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/fs/romfs/super.c

https://bitbucket.org/cyanogenmod/android_kernel_asus_tf300t
C | 662 lines | 441 code | 92 blank | 129 comment | 61 complexity | f2d878120c83f96156422aeb324e8f00 MD5 | raw file
Possible License(s): LGPL-2.0, AGPL-1.0, GPL-2.0
  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
 77static struct kmem_cache *romfs_inode_cachep;
 78
 79static 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
 90static 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
 94static struct inode *romfs_iget(struct super_block *sb, unsigned long pos);
 95
 96/*
 97 * read a page worth of data from the image
 98 */
 99static 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
141static const struct address_space_operations romfs_aops = {
142	.readpage	= romfs_readpage
143};
144
145/*
146 * read the entries from a directory
147 */
148static int romfs_readdir(struct file *filp, void *dirent, filldir_t filldir)
149{
150	struct inode *i = filp->f_dentry->d_inode;
151	struct romfs_inode ri;
152	unsigned long offset, maxoff;
153	int j, ino, nextfh;
154	int stored = 0;
155	char fsname[ROMFS_MAXFN];	/* XXX dynamic? */
156	int ret;
157
158	maxoff = romfs_maxsize(i->i_sb);
159
160	offset = filp->f_pos;
161	if (!offset) {
162		offset = i->i_ino & ROMFH_MASK;
163		ret = romfs_dev_read(i->i_sb, offset, &ri, ROMFH_SIZE);
164		if (ret < 0)
165			goto out;
166		offset = be32_to_cpu(ri.spec) & ROMFH_MASK;
167	}
168
169	/* Not really failsafe, but we are read-only... */
170	for (;;) {
171		if (!offset || offset >= maxoff) {
172			offset = maxoff;
173			filp->f_pos = offset;
174			goto out;
175		}
176		filp->f_pos = offset;
177
178		/* Fetch inode info */
179		ret = romfs_dev_read(i->i_sb, offset, &ri, ROMFH_SIZE);
180		if (ret < 0)
181			goto out;
182
183		j = romfs_dev_strnlen(i->i_sb, offset + ROMFH_SIZE,
184				      sizeof(fsname) - 1);
185		if (j < 0)
186			goto out;
187
188		ret = romfs_dev_read(i->i_sb, offset + ROMFH_SIZE, fsname, j);
189		if (ret < 0)
190			goto out;
191		fsname[j] = '\0';
192
193		ino = offset;
194		nextfh = be32_to_cpu(ri.next);
195		if ((nextfh & ROMFH_TYPE) == ROMFH_HRD)
196			ino = be32_to_cpu(ri.spec);
197		if (filldir(dirent, fsname, j, offset, ino,
198			    romfs_dtype_table[nextfh & ROMFH_TYPE]) < 0)
199			goto out;
200
201		stored++;
202		offset = nextfh & ROMFH_MASK;
203	}
204
205out:
206	return stored;
207}
208
209/*
210 * look up an entry in a directory
211 */
212static struct dentry *romfs_lookup(struct inode *dir, struct dentry *dentry,
213				   struct nameidata *nd)
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	 */
273out0:
274	inode = NULL;
275outi:
276	d_add(dentry, inode);
277	ret = 0;
278error:
279	return ERR_PTR(ret);
280}
281
282static const struct file_operations romfs_dir_operations = {
283	.read		= generic_read_dir,
284	.readdir	= romfs_readdir,
285	.llseek		= default_llseek,
286};
287
288static 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 */
296static 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	i->i_nlink = 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 (i->i_sb->s_mtd)
360			i->i_data.backing_dev_info =
