ia64/linux-2.6.18-xen.hg

view fs/romfs/inode.c @ 524:7f8b544237bf

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Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
author Keir Fraser <keir.fraser@citrix.com>
date Tue Apr 15 15:18:58 2008 +0100 (2008-04-15)
parents 831230e53067
children
line source
1 /*
2 * ROMFS file system, Linux implementation
3 *
4 * Copyright (C) 1997-1999 Janos Farkas <chexum@shadow.banki.hu>
5 *
6 * Using parts of the minix filesystem
7 * Copyright (C) 1991, 1992 Linus Torvalds
8 *
9 * and parts of the affs filesystem additionally
10 * Copyright (C) 1993 Ray Burr
11 * Copyright (C) 1996 Hans-Joachim Widmaier
12 *
13 * This program is free software; you can redistribute it and/or
14 * modify it under the terms of the GNU General Public License
15 * as published by the Free Software Foundation; either version
16 * 2 of the License, or (at your option) any later version.
17 *
18 * Changes
19 * Changed for 2.1.19 modules
20 * Jan 1997 Initial release
21 * Jun 1997 2.1.43+ changes
22 * Proper page locking in readpage
23 * Changed to work with 2.1.45+ fs
24 * Jul 1997 Fixed follow_link
25 * 2.1.47
26 * lookup shouldn't return -ENOENT
27 * from Horst von Brand:
28 * fail on wrong checksum
29 * double unlock_super was possible
30 * correct namelen for statfs
31 * spotted by Bill Hawes:
32 * readlink shouldn't iput()
33 * Jun 1998 2.1.106 from Avery Pennarun: glibc scandir()
34 * exposed a problem in readdir
35 * 2.1.107 code-freeze spellchecker run
36 * Aug 1998 2.1.118+ VFS changes
37 * Sep 1998 2.1.122 another VFS change (follow_link)
38 * Apr 1999 2.2.7 no more EBADF checking in
39 * lookup/readdir, use ERR_PTR
40 * Jun 1999 2.3.6 d_alloc_root use changed
41 * 2.3.9 clean up usage of ENOENT/negative
42 * dentries in lookup
43 * clean up page flags setting
44 * (error, uptodate, locking) in
45 * in readpage
46 * use init_special_inode for
47 * fifos/sockets (and streamline) in
48 * read_inode, fix _ops table order
49 * Aug 1999 2.3.16 __initfunc() => __init change
50 * Oct 1999 2.3.24 page->owner hack obsoleted
51 * Nov 1999 2.3.27 2.3.25+ page->offset => index change
52 */
54 /* todo:
55 * - see Documentation/filesystems/romfs.txt
56 * - use allocated, not stack memory for file names?
57 * - considering write access...
58 * - network (tftp) files?
59 * - merge back some _op tables
60 */
62 /*
63 * Sorry about some optimizations and for some goto's. I just wanted
64 * to squeeze some more bytes out of this code.. :)
65 */
67 #include <linux/module.h>
68 #include <linux/types.h>
69 #include <linux/errno.h>
70 #include <linux/slab.h>
71 #include <linux/romfs_fs.h>
72 #include <linux/fs.h>
73 #include <linux/init.h>
74 #include <linux/pagemap.h>
75 #include <linux/smp_lock.h>
76 #include <linux/buffer_head.h>
77 #include <linux/vfs.h>
79 #include <asm/uaccess.h>
81 struct romfs_inode_info {
82 unsigned long i_metasize; /* size of non-data area */
83 unsigned long i_dataoffset; /* from the start of fs */
84 struct inode vfs_inode;
85 };
87 /* instead of private superblock data */
88 static inline unsigned long romfs_maxsize(struct super_block *sb)
89 {
90 return (unsigned long)sb->s_fs_info;
91 }
93 static inline struct romfs_inode_info *ROMFS_I(struct inode *inode)
94 {
95 return list_entry(inode, struct romfs_inode_info, vfs_inode);
96 }
98 static __u32
99 romfs_checksum(void *data, int size)
100 {
101 __u32 sum;
102 __be32 *ptr;
104 sum = 0; ptr = data;
105 size>>=2;
106 while (size>0) {
107 sum += be32_to_cpu(*ptr++);
108 size--;
109 }
110 return sum;
111 }
113 static struct super_operations romfs_ops;
