Version:  2.0.40 2.2.26 2.4.37 3.13 3.14 3.15 3.16 3.17 3.18 3.19 4.0 4.1 4.2 4.3 4.4 4.5 4.6 4.7 4.8 4.9 4.10

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 <linux/major.h>
 78 #include "internal.h"
 79 
 80 static struct kmem_cache *romfs_inode_cachep;
 81 
 82 static const umode_t romfs_modemap[8] = {
 83         0,                      /* hard link */
 84         S_IFDIR  | 0644,        /* directory */
 85         S_IFREG  | 0644,        /* regular file */
 86         S_IFLNK  | 0777,        /* symlink */
 87         S_IFBLK  | 0600,        /* blockdev */
 88         S_IFCHR  | 0600,        /* chardev */
 89         S_IFSOCK | 0644,        /* socket */
 90         S_IFIFO  | 0644         /* FIFO */
 91 };
 92 
 93 static const unsigned char romfs_dtype_table[] = {
 94         DT_UNKNOWN, DT_DIR, DT_REG, DT_LNK, DT_BLK, DT_CHR, DT_SOCK, DT_FIFO
 95 };
 96 
 97 static struct inode *romfs_iget(struct super_block *sb, unsigned long pos);
 98 
 99 /*
100  * read a page worth of data from the image
101  */
102 static int romfs_readpage(struct file *file, struct page *page)
103 {
104         struct inode *inode = page->mapping->host;
105         loff_t offset, size;
106         unsigned long fillsize, pos;
107         void *buf;
108         int ret;
109 
110         buf = kmap(page);
111         if (!buf)
112                 return -ENOMEM;
113 
114         /* 32 bit warning -- but not for us :) */
115         offset = page_offset(page);
116         size = i_size_read(inode);
117         fillsize = 0;
118         ret = 0;
119         if (offset < size) {
120                 size -= offset;
121                 fillsize = size > PAGE_SIZE ? PAGE_SIZE : size;
122 
123                 pos = ROMFS_I(inode)->i_dataoffset + offset;
124 
125                 ret = romfs_dev_read(inode->i_sb, pos, buf, fillsize);
126                 if (ret < 0) {
127                         SetPageError(page);
128                         fillsize = 0;
129                         ret = -EIO;
130                 }
131         }
132 
133         if (fillsize < PAGE_SIZE)
134                 memset(buf + fillsize, 0, PAGE_SIZE - fillsize);
135         if (ret == 0)
136                 SetPageUptodate(page);
137 
138         flush_dcache_page(page);
139         kunmap(page);
140         unlock_page(page);
141         return ret;
142 }
143 
144 static const struct address_space_operations romfs_aops = {
145         .readpage       = romfs_readpage
146 };
147 
148 /*
149  * read the entries from a directory
150  */
151 static int romfs_readdir(struct file *file, struct dir_context *ctx)
152 {
153         struct inode *i = file_inode(file);
154         struct romfs_inode ri;
155         unsigned long offset, maxoff;
156         int j, ino, nextfh;
157         char fsname[ROMFS_MAXFN];       /* XXX dynamic? */
158         int ret;
159 
160         maxoff = romfs_maxsize(i->i_sb);
161 
162         offset = ctx->pos;
163         if (!offset) {
164                 offset = i->i_ino & ROMFH_MASK;
165                 ret = romfs_dev_read(i->i_sb, offset, &ri, ROMFH_SIZE);
166                 if (ret < 0)
167                         goto out;
168                 offset = be32_to_cpu(ri.spec) & ROMFH_MASK;
169         }
170 
171         /* Not really failsafe, but we are read-only... */
172         for (;;) {
173                 if (!offset || offset >= maxoff) {
174                         offset = maxoff;
175                         ctx->pos = offset;
176                         goto out;
177                 }
178                 ctx->pos = offset;
179 
180                 /* Fetch inode info */
181                 ret = romfs_dev_read(i->i_sb, offset, &ri, ROMFH_SIZE);
182                 if (ret < 0)
183                         goto out;
184 
185                 j = romfs_dev_strnlen(i->i_sb, offset + ROMFH_SIZE,
186                                       sizeof(fsname) - 1);
187                 if (j < 0)
188                         goto out;
189 
