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 #include <linux/major.h>
  21 #include <linux/backing-dev.h>
  22
  23 /*
  24  * compare superblocks to see if they're equivalent
  25  * - they are if the underlying MTD device is the same
  26  */
  27 static int get_sb_mtd_compare(struct super_block *sb, void *_mtd)
  28 {
  29         struct mtd_info *mtd = _mtd;
  30
  31         if (sb->s_mtd == mtd) {
  32                 pr_debug("MTDSB: Match on device %d (\"%s\")\n",
  33                       mtd->index, mtd->name);
  34                 return 1;
  35         }
  36
  37         pr_debug("MTDSB: No match, device %d (\"%s\"), device %d (\"%s\")\n",
  38               sb->s_mtd->index, sb->s_mtd->name, mtd->index, mtd->name);
  39         return 0;
  40 }
  41
  42 extern struct backing_dev_info *mtd_bdi;
  43
  44 /*
  45  * mark the superblock by the MTD device it is using
  46  * - set the device number to be the correct MTD block device for pesuperstence
  47  *   of NFS exports
  48  */
  49 static int get_sb_mtd_set(struct super_block *sb, void *_mtd)
  50 {
  51         struct mtd_info *mtd = _mtd;
  52
  53         sb->s_mtd = mtd;
  54         sb->s_dev = MKDEV(MTD_BLOCK_MAJOR, mtd->index);
  55         sb->s_bdi = bdi_get(mtd_bdi);
  56
  57         return 0;
  58 }
  59
  60 /*
  61  * get a superblock on an MTD-backed filesystem
  62  */
  63 static struct dentry *mount_mtd_aux(struct file_system_type *fs_type, int flags,
  64                           const char *dev_name, void *data,
  65                           struct mtd_info *mtd,
  66                           int (*fill_super)(struct super_block *, void *, int))
  67 {
  68         struct super_block *sb;
  69         int ret;
  70
  71         sb = sget(fs_type, get_sb_mtd_compare, get_sb_mtd_set, flags, mtd);
  72         if (IS_ERR(sb))
  73                 goto out_error;
  74
  75         if (sb->s_root)
  76                 goto already_mounted;
  77
  78         /* fresh new superblock */
  79         pr_debug("MTDSB: New superblock for device %d (\"%s\")\n",
  80               mtd->index, mtd->name);
  81
  82         ret = fill_super(sb, data, flags & MS_SILENT ? 1 : 0);
  83         if (ret < 0) {
  84                 deactivate_locked_super(sb);
  85                 return ERR_PTR(ret);
  86         }
  87
  88         /* go */
  89         sb->s_flags |= MS_ACTIVE;
  90         return dget(sb->s_root);
  91
  92         /* new mountpoint for an already mounted superblock */
  93 already_mounted:
  94         pr_debug("MTDSB: Device %d (\"%s\") is already mounted\n",
  95               mtd->index, mtd->name);
  96         put_mtd_device(mtd);
  97         return dget(sb->s_root);
  98
  99 out_error:
 100         put_mtd_device(mtd);
 101         return ERR_CAST(sb);
 102 }
 103
 104 /*
 105  * get a superblock on an MTD-backed filesystem by MTD device number
 106  */
 107 static struct dentry *mount_mtd_nr(struct file_system_type *fs_type, int flags,
 108                          const char *dev_name, void *data, int mtdnr,
 109                          int (*fill_super)(struct super_block *, void *, int))
 110 {
 111         struct mtd_info *mtd;
 112
 113         mtd = get_mtd_device(NULL, mtdnr);
 114         if (IS_ERR(mtd)) {
 115                 pr_debug("MTDSB: Device #%u doesn't appear to exist\n", mtdnr);
 116                 return ERR_CAST(mtd);
 117         }
 118
 119         return mount_mtd_aux(fs_type, flags, dev_name, data, mtd, fill_super);
 120 }
 121
 122 /*
 123  * set up an MTD-based superblock
 124  */
 125 struct dentry *mount_mtd(struct file_system_type *fs_type, int flags,
 126                const char *dev_name, void *data,
 127                int (*fill_super)(struct super_block *, void *, int))
 128 {
 129 #ifdef CONFIG_BLOCK
