Version:  2.0.40 2.2.26 2.4.37 3.2 3.3 3.4 3.5 3.6 3.7 3.8 3.9 3.10 3.11 3.12 3.13 3.14 3.15 3.16 3.17 3.18

Linux/fs/romfs/super.c

  1 /* Block- or MTD-based romfs
  2  *
  3  * Copyright © 2007 Red Hat, Inc. All Rights Reserved.
  4  * Written by David Howells (dhowells@redhat.com)
  5  *
  6  * Derived from: ROMFS file system, Linux implementation
  7  *
  8  * Copyright © 1997-1999  Janos Farkas <chexum@shadow.banki.hu>
  9  *
 10  * Using parts of the minix filesystem
 11  * Copyright © 1991, 1992  Linus Torvalds
 12  *
 13  * and parts of the affs filesystem additionally
 14  * Copyright © 1993  Ray Burr
 15  * Copyright © 1996  Hans-Joachim Widmaier
 16  *
 17  * Changes
 18  *                                      Changed for 2.1.19 modules
 19  *      Jan 1997                        Initial release
 20  *      Jun 1997                        2.1.43+ changes
 21  *                                      Proper page locking in readpage
 22  *                                      Changed to work with 2.1.45+ fs
 23  *      Jul 1997                        Fixed follow_link
 24  *                      2.1.47
 25  *                                      lookup shouldn't return -ENOENT
 26  *                                      from Horst von Brand:
 27  *                                        fail on wrong checksum
 28  *                                        double unlock_super was possible
 29  *                                        correct namelen for statfs
 30  *                                      spotted by Bill Hawes:
 31  *                                        readlink shouldn't iput()
 32  *      Jun 1998        2.1.106         from Avery Pennarun: glibc scandir()
 33  *                                        exposed a problem in readdir
 34  *                      2.1.107         code-freeze spellchecker run
 35  *      Aug 1998                        2.1.118+ VFS changes
 36  *      Sep 1998        2.1.122         another VFS change (follow_link)
 37  *      Apr 1999        2.2.7           no more EBADF checking in
 38  *                                        lookup/readdir, use ERR_PTR
 39  *      Jun 1999        2.3.6           d_alloc_root use changed
 40  *                      2.3.9           clean up usage of ENOENT/negative
 41  *                                        dentries in lookup
 42  *                                      clean up page flags setting
 43  *                                        (error, uptodate, locking) in
 44  *                                        in readpage
 45  *                                      use init_special_inode for
 46  *                                        fifos/sockets (and streamline) in
 47  *                                        read_inode, fix _ops table order
 48  *      Aug 1999        2.3.16          __initfunc() => __init change
 49  *      Oct 1999        2.3.24          page->owner hack obsoleted
 50  *      Nov 1999        2.3.27          2.3.25+ page->offset => index change
 51  *
 52  *
 53  * This program is free software; you can redistribute it and/or
 54  * modify it under the terms of the GNU General Public Licence
 55  * as published by the Free Software Foundation; either version
 56  * 2 of the Licence, or (at your option) any later version.
