intrep.c

Linux内核源代码 为压缩文件 是<<Linux内核>>一书中的源代码

		kfree(root);
		DJM(no_jffs_file--);
		return -ENOMEM;
	}
	DJM(no_jffs_node++);
	memset(node, 0, sizeof(struct jffs_node));
	node->ino = JFFS_MIN_INO;
	memset(root, 0, sizeof(struct jffs_file));
	root->ino = JFFS_MIN_INO;
	root->mode = S_IFDIR | S_IRWXU | S_IRGRP
		     | S_IXGRP | S_IROTH | S_IXOTH;
	root->atime = root->mtime = root->ctime = CURRENT_TIME;
	root->nlink = 1;
	root->c = c;
	root->version_head = root->version_tail = node;
	jffs_insert_file_into_hash(root);
	return 0;
}


/* This is where the file system is built and initialized.  */
int
jffs_build_fs(struct super_block *sb)
{
	struct jffs_control *c;
	int err = 0;

	D2(printk("jffs_build_fs()\n"));

	if (!(c = jffs_create_control(sb->s_dev))) {
		return -ENOMEM;
	}
	c->building_fs = 1;
	c->sb = sb;
	if ((err = jffs_scan_flash(c)) < 0) {
		goto jffs_build_fs_fail;
	}

	/* Add a virtual root node if no one exists.  */
	if (!jffs_find_file(c, JFFS_MIN_INO)) {
		if ((err = jffs_add_virtual_root(c)) < 0) {
			goto jffs_build_fs_fail;
		}
	}

	while (c->delete_list) {
		struct jffs_file *f;
		struct jffs_delete_list *delete_list_element;

		if ((f = jffs_find_file(c, c->delete_list->ino))) {
			f->deleted = 1;
		}
		delete_list_element = c->delete_list;
		c->delete_list = c->delete_list->next;
		kfree(delete_list_element);
	}

	/* Remove deleted nodes.  */
	if ((err = jffs_foreach_file(c, jffs_possibly_delete_file)) < 0) {
		printk(KERN_ERR "JFFS: Failed to remove deleted nodes.\n");
		goto jffs_build_fs_fail;
	}
	/* Remove redundant nodes.  (We are not interested in the
	   return value in this case.)  */
	jffs_foreach_file(c, jffs_remove_redundant_nodes);
	/* Try to build a tree from all the nodes.  */
	if ((err = jffs_foreach_file(c, jffs_insert_file_into_tree)) < 0) {
		printk("JFFS: Failed to build tree.\n");
		goto jffs_build_fs_fail;
	}
	/* Compute the sizes of all files in the filesystem.  Adjust if
	   necessary.  */
	if ((err = jffs_foreach_file(c, jffs_build_file)) < 0) {
		printk("JFFS: Failed to build file system.\n");
		goto jffs_build_fs_fail;
	}
	sb->u.generic_sbp = (void *)c;
	c->building_fs = 0;

	D1(jffs_print_hash_table(c));
	D1(jffs_print_tree(c->root, 0));

	return 0;

jffs_build_fs_fail:
	jffs_cleanup_control(c);
	return err;
} /* jffs_build_fs()  */


/* Scan the whole flash memory in order to find all nodes in the
   file systems.  */
static int
jffs_scan_flash(struct jffs_control *c)
{
	char name[JFFS_MAX_NAME_LEN + 2];
	struct jffs_raw_inode raw_inode;
	struct jffs_node *node = 0;
	struct jffs_fmcontrol *fmc = c->fmc;
	__u32 checksum;
	__u8 tmp_accurate;
	__u16 tmp_chksum;
	__u32 deleted_file;
	loff_t pos = fmc->flash_start;
	loff_t start;
	loff_t end = fmc->flash_start + fmc->flash_size;
	__u8 *read_buf;
	int i, len, retlen;

	D1(printk("jffs_scan_flash(): start pos = 0x%lx, end = 0x%lx\n",
		  (long)pos, (long)end));

	flash_safe_acquire(fmc->mtd);

	/* Allocate read buffer */
	read_buf = (__u8 *) kmalloc (sizeof(__u8) * 4096, GFP_KERNEL);

	/* Start the scan.  */
	while (pos < end) {
		deleted_file = 0;

