Version:  2.0.40 2.2.26 2.4.37 3.0 3.1 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

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

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