 57  */
 58 
 59 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
 60 
 61 #include <linux/module.h>
 62 #include <linux/string.h>
 63 #include <linux/fs.h>
 64 #include <linux/time.h>
 65 #include <linux/slab.h>
 66 #include <linux/init.h>
 67 #include <linux/blkdev.h>
 68 #include <linux/parser.h>
 69 #include <linux/mount.h>
 70 #include <linux/namei.h>
 71 #include <linux/statfs.h>
 72 #include <linux/mtd/super.h>
 73 #include <linux/ctype.h>
 74 #include <linux/highmem.h>
 75 #include <linux/pagemap.h>
 76 #include <linux/uaccess.h>
 77 #include "internal.h"
 78 
 79 static struct kmem_cache *romfs_inode_cachep;
 80 
 81 static const umode_t romfs_modemap[8] = {
 82         0,                      /* hard link */
 83         S_IFDIR  | 0644,        /* directory */
 84         S_IFREG  | 0644,        /* regular file */
 85         S_IFLNK  | 0777,        /* symlink */
 86         S_IFBLK  | 0600,        /* blockdev */
 87         S_IFCHR  | 0600,        /* chardev */
 88         S_IFSOCK | 0644,        /* socket */
 89         S_IFIFO  | 0644         /* FIFO */
 90 };
 91 
 92 static const unsigned char romfs_dtype_table[] = {
 93         DT_UNKNOWN, DT_DIR, DT_REG, DT_LNK, DT_BLK, DT_CHR, DT_SOCK, DT_FIFO
 94 };
 95 
 96 static struct inode *romfs_iget(struct super_block *sb, unsigned long pos);
 97 
 98 /*
 99  * read a page worth of data from the image
100  */
101 static int romfs_readpage(struct file *file, struct page *page)
102 {
103         struct inode *inode = page->mapping->host;
104         loff_t offset, size;
105         unsigned long fillsize, pos;
106         void *buf;
107         int ret;
108 
109         buf = kmap(page);
110         if (!buf)
111                 return -ENOMEM;
112 
113         /* 32 bit warning -- but not for us :) */
114         offset = page_offset(page);
115         size = i_size_read(inode);
116         fillsize = 0;
117         ret = 0;
118         if (offset < size) {
119                 size -= offset;
120                 fillsize = size > PAGE_SIZE ? PAGE_SIZE : size;
121 
122                 pos = ROMFS_I(inode)->i_dataoffset + offset;
123 
124                 ret = romfs_dev_read(inode->i_sb, pos, buf, fillsize);
125                 if (ret < 0) {
126                         SetPageError(page);
127                         fillsize = 0;
128                         ret = -EIO;
129                 }
130         }
131 
132         if (fillsize < PAGE_SIZE)
133                 memset(buf + fillsize, 0, PAGE_SIZE - fillsize);
134         if (ret == 0)
135                 SetPageUptodate(page);
136 
137         flush_dcache_page(page);
138         kunmap(page);
139         unlock_page(page);
140         return ret;
141 }
142 
143 static const struct address_space_operations romfs_aops = {
144         .readpage       = romfs_readpage
145 };
146 
147 /*
148  * read the entries from a directory
149  */
150 static int romfs_readdir(struct file *file, struct dir_context *ctx)
151 {
152         struct inode *i = file_inode(file);
153         struct romfs_inode ri;
154         unsigned long offset, maxoff;
155         int j, ino, nextfh;
156         char fsname[ROMFS_MAXFN];       /* XXX dynamic? */
157         int ret;
158 
159         maxoff = romfs_maxsize(i->i_sb);
160 
161         offset = ctx->pos;
162         if (!offset) {
163                 offset = i->i_ino & ROMFH_MASK;
164                 ret = romfs_dev_read(i->i_sb, offset, &ri, ROMFH_SIZE);
165                 if (ret < 0)
166                         goto out;
167                 offset = be32_to_cpu(ri.spec) & ROMFH_MASK;
168         }
169 
170         /* Not really failsafe, but we are read-only... */
171         for (;;) {
172                 if (!offset || offset >= maxoff) {
173                         offset = maxoff;
174                         ctx->pos = offset;
175                         goto out;
176                 }
177                 ctx->pos = offset;
178 