115 static int romfs_fill_super(struct super_block *s, void *data, int silent)
116 {
117 struct buffer_head *bh;
118 struct romfs_super_block *rsb;
119 struct inode *root;
120 int sz;
122 /* I would parse the options here, but there are none.. :) */
124 sb_set_blocksize(s, ROMBSIZE);
125 s->s_maxbytes = 0xFFFFFFFF;
127 bh = sb_bread(s, 0);
128 if (!bh) {
129 /* XXX merge with other printk? */
130 printk ("romfs: unable to read superblock\n");
131 goto outnobh;
132 }
134 rsb = (struct romfs_super_block *)bh->b_data;
135 sz = be32_to_cpu(rsb->size);
136 if (rsb->word0 != ROMSB_WORD0 || rsb->word1 != ROMSB_WORD1
137 || sz < ROMFH_SIZE) {
138 if (!silent)
139 printk ("VFS: Can't find a romfs filesystem on dev "
140 "%s.\n", s->s_id);
141 goto out;
142 }
143 if (romfs_checksum(rsb, min_t(int, sz, 512))) {
144 printk ("romfs: bad initial checksum on dev "
145 "%s.\n", s->s_id);
146 goto out;
147 }
149 s->s_magic = ROMFS_MAGIC;
150 s->s_fs_info = (void *)(long)sz;
152 s->s_flags |= MS_RDONLY;
154 /* Find the start of the fs */
155 sz = (ROMFH_SIZE +
156 strnlen(rsb->name, ROMFS_MAXFN) + 1 + ROMFH_PAD)
157 & ROMFH_MASK;
159 s->s_op = &romfs_ops;
160 root = iget(s, sz);
161 if (!root)
162 goto out;
164 s->s_root = d_alloc_root(root);
165 if (!s->s_root)
166 goto outiput;
168 brelse(bh);
169 return 0;
171 outiput:
172 iput(root);
173 out:
174 brelse(bh);
175 outnobh:
176 return -EINVAL;
177 }
179 /* That's simple too. */
181 static int
182 romfs_statfs(struct dentry *dentry, struct kstatfs *buf)
183 {
184 buf->f_type = ROMFS_MAGIC;
185 buf->f_bsize = ROMBSIZE;
186 buf->f_bfree = buf->f_bavail = buf->f_ffree;
187 buf->f_blocks = (romfs_maxsize(dentry->d_sb)+ROMBSIZE-1)>>ROMBSBITS;
188 buf->f_namelen = ROMFS_MAXFN;
189 return 0;
190 }
192 /* some helper routines */
194 static int
195 romfs_strnlen(struct inode *i, unsigned long offset, unsigned long count)
196 {
197 struct buffer_head *bh;
198 unsigned long avail, maxsize, res;
200 maxsize = romfs_maxsize(i->i_sb);
201 if (offset >= maxsize)
202 return -1;
204 /* strnlen is almost always valid */
205 if (count > maxsize || offset+count > maxsize)
206 count = maxsize-offset;
208 bh = sb_bread(i->i_sb, offset>>ROMBSBITS);
209 if (!bh)
210 return -1; /* error */
212 avail = ROMBSIZE - (offset & ROMBMASK);
213 maxsize = min_t(unsigned long, count, avail);
214 res = strnlen(((char *)bh->b_data)+(offset&ROMBMASK), maxsize);
215 brelse(bh);
217 if (res < maxsize)
218 return res; /* found all of it */
220 while (res < count) {
221 offset += maxsize;
223 bh = sb_bread(i->i_sb, offset>>ROMBSBITS);
224 if (!bh)
225 return -1;
226 maxsize = min_t(unsigned long, count - res, ROMBSIZE);
227 avail = strnlen(bh->b_data, maxsize);
228 res += avail;
229 brelse(bh);
230 if (avail < maxsize)
231 return res;
232 }
233 return res;
234 }
236 static int
237 romfs_copyfrom(struct inode *i, void *dest, unsigned long offset, unsigned long count)
238 {
239 struct buffer_head *bh;
240 unsigned long avail, maxsize, res;
242 maxsize = romfs_maxsize(i->i_sb);
243 if (offset >= maxsize || count > maxsize || offset+count>maxsize)
244 return -1;
246 bh = sb_bread(i->i_sb, offset>>ROMBSBITS);
247 if (!bh)
248 return -1; /* error */
250 avail = ROMBSIZE - (offset & ROMBMASK);
251 maxsize = min_t(unsigned long, count, avail);
252 memcpy(dest, ((char *)bh->b_data) + (offset & ROMBMASK), maxsize);
253 brelse(bh);
255 res = maxsize; /* all of it */
257 while (res < count) {
258 offset += maxsize;
259 dest += maxsize;
261 bh = sb_bread(i->i_sb, offset>>ROMBSBITS);
262 if (!bh)
263 return -1;
264 maxsize = min_t(unsigned long, count - res, ROMBSIZE);
265 memcpy(dest, bh->b_data, maxsize);