190                 ret = romfs_dev_read(i->i_sb, offset + ROMFH_SIZE, fsname, j);
191                 if (ret < 0)
192                         goto out;
193                 fsname[j] = '\0';
194 
195                 ino = offset;
196                 nextfh = be32_to_cpu(ri.next);
197                 if ((nextfh & ROMFH_TYPE) == ROMFH_HRD)
198                         ino = be32_to_cpu(ri.spec);
199                 if (!dir_emit(ctx, fsname, j, ino,
200                             romfs_dtype_table[nextfh & ROMFH_TYPE]))
201                         goto out;
202 
203                 offset = nextfh & ROMFH_MASK;
204         }
205 out:
206         return 0;
207 }
208 
209 /*
210  * look up an entry in a directory
211  */
212 static struct dentry *romfs_lookup(struct inode *dir, struct dentry *dentry,
213                                    unsigned int flags)
214 {
215         unsigned long offset, maxoff;
216         struct inode *inode;
217         struct romfs_inode ri;
218         const char *name;               /* got from dentry */
219         int len, ret;
220 
221         offset = dir->i_ino & ROMFH_MASK;
222         ret = romfs_dev_read(dir->i_sb, offset, &ri, ROMFH_SIZE);
223         if (ret < 0)
224                 goto error;
225 
226         /* search all the file entries in the list starting from the one
227          * pointed to by the directory's special data */
228         maxoff = romfs_maxsize(dir->i_sb);
229         offset = be32_to_cpu(ri.spec) & ROMFH_MASK;
230 
231         name = dentry->d_name.name;
232         len = dentry->d_name.len;
233 
234         for (;;) {
235                 if (!offset || offset >= maxoff)
236                         goto out0;
237 
238                 ret = romfs_dev_read(dir->i_sb, offset, &ri, sizeof(ri));
239                 if (ret < 0)
240                         goto error;
241 
242                 /* try to match the first 16 bytes of name */
243                 ret = romfs_dev_strcmp(dir->i_sb, offset + ROMFH_SIZE, name,
244                                        len);
245                 if (ret < 0)
246                         goto error;
247                 if (ret == 1)
248                         break;
249 
250                 /* next entry */
251                 offset = be32_to_cpu(ri.next) & ROMFH_MASK;
252         }
253 
254         /* Hard link handling */
255         if ((be32_to_cpu(ri.next) & ROMFH_TYPE) == ROMFH_HRD)
256                 offset = be32_to_cpu(ri.spec) & ROMFH_MASK;
257 
258         inode = romfs_iget(dir->i_sb, offset);
259         if (IS_ERR(inode)) {
260                 ret = PTR_ERR(inode);
261                 goto error;
262         }
263         goto outi;
264 
265         /*
266          * it's a bit funky, _lookup needs to return an error code
267          * (negative) or a NULL, both as a dentry.  ENOENT should not
268          * be returned, instead we need to create a negative dentry by
269          * d_add(dentry, NULL); and return 0 as no error.
270          * (Although as I see, it only matters on writable file
271          * systems).
272          */
273 out0:
274         inode = NULL;
275 outi:
276         d_add(dentry, inode);
277         ret = 0;
278 error:
279         return ERR_PTR(ret);
280 }
281 
282 static const struct file_operations romfs_dir_operations = {
283         .read           = generic_read_dir,
284         .iterate_shared = romfs_readdir,
285         .llseek         = generic_file_llseek,
286 };
287 
288 static const struct inode_operations romfs_dir_inode_operations = {
289         .lookup         = romfs_lookup,
290 };
291 
292 /*
293  * get a romfs inode based on its position in the image (which doubles as the
294  * inode number)
295  */
296 static struct inode *romfs_iget(struct super_block *sb, unsigned long pos)
297 {
298         struct romfs_inode_info *inode;
299         struct romfs_inode ri;
300         struct inode *i;
301         unsigned long nlen;
302         unsigned nextfh;
303         int ret;
304         umode_t mode;
305 
