drivers/mtd/mtdsuper.c

   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);