		/* Remember the position from where we started this scan.  */
		start = pos;

		switch (flash_read_u32(fmc->mtd, pos)) {
		case JFFS_EMPTY_BITMASK:
			/* We have found 0xff at this position.  We have to
			   scan the rest of the flash till the end or till
			   something else than 0xff is found.  */
			D1(printk("jffs_scan_flash(): 0xff at pos 0x%lx.\n",
				  (long)pos));

			len = end - pos < 4096 ? end - pos : 4096;

			retlen = flash_safe_read(fmc->mtd, pos,
						 &read_buf[0], len);

			retlen &= ~3;

			for (i=0 ; i < retlen ; i+=4, pos += 4) {
				if(*((__u32 *) &read_buf[i]) !=
						JFFS_EMPTY_BITMASK)
					break;
			}
			if (i == retlen)
				continue;

			D1(printk("jffs_scan_flash(): 0xff ended at "
				  "pos 0x%lx.\n", (long)pos));

			/* If some free space ends in the middle of a sector,
				treat it as dirty rather than clean.
			   This is to handle the case where one thread 
			   allocated space for a node, but didn't get to
			   actually _write_ it before power was lost, leaving
			   a gap in the log. Shifting all node writes into
			   a single kernel thread will fix the original problem.
			*/
			if ((__u32) pos % fmc->sector_size) {
				/* If there was free space in previous 
				   sectors, don't mark that dirty too - 
				   only from the beginning of this sector
				   (or from start) 
				*/
				if (start < (pos & ~(fmc->sector_size-1))) {
					D1(printk("Reducing start to 0x%x from 0x%x\n", pos & ~(fmc->sector_size-1), start));
					start = pos & ~(fmc->sector_size-1);
				}
				D1(printk("Dirty space: 0x%x for 0x%x bytes\n", start, (pos - start)));
				jffs_fmalloced(fmc, (__u32) start,
					       (__u32) (pos - start), 0);
			}
			continue;

		case JFFS_DIRTY_BITMASK:
			/* We have found 0x00 at this position.  Scan as far
			   as possible to find out how much is dirty.  */
			D1(printk("jffs_scan_flash(): 0x00 at pos 0x%lx.\n",
				  (long)pos));
			for (; pos < end
			       && JFFS_DIRTY_BITMASK == flash_read_u32(fmc->mtd, pos);
			     pos += 4);
			D1(printk("jffs_scan_flash(): 0x00 ended at "
				  "pos 0x%lx.\n", (long)pos));
			jffs_fmalloced(fmc, (__u32) start,
				       (__u32) (pos - start), 0);
			continue;

		case JFFS_MAGIC_BITMASK:
			/* We have probably found a new raw inode.  */
			break;

		default:
		bad_inode:
			/* We're f*cked.  This is not solved yet.  We have
			   to scan for the magic pattern.  */
			D1(printk("*************** Dirty flash memory or "
				  "bad inode: "
				  "hexdump(pos = 0x%lx, len = 128):\n",
				  (long)pos));
			D1(jffs_hexdump(fmc->mtd, pos, 128));
		cont_dirty:
			for (pos += 4; pos < end; pos += 4) {
				switch (flash_read_u32(fmc->mtd, pos)) {
				case JFFS_MAGIC_BITMASK:
					jffs_fmalloced(fmc, (__u32) start,
						       (__u32) (pos - start),
						       0);
					goto cont_scan;
				case JFFS_EMPTY_BITMASK:
					/* First, mark as dirty the region
					   which really does contain crap. */
					jffs_fmalloced(fmc, (__u32) start,
						       (__u32) (pos - start),
						       0);

					/* Then, scan the region which looks free.
					   Depending on how large it is, we may
					   mark it dirty too.
					*/
					start = pos;
					for (; pos < end ; pos += 4) {
						switch (flash_read_u32(fmc->mtd, pos)) {
						case JFFS_MAGIC_BITMASK:
							if (pos - start < fmc->max_chunk_size) {
								/* Not much free space. Mark it dirty. */
								jffs_fmalloced(fmc, (__u32)start,
									       (__u32)pos-start, 0);
							}
							goto cont_scan;

						case JFFS_EMPTY_BITMASK:
							/* More empty space */
							continue;
				
						default: 
							/* i.e. more dirt */
							if (pos - start < fmc->max_chunk_size) {
								/* There wasn't much before the dirt
								   started again. Just mark it all dirty
								*/
								goto cont_dirty;
							}
							/* There was quite a lot of free space. Leave it
							   free.
							*/
							goto cont_scan;
						}
					}
				default:
					break;
				}
			}
			cont_scan:
			continue;
		}