266 brelse(bh);
267 res += maxsize;
268 }
269 return res;
270 }
272 static unsigned char romfs_dtype_table[] = {
273 DT_UNKNOWN, DT_DIR, DT_REG, DT_LNK, DT_BLK, DT_CHR, DT_SOCK, DT_FIFO
274 };
276 static int
277 romfs_readdir(struct file *filp, void *dirent, filldir_t filldir)
278 {
279 struct inode *i = filp->f_dentry->d_inode;
280 struct romfs_inode ri;
281 unsigned long offset, maxoff;
282 int j, ino, nextfh;
283 int stored = 0;
284 char fsname[ROMFS_MAXFN]; /* XXX dynamic? */
286 lock_kernel();
288 maxoff = romfs_maxsize(i->i_sb);
290 offset = filp->f_pos;
291 if (!offset) {
292 offset = i->i_ino & ROMFH_MASK;
293 if (romfs_copyfrom(i, &ri, offset, ROMFH_SIZE) <= 0)
294 goto out;
295 offset = be32_to_cpu(ri.spec) & ROMFH_MASK;
296 }
298 /* Not really failsafe, but we are read-only... */
299 for(;;) {
300 if (!offset || offset >= maxoff) {
301 offset = maxoff;
302 filp->f_pos = offset;
303 goto out;
304 }
305 filp->f_pos = offset;
307 /* Fetch inode info */
308 if (romfs_copyfrom(i, &ri, offset, ROMFH_SIZE) <= 0)
309 goto out;
311 j = romfs_strnlen(i, offset+ROMFH_SIZE, sizeof(fsname)-1);
312 if (j < 0)
313 goto out;
315 fsname[j]=0;
316 romfs_copyfrom(i, fsname, offset+ROMFH_SIZE, j);
318 ino = offset;
319 nextfh = be32_to_cpu(ri.next);
320 if ((nextfh & ROMFH_TYPE) == ROMFH_HRD)
321 ino = be32_to_cpu(ri.spec);
322 if (filldir(dirent, fsname, j, offset, ino,
323 romfs_dtype_table[nextfh & ROMFH_TYPE]) < 0) {
324 goto out;
325 }
326 stored++;
327 offset = nextfh & ROMFH_MASK;
328 }
329 out:
330 unlock_kernel();
331 return stored;
332 }
334 static struct dentry *
335 romfs_lookup(struct inode *dir, struct dentry *dentry, struct nameidata *nd)
336 {
337 unsigned long offset, maxoff;
338 int fslen, res;
339 struct inode *inode;
340 char fsname[ROMFS_MAXFN]; /* XXX dynamic? */
341 struct romfs_inode ri;
342 const char *name; /* got from dentry */
343 int len;
345 res = -EACCES; /* placeholder for "no data here" */
346 offset = dir->i_ino & ROMFH_MASK;
347 lock_kernel();
348 if (romfs_copyfrom(dir, &ri, offset, ROMFH_SIZE) <= 0)
349 goto out;
351 maxoff = romfs_maxsize(dir->i_sb);
352 offset = be32_to_cpu(ri.spec) & ROMFH_MASK;
354 /* OK, now find the file whose name is in "dentry" in the
355 * directory specified by "dir". */
357 name = dentry->d_name.name;
358 len = dentry->d_name.len;
360 for(;;) {
361 if (!offset || offset >= maxoff)
362 goto out0;
363 if (romfs_copyfrom(dir, &ri, offset, ROMFH_SIZE) <= 0)
364 goto out;
366 /* try to match the first 16 bytes of name */
367 fslen = romfs_strnlen(dir, offset+ROMFH_SIZE, ROMFH_SIZE);
368 if (len < ROMFH_SIZE) {
369 if (len == fslen) {
370 /* both are shorter, and same size */
371 romfs_copyfrom(dir, fsname, offset+ROMFH_SIZE, len+1);
372 if (strncmp (name, fsname, len) == 0)
373 break;
374 }
375 } else if (fslen >= ROMFH_SIZE) {
376 /* both are longer; XXX optimize max size */
377 fslen = romfs_strnlen(dir, offset+ROMFH_SIZE, sizeof(fsname)-1);
378 if (len == fslen) {
379 romfs_copyfrom(dir, fsname, offset+ROMFH_SIZE, len+1);
380 if (strncmp(name, fsname, len) == 0)
381 break;
382 }
383 }
384 /* next entry */
385 offset = be32_to_cpu(ri.next) & ROMFH_MASK;
386 }
388 /* Hard link handling */
389 if ((be32_to_cpu(ri.next) & ROMFH_TYPE) == ROMFH_HRD)
390 offset = be32_to_cpu(ri.spec) & ROMFH_MASK;
392 if ((inode = iget(dir->i_sb, offset)))
393 goto outi;
395 /*
396 * it's a bit funky, _lookup needs to return an error code
397 * (negative) or a NULL, both as a dentry. ENOENT should not
398 * be returned, instead we need to create a negative dentry by
399 * d_add(dentry, NULL); and return 0 as no error.