 130         struct block_device *bdev;
 131         int ret, major;
 132         int perm;
 133 #endif
 134         int mtdnr;
 135
 136         if (!dev_name)
 137                 return ERR_PTR(-EINVAL);
 138
 139         pr_debug("MTDSB: dev_name \"%s\"\n", dev_name);
 140
 141         /* the preferred way of mounting in future; especially when
 142          * CONFIG_BLOCK=n - we specify the underlying MTD device by number or
 143          * by name, so that we don't require block device support to be present
 144          * in the kernel. */
 145         if (dev_name[0] == 'm' && dev_name[1] == 't' && dev_name[2] == 'd') {
 146                 if (dev_name[3] == ':') {
 147                         struct mtd_info *mtd;
 148
 149                         /* mount by MTD device name */
 150                         pr_debug("MTDSB: mtd:%%s, name \"%s\"\n",
 151                               dev_name + 4);
 152
 153                         mtd = get_mtd_device_nm(dev_name + 4);
 154                         if (!IS_ERR(mtd))
 155                                 return mount_mtd_aux(
 156                                         fs_type, flags,
 157                                         dev_name, data, mtd,
 158                                         fill_super);
 159
 160                         printk(KERN_NOTICE "MTD:"
 161                                " MTD device with name \"%s\" not found.\n",
 162                                dev_name + 4);
 163
 164                 } else if (isdigit(dev_name[3])) {
 165                         /* mount by MTD device number name */
 166                         char *endptr;
 167
 168                         mtdnr = simple_strtoul(dev_name + 3, &endptr, 0);
 169                         if (!*endptr) {
 170                                 /* It was a valid number */
 171                                 pr_debug("MTDSB: mtd%%d, mtdnr %d\n",
 172                                       mtdnr);
 173                                 return mount_mtd_nr(fs_type, flags,
 174                                                      dev_name, data,
 175                                                      mtdnr, fill_super);
 176                         }
 177                 }
 178         }
 179
 180 #ifdef CONFIG_BLOCK
 181         /* try the old way - the hack where we allowed users to mount
 182          * /dev/mtdblock$(n) but didn't actually _use_ the blockdev
 183          */
 184         perm = MAY_READ;
 185         if (!(flags & MS_RDONLY))
 186                 perm |= MAY_WRITE;
 187         bdev = lookup_bdev(dev_name, perm);
 188         if (IS_ERR(bdev)) {
 189                 ret = PTR_ERR(bdev);
 190                 pr_debug("MTDSB: lookup_bdev() returned %d\n", ret);
 191                 return ERR_PTR(ret);
 192         }
 193         pr_debug("MTDSB: lookup_bdev() returned 0\n");
 194
 195         ret = -EINVAL;
 196
 197         major = MAJOR(bdev->bd_dev);
 198         mtdnr = MINOR(bdev->bd_dev);
 199         bdput(bdev);
 200
 201         if (major != MTD_BLOCK_MAJOR)
 202                 goto not_an_MTD_device;
 203
 204         return mount_mtd_nr(fs_type, flags, dev_name, data, mtdnr, fill_super);
 205
 206 not_an_MTD_device:
 207 #endif /* CONFIG_BLOCK */
 208
 209         if (!(flags & MS_SILENT))
 210                 printk(KERN_NOTICE
 211                        "MTD: Attempt to mount non-MTD device \"%s\"\n",
 212                        dev_name);
 213         return ERR_PTR(-EINVAL);
 214 }
 215
 216 EXPORT_SYMBOL_GPL(mount_mtd);
 217
 218 /*
 219  * destroy an MTD-based superblock
 220  */
 221 void kill_mtd_super(struct super_block *sb)
 222 {
 223         generic_shutdown_super(sb);
 224         put_mtd_device(sb->s_mtd);
 225         sb->s_mtd = NULL;
 226 }
 227
 228 EXPORT_SYMBOL_GPL(kill_mtd_super);