		/* We have found the beginning of an inode.  Create a
		   node for it unless there already is one available.  */
		if (!node) {
			if (!(node = (struct jffs_node *)
				     kmalloc(sizeof(struct jffs_node),
					     GFP_KERNEL))) {
				/* Free read buffer */
				kfree (read_buf);

				/* Release the flash device */
				flash_safe_release(fmc->mtd);
	
				return -ENOMEM;
			}
			DJM(no_jffs_node++);
		}

		/* Read the next raw inode.  */

		flash_safe_read(fmc->mtd, pos, (u_char *) &raw_inode,
				sizeof(struct jffs_raw_inode));

		/* When we compute the checksum for the inode, we never
		   count the 'accurate' or the 'checksum' fields.  */
		tmp_accurate = raw_inode.accurate;
		tmp_chksum = raw_inode.chksum;
		raw_inode.accurate = 0;
		raw_inode.chksum = 0;
		checksum = jffs_checksum(&raw_inode,
					 sizeof(struct jffs_raw_inode));
		raw_inode.accurate = tmp_accurate;
		raw_inode.chksum = tmp_chksum;

		D3(printk("*** We have found this raw inode at pos 0x%lx "
			  "on the flash:\n", (long)pos));
		D3(jffs_print_raw_inode(&raw_inode));

		if (checksum != raw_inode.chksum) {
			D1(printk("jffs_scan_flash(): Bad checksum: "
				  "checksum = %u, "
				  "raw_inode.chksum = %u\n",
				  checksum, raw_inode.chksum));
			pos += sizeof(struct jffs_raw_inode);
			jffs_fmalloced(fmc, (__u32) start,
				       (__u32) (pos - start), 0);
			/* Reuse this unused struct jffs_node.  */
			continue;
		}

		/* Check the raw inode read so far.  Start with the
		   maximum length of the filename.  */
		if (raw_inode.nsize > JFFS_MAX_NAME_LEN) {
			printk(KERN_WARNING "jffs_scan_flash: Found a "
			       "JFFS node with name too large\n");
			goto bad_inode;
		}

		if (raw_inode.rename && raw_inode.dsize != sizeof(__u32)) {
			printk(KERN_WARNING "jffs_scan_flash: Found a "
			       "rename node with dsize %u.\n",
			       raw_inode.dsize);
			jffs_print_raw_inode(&raw_inode);
			goto bad_inode;
		}

		/* The node's data segment should not exceed a
		   certain length.  */
		if (raw_inode.dsize > fmc->max_chunk_size) {
			printk(KERN_WARNING "jffs_scan_flash: Found a "
			       "JFFS node with dsize (0x%x) > max_chunk_size (0x%x)\n",
			       raw_inode.dsize, fmc->max_chunk_size);
			goto bad_inode;
		}

		pos += sizeof(struct jffs_raw_inode);

		/* This shouldn't be necessary because a node that
		   violates the flash boundaries shouldn't be written
		   in the first place. */
		if (pos >= end) {
			goto check_node;
		}

		/* Read the name.  */
		*name = 0;
		if (raw_inode.nsize) {
		        flash_safe_read(fmc->mtd, pos, name, raw_inode.nsize);
			name[raw_inode.nsize] = '\0';
			pos += raw_inode.nsize
			       + JFFS_GET_PAD_BYTES(raw_inode.nsize);
			D3(printk("name == \"%s\"\n", name));
			checksum = jffs_checksum(name, raw_inode.nsize);
			if (checksum != raw_inode.nchksum) {
				D1(printk("jffs_scan_flash(): Bad checksum: "
					  "checksum = %u, "
					  "raw_inode.nchksum = %u\n",
					  checksum, raw_inode.nchksum));
				jffs_fmalloced(fmc, (__u32) start,
					       (__u32) (pos - start), 0);
				/* Reuse this unused struct jffs_node.  */
				continue;
			}
			if (pos >= end) {
				goto check_node;
			}
		}