361				i->i_sb->s_mtd->backing_dev_info;
362		if (nextfh & ROMFH_EXEC)
363			mode |= S_IXUGO;
364		break;
365	case ROMFH_SYM:
366		i->i_op = &page_symlink_inode_operations;
367		i->i_data.a_ops = &romfs_aops;
368		mode |= S_IRWXUGO;
369		break;
370	default:
371		/* depending on MBZ for sock/fifos */
372		nextfh = be32_to_cpu(ri.spec);
373		init_special_inode(i, mode, MKDEV(nextfh >> 16,
374						  nextfh & 0xffff));
375		break;
376	}
377
378	i->i_mode = mode;
379
380	unlock_new_inode(i);
381	return i;
382
383eio:
384	ret = -EIO;
385error:
386	printk(KERN_ERR "ROMFS: read error for inode 0x%lx\n", pos);
387	return ERR_PTR(ret);
388}
389
390/*
391 * allocate a new inode
392 */
393static struct inode *romfs_alloc_inode(struct super_block *sb)
394{
395	struct romfs_inode_info *inode;
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 */
403static void romfs_i_callback(struct rcu_head *head)
404{
405	struct inode *inode = container_of(head, struct inode, i_rcu);
406	INIT_LIST_HEAD(&inode->i_dentry);
407	kmem_cache_free(romfs_inode_cachep, ROMFS_I(inode));
408}
409
410static 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 */
418static 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 */
437static int romfs_remount(struct super_block *sb, int *flags, char *data)
438{
439	*flags |= MS_RDONLY;
440	return 0;
441}
442
443static const struct super_operations romfs_super_ops = {
444	.alloc_inode	= romfs_alloc_inode,
445	.destroy_inode	= romfs_destroy_inode,
446	.statfs		= romfs_statfs,
447	.remount_fs	= romfs_remount,
448};
449
450/*
451 * checksum check on part of a romfs filesystem
452 */
453static __u32 romfs_checksum(const void *data, int size)
454{
455	const __be32 *ptr = data;
456	__u32 sum;
457
458	sum = 0;
459	size >>= 2;
460	while (size > 0) {
461		sum += be32_to_cpu(*ptr++);
462		size--;
463	}
464	return sum;
465}
466
467/*
468 * fill in the superblock
469 */
470static int romfs_fill_super(struct super_block *sb, void *data, int silent)
471{
472	struct romfs_super_block *rsb;
473	struct inode *root;
474	unsigned long pos, img_size;
475	const char *storage;
476	size_t len;
477	int ret;
478
479#ifdef CONFIG_BLOCK
480	if (!sb->s_mtd) {
481		sb_set_blocksize(sb, ROMBSIZE);
482	} else {
483		sb->s_blocksize = ROMBSIZE;
484		sb->s_blocksize_bits = blksize_bits(ROMBSIZE);
485	}
486#endif
487
488	sb->s_maxbytes = 0xFFFFFFFF;
489	sb->s_magic = ROMFS_MAGIC;
490	sb->s_flags |= MS_RDONLY | MS_NOATIME;
491	sb->s_op = &romfs_super_ops;
492
493	/* read the image superblock and check it */
494	rsb = kmalloc(512, GFP_KERNEL);
495	if (!rsb)
496		return -ENOMEM;
497
498	sb->s_fs_info = (void *) 512;
499	ret = romfs_dev_read(sb, 0, rsb, 512);
500	if (ret < 0)
501		goto error_rsb;
502
503	img_size = be32_to_cpu(rsb->size);
504
505	if (sb->s_mtd && img_size > sb->s_mtd->size)
506		goto error_rsb_inval;
507
508	sb->s_fs_info = (void *) img_size;
509
510	if (rsb->word0 != ROMSB_WORD0 || rsb->word1 != ROMSB_WORD1 ||
511	    img_size < ROMFH_SIZE) {
512		if (!silent)
513			printk(KERN_WARNING "VFS:"
514			       " 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		printk(KERN_ERR "ROMFS: bad initial checksum on dev %s.\n",
521		       sb->s_id);
522		goto error_rsb_inval;
