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/fs_context.h>
19 #include "mtdcore.h"
20
21 /*
22 * compare superblocks to see if they're equivalent
23 * - they are if the underlying MTD device is the same
24 */
mtd_test_super(struct super_block * sb,struct fs_context * fc)25 static int mtd_test_super(struct super_block *sb, struct fs_context *fc)
26 {
27 struct mtd_info *mtd = fc->sget_key;
28
29 if (sb->s_mtd == fc->sget_key) {
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 */
mtd_set_super(struct super_block * sb,struct fs_context * fc)45 static int mtd_set_super(struct super_block *sb, struct fs_context *fc)
46 {
47 sb->s_mtd = fc->sget_key;
48 sb->s_dev = MKDEV(MTD_BLOCK_MAJOR, sb->s_mtd->index);
49 sb->s_bdi = bdi_get(mtd_bdi);
50 return 0;
51 }
52
53 /*
54 * get a superblock on an MTD-backed filesystem
55 */
mtd_get_sb(struct fs_context * fc,struct mtd_info * mtd,int (* fill_super)(struct super_block *,struct fs_context *))56 static int mtd_get_sb(struct fs_context *fc,
57 struct mtd_info *mtd,
58 int (*fill_super)(struct super_block *,
59 struct fs_context *))
60 {
61 struct super_block *sb;
62 int ret;
63
64 fc->sget_key = mtd;
65 sb = sget_fc(fc, mtd_test_super, mtd_set_super);
66 if (IS_ERR(sb))
67 return PTR_ERR(sb);
68
69 if (sb->s_root) {
70 /* new mountpoint for an already mounted superblock */
71 pr_debug("MTDSB: Device %d (\"%s\") is already mounted\n",
72 mtd->index, mtd->name);
73 put_mtd_device(mtd);
74 } else {
75 /* fresh new superblock */
76 pr_debug("MTDSB: New superblock for device %d (\"%s\")\n",
77 mtd->index, mtd->name);
78
79 ret = fill_super(sb, fc);
80 if (ret < 0)
81 goto error_sb;
82
83 sb->s_flags |= SB_ACTIVE;
84 }
85
86 BUG_ON(fc->root);
87 fc->root = dget(sb->s_root);
88 return 0;
89
90 error_sb:
91 deactivate_locked_super(sb);
92 return ret;
93 }
94
95 /*
96 * get a superblock on an MTD-backed filesystem by MTD device number
97 */
mtd_get_sb_by_nr(struct fs_context * fc,int mtdnr,int (* fill_super)(struct super_block *,struct fs_context *))98 static int mtd_get_sb_by_nr(struct fs_context *fc, int mtdnr,
99 int (*fill_super)(struct super_block *,
100 struct fs_context *))
101 {
102 struct mtd_info *mtd;
103
104 mtd = get_mtd_device(NULL, mtdnr);
105 if (IS_ERR(mtd)) {
106 errorf(fc, "MTDSB: Device #%u doesn't appear to exist\n", mtdnr);
107 return PTR_ERR(mtd);
108 }
109
110 return mtd_get_sb(fc, mtd, fill_super);
111 }
112
113 /**
114 * get_tree_mtd - Get a superblock based on a single MTD device
115 * @fc: The filesystem context holding the parameters
116 * @fill_super: Helper to initialise a new superblock
117 */
get_tree_mtd(struct fs_context * fc,int (* fill_super)(struct super_block * sb,struct fs_context * fc))118 int get_tree_mtd(struct fs_context *fc,
119 int (*fill_super)(struct super_block *sb,
120 struct fs_context *fc))
121 {
122 #ifdef CONFIG_BLOCK
123 struct block_device *bdev;
124 int ret, major;
125 #endif
126 int mtdnr;
127
128 if (!fc->source)
129 return invalf(fc, "No source specified");
130
131 pr_debug("MTDSB: dev_name \"%s\"\n", fc->source);
132
133 /* the preferred way of mounting in future; especially when
134 * CONFIG_BLOCK=n - we specify the underlying MTD device by number or
135 * by name, so that we don't require block device support to be present
136 * in the kernel.
137 */
138 if (fc->source[0] == 'm' &&
139 fc->source[1] == 't' &&
140 fc->source[2] == 'd') {
141 if (fc->source[3] == ':') {
142 struct mtd_info *mtd;
143
144 /* mount by MTD device name */
145 pr_debug("MTDSB: mtd:%%s, name \"%s\"\n",
146 fc->source + 4);
147
148 mtd = get_mtd_device_nm(fc->source + 4);
149 if (!IS_ERR(mtd))
150 return mtd_get_sb(fc, mtd, fill_super);
151
152 errorf(fc, "MTD: MTD device with name \"%s\" not found",
153 fc->source + 4);
154
155 } else if (isdigit(fc->source[3])) {
156 /* mount by MTD device number name */
157 char *endptr;
158
159 mtdnr = simple_strtoul(fc->source + 3, &endptr, 0);
160 if (!*endptr) {
161 /* It was a valid number */
162 pr_debug("MTDSB: mtd%%d, mtdnr %d\n", mtdnr);
163 return mtd_get_sb_by_nr(fc, mtdnr, fill_super);
164 }
165 }
166 }
167
168 #ifdef CONFIG_BLOCK
169 /* try the old way - the hack where we allowed users to mount
170 * /dev/mtdblock$(n) but didn't actually _use_ the blockdev
171 */
172 bdev = lookup_bdev(fc->source);
173 if (IS_ERR(bdev)) {
174 ret = PTR_ERR(bdev);
175 errorf(fc, "MTD: Couldn't look up '%s': %d", fc->source, ret);
176 return ret;
177 }
178 pr_debug("MTDSB: lookup_bdev() returned 0\n");
179
180 major = MAJOR(bdev->bd_dev);
181 mtdnr = MINOR(bdev->bd_dev);
182 bdput(bdev);
183
184 if (major == MTD_BLOCK_MAJOR)
185 return mtd_get_sb_by_nr(fc, mtdnr, fill_super);
186
187 #endif /* CONFIG_BLOCK */
188
189 if (!(fc->sb_flags & SB_SILENT))
190 errorf(fc, "MTD: Attempt to mount non-MTD device \"%s\"",
191 fc->source);
192 return -EINVAL;
193 }
194 EXPORT_SYMBOL_GPL(get_tree_mtd);
195
196 /*
197 * destroy an MTD-based superblock
198 */
kill_mtd_super(struct super_block * sb)199 void kill_mtd_super(struct super_block *sb)
200 {
201 generic_shutdown_super(sb);
202 put_mtd_device(sb->s_mtd);
203 sb->s_mtd = NULL;
204 }
205
206 EXPORT_SYMBOL_GPL(kill_mtd_super);
207