179                 /* Fetch inode info */
180                 ret = romfs_dev_read(i->i_sb, offset, &ri, ROMFH_SIZE);
181                 if (ret < 0)
182                         goto out;
183 
184                 j = romfs_dev_strnlen(i->i_sb, offset + ROMFH_SIZE,
185                                       sizeof(fsname) - 1);
186                 if (j < 0)
187                         goto out;
188 
189                 ret = romfs_dev_read(i->i_sb, offset + ROMFH_SIZE, fsname, j);
190                 if (ret < 0)
191                         goto out;
192                 fsname[j] = '\0';
193 
194                 ino = offset;
195                 nextfh = be32_to_cpu(ri.next);
196                 if ((nextfh & ROMFH_TYPE) == ROMFH_HRD)
197                         ino = be32_to_cpu(ri.spec);
198                 if (!dir_emit(ctx, fsname, j, ino,
199                             romfs_dtype_table[nextfh & ROMFH_TYPE]))
200                         goto out;
201 
202                 offset = nextfh & ROMFH_MASK;
203         }
204 out:
205         return 0;
206 }
207 
208 /*
209  * look up an entry in a directory
210  */
211 static struct dentry *romfs_lookup(struct inode *dir, struct dentry *dentry,
212                                    unsigned int flags)
213 {
214         unsigned long offset, maxoff;
215         struct inode *inode;
216         struct romfs_inode ri;
217         const char *name;               /* got from dentry */
218         int len, ret;
219 
220         offset = dir->i_ino & ROMFH_MASK;
221         ret = romfs_dev_read(dir->i_sb, offset, &ri, ROMFH_SIZE);
222         if (ret < 0)
223                 goto error;
224 
225         /* search all the file entries in the list starting from the one
226          * pointed to by the directory's special data */
227         maxoff = romfs_maxsize(dir->i_sb);
228         offset = be32_to_cpu(ri.spec) & ROMFH_MASK;
229 
230         name = dentry->d_name.name;
231         len = dentry->d_name.len;
232 
233         for (;;) {
234                 if (!offset || offset >= maxoff)
235                         goto out0;
236 
237                 ret = romfs_dev_read(dir->i_sb, offset, &ri, sizeof(ri));
238                 if (ret < 0)
239                         goto error;
240 
241                 /* try to match the first 16 bytes of name */
242                 ret = romfs_dev_strcmp(dir->i_sb, offset + ROMFH_SIZE, name,
243                                        len);
244                 if (ret < 0)
245                         goto error;
246                 if (ret == 1)
247                         break;
248 
249                 /* next entry */
250                 offset = be32_to_cpu(ri.next) & ROMFH_MASK;
251         }
252 
253         /* Hard link handling */
254         if ((be32_to_cpu(ri.next) & ROMFH_TYPE) == ROMFH_HRD)
255                 offset = be32_to_cpu(ri.spec) & ROMFH_MASK;
256 
257         inode = romfs_iget(dir->i_sb, offset);
258         if (IS_ERR(inode)) {
259                 ret = PTR_ERR(inode);
260                 goto error;
261         }
262         goto outi;
263 
264         /*
265          * it's a bit funky, _lookup needs to return an error code
266          * (negative) or a NULL, both as a dentry.  ENOENT should not
267          * be returned, instead we need to create a negative dentry by
268          * d_add(dentry, NULL); and return 0 as no error.
269          * (Although as I see, it only matters on writable file
270          * systems).
271          */
272 out0:
273         inode = NULL;
274 outi:
275         d_add(dentry, inode);
276         ret = 0;
277 error:
278         return ERR_PTR(ret);
279 }
280 
281 static const struct file_operations romfs_dir_operations = {
282         .read           = generic_read_dir,
283         .iterate        = romfs_readdir,
284         .llseek         = default_llseek,
285 };
286 
287 static const struct inode_operations romfs_dir_inode_operations = {
