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 * compare superblocks to see if they're equivalent 24 * - they are if the underlying MTD device is the same 25 */ 26 static int mtd_test_super(struct super_block *sb, struct fs_context *fc) 27 { 28 struct mtd_info *mtd = fc->sget_key; 29 30 if (sb->s_mtd == fc->sget_key) { 31 pr_debug("MTDSB: Match on device %d (\"%s\")\n", 32 mtd->index, mtd->name); 33 return 1; 34 } 35 36 pr_debug("MTDSB: No match, device %d (\"%s\"), device %d (\"%s\")\n", 37 sb->s_mtd->index, sb->s_mtd->name, mtd->index, mtd->name); 38 return 0; 39 } 40 41 /* 42 * mark the superblock by the MTD device it is using 43 * - set the device number to be the correct MTD block device for pesuperstence 44 * of NFS exports 45 */ 46 static int mtd_set_super(struct super_block *sb, struct fs_context *fc) 47 { 48 sb->s_mtd = fc->sget_key; 49 sb->s_dev = MKDEV(MTD_BLOCK_MAJOR, sb->s_mtd->index); 50 sb->s_bdi = bdi_get(mtd_bdi); 51 return 0; 52 } 53 54 /* 55 * get a superblock on an MTD-backed filesystem 56 */ 57 static int mtd_get_sb(struct fs_context *fc, 58 struct mtd_info *mtd, 59 int (*fill_super)(struct super_block *, 60 struct fs_context *)) 61 { 62 struct super_block *sb; 63 int ret; 64 65 fc->sget_key = mtd; 66 sb = sget_fc(fc, mtd_test_super, mtd_set_super); 67 if (IS_ERR(sb)) 68 return PTR_ERR(sb); 69 70 if (sb->s_root) { 71 /* new mountpoint for an already mounted superblock */ 72 pr_debug("MTDSB: Device %d (\"%s\") is already mounted\n", 73 mtd->index, mtd->name); 74 put_mtd_device(mtd); 75 } else { 76 /* fresh new superblock */ 77 pr_debug("MTDSB: New superblock for device %d (\"%s\")\n", 78 mtd->index, mtd->name); 79 80 ret = fill_super(sb, fc); 81 if (ret < 0) 82 goto error_sb; 83 84 sb->s_flags |= SB_ACTIVE; 85 } 86 87 BUG_ON(fc->root); 88 fc->root = dget(sb->s_root); 89 return 0; 90 91 error_sb: 92 deactivate_locked_super(sb); 93 return ret; 94 } 95 96 /* 97 * get a superblock on an MTD-backed filesystem by MTD device number 98 */ 99 static int mtd_get_sb_by_nr(struct fs_context *fc, int mtdnr, 100 int (*fill_super)(struct super_block *, 101 struct fs_context *)) 102 { 103 struct mtd_info *mtd; 104 105 mtd = get_mtd_device(NULL, mtdnr); 106 if (IS_ERR(mtd)) { 107 errorf(fc, "MTDSB: Device #%u doesn't appear to exist\n", mtdnr); 108 return PTR_ERR(mtd); 109 } 110 111 return mtd_get_sb(fc, mtd, fill_super); 112 } 113 114 /** 115 * get_tree_mtd - Get a superblock based on a single MTD device 116 * @fc: The filesystem context holding the parameters 117 * @fill_super: Helper to initialise a new superblock 118 */ 119 int get_tree_mtd(struct fs_context *fc, 120 int (*fill_super)(struct super_block *sb, 121 struct fs_context *fc)) 122 { 123 #ifdef CONFIG_BLOCK 124 dev_t dev; 125 int ret; 126 #endif 127 int mtdnr; 128 129 if (!fc->source) 130 return invalf(fc, "No source specified"); 131 132 pr_debug("MTDSB: dev_name \"%s\"\n", fc->source); 133 134 /* the preferred way of mounting in future; especially when 135 * CONFIG_BLOCK=n - we specify the underlying MTD device by number or 136 * by name, so that we don't require block device support to be present 137 * in the kernel. 138 */ 139 if (fc->source[0] == 'm' && 140 fc->source[1] == 't' && 141 fc->source[2] == 'd') { 142 if (fc->source[3] == ':') { 143 struct mtd_info *mtd; 144 145 /* mount by MTD device name */ 146 pr_debug("MTDSB: mtd:%%s, name \"%s\"\n", 147 fc->source + 4); 148 149 mtd = get_mtd_device_nm(fc->source + 4); 150 if (!IS_ERR(mtd)) 151 return mtd_get_sb(fc, mtd, fill_super); 152 153 errorf(fc, "MTD: MTD device with name \"%s\" not found", 154 fc->source + 4); 155 156 } else if (isdigit(fc->source[3])) { 157 /* mount by MTD device number name */ 158 char *endptr; 159 160 mtdnr = simple_strtoul(fc->source + 3, &endptr, 0); 161 if (!*endptr) { 162 /* It was a valid number */ 163 pr_debug("MTDSB: mtd%%d, mtdnr %d\n", mtdnr); 164 return mtd_get_sb_by_nr(fc, mtdnr, fill_super); 165 } 166 } 167 } 168 169 #ifdef CONFIG_BLOCK 170 /* try the old way - the hack where we allowed users to mount 171 * /dev/mtdblock$(n) but didn't actually _use_ the blockdev 172 */ 173 ret = lookup_bdev(fc->source, &dev); 174 if (ret) { 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 if (MAJOR(dev) == MTD_BLOCK_MAJOR) 181 return mtd_get_sb_by_nr(fc, MINOR(dev), fill_super); 182 183 #endif /* CONFIG_BLOCK */ 184 185 if (!(fc->sb_flags & SB_SILENT)) 186 errorf(fc, "MTD: Attempt to mount non-MTD device \"%s\"", 187 fc->source); 188 return -EINVAL; 189 } 190 EXPORT_SYMBOL_GPL(get_tree_mtd); 191 192 /* 193 * destroy an MTD-based superblock 194 */ 195 void kill_mtd_super(struct super_block *sb) 196 { 197 generic_shutdown_super(sb); 198 put_mtd_device(sb->s_mtd); 199 sb->s_mtd = NULL; 200 } 201 202 EXPORT_SYMBOL_GPL(kill_mtd_super); 203