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 19 /* 20 * compare superblocks to see if they're equivalent 21 * - they are if the underlying MTD device is the same 22 */ 23 static int get_sb_mtd_compare(struct super_block *sb, void *_mtd) 24 { 25 struct mtd_info *mtd = _mtd; 26 27 if (sb->s_mtd == mtd) { 28 pr_debug("MTDSB: Match on device %d (\"%s\")\n", 29 mtd->index, mtd->name); 30 return 1; 31 } 32 33 pr_debug("MTDSB: No match, device %d (\"%s\"), device %d (\"%s\")\n", 34 sb->s_mtd->index, sb->s_mtd->name, mtd->index, mtd->name); 35 return 0; 36 } 37 38 extern struct backing_dev_info *mtd_bdi; 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 get_sb_mtd_set(struct super_block *sb, void *_mtd) 46 { 47 struct mtd_info *mtd = _mtd; 48 49 sb->s_mtd = mtd; 50 sb->s_dev = MKDEV(MTD_BLOCK_MAJOR, mtd->index); 51 sb->s_bdi = bdi_get(mtd_bdi); 52 53 return 0; 54 } 55 56 /* 57 * get a superblock on an MTD-backed filesystem 58 */ 59 static struct dentry *mount_mtd_aux(struct file_system_type *fs_type, int flags, 60 const char *dev_name, void *data, 61 struct mtd_info *mtd, 62 int (*fill_super)(struct super_block *, void *, int)) 63 { 64 struct super_block *sb; 65 int ret; 66 67 sb = sget(fs_type, get_sb_mtd_compare, get_sb_mtd_set, flags, mtd); 68 if (IS_ERR(sb)) 69 goto out_error; 70 71 if (sb->s_root) 72 goto already_mounted; 73 74 /* fresh new superblock */ 75 pr_debug("MTDSB: New superblock for device %d (\"%s\")\n", 76 mtd->index, mtd->name); 77 78 ret = fill_super(sb, data, flags & SB_SILENT ? 1 : 0); 79 if (ret < 0) { 80 deactivate_locked_super(sb); 81 return ERR_PTR(ret); 82 } 83 84 /* go */ 85 sb->s_flags |= SB_ACTIVE; 86 return dget(sb->s_root); 87 88 /* new mountpoint for an already mounted superblock */ 89 already_mounted: 90 pr_debug("MTDSB: Device %d (\"%s\") is already mounted\n", 91 mtd->index, mtd->name); 92 put_mtd_device(mtd); 93 return dget(sb->s_root); 94 95 out_error: 96 put_mtd_device(mtd); 97 return ERR_CAST(sb); 98 } 99 100 /* 101 * get a superblock on an MTD-backed filesystem by MTD device number 102 */ 103 static struct dentry *mount_mtd_nr(struct file_system_type *fs_type, int flags, 104 const char *dev_name, void *data, int mtdnr, 105 int (*fill_super)(struct super_block *, void *, int)) 106 { 107 struct mtd_info *mtd; 108 109 mtd = get_mtd_device(NULL, mtdnr); 110 if (IS_ERR(mtd)) { 111 pr_debug("MTDSB: Device #%u doesn't appear to exist\n", mtdnr); 112 return ERR_CAST(mtd); 113 } 114 115 return mount_mtd_aux(fs_type, flags, dev_name, data, mtd, fill_super); 116 } 117 118 /* 119 * set up an MTD-based superblock 120 */ 121 struct dentry *mount_mtd(struct file_system_type *fs_type, int flags, 122 const char *dev_name, void *data, 123 int (*fill_super)(struct super_block *, void *, int)) 124 { 125 #ifdef CONFIG_BLOCK 126 struct block_device *bdev; 127 int ret, major; 128 #endif 129 int mtdnr; 130 131 if (!dev_name) 132 return ERR_PTR(-EINVAL); 133 134 pr_debug("MTDSB: dev_name \"%s\"\n", dev_name); 135 136 /* the preferred way of mounting in future; especially when 137 * CONFIG_BLOCK=n - we specify the underlying MTD device by number or 138 * by name, so that we don't require block device support to be present 139 * in the kernel. */ 140 if (dev_name[0] == 'm' && dev_name[1] == 't' && dev_name[2] == 'd') { 141 if (dev_name[3] == ':') { 142 struct mtd_info *mtd; 143 144 /* mount by MTD device name */ 145 pr_debug("MTDSB: mtd:%%s, name \"%s\"\n", 146 dev_name + 4); 147 148 mtd = get_mtd_device_nm(dev_name + 4); 149 if (!IS_ERR(mtd)) 150 return mount_mtd_aux( 151 fs_type, flags, 152 dev_name, data, mtd, 153 fill_super); 154 155 printk(KERN_NOTICE "MTD:" 156 " MTD device with name \"%s\" not found.\n", 157 dev_name + 4); 158 159 } else if (isdigit(dev_name[3])) { 160 /* mount by MTD device number name */ 161 char *endptr; 162 163 mtdnr = simple_strtoul(dev_name + 3, &endptr, 0); 164 if (!*endptr) { 165 /* It was a valid number */ 166 pr_debug("MTDSB: mtd%%d, mtdnr %d\n", 167 mtdnr); 168 return mount_mtd_nr(fs_type, flags, 169 dev_name, data, 170 mtdnr, fill_super); 171 } 172 } 173 } 174 175 #ifdef CONFIG_BLOCK 176 /* try the old way - the hack where we allowed users to mount 177 * /dev/mtdblock$(n) but didn't actually _use_ the blockdev 178 */ 179 bdev = lookup_bdev(dev_name); 180 if (IS_ERR(bdev)) { 181 ret = PTR_ERR(bdev); 182 pr_debug("MTDSB: lookup_bdev() returned %d\n", ret); 183 return ERR_PTR(ret); 184 } 185 pr_debug("MTDSB: lookup_bdev() returned 0\n"); 186 187 ret = -EINVAL; 188 189 major = MAJOR(bdev->bd_dev); 190 mtdnr = MINOR(bdev->bd_dev); 191 bdput(bdev); 192 193 if (major != MTD_BLOCK_MAJOR) 194 goto not_an_MTD_device; 195 196 return mount_mtd_nr(fs_type, flags, dev_name, data, mtdnr, fill_super); 197 198 not_an_MTD_device: 199 #endif /* CONFIG_BLOCK */ 200 201 if (!(flags & SB_SILENT)) 202 printk(KERN_NOTICE 203 "MTD: Attempt to mount non-MTD device \"%s\"\n", 204 dev_name); 205 return ERR_PTR(-EINVAL); 206 } 207 208 EXPORT_SYMBOL_GPL(mount_mtd); 209 210 /* 211 * destroy an MTD-based superblock 212 */ 213 void kill_mtd_super(struct super_block *sb) 214 { 215 generic_shutdown_super(sb); 216 put_mtd_device(sb->s_mtd); 217 sb->s_mtd = NULL; 218 } 219 220 EXPORT_SYMBOL_GPL(kill_mtd_super); 221