523	}
524
525	storage = sb->s_mtd ? "MTD" : "the block layer";
526
527	len = strnlen(rsb->name, ROMFS_MAXFN);
528	if (!silent)
529		printk(KERN_NOTICE "ROMFS: Mounting image '%*.*s' through %s\n",
530		       (unsigned) len, (unsigned) len, rsb->name, storage);
531
532	kfree(rsb);
533	rsb = NULL;
534
535	/* find the root directory */
536	pos = (ROMFH_SIZE + len + 1 + ROMFH_PAD) & ROMFH_MASK;
537
538	root = romfs_iget(sb, pos);
539	if (IS_ERR(root))
540		goto error;
541
542	sb->s_root = d_alloc_root(root);
543	if (!sb->s_root)
544		goto error_i;
545
546	return 0;
547
548error_i:
549	iput(root);
550error:
551	return -EINVAL;
552error_rsb_inval:
553	ret = -EINVAL;
554error_rsb:
555	kfree(rsb);
556	return ret;
557}
558
559/*
560 * get a superblock for mounting
561 */
562static struct dentry *romfs_mount(struct file_system_type *fs_type,
563			int flags, const char *dev_name,
564			void *data)
565{
566	struct dentry *ret = ERR_PTR(-EINVAL);
567
568#ifdef CONFIG_ROMFS_ON_MTD
569	ret = mount_mtd(fs_type, flags, dev_name, data, romfs_fill_super);
570#endif
571#ifdef CONFIG_ROMFS_ON_BLOCK
572	if (ret == ERR_PTR(-EINVAL))
573		ret = mount_bdev(fs_type, flags, dev_name, data,
574				  romfs_fill_super);
575#endif
576	return ret;
577}
578
579/*
580 * destroy a romfs superblock in the appropriate manner
581 */
582static void romfs_kill_sb(struct super_block *sb)
583{
584#ifdef CONFIG_ROMFS_ON_MTD
585	if (sb->s_mtd) {
586		kill_mtd_super(sb);
587		return;
588	}
589#endif
590#ifdef CONFIG_ROMFS_ON_BLOCK
591	if (sb->s_bdev) {
592		kill_block_super(sb);
593		return;
594	}
595#endif
596}
597
598static struct file_system_type romfs_fs_type = {
599	.owner		= THIS_MODULE,
600	.name		= "romfs",
601	.mount		= romfs_mount,
602	.kill_sb	= romfs_kill_sb,
603	.fs_flags	= FS_REQUIRES_DEV,
604};
605
606/*
607 * inode storage initialiser
608 */
609static void romfs_i_init_once(void *_inode)
610{
611	struct romfs_inode_info *inode = _inode;
612
613	inode_init_once(&inode->vfs_inode);
614}
615
616/*
617 * romfs module initialisation
618 */
619static int __init init_romfs_fs(void)
620{
621	int ret;
622
623	printk(KERN_INFO "ROMFS MTD (C) 2007 Red Hat, Inc.\n");
624
625	romfs_inode_cachep =
626		kmem_cache_create("romfs_i",
627				  sizeof(struct romfs_inode_info), 0,
628				  SLAB_RECLAIM_ACCOUNT | SLAB_MEM_SPREAD,
629				  romfs_i_init_once);
630
631	if (!romfs_inode_cachep) {
632		printk(KERN_ERR
633		       "ROMFS error: Failed to initialise inode cache\n");
634		return -ENOMEM;
635	}
636	ret = register_filesystem(&romfs_fs_type);
637	if (ret) {
638		printk(KERN_ERR "ROMFS error: Failed to register filesystem\n");
639		goto error_register;
640	}
641	return 0;
642
643error_register:
644	kmem_cache_destroy(romfs_inode_cachep);
645	return ret;
646}
647
648/*
649 * romfs module removal
650 */
651static void __exit exit_romfs_fs(void)
652{
653	unregister_filesystem(&romfs_fs_type);
654	kmem_cache_destroy(romfs_inode_cachep);
655}
656
657module_init(init_romfs_fs);
658module_exit(exit_romfs_fs);
659
660MODULE_DESCRIPTION("Direct-MTD Capable RomFS");
661MODULE_AUTHOR("Red Hat, Inc.");
662MODULE_LICENSE("GPL"); /* Actually dual-licensed, but it doesn't matter for */