288         .lookup         = romfs_lookup,
289 };
290 
291 /*
292  * get a romfs inode based on its position in the image (which doubles as the
293  * inode number)
294  */
295 static struct inode *romfs_iget(struct super_block *sb, unsigned long pos)
296 {
297         struct romfs_inode_info *inode;
298         struct romfs_inode ri;
299         struct inode *i;
300         unsigned long nlen;
301         unsigned nextfh;
302         int ret;
303         umode_t mode;
304 
305         /* we might have to traverse a chain of "hard link" file entries to get
306          * to the actual file */
307         for (;;) {
308                 ret = romfs_dev_read(sb, pos, &ri, sizeof(ri));
309                 if (ret < 0)
310                         goto error;
311 
312                 /* XXX: do romfs_checksum here too (with name) */
313 
314                 nextfh = be32_to_cpu(ri.next);
315                 if ((nextfh & ROMFH_TYPE) != ROMFH_HRD)
316                         break;
317 
318                 pos = be32_to_cpu(ri.spec) & ROMFH_MASK;
319         }
320 
321         /* determine the length of the filename */
322         nlen = romfs_dev_strnlen(sb, pos + ROMFH_SIZE, ROMFS_MAXFN);
323         if (IS_ERR_VALUE(nlen))
324                 goto eio;
325 
326         /* get an inode for this image position */
327         i = iget_locked(sb, pos);
328         if (!i)
329                 return ERR_PTR(-ENOMEM);
330 
331         if (!(i->i_state & I_NEW))
332                 return i;
333 
334         /* precalculate the data offset */
335         inode = ROMFS_I(i);
336         inode->i_metasize = (ROMFH_SIZE + nlen + 1 + ROMFH_PAD) & ROMFH_MASK;
337         inode->i_dataoffset = pos + inode->i_metasize;
338 
339         set_nlink(i, 1);                /* Hard to decide.. */
340         i->i_size = be32_to_cpu(ri.size);
341         i->i_mtime.tv_sec = i->i_atime.tv_sec = i->i_ctime.tv_sec = 0;
342         i->i_mtime.tv_nsec = i->i_atime.tv_nsec = i->i_ctime.tv_nsec = 0;
343 
344         /* set up mode and ops */
345         mode = romfs_modemap[nextfh & ROMFH_TYPE];
346 
347         switch (nextfh & ROMFH_TYPE) {
348         case ROMFH_DIR:
349                 i->i_size = ROMFS_I(i)->i_metasize;
350                 i->i_op = &romfs_dir_inode_operations;
351                 i->i_fop = &romfs_dir_operations;
352                 if (nextfh & ROMFH_EXEC)
353                         mode |= S_IXUGO;
354                 break;
355         case ROMFH_REG:
356                 i->i_fop = &romfs_ro_fops;
357                 i->i_data.a_ops = &romfs_aops;
358                 if (i->i_sb->s_mtd)
359                         i->i_data.backing_dev_info =
360                                 i->i_sb->s_mtd->backing_dev_info;
361                 if (nextfh & ROMFH_EXEC)
362                         mode |= S_IXUGO;
363                 break;
364         case ROMFH_SYM:
365                 i->i_op = &page_symlink_inode_operations;
366                 i->i_data.a_ops = &romfs_aops;
367                 mode |= S_IRWXUGO;
368                 break;
369         default:
370                 /* depending on MBZ for sock/fifos */
371                 nextfh = be32_to_cpu(ri.spec);
372                 init_special_inode(i, mode, MKDEV(nextfh >> 16,
373                                                   nextfh & 0xffff));
374                 break;
375         }
376 
377         i->i_mode = mode;
378 
379         unlock_new_inode(i);
380         return i;
381 
382 eio:
383         ret = -EIO;
384 error:
385         pr_err("read error for inode 0x%lx\n", pos);
386         return ERR_PTR(ret);
387 }
388 
389 /*
390  * allocate a new inode
391  */
392 static struct inode *romfs_alloc_inode(struct super_block *sb)
393 {
394         struct romfs_inode_info *inode;
395 
396         inode = kmem_cache_alloc(romfs_inode_cachep, GFP_KERNEL);
397         return inode ? &inode->vfs_inode : NULL;
398 }
399 
400 /*
