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, 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         sb->s_flags = flags;
  78
  79         ret = fill_super(sb, data, flags & MS_SILENT ? 1 : 0);
  80         if (ret < 0) {
  81                 deactivate_locked_super(sb);
  82                 return ERR_PTR(ret);
  83         }
  84
  85         /* go */
  86         sb->s_flags |= MS_ACTIVE;
  87         return dget(sb->s_root);
  88
  89         /* new mountpoint for an already mounted superblock */
  90 already_mounted:
  91         pr_debug("MTDSB: Device %d (\"%s\") is already mounted\n",
  92               mtd->index, mtd->name);
  93         put_mtd_device(mtd);
  94         return dget(sb->s_root);
  95
  96 out_error:
  97         put_mtd_device(mtd);
  98         return ERR_CAST(sb);
  99 }
 100
 101 /*
 102  * get a superblock on an MTD-backed filesystem by MTD device number
 103  */
 104 static struct dentry *mount_mtd_nr(struct file_system_type *fs_type, int flags,
 105                          const char *dev_name, void *data, int mtdnr,
 106                          int (*fill_super)(struct super_block *, void *, int))
 107 {
 108         struct mtd_info *mtd;
 109
 110         mtd = get_mtd_device(NULL, mtdnr);
 111         if (IS_ERR(mtd)) {
 112                 pr_debug("MTDSB: Device #%u doesn't appear to exist\n", mtdnr);
 113                 return ERR_CAST(mtd);
 114         }
 115
 116         return mount_mtd_aux(fs_type, flags, dev_name, data, mtd, fill_super);
 117 }
 118
 119 /*
 120  * set up an MTD-based superblock
 121  */
 122 struct dentry *mount_mtd(struct file_system_type *fs_type, int flags,
 123                const char *dev_name, void *data,
 124                int (*fill_super)(struct super_block *, void *, int))
 125 {
 126 #ifdef CONFIG_BLOCK
 127         struct block_device *bdev;
 128         int ret, major;
 129 #endif
 130         int mtdnr;
 131
 132         if (!dev_name)
 133                 return ERR_PTR(-EINVAL);
 134
 135         pr_debug("MTDSB: dev_name \"%s\"\n", dev_name);
 136
 137         /* the preferred way of mounting in future; especially when
 138          * CONFIG_BLOCK=n - we specify the underlying MTD device by number or
 139          * by name, so that we don't require block device support to be present
 140          * in the kernel. */
 141         if (dev_name[0] == 'm' && dev_name[1] == 't' && dev_name[2] == 'd') {
 142                 if (dev_name[3] == ':') {
 143                         struct mtd_info *mtd;
 144
 145                         /* mount by MTD device name */
 146                         pr_debug("MTDSB: mtd:%%s, name \"%s\"\n",
 147                               dev_name + 4);
 148
 149                         mtd = get_mtd_device_nm(dev_name + 4);
 150                         if (!IS_ERR(mtd))
 151                                 return mount_mtd_aux(
 152                                         fs_type, flags,
 153                                         dev_name, data, mtd,
 154                                         fill_super);
 155
 156                         printk(KERN_NOTICE "MTD:"
 157                                " MTD device with name \"%s\" not found.\n",
 158                                dev_name + 4);
 159
 160                 } else if (isdigit(dev_name[3])) {
 161                         /* mount by MTD device number name */
 162                         char *endptr;
 163
 164                         mtdnr = simple_strtoul(dev_name + 3, &endptr, 0);
 165                         if (!*endptr) {
 166                                 /* It was a valid number */
 167                                 pr_debug("MTDSB: mtd%%d, mtdnr %d\n",
 168                                       mtdnr);
 169                                 return mount_mtd_nr(fs_type, flags,
 170                                                      dev_name, data,
 171                                                      mtdnr, fill_super);
 172                         }
 173                 }
 174         }
 175
 176 #ifdef CONFIG_BLOCK
 177         /* try the old way - the hack where we allowed users to mount
 178          * /dev/mtdblock$(n) but didn't actually _use_ the blockdev
 179          */
 180         bdev = lookup_bdev(dev_name);
 181         if (IS_ERR(bdev)) {
 182                 ret = PTR_ERR(bdev);
 183                 pr_debug("MTDSB: lookup_bdev() returned %d\n", ret);
 184                 return ERR_PTR(ret);
 185         }
 186         pr_debug("MTDSB: lookup_bdev() returned 0\n");
 187
 188         ret = -EINVAL;
 189
 190         major = MAJOR(bdev->bd_dev);
 191         mtdnr = MINOR(bdev->bd_dev);
 192         bdput(bdev);
 193
 194         if (major != MTD_BLOCK_MAJOR)
 195                 goto not_an_MTD_device;
 196
 197         return mount_mtd_nr(fs_type, flags, dev_name, data, mtdnr, fill_super);
 198
 199 not_an_MTD_device:
 200 #endif /* CONFIG_BLOCK */
 201
 202         if (!(flags & MS_SILENT))
 203                 printk(KERN_NOTICE
 204                        "MTD: Attempt to mount non-MTD device \"%s\"\n",
 205                        dev_name);
 206         return ERR_PTR(-EINVAL);
 207 }
 208
 209 EXPORT_SYMBOL_GPL(mount_mtd);
 210
 211 /*
 212  * destroy an MTD-based superblock
 213  */
 214 void kill_mtd_super(struct super_block *sb)
 215 {
 216         generic_shutdown_super(sb);
 217         put_mtd_device(sb->s_mtd);
 218         sb->s_mtd = NULL;
 219 }
 220
 221 EXPORT_SYMBOL_GPL(kill_mtd_super);