400 * (Although as I see, it only matters on writable file
401 * systems).
402 */
404 out0: inode = NULL;
405 outi: res = 0;
406 d_add (dentry, inode);
408 out: unlock_kernel();
409 return ERR_PTR(res);
410 }
412 /*
413 * Ok, we do readpage, to be able to execute programs. Unfortunately,
414 * we can't use bmap, since we may have looser alignments.
415 */
417 static int
418 romfs_readpage(struct file *file, struct page * page)
419 {
420 struct inode *inode = page->mapping->host;
421 loff_t offset, avail, readlen;
422 void *buf;
423 int result = -EIO;
425 page_cache_get(page);
426 lock_kernel();
427 buf = kmap(page);
428 if (!buf)
429 goto err_out;
431 /* 32 bit warning -- but not for us :) */
432 offset = page_offset(page);
433 if (offset < i_size_read(inode)) {
434 avail = inode->i_size-offset;
435 readlen = min_t(unsigned long, avail, PAGE_SIZE);
436 if (romfs_copyfrom(inode, buf, ROMFS_I(inode)->i_dataoffset+offset, readlen) == readlen) {
437 if (readlen < PAGE_SIZE) {
438 memset(buf + readlen,0,PAGE_SIZE-readlen);
439 }
440 SetPageUptodate(page);
441 result = 0;
442 }
443 }
444 if (result) {
445 memset(buf, 0, PAGE_SIZE);
446 SetPageError(page);
447 }
448 flush_dcache_page(page);
450 unlock_page(page);
452 kunmap(page);
453 err_out:
454 page_cache_release(page);
455 unlock_kernel();
457 return result;
458 }
460 /* Mapping from our types to the kernel */
462 static const struct address_space_operations romfs_aops = {
463 .readpage = romfs_readpage
464 };
466 static const struct file_operations romfs_dir_operations = {
467 .read = generic_read_dir,
468 .readdir = romfs_readdir,
469 };
471 static struct inode_operations romfs_dir_inode_operations = {
472 .lookup = romfs_lookup,
473 };
475 static mode_t romfs_modemap[] =
476 {
477 0, S_IFDIR+0644, S_IFREG+0644, S_IFLNK+0777,
478 S_IFBLK+0600, S_IFCHR+0600, S_IFSOCK+0644, S_IFIFO+0644
479 };
481 static void
482 romfs_read_inode(struct inode *i)
483 {
484 int nextfh, ino;
485 struct romfs_inode ri;
487 ino = i->i_ino & ROMFH_MASK;
488 i->i_mode = 0;
490 /* Loop for finding the real hard link */
491 for(;;) {
492 if (romfs_copyfrom(i, &ri, ino, ROMFH_SIZE) <= 0) {
493 printk("romfs: read error for inode 0x%x\n", ino);
494 return;
495 }
496 /* XXX: do romfs_checksum here too (with name) */
498 nextfh = be32_to_cpu(ri.next);
499 if ((nextfh & ROMFH_TYPE) != ROMFH_HRD)
500 break;
502 ino = be32_to_cpu(ri.spec) & ROMFH_MASK;
503 }
505 i->i_nlink = 1; /* Hard to decide.. */
506 i->i_size = be32_to_cpu(ri.size);
507 i->i_mtime.tv_sec = i->i_atime.tv_sec = i->i_ctime.tv_sec = 0;
508 i->i_mtime.tv_nsec = i->i_atime.tv_nsec = i->i_ctime.tv_nsec = 0;
509 i->i_uid = i->i_gid = 0;
511 /* Precalculate the data offset */
512 ino = romfs_strnlen(i, ino+ROMFH_SIZE, ROMFS_MAXFN);
513 if (ino >= 0)
514 ino = ((ROMFH_SIZE+ino+1+ROMFH_PAD)&ROMFH_MASK);
515 else
516 ino = 0;
518 ROMFS_I(i)->i_metasize = ino;
519 ROMFS_I(i)->i_dataoffset = ino+(i->i_ino&ROMFH_MASK);
521 /* Compute permissions */
522 ino = romfs_modemap[nextfh & ROMFH_TYPE];
523 /* only "normal" files have ops */
524 switch (nextfh & ROMFH_TYPE) {
525 case 1:
526 i->i_size = ROMFS_I(i)->i_metasize;