306         /* we might have to traverse a chain of "hard link" file entries to get
307          * to the actual file */
308         for (;;) {
309                 ret = romfs_dev_read(sb, pos, &ri, sizeof(ri));
310                 if (ret < 0)
311                         goto error;
312 
313                 /* XXX: do romfs_checksum here too (with name) */
314 
315                 nextfh = be32_to_cpu(ri.next);
316                 if ((nextfh & ROMFH_TYPE) != ROMFH_HRD)
317                         break;
318 
319                 pos = be32_to_cpu(ri.spec) & ROMFH_MASK;
320         }
321 
322         /* determine the length of the filename */
323         nlen = romfs_dev_strnlen(sb, pos + ROMFH_SIZE, ROMFS_MAXFN);
324         if (IS_ERR_VALUE(nlen))
325                 goto eio;
326 
327         /* get an inode for this image position */
328         i = iget_locked(sb, pos);
329         if (!i)
330                 return ERR_PTR(-ENOMEM);
331 
332         if (!(i->i_state & I_NEW))
333                 return i;
334 
335         /* precalculate the data offset */
336         inode = ROMFS_I(i);
337         inode->i_metasize = (ROMFH_SIZE + nlen + 1 + ROMFH_PAD) & ROMFH_MASK;
338         inode->i_dataoffset = pos + inode->i_metasize;
339 
340         set_nlink(i, 1);                /* Hard to decide.. */
341         i->i_size = be32_to_cpu(ri.size);
342         i->i_mtime.tv_sec = i->i_atime.tv_sec = i->i_ctime.tv_sec = 0;
343         i->i_mtime.tv_nsec = i->i_atime.tv_nsec = i->i_ctime.tv_nsec = 0;
344 
345         /* set up mode and ops */
346         mode = romfs_modemap[nextfh & ROMFH_TYPE];
347 
348         switch (nextfh & ROMFH_TYPE) {
349         case ROMFH_DIR:
350                 i->i_size = ROMFS_I(i)->i_metasize;
351                 i->i_op = &romfs_dir_inode_operations;
352                 i->i_fop = &romfs_dir_operations;
353                 if (nextfh & ROMFH_EXEC)
354                         mode |= S_IXUGO;
355                 break;
356         case ROMFH_REG:
357                 i->i_fop = &romfs_ro_fops;
358                 i->i_data.a_ops = &romfs_aops;
359                 if (nextfh & ROMFH_EXEC)
360                         mode |= S_IXUGO;
361                 break;
362         case ROMFH_SYM:
363                 i->i_op = &page_symlink_inode_operations;
364                 inode_nohighmem(i);
365                 i->i_data.a_ops = &romfs_aops;
366                 mode |= S_IRWXUGO;
367                 break;
368         default:
369                 /* depending on MBZ for sock/fifos */
370                 nextfh = be32_to_cpu(ri.spec);
371                 init_special_inode(i, mode, MKDEV(nextfh >> 16,
372                                                   nextfh & 0xffff));
373                 break;
374         }
375 
376         i->i_mode = mode;
377 
378         unlock_new_inode(i);
379         return i;
380 
381 eio:
382         ret = -EIO;
383 error:
384         pr_err("read error for inode 0x%lx\n", pos);
385         return ERR_PTR(ret);
386 }
387 
388 /*
389  * allocate a new inode
390  */
391 static struct inode *romfs_alloc_inode(struct super_block *sb)
392 {
393         struct romfs_inode_info *inode;
394 
395         inode = kmem_cache_alloc(romfs_inode_cachep, GFP_KERNEL);
396         return inode ? &inode->vfs_inode : NULL;
397 }
398 
399 /*
400  * return a spent inode to the slab cache
401  */
402 static void romfs_i_callback(struct rcu_head *head)
403 {
404         struct inode *inode = container_of(head, struct inode, i_rcu);
405 
406         kmem_cache_free(romfs_inode_cachep, ROMFS_I(inode));
407 }
408 
409 static void romfs_destroy_inode(struct inode *inode)
410 {
411         call_rcu(&inode->i_rcu, romfs_i_callback);
412 }
413 
414 /*
415  * get filesystem statistics
416  */
417 static int romfs_statfs(struct dentry *dentry, struct kstatfs *buf)
418 {
419         struct super_block *sb = dentry->d_sb;
420         u64 id = 0;
421 
422         /* When calling huge_encode_dev(),
423          * use sb->s_bdev->bd_dev when,
