drivers/mtd/mtdsuper.c

   1 /* MTD-based superblock management
   2  *
   3  * Copyright © 2001-2007 Red Hat, Inc. All Rights Reserved.
   4  * Copyright © 2001-2010 David Woodhouse <dwmw2@infradead.org>
   5  *
   6  * Written by:  David Howells <dhowells@redhat.com>
   7  *              David Woodhouse <dwmw2@infradead.org>
   8  *
   9  * This program is free software; you can redistribute it and/or
  10  * modify it under the terms of the GNU General Public License
  11  * as published by the Free Software Foundation; either version
  12  * 2 of the License, or (at your option) any later version.
  13  */
  14
  15 #include <linux/mtd/super.h>
  16 #include <linux/namei.h>
  17 #include <linux/export.h>
  18 #include <linux/ctype.h>
  19 #include <linux/slab.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 get_sb_mtd_compare(struct super_block *sb, void *_mtd)
  26 {
  27         struct mtd_info *mtd = _mtd;
  28
  29         if (sb->s_mtd == mtd) {
  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 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 = mtd->backing_dev_info;
  52         return 0;
  53 }
  54
  55 /*
  56  * get a superblock on an MTD-backed filesystem
  57  */
  58 static struct dentry *mount_mtd_aux(struct file_system_type *fs_type, int flags,
  59                           const char *dev_name, void *data,
  60                           struct mtd_info *mtd,
  61                           int (*fill_super)(struct super_block *, void *, int))
  62 {
  63         struct super_block *sb;
  64         int ret;
  65
  66         sb = sget(fs_type, get_sb_mtd_compare, get_sb_mtd_set, flags, mtd);
  67         if (IS_ERR(sb))
  68                 goto out_error;
  69
  70         if (sb->s_root)
  71                 goto already_mounted;
  72
  73         /* fresh new superblock */
  74         pr_debug("MTDSB: New superblock for device %d (\"%s\")\n",
  75               mtd->index, mtd->name);
  76
  77         ret = fill_super(sb, data, flags & MS_SILENT ? 1 : 0);
  78         if (ret < 0) {
  79                 deactivate_locked_super(sb);
  80                 return ERR_PTR(ret);
  81         }
  82
  83         /* go */
  84         sb->s_flags |= MS_ACTIVE;
  85         return dget(sb->s_root);
  86
  87         /* new mountpoint for an already mounted superblock */
  88 already_mounted:
  89         pr_debug("MTDSB: Device %d (\"%s\") is already mounted\n",
  90               mtd->index, mtd->name);
  91         put_mtd_device(mtd);
  92         return dget(sb->s_root);
  93
  94 out_error:
  95         put_mtd_device(mtd);
  96         return ERR_CAST(sb);
  97 }
  98
  99 /*
 100  * get a superblock on an MTD-backed filesystem by MTD device number
 101  */
 102 static struct dentry *mount_mtd_nr(struct file_system_type *fs_type, int flags,
 103                          const char *dev_name, void *data, int mtdnr,
 104                          int (*fill_super)(struct super_block *, void *, int))
 105 {
 106         struct mtd_info *mtd;
 107
 108         mtd = get_mtd_device(NULL, mtdnr);
 109         if (IS_ERR(mtd)) {
 110                 pr_debug("MTDSB: Device #%u doesn't appear to exist\n", mtdnr);
 111                 return ERR_CAST(mtd);
 112         }
 113
 114         return mount_mtd_aux(fs_type, flags, dev_name, data, mtd, fill_super);
 115 }
 116
 117 /*
 118  * set up an MTD-based superblock
 119  */
 120 struct dentry *mount_mtd(struct file_system_type *fs_type, int flags,
 121                const char *dev_name, void *data,
 122                int (*fill_super)(struct super_block *, void *, int))
 123 {
 124 #ifdef CONFIG_BLOCK
 125         struct block_device *bdev;
 126         int ret, major;
 127 #endif
 128         int mtdnr;
 129
 130         if (!dev_name)
 131                 return ERR_PTR(-EINVAL);
 132
 133         pr_debug("MTDSB: dev_name \"%s\"\n", dev_name);
 134
 135         /* the preferred way of mounting in future; especially when
 136          * CONFIG_BLOCK=n - we specify the underlying MTD device by number or
 137          * by name, so that we don't require block device support to be present
 138          * in the kernel. */
 139         if (dev_name[0] == 'm' && dev_name[1] == 't' && dev_name[2] == 'd') {
 140                 if (dev_name[3] == ':') {
 141                         struct mtd_info *mtd;
 142
 143                         /* mount by MTD device name */
 144                         pr_debug("MTDSB: mtd:%%s, name \"%s\"\n",
 145                               dev_name + 4);
 146
 147                         mtd = get_mtd_device_nm(dev_name + 4);
 148                         if (!IS_ERR(mtd))
 149                                 return mount_mtd_aux(
 150                                         fs_type, flags,
 151                                         dev_name, data, mtd,
 152                                         fill_super);
 153
 154                         printk(KERN_NOTICE "MTD:"
 155                                " MTD device with name \"%s\" not found.\n",
 156                                dev_name + 4);
 157
 158                 } else if (isdigit(dev_name[3])) {
 159                         /* mount by MTD device number name */
 160                         char *endptr;
 161
 162                         mtdnr = simple_strtoul(dev_name + 3, &endptr, 0);
 163                         if (!*endptr) {
 164                                 /* It was a valid number */
 165                                 pr_debug("MTDSB: mtd%%d, mtdnr %d\n",
 166                                       mtdnr);
 167                                 return mount_mtd_nr(fs_type, flags,
 168                                                      dev_name, data,
 169                                                      mtdnr, fill_super);
 170                         }
 171                 }
 172         }
 173
 174 #ifdef CONFIG_BLOCK
 175         /* try the old way - the hack where we allowed users to mount
 176          * /dev/mtdblock$(n) but didn't actually _use_ the blockdev
 177          */
 178         bdev = lookup_bdev(dev_name);
 179         if (IS_ERR(bdev)) {
 180                 ret = PTR_ERR(bdev);
 181                 pr_debug("MTDSB: lookup_bdev() returned %d\n", ret);
 182                 return ERR_PTR(ret);
 183         }
 184         pr_debug("MTDSB: lookup_bdev() returned 0\n");
 185
 186         ret = -EINVAL;
 187
 188         major = MAJOR(bdev->bd_dev);
 189         mtdnr = MINOR(bdev->bd_dev);
 190         bdput(bdev);
 191
 192         if (major != MTD_BLOCK_MAJOR)
 193                 goto not_an_MTD_device;
 194
 195         return mount_mtd_nr(fs_type, flags, dev_name, data, mtdnr, fill_super);
 196
 197 not_an_MTD_device:
 198 #endif /* CONFIG_BLOCK */
 199
 200         if (!(flags & MS_SILENT))
 201                 printk(KERN_NOTICE
 202                        "MTD: Attempt to mount non-MTD device \"%s\"\n",
 203                        dev_name);
 204         return ERR_PTR(-EINVAL);
 205 }
 206
 207 EXPORT_SYMBOL_GPL(mount_mtd);
 208
 209 /*
 210  * destroy an MTD-based superblock
 211  */
 212 void kill_mtd_super(struct super_block *sb)
 213 {
 214         generic_shutdown_super(sb);
 215         put_mtd_device(sb->s_mtd);
 216         sb->s_mtd = NULL;
 217 }
 218
 219 EXPORT_SYMBOL_GPL(kill_mtd_super);