401  * return a spent inode to the slab cache
402  */
403 static void romfs_i_callback(struct rcu_head *head)
404 {
405         struct inode *inode = container_of(head, struct inode, i_rcu);
406 
407         kmem_cache_free(romfs_inode_cachep, ROMFS_I(inode));
408 }
409 
410 static void romfs_destroy_inode(struct inode *inode)
411 {
412         call_rcu(&inode->i_rcu, romfs_i_callback);
413 }
414 
415 /*
416  * get filesystem statistics
417  */
418 static int romfs_statfs(struct dentry *dentry, struct kstatfs *buf)
419 {
420         struct super_block *sb = dentry->d_sb;
421         u64 id = huge_encode_dev(sb->s_bdev->bd_dev);
422 
423         buf->f_type = ROMFS_MAGIC;
424         buf->f_namelen = ROMFS_MAXFN;
425         buf->f_bsize = ROMBSIZE;
426         buf->f_bfree = buf->f_bavail = buf->f_ffree;
427         buf->f_blocks =
428                 (romfs_maxsize(dentry->d_sb) + ROMBSIZE - 1) >> ROMBSBITS;
429         buf->f_fsid.val[0] = (u32)id;
430         buf->f_fsid.val[1] = (u32)(id >> 32);
431         return 0;
432 }
433 
434 /*
435  * remounting must involve read-only
436  */
437 static int romfs_remount(struct super_block *sb, int *flags, char *data)
438 {
439         sync_filesystem(sb);
440         *flags |= MS_RDONLY;
441         return 0;
442 }
443 
444 static const struct super_operations romfs_super_ops = {
445         .alloc_inode    = romfs_alloc_inode,
446         .destroy_inode  = romfs_destroy_inode,
447         .statfs         = romfs_statfs,
448         .remount_fs     = romfs_remount,
449 };
450 
451 /*
452  * checksum check on part of a romfs filesystem
453  */
454 static __u32 romfs_checksum(const void *data, int size)
455 {
456         const __be32 *ptr = data;
457         __u32 sum;
458 
459         sum = 0;
460         size >>= 2;
461         while (size > 0) {
462                 sum += be32_to_cpu(*ptr++);
463                 size--;
464         }
465         return sum;
466 }
467 
468 /*
469  * fill in the superblock
470  */
471 static int romfs_fill_super(struct super_block *sb, void *data, int silent)
472 {
473         struct romfs_super_block *rsb;
474         struct inode *root;
475         unsigned long pos, img_size;
476         const char *storage;
477         size_t len;
478         int ret;
479 
480 #ifdef CONFIG_BLOCK
481         if (!sb->s_mtd) {
482                 sb_set_blocksize(sb, ROMBSIZE);
483         } else {
484                 sb->s_blocksize = ROMBSIZE;
485                 sb->s_blocksize_bits = blksize_bits(ROMBSIZE);
486         }
487 #endif
488 
489         sb->s_maxbytes = 0xFFFFFFFF;
490         sb->s_magic = ROMFS_MAGIC;
491         sb->s_flags |= MS_RDONLY | MS_NOATIME;
492         sb->s_op = &romfs_super_ops;
493 
494         /* read the image superblock and check it */
495         rsb = kmalloc(512, GFP_KERNEL);
496         if (!rsb)
497                 return -ENOMEM;
498 
499         sb->s_fs_info = (void *) 512;
500         ret = romfs_dev_read(sb, 0, rsb, 512);
501         if (ret < 0)
502                 goto error_rsb;
503 
504         img_size = be32_to_cpu(rsb->size);
505 
506         if (sb->s_mtd && img_size > sb->s_mtd->size)
507                 goto error_rsb_inval;
508 
509         sb->s_fs_info = (void *) img_size;
510 
511         if (rsb->word0 != ROMSB_WORD0 || rsb->word1 != ROMSB_WORD1 ||
512             img_size < ROMFH_SIZE) {
513                 if (!silent)
514                         pr_warn("VFS: Can't find a romfs filesystem on dev %s.\n",
515                                sb->s_id);
516                 goto error_rsb_inval;
517         }
518 
519         if (romfs_checksum(rsb, min_t(size_t, img_size, 512))) {
520                 pr_err("bad initial checksum on dev %s.\n", sb->s_id);
521                 goto error_rsb_inval;
522         }
523 
524         storage = sb->s_mtd ? "MTD" : "the block layer";
525 
526         len = strnlen(rsb->name, ROMFS_MAXFN);
527         if (!silent)