527 i->i_op = &romfs_dir_inode_operations;
528 i->i_fop = &romfs_dir_operations;
529 if (nextfh & ROMFH_EXEC)
530 ino |= S_IXUGO;
531 i->i_mode = ino;
532 break;
533 case 2:
534 i->i_fop = &generic_ro_fops;
535 i->i_data.a_ops = &romfs_aops;
536 if (nextfh & ROMFH_EXEC)
537 ino |= S_IXUGO;
538 i->i_mode = ino;
539 break;
540 case 3:
541 i->i_op = &page_symlink_inode_operations;
542 i->i_data.a_ops = &romfs_aops;
543 i->i_mode = ino | S_IRWXUGO;
544 break;
545 default:
546 /* depending on MBZ for sock/fifos */
547 nextfh = be32_to_cpu(ri.spec);
548 init_special_inode(i, ino,
549 MKDEV(nextfh>>16,nextfh&0xffff));
550 }
551 }
553 static kmem_cache_t * romfs_inode_cachep;
555 static struct inode *romfs_alloc_inode(struct super_block *sb)
556 {
557 struct romfs_inode_info *ei;
558 ei = (struct romfs_inode_info *)kmem_cache_alloc(romfs_inode_cachep, SLAB_KERNEL);
559 if (!ei)
560 return NULL;
561 return &ei->vfs_inode;
562 }
564 static void romfs_destroy_inode(struct inode *inode)
565 {
566 kmem_cache_free(romfs_inode_cachep, ROMFS_I(inode));
567 }
569 static void init_once(void * foo, kmem_cache_t * cachep, unsigned long flags)
570 {
571 struct romfs_inode_info *ei = (struct romfs_inode_info *) foo;
573 if ((flags & (SLAB_CTOR_VERIFY|SLAB_CTOR_CONSTRUCTOR)) ==
574 SLAB_CTOR_CONSTRUCTOR)
575 inode_init_once(&ei->vfs_inode);
576 }
578 static int init_inodecache(void)
579 {
580 romfs_inode_cachep = kmem_cache_create("romfs_inode_cache",
581 sizeof(struct romfs_inode_info),
582 0, (SLAB_RECLAIM_ACCOUNT|
583 SLAB_MEM_SPREAD),
584 init_once, NULL);
585 if (romfs_inode_cachep == NULL)
586 return -ENOMEM;
587 return 0;
588 }
590 static void destroy_inodecache(void)
591 {
592 if (kmem_cache_destroy(romfs_inode_cachep))
593 printk(KERN_INFO "romfs_inode_cache: not all structures were freed\n");
594 }
596 static int romfs_remount(struct super_block *sb, int *flags, char *data)
597 {
598 *flags |= MS_RDONLY;
599 return 0;
600 }
602 static struct super_operations romfs_ops = {
603 .alloc_inode = romfs_alloc_inode,
604 .destroy_inode = romfs_destroy_inode,
605 .read_inode = romfs_read_inode,
606 .statfs = romfs_statfs,
607 .remount_fs = romfs_remount,
608 };
610 static int romfs_get_sb(struct file_system_type *fs_type,
611 int flags, const char *dev_name, void *data, struct vfsmount *mnt)
612 {
613 return get_sb_bdev(fs_type, flags, dev_name, data, romfs_fill_super,
614 mnt);
615 }
617 static struct file_system_type romfs_fs_type = {
618 .owner = THIS_MODULE,
619 .name = "romfs",
620 .get_sb = romfs_get_sb,
621 .kill_sb = kill_block_super,
622 .fs_flags = FS_REQUIRES_DEV,
623 };
625 static int __init init_romfs_fs(void)
626 {
627 int err = init_inodecache();
628 if (err)
629 goto out1;
630 err = register_filesystem(&romfs_fs_type);
631 if (err)
632 goto out;
633 return 0;
634 out:
635 destroy_inodecache();
636 out1:
637 return err;
638 }
640 static void __exit exit_romfs_fs(void)
641 {
642 unregister_filesystem(&romfs_fs_type);
643 destroy_inodecache();
644 }
646 /* Yes, works even as a module... :) */
648 module_init(init_romfs_fs)
649 module_exit(exit_romfs_fs)
650 MODULE_LICENSE("GPL");