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 */ 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 */ 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 */ 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 */ 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 */ 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 dev_t dev; 124 int ret; 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 ret = lookup_bdev(fc->source, &dev); 173 if (ret) { 174 errorf(fc, "MTD: Couldn't look up '%s': %d", fc->source, ret); 175 return ret; 176 } 177 pr_debug("MTDSB: lookup_bdev() returned 0\n"); 178 179 if (MAJOR(dev) == MTD_BLOCK_MAJOR) 180 return mtd_get_sb_by_nr(fc, MINOR(dev), fill_super); 181 182 #endif /* CONFIG_BLOCK */ 183 184 if (!(fc->sb_flags & SB_SILENT)) 185 errorf(fc, "MTD: Attempt to mount non-MTD device \"%s\"", 186 fc->source); 187 return -EINVAL; 188 } 189 EXPORT_SYMBOL_GPL(get_tree_mtd); 190 191 /* 192 * destroy an MTD-based superblock 193 */ 194 void kill_mtd_super(struct super_block *sb) 195 { 196 generic_shutdown_super(sb); 197 put_mtd_device(sb->s_mtd); 198 sb->s_mtd = NULL; 199 } 200 201 EXPORT_SYMBOL_GPL(kill_mtd_super); 202