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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#include <linux/blkdev.h>
19#include <linux/fs_context.h>
20#include "mtdcore.h"
21
22/*
23 * get a superblock on an MTD-backed filesystem
24 */
25static int mtd_get_sb(struct fs_context *fc,
26 struct mtd_info *mtd,
27 int (*fill_super)(struct super_block *,
28 struct fs_context *))
29{
30 struct super_block *sb;
31 int ret;
32
33 sb = sget_dev(fc, MKDEV(MTD_BLOCK_MAJOR, mtd->index));
34 if (IS_ERR(sb))
35 return PTR_ERR(sb);
36
37 if (sb->s_root) {
38 /* new mountpoint for an already mounted superblock */
39 pr_debug("MTDSB: Device %d (\"%s\") is already mounted\n",
40 mtd->index, mtd->name);
41 put_mtd_device(mtd);
42 } else {
43 /* fresh new superblock */
44 pr_debug("MTDSB: New superblock for device %d (\"%s\")\n",
45 mtd->index, mtd->name);
46
47 /*
48 * Would usually have been set with @sb_lock held but in
49 * contrast to sb->s_bdev that's checked with only
50 * @sb_lock held, nothing checks sb->s_mtd without also
51 * holding sb->s_umount and we're holding sb->s_umount
52 * here.
53 */
54 sb->s_mtd = mtd;
55 sb->s_bdi = bdi_get(mtd_bdi);
56
57 ret = fill_super(sb, fc);
58 if (ret < 0)
59 goto error_sb;
60
61 sb->s_flags |= SB_ACTIVE;
62 }
63
64 BUG_ON(fc->root);
65 fc->root = dget(sb->s_root);
66 return 0;
67
68error_sb:
69 deactivate_locked_super(sb);
70 return ret;
71}
72
73/*
74 * get a superblock on an MTD-backed filesystem by MTD device number
75 */
76static int mtd_get_sb_by_nr(struct fs_context *fc, int mtdnr,
77 int (*fill_super)(struct super_block *,
78 struct fs_context *))
79{
80 struct mtd_info *mtd;
81
82 mtd = get_mtd_device(NULL, mtdnr);
83 if (IS_ERR(mtd)) {
84 errorf(fc, "MTDSB: Device #%u doesn't appear to exist\n", mtdnr);
85 return PTR_ERR(mtd);
86 }
87
88 return mtd_get_sb(fc, mtd, fill_super);
89}
90
91/**
92 * get_tree_mtd - Get a superblock based on a single MTD device
93 * @fc: The filesystem context holding the parameters
94 * @fill_super: Helper to initialise a new superblock
95 */
96int get_tree_mtd(struct fs_context *fc,
97 int (*fill_super)(struct super_block *sb,
98 struct fs_context *fc))
99{
100#ifdef CONFIG_BLOCK
101 dev_t dev;
102 int ret;
103#endif
104 int mtdnr;
105
106 if (!fc->source)
107 return invalf(fc, "No source specified");
108
109 pr_debug("MTDSB: dev_name \"%s\"\n", fc->source);
110
111 /* the preferred way of mounting in future; especially when
112 * CONFIG_BLOCK=n - we specify the underlying MTD device by number or
113 * by name, so that we don't require block device support to be present
114 * in the kernel.
