1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /* MTD-based superblock management
4 * Copyright © 2001-2007 Red Hat, Inc. All Rights Reserved.
5 * Copyright © 2001-2010 David Woodhouse <dwmw2@infradead.org>
7 * Written by: David Howells <dhowells@redhat.com>
8 * David Woodhouse <dwmw2@infradead.org>
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>
20 * compare superblocks to see if they're equivalent
21 * - they are if the underlying MTD device is the same
23 static int get_sb_mtd_compare(struct super_block *sb, void *_mtd)
25 struct mtd_info *mtd = _mtd;
27 if (sb->s_mtd == mtd) {
28 pr_debug("MTDSB: Match on device %d (\"%s\")\n",
29 mtd->index, mtd->name);
33 pr_debug("MTDSB: No match, device %d (\"%s\"), device %d (\"%s\")\n",
34 sb->s_mtd->index, sb->s_mtd->name, mtd->index, mtd->name);
38 extern struct backing_dev_info *mtd_bdi;
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
45 static int get_sb_mtd_set(struct super_block *sb, void *_mtd)
47 struct mtd_info *mtd = _mtd;
50 sb->s_dev = MKDEV(MTD_BLOCK_MAJOR, mtd->index);
51 sb->s_bdi = bdi_get(mtd_bdi);
57 * get a superblock on an MTD-backed filesystem
59 static struct dentry *mount_mtd_aux(struct file_system_type *fs_type, int flags,
60 const char *dev_name, void *data,
62 int (*fill_super)(struct super_block *, void *, int))
64 struct super_block *sb;
67 sb = sget(fs_type, get_sb_mtd_compare, get_sb_mtd_set, flags, mtd);
74 /* fresh new superblock */
75 pr_debug("MTDSB: New superblock for device %d (\"%s\")\n",
76 mtd->index, mtd->name);
78 ret = fill_super(sb, data, flags & SB_SILENT ? 1 : 0);
80 deactivate_locked_super(sb);
85 sb->s_flags |= SB_ACTIVE;
86 return dget(sb->s_root);
88 /* new mountpoint for an already mounted superblock */
90 pr_debug("MTDSB: Device %d (\"%s\") is already mounted\n",
91 mtd->index, mtd->name);
93 return dget(sb->s_root);
101 * get a superblock on an MTD-backed filesystem by MTD device number
103 static struct dentry *mount_mtd_nr(struct file_system_type *fs_type, int flags,
104 const char *dev_name, void *data, int mtdnr,
105 int (*fill_super)(struct super_block *, void *, int))
107 struct mtd_info *mtd;
109 mtd = get_mtd_device(NULL, mtdnr);
111 pr_debug("MTDSB: Device #%u doesn't appear to exist\n", mtdnr);
112 return ERR_CAST(mtd);
115 return mount_mtd_aux(fs_type, flags, dev_name, data, mtd, fill_super);
119 * set up an MTD-based superblock
121 struct dentry *mount_mtd(struct file_system_type *fs_type, int flags,
122 const char *dev_name, void *data,
123 int (*fill_super)(struct super_block *, void *, int))
126 struct block_device *bdev;
132 return ERR_PTR(-EINVAL);
134 pr_debug("MTDSB: dev_name \"%s\"\n", dev_name);
136 /* the preferred way of mounting in future; especially when
137 * CONFIG_BLOCK=n - we specify the underlying MTD device by number or
138 * by name, so that we don't require block device support to be present
140 if (dev_name[0] == 'm' && dev_name[1] == 't' && dev_name[2] == 'd') {
141 if (dev_name[3] == ':') {
142 struct mtd_info *mtd;
144 /* mount by MTD device name */
145 pr_debug("MTDSB: mtd:%%s, name \"%s\"\n",
148 mtd = get_mtd_device_nm(dev_name + 4);
150 return mount_mtd_aux(
155 printk(KERN_NOTICE "MTD:"
156 " MTD device with name \"%s\" not found.\n",
159 } else if (isdigit(dev_name[3])) {
160 /* mount by MTD device number name */
163 mtdnr = simple_strtoul(dev_name + 3, &endptr, 0);
165 /* It was a valid number */
166 pr_debug("MTDSB: mtd%%d, mtdnr %d\n",
168 return mount_mtd_nr(fs_type, flags,
176 /* try the old way - the hack where we allowed users to mount
177 * /dev/mtdblock$(n) but didn't actually _use_ the blockdev
179 bdev = lookup_bdev(dev_name);
182 pr_debug("MTDSB: lookup_bdev() returned %d\n", ret);
185 pr_debug("MTDSB: lookup_bdev() returned 0\n");
189 major = MAJOR(bdev->bd_dev);
190 mtdnr = MINOR(bdev->bd_dev);
193 if (major != MTD_BLOCK_MAJOR)
194 goto not_an_MTD_device;
196 return mount_mtd_nr(fs_type, flags, dev_name, data, mtdnr, fill_super);
199 #endif /* CONFIG_BLOCK */
201 if (!(flags & SB_SILENT))
203 "MTD: Attempt to mount non-MTD device \"%s\"\n",
205 return ERR_PTR(-EINVAL);
208 EXPORT_SYMBOL_GPL(mount_mtd);
211 * destroy an MTD-based superblock
213 void kill_mtd_super(struct super_block *sb)
215 generic_shutdown_super(sb);
216 put_mtd_device(sb->s_mtd);
220 EXPORT_SYMBOL_GPL(kill_mtd_super);