		/* Read the data, if it exists, in order to be sure it
		   matches the checksum.  */
		if (raw_inode.dsize) {
			if (raw_inode.rename) {
				deleted_file = flash_read_u32(fmc->mtd, pos);
			}
			checksum = jffs_checksum_flash(fmc->mtd, pos, raw_inode.dsize);
			pos += raw_inode.dsize
			       + JFFS_GET_PAD_BYTES(raw_inode.dsize);

			if (checksum != raw_inode.dchksum) {
				D1(printk("jffs_scan_flash(): Bad checksum: "
					  "checksum = %u, "
					  "raw_inode.dchksum = %u\n",
					  checksum, raw_inode.dchksum));
				jffs_fmalloced(fmc, (__u32) start,
					       (__u32) (pos - start), 0);
				/* Reuse this unused struct jffs_node.  */
				continue;
			}
		}

		check_node:

		/* Remember the highest inode number in the whole file
		   system.  This information will be used when assigning
		   new files new inode numbers.  */
		if (c->next_ino <= raw_inode.ino) {
			c->next_ino = raw_inode.ino + 1;
		}

		if (raw_inode.accurate) {
			int err;
			node->data_offset = raw_inode.offset;
			node->data_size = raw_inode.dsize;
			node->removed_size = raw_inode.rsize;
			/* Compute the offset to the actual data in the
			   on-flash node.  */
			node->fm_offset
			= sizeof(struct jffs_raw_inode)
			  + raw_inode.nsize
			  + JFFS_GET_PAD_BYTES(raw_inode.nsize);
			node->fm = jffs_fmalloced(fmc, (__u32) start,
						  (__u32) (pos - start),
						  node);
			if (!node->fm) {
				D(printk("jffs_scan_flash(): !node->fm\n"));
				kfree(node);
				DJM(no_jffs_node--);

				/* Free read buffer */
				kfree (read_buf);

				/* Release the flash device */
				flash_safe_release(fmc->mtd);

				return -ENOMEM;
			}
			if ((err = jffs_insert_node(c, 0, &raw_inode,
						    name, node)) < 0) {
				printk("JFFS: Failed to handle raw inode. "
				       "(err = %d)\n", err);
				break;
			}
			if (raw_inode.rename) {
				struct jffs_delete_list *dl
				= (struct jffs_delete_list *)
				  kmalloc(sizeof(struct jffs_delete_list),
					  GFP_KERNEL);
				if (!dl) {
					D(printk("jffs_scan_flash: !dl\n"));
					kfree(node);
					DJM(no_jffs_node--);

					/* Release the flash device */
					flash_safe_release(fmc->flash_part);

					/* Free read buffer */
					kfree (read_buf);

					return -ENOMEM;
				}
				dl->ino = deleted_file;
				dl->next = c->delete_list;
				c->delete_list = dl;
				node->data_size = 0;
			}
			D3(jffs_print_node(node));
			node = 0; /* Don't free the node!  */
		}
		else {
			jffs_fmalloced(fmc, (__u32) start,
				       (__u32) (pos - start), 0);
			D3(printk("jffs_scan_flash(): Just found an obsolete "
				  "raw_inode. Continuing the scan...\n"));
			/* Reuse this unused struct jffs_node.  */
		}
	}

	if (node) {
		kfree(node);
		DJM(no_jffs_node--);
	}
	jffs_build_end(fmc);

	/* Free read buffer */
	kfree (read_buf);

	/* Return happy */
	D3(printk("jffs_scan_flash(): Leaving...\n"));
	flash_safe_release(fmc->mtd);
	return 0;
} /* jffs_scan_flash()  */


/* Insert any kind of node into the file system.  Take care of data
   insertions and deletions.  Also remove redundant information. The
   memory allocated for the `name' is regarded as "given away" in the
   caller's perspective.  */
int
jffs_insert_node(struct jffs_control *c, struct jffs_file *f,
		 const struct jffs_raw_inode *raw_inode,
		 const char *name, struct jffs_node *node)
{
	int update_name = 0;
	int insert_into_tree = 0;

	D2(printk("jffs_insert_node(): ino = %u, version = %u, "