115 */
116 if (fc->source[0] == 'm' &&
117 fc->source[1] == 't' &&
118 fc->source[2] == 'd') {
119 if (fc->source[3] == ':') {
120 struct mtd_info *mtd;
121
122 /* mount by MTD device name */
123 pr_debug("MTDSB: mtd:%%s, name \"%s\"\n",
124 fc->source + 4);
125
126 mtd = get_mtd_device_nm(fc->source + 4);
127 if (!IS_ERR(mtd))
128 return mtd_get_sb(fc, mtd, fill_super);
129
130 errorf(fc, "MTD: MTD device with name \"%s\" not found",
131 fc->source + 4);
132
133 } else if (isdigit(fc->source[3])) {
134 /* mount by MTD device number name */
135 char *endptr;
136
137 mtdnr = simple_strtoul(fc->source + 3, &endptr, 0);
138 if (!*endptr) {
139 /* It was a valid number */
140 pr_debug("MTDSB: mtd%%d, mtdnr %d\n", mtdnr);
141 return mtd_get_sb_by_nr(fc, mtdnr, fill_super);
142 }
143 }
144 }
145
146#ifdef CONFIG_BLOCK
147 /* try the old way - the hack where we allowed users to mount
148 * /dev/mtdblock$(n) but didn't actually _use_ the blockdev
149 */
150 ret = lookup_bdev(fc->source, &dev);
151 if (ret) {
152 errorf(fc, "MTD: Couldn't look up '%s': %d", fc->source, ret);
153 return ret;
154 }
155 pr_debug("MTDSB: lookup_bdev() returned 0\n");
156
157 if (MAJOR(dev) == MTD_BLOCK_MAJOR)
158 return mtd_get_sb_by_nr(fc, MINOR(dev), fill_super);
159
160#endif /* CONFIG_BLOCK */
161
162 if (!(fc->sb_flags & SB_SILENT))
163 errorf(fc, "MTD: Attempt to mount non-MTD device \"%s\"",
164 fc->source);
165 return -EINVAL;
166}
167EXPORT_SYMBOL_GPL(get_tree_mtd);
168
169/*
170 * destroy an MTD-based superblock
171 */
172void kill_mtd_super(struct super_block *sb)
173{
174 generic_shutdown_super(sb);
175 put_mtd_device(sb->s_mtd);
176 sb->s_mtd = NULL;
177}
178
179EXPORT_SYMBOL_GPL(kill_mtd_super);
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 */
27static 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
42extern 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 */
49static 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 */
63static 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 & SB_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 |= SB_ACTIVE;
90 return dget(sb->s_root);
91
92 /* new mountpoint for an already mounted superblock */
93already_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
99out_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 */
107static 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 */
125struct 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#endif
133 int mtdnr;
134
135 if (!dev_name)
136 return ERR_PTR(-EINVAL);
137
138 pr_debug("MTDSB: dev_name \"%s\"\n", dev_name);
139
140 /* the preferred way of mounting in future; especially when
141 * CONFIG_BLOCK=n - we specify the underlying MTD device by number or
142 * by name, so that we don't require block device support to be present
143 * in the kernel. */
144 if (dev_name[0] == 'm' && dev_name[1] == 't' && dev_name[2] == 'd') {
145 if (dev_name[3] == ':') {
146 struct mtd_info *mtd;
147
148 /* mount by MTD device name */
149 pr_debug("MTDSB: mtd:%%s, name \"%s\"\n",
150 dev_name + 4);
151
152 mtd = get_mtd_device_nm(dev_name + 4);
153 if (!IS_ERR(mtd))
154 return mount_mtd_aux(
155 fs_type, flags,
156 dev_name, data, mtd,
157 fill_super);
158
159 printk(KERN_NOTICE "MTD:"
160 " MTD device with name \"%s\" not found.\n",
161 dev_name + 4);
162
163 } else if (isdigit(dev_name[3])) {
164 /* mount by MTD device number name */
165 char *endptr;
166
167 mtdnr = simple_strtoul(dev_name + 3, &endptr, 0);
168 if (!*endptr) {
169 /* It was a valid number */
170 pr_debug("MTDSB: mtd%%d, mtdnr %d\n",
171 mtdnr);
172 return mount_mtd_nr(fs_type, flags,
173 dev_name, data,
174 mtdnr, fill_super);
175 }
176 }
177 }
178
179#ifdef CONFIG_BLOCK
180 /* try the old way - the hack where we allowed users to mount
181 * /dev/mtdblock$(n) but didn't actually _use_ the blockdev
182 */
183 bdev = lookup_bdev(dev_name);
184 if (IS_ERR(bdev)) {
185 ret = PTR_ERR(bdev);
186 pr_debug("MTDSB: lookup_bdev() returned %d\n", ret);
187 return ERR_PTR(ret);
188 }
189 pr_debug("MTDSB: lookup_bdev() returned 0\n");
190
191 ret = -EINVAL;
192
193 major = MAJOR(bdev->bd_dev);
194 mtdnr = MINOR(bdev->bd_dev);
195 bdput(bdev);
196
197 if (major != MTD_BLOCK_MAJOR)
198 goto not_an_MTD_device;
199
200 return mount_mtd_nr(fs_type, flags, dev_name, data, mtdnr, fill_super);
201
202not_an_MTD_device:
203#endif /* CONFIG_BLOCK */
204
205 if (!(flags & SB_SILENT))
206 printk(KERN_NOTICE
207 "MTD: Attempt to mount non-MTD device \"%s\"\n",
208 dev_name);
209 return ERR_PTR(-EINVAL);
210}
211
212EXPORT_SYMBOL_GPL(mount_mtd);
213
214/*
215 * destroy an MTD-based superblock
216 */
217void kill_mtd_super(struct super_block *sb)
218{
219 generic_shutdown_super(sb);
220 put_mtd_device(sb->s_mtd);
221 sb->s_mtd = NULL;
222}
223
224EXPORT_SYMBOL_GPL(kill_mtd_super);