424          *   - CONFIG_ROMFS_ON_BLOCK defined
425          * use sb->s_dev when,
426          *   - CONFIG_ROMFS_ON_BLOCK undefined and
427          *   - CONFIG_ROMFS_ON_MTD defined
428          * leave id as 0 when,
429          *   - CONFIG_ROMFS_ON_BLOCK undefined and
430          *   - CONFIG_ROMFS_ON_MTD undefined
431          */
432         if (sb->s_bdev)
433                 id = huge_encode_dev(sb->s_bdev->bd_dev);
434         else if (sb->s_dev)
435                 id = huge_encode_dev(sb->s_dev);
436 
437         buf->f_type = ROMFS_MAGIC;
438         buf->f_namelen = ROMFS_MAXFN;
439         buf->f_bsize = ROMBSIZE;
440         buf->f_bfree = buf->f_bavail = buf->f_ffree;
441         buf->f_blocks =
442                 (romfs_maxsize(dentry->d_sb) + ROMBSIZE - 1) >> ROMBSBITS;
443         buf->f_fsid.val[0] = (u32)id;
444         buf->f_fsid.val[1] = (u32)(id >> 32);
445         return 0;
446 }
447 
448 /*
449  * remounting must involve read-only
450  */
451 static int romfs_remount(struct super_block *sb, int *flags, char *data)
452 {
453         sync_filesystem(sb);
454         *flags |= MS_RDONLY;
455         return 0;
456 }
457 
458 static const struct super_operations romfs_super_ops = {
459         .alloc_inode    = romfs_alloc_inode,
460         .destroy_inode  = romfs_destroy_inode,
461         .statfs         = romfs_statfs,
462         .remount_fs     = romfs_remount,
463 };
464 
465 /*
466  * checksum check on part of a romfs filesystem
467  */
468 static __u32 romfs_checksum(const void *data, int size)
469 {
470         const __be32 *ptr = data;
471         __u32 sum;
472 
473         sum = 0;
474         size >>= 2;
475         while (size > 0) {
476                 sum += be32_to_cpu(*ptr++);
477                 size--;
478         }
479         return sum;
480 }
481 
482 /*
483  * fill in the superblock
484  */
485 static int romfs_fill_super(struct super_block *sb, void *data, int silent)
486 {
487         struct romfs_super_block *rsb;
488         struct inode *root;
489         unsigned long pos, img_size;
490         const char *storage;
491         size_t len;
492         int ret;
493 
494 #ifdef CONFIG_BLOCK
495         if (!sb->s_mtd) {
496                 sb_set_blocksize(sb, ROMBSIZE);
497         } else {
498                 sb->s_blocksize = ROMBSIZE;
499                 sb->s_blocksize_bits = blksize_bits(ROMBSIZE);
500         }
501 #endif
502 
503         sb->s_maxbytes = 0xFFFFFFFF;
504         sb->s_magic = ROMFS_MAGIC;
505         sb->s_flags |= MS_RDONLY | MS_NOATIME;
506         sb->s_op = &romfs_super_ops;
507 
508 #ifdef CONFIG_ROMFS_ON_MTD
509         /* Use same dev ID from the underlying mtdblock device */
510         if (sb->s_mtd)
511                 sb->s_dev = MKDEV(MTD_BLOCK_MAJOR, sb->s_mtd->index);
512 #endif
513         /* read the image superblock and check it */
514         rsb = kmalloc(512, GFP_KERNEL);
515         if (!rsb)
516                 return -ENOMEM;
517 
518         sb->s_fs_info = (void *) 512;
519         ret = romfs_dev_read(sb, 0, rsb, 512);
520         if (ret < 0)
521                 goto error_rsb;
522 
523         img_size = be32_to_cpu(rsb->size);
524 
525         if (sb->s_mtd && img_size > sb->s_mtd->size)
526                 goto error_rsb_inval;
527 
528         sb->s_fs_info = (void *) img_size;
529 
530         if (rsb->word0 != ROMSB_WORD0 || rsb->word1 != ROMSB_WORD1 ||
531             img_size < ROMFH_SIZE) {
532                 if (!silent)
533                         pr_warn("VFS: Can't find a romfs filesystem on dev %s.\n",
534                                sb->s_id);
535                 goto error_rsb_inval;
536         }
537 
538         if (romfs_checksum(rsb, min_t(size_t, img_size, 512))) {
539                 pr_err("bad initial checksum on dev %s.\n", sb->s_id);
540                 goto error_rsb_inval;
541         }
542 
543         storage = sb->s_mtd ? "MTD" : "the block layer";
544 
545         len = strnlen(rsb->name, ROMFS_MAXFN);
