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 */ 25 static 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 68 error_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 */ 76 static 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 */ 96 int 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 } 167 EXPORT_SYMBOL_GPL(get_tree_mtd); 168 169 /* 170 * destroy an MTD-based superblock 171 */ 172 void 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 } 178 179 EXPORT_SYMBOL_GPL(kill_mtd_super); 180