type, flags, dev_name, data, mtd, fill_super); 291 } 292 293 /* 294 * set up an MTD-based superblock 295 */ 296 struct dentry *mount_mtd(struct file_system_type *fs_type, int flags, 297 const char *dev_name, void *data, 298 int (*fill_super)(struct super_block *, void *, int)) 299 { 300 #ifdef CONFIG_BLOCK 301 struct block_device *bdev; 302 int ret, major; 303 #endif 304 int mtdnr; 305 306 if (!dev_name) 307 return ERR_PTR(-EINVAL); 308 309 pr_debug("MTDSB: dev_name \"%s\"\n", dev_name); 310 311 /* the preferred way of mounting in future; especially when 312 * CONFIG_BLOCK=n - we specify the underlying MTD device by number or 313 * by name, so that we don't require block device support to be present 314 * in the kernel. */ 315 if (dev_name[0] == 'm' && dev_name[1] == 't' && dev_name[2] == 'd') { 316 if (dev_name[3] == ':') { 317 struct mtd_info *mtd; 318 319 /* mount by MTD device name */ 320 pr_debug("MTDSB: mtd:%%s, name \"%s\"\n", 321 dev_name + 4); 322 323 mtd = get_mtd_device_nm(dev_name + 4); 324 if (!IS_ERR(mtd)) 325 return mount_mtd_aux( 326 fs_type, flags, 327 dev_name, data, mtd, 328 fill_super); 329 330 printk(KERN_NOTICE "MTD:" 331 " MTD device with name \"%s\" not found.\n", 332 dev_name + 4); 333 334 } else if (isdigit(dev_name[3])) { 335 /* mount by MTD device number name */ 336 char *endptr; 337 338 mtdnr = simple_strtoul(dev_name + 3, &endptr, 0); 339 if (!*endptr) { 340 /* It was a valid number */ 341 pr_debug("MTDSB: mtd%%d, mtdnr %d\n", 342 mtdnr); 343 return mount_mtd_nr(fs_type, flags, 344 dev_name, data, 345 mtdnr, fill_super); 346 } 347 } 348 } 349 350 #ifdef CONFIG_BLOCK 351 /* try the old way - the hack where we allowed users to mount 352 * /dev/mtdblock$(n) but didn't actually _use_ the blockdev 353 */ 354 bdev = lookup_bdev(dev_name); 355 if (IS_ERR(bdev)) { 356 ret = PTR_ERR(bdev); 357 pr_debug("MTDSB: lookup_bdev() returned %d\n", ret); 358 return ERR_PTR(ret); 359 } 360 pr_debug("MTDSB: lookup_bdev() returned 0\n"); 361 362 ret = -EINVAL; 363 364 major = MAJOR(bdev->bd_dev); 365 mtdnr = MINOR(bdev->bd_dev); 366 bdput(bdev); 367 368 if (major != MTD_BLOCK_MAJOR) 369 goto not_an_MTD_device; 370 371 return mount_mtd_nr(fs_type, flags, dev_name, data, mtdnr, fill_super); 372 373 not_an_MTD_device: 374 #endif /* CONFIG_BLOCK */ 375 376 if (!(flags & SB_SILENT)) 377 printk(KERN_NOTICE 378 "MTD: Attempt to mount non-MTD device \"%s\"\n", 379 dev_name); 380 return ERR_PTR(-EINVAL); 381 } 382 383 EXPORT_SYMBOL_GPL(mount_mtd); 384 385 /* 386 * destroy an MTD-based superblock 387 */ 388 void kill_mtd_super(struct super_block *sb) 389 { 390 generic_shutdown_super(sb); 391 put_mtd_device(sb->s_mtd); 392 sb->s_mtd = NULL; 393 } 394 395 EXPORT_SYMBOL_GPL(kill_mtd_super); 396