546         if (!silent)
547                 pr_notice("Mounting image '%*.*s' through %s\n",
548                           (unsigned) len, (unsigned) len, rsb->name, storage);
549 
550         kfree(rsb);
551         rsb = NULL;
552 
553         /* find the root directory */
554         pos = (ROMFH_SIZE + len + 1 + ROMFH_PAD) & ROMFH_MASK;
555 
556         root = romfs_iget(sb, pos);
557         if (IS_ERR(root))
558                 return PTR_ERR(root);
559 
560         sb->s_root = d_make_root(root);
561         if (!sb->s_root)
562                 return -ENOMEM;
563 
564         return 0;
565 
566 error_rsb_inval:
567         ret = -EINVAL;
568 error_rsb:
569         kfree(rsb);
570         return ret;
571 }
572 
573 /*
574  * get a superblock for mounting
575  */
576 static struct dentry *romfs_mount(struct file_system_type *fs_type,
577                         int flags, const char *dev_name,
578                         void *data)
579 {
580         struct dentry *ret = ERR_PTR(-EINVAL);
581 
582 #ifdef CONFIG_ROMFS_ON_MTD
583         ret = mount_mtd(fs_type, flags, dev_name, data, romfs_fill_super);
584 #endif
585 #ifdef CONFIG_ROMFS_ON_BLOCK
586         if (ret == ERR_PTR(-EINVAL))
587                 ret = mount_bdev(fs_type, flags, dev_name, data,
588                                   romfs_fill_super);
589 #endif
590         return ret;
591 }
592 
593 /*
594  * destroy a romfs superblock in the appropriate manner
595  */
596 static void romfs_kill_sb(struct super_block *sb)
597 {
598 #ifdef CONFIG_ROMFS_ON_MTD
599         if (sb->s_mtd) {
600                 kill_mtd_super(sb);
601                 return;
602         }
603 #endif
604 #ifdef CONFIG_ROMFS_ON_BLOCK
605         if (sb->s_bdev) {
606                 kill_block_super(sb);
607                 return;
608         }
609 #endif
610 }
611 
612 static struct file_system_type romfs_fs_type = {
613         .owner          = THIS_MODULE,
614         .name           = "romfs",
615         .mount          = romfs_mount,
616         .kill_sb        = romfs_kill_sb,
617         .fs_flags       = FS_REQUIRES_DEV,
618 };
619 MODULE_ALIAS_FS("romfs");
620 
621 /*
622  * inode storage initialiser
623  */
624 static void romfs_i_init_once(void *_inode)
625 {
626         struct romfs_inode_info *inode = _inode;
627 
628         inode_init_once(&inode->vfs_inode);
629 }
630 
631 /*
632  * romfs module initialisation
633  */
634 static int __init init_romfs_fs(void)
635 {
636         int ret;
637 
638         pr_info("ROMFS MTD (C) 2007 Red Hat, Inc.\n");
639 
640         romfs_inode_cachep =
641                 kmem_cache_create("romfs_i",
642                                   sizeof(struct romfs_inode_info), 0,
643                                   SLAB_RECLAIM_ACCOUNT | SLAB_MEM_SPREAD |
644                                   SLAB_ACCOUNT, romfs_i_init_once);
645 
646         if (!romfs_inode_cachep) {
647                 pr_err("Failed to initialise inode cache\n");
648                 return -ENOMEM;
649         }
650         ret = register_filesystem(&romfs_fs_type);
651         if (ret) {
652                 pr_err("Failed to register filesystem\n");
653                 goto error_register;
654         }
655         return 0;
656 
657 error_register:
658         kmem_cache_destroy(romfs_inode_cachep);
659         return ret;
660 }
661 
662 /*
663  * romfs module removal
664  */
665 static void __exit exit_romfs_fs(void)
666 {
667         unregister_filesystem(&romfs_fs_type);
668         /*
669          * Make sure all delayed rcu free inodes are flushed before we
670          * destroy cache.
671          */
672         rcu_barrier();
673         kmem_cache_destroy(romfs_inode_cachep);
674 }
675 
676 module_init(init_romfs_fs);
677 module_exit(exit_romfs_fs);
678 
679 MODULE_DESCRIPTION("Direct-MTD Capable RomFS");
680 MODULE_AUTHOR("Red Hat, Inc.");
681 MODULE_LICENSE("GPL"); /* Actually dual-licensed, but it doesn't matter for */
682 

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