Root/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 */
25static 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 */
45static 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 */
58static 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 */
88already_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
94out_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 */
102static 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 */
120struct 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
197not_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
207EXPORT_SYMBOL_GPL(mount_mtd);
208
209/*
210 * destroy an MTD-based superblock
211 */
212void 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
219EXPORT_SYMBOL_GPL(kill_mtd_super);
220

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