528                 pr_notice("Mounting image '%*.*s' through %s\n",
529                           (unsigned) len, (unsigned) len, rsb->name, storage);
530 
531         kfree(rsb);
532         rsb = NULL;
533 
534         /* find the root directory */
535         pos = (ROMFH_SIZE + len + 1 + ROMFH_PAD) & ROMFH_MASK;
536 
537         root = romfs_iget(sb, pos);
538         if (IS_ERR(root))
539                 return PTR_ERR(root);
540 
541         sb->s_root = d_make_root(root);
542         if (!sb->s_root)
543                 return -ENOMEM;
544 
545         return 0;
546 
547 error_rsb_inval:
548         ret = -EINVAL;
549 error_rsb:
550         kfree(rsb);
551         return ret;
552 }
553 
554 /*
555  * get a superblock for mounting
556  */
557 static struct dentry *romfs_mount(struct file_system_type *fs_type,
558                         int flags, const char *dev_name,
559                         void *data)
560 {
561         struct dentry *ret = ERR_PTR(-EINVAL);
562 
563 #ifdef CONFIG_ROMFS_ON_MTD
564         ret = mount_mtd(fs_type, flags, dev_name, data, romfs_fill_super);
565 #endif
566 #ifdef CONFIG_ROMFS_ON_BLOCK
567         if (ret == ERR_PTR(-EINVAL))
568                 ret = mount_bdev(fs_type, flags, dev_name, data,
569                                   romfs_fill_super);
570 #endif
571         return ret;
572 }
573 
574 /*
575  * destroy a romfs superblock in the appropriate manner
576  */
577 static void romfs_kill_sb(struct super_block *sb)
578 {
579 #ifdef CONFIG_ROMFS_ON_MTD
580         if (sb->s_mtd) {
581                 kill_mtd_super(sb);
582                 return;
583         }
584 #endif
585 #ifdef CONFIG_ROMFS_ON_BLOCK
586         if (sb->s_bdev) {
587                 kill_block_super(sb);
588                 return;
589         }
590 #endif
591 }
592 
593 static struct file_system_type romfs_fs_type = {
594         .owner          = THIS_MODULE,
595         .name           = "romfs",
596         .mount          = romfs_mount,
597         .kill_sb        = romfs_kill_sb,
598         .fs_flags       = FS_REQUIRES_DEV,
599 };
600 MODULE_ALIAS_FS("romfs");
601 
602 /*
603  * inode storage initialiser
604  */
605 static void romfs_i_init_once(void *_inode)
606 {
607         struct romfs_inode_info *inode = _inode;
608 
609         inode_init_once(&inode->vfs_inode);
610 }
611 
612 /*
613  * romfs module initialisation
614  */
615 static int __init init_romfs_fs(void)
616 {
617         int ret;
618 
619         pr_info("ROMFS MTD (C) 2007 Red Hat, Inc.\n");
620 
621         romfs_inode_cachep =
622                 kmem_cache_create("romfs_i",
623                                   sizeof(struct romfs_inode_info), 0,
624                                   SLAB_RECLAIM_ACCOUNT | SLAB_MEM_SPREAD,
625                                   romfs_i_init_once);
626 
627         if (!romfs_inode_cachep) {
628                 pr_err("Failed to initialise inode cache\n");
629                 return -ENOMEM;
630         }
631         ret = register_filesystem(&romfs_fs_type);
632         if (ret) {
633                 pr_err("Failed to register filesystem\n");
634                 goto error_register;
635         }
636         return 0;
637 
638 error_register:
639         kmem_cache_destroy(romfs_inode_cachep);
640         return ret;
641 }
642 
643 /*
644  * romfs module removal
645  */
646 static void __exit exit_romfs_fs(void)
647 {
648         unregister_filesystem(&romfs_fs_type);
649         /*
650          * Make sure all delayed rcu free inodes are flushed before we
651          * destroy cache.
652          */
653         rcu_barrier();
654         kmem_cache_destroy(romfs_inode_cachep);
655 }
656 
657 module_init(init_romfs_fs);
658 module_exit(exit_romfs_fs);
659 
660 MODULE_DESCRIPTION("Direct-MTD Capable RomFS");
661 MODULE_AUTHOR("Red Hat, Inc.");
662 MODULE_LICENSE("GPL"); /* Actually dual-licensed, but it doesn't matter for */
663 

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