intrep.c

mtd最新cvs jffs文件系统分析

	/* Get data and size if there is any */
	if (raw_inode->dsize) {
		node_iovec[iovec_cnt].iov_base = (void *) data;
		node_iovec[iovec_cnt].iov_len = (size_t) raw_inode->dsize;
		iovec_cnt++;
		/* No need to pad this because we're not actually putting
		   anything after it.
		*/
	}

	if ((err = flash_safe_writev(fmc->mtd, node_iovec, iovec_cnt,
				    pos) < 0)) {
		jffs_fmfree_partly(fmc, fm, 0);
		jffs_fm_write_unlock(fmc);
		printk(KERN_ERR "JFFS: jffs_write_node: Failed to write, "
		       "requested %i, wrote %i\n", total_size, err);
		goto retry;
	}
	if (raw_inode->deleted)
		f->deleted = 1;

	jffs_fm_write_unlock(fmc);
	D3(printk("jffs_write_node(): Leaving...\n"));
	return raw_inode->dsize;
} /* jffs_write_node()  */


/* Read data from the node and write it to the buffer.  'node_offset'
   is how much we have read from this particular node before and which
   shouldn't be read again.  'max_size' is how much space there is in
   the buffer.  */
static int
jffs_get_node_data(struct jffs_file *f, struct jffs_node *node, 
		   unsigned char *buf,__u32 node_offset, __u32 max_size,
		   kdev_t dev)
{
	struct jffs_fmcontrol *fmc = f->c->fmc;
	__u32 pos = node->fm->offset + node->fm_offset + node_offset;
	__u32 avail = node->data_size - node_offset;
	__u32 r;

	D2(printk("  jffs_get_node_data(): file: \"%s\", ino: %u, "
		  "version: %u, node_offset: %u\n",
		  f->name, node->ino, node->version, node_offset));

	r = min(avail, max_size);
	D3(printk(KERN_NOTICE "jffs_get_node_data\n"));
	flash_safe_read(fmc->mtd, pos, buf, r);

	D3(printk("  jffs_get_node_data(): Read %u byte%s.\n",
		  r, (r == 1 ? "" : "s")));

	return r;
}


/* Read data from the file's nodes.  Write the data to the buffer
   'buf'.  'read_offset' tells how much data we should skip.  */
int
jffs_read_data(struct jffs_file *f, unsigned char *buf, __u32 read_offset,
	       __u32 size)
{
	struct jffs_node *node;
	__u32 read_data = 0; /* Total amount of read data.  */
	__u32 node_offset = 0;
	__u32 pos = 0; /* Number of bytes traversed.  */

	D2(printk("jffs_read_data(): file = \"%s\", read_offset = %d, "
		  "size = %u\n",
		  (f->name ? f->name : ""), read_offset, size));

	if (read_offset >= f->size) {
		D(printk("  f->size: %d\n", f->size));
		return 0;
	}

	/* First find the node to read data from.  */
	node = f->range_head;
	while (pos <= read_offset) {
		node_offset = read_offset - pos;
		if (node_offset >= node->data_size) {
			pos += node->data_size;
			node = node->range_next;
		}
		else {
			break;
		}
	}

	/* "Cats are living proof that not everything in nature
	   has to be useful."
	   - Garrison Keilor ('97)  */

	/* Fill the buffer.  */
	while (node && (read_data < size)) {
		int r;
		if (!node->fm) {
			/* This node does not refer to real data.  */
			r = min(size - read_data,
				     node->data_size - node_offset);
			memset(&buf[read_data], 0, r);
		}
		else if ((r = jffs_get_node_data(f, node, &buf[read_data],
						 node_offset,
						 size - read_data,
						 f->c->sb->s_dev)) < 0) {
			return r;
		}
		read_data += r;
		node_offset = 0;
		node = node->range_next;
	}
	D3(printk("  jffs_read_data(): Read %u bytes.\n", read_data));
	return read_data;
}


/* Used for traversing all nodes in the hash table.  */
int
jffs_foreach_file(struct jffs_control *c, int (*func)(struct jffs_file *))
{
	int pos;
	int r;
	int result = 0;

	for (pos = 0; pos < c->hash_len; pos++) {
		struct list_head *p, *next;
		for (p = c->hash[pos].next; p != &c->hash[pos]; p = next) {
			/* We need a reference to the next file in the
			   list because `func' might remove the current
			   file `f'.  */
			next = p->next;
			r = func(list_entry(p, struct jffs_file, hash));
			if (r < 0)
				return r;
			result += r;
		}
	}

	return result;
}


/* Free all nodes associated with a file.  */
int
jffs_free_node_list(struct jffs_file *f)
{
	struct jffs_node *node;
	struct jffs_node *p;

	D3(printk("jffs_free_node_list(): f #%u, \"%s\"\n",
		  f->ino, (f->name ? f->name : "")));
	node = f->version_head;
	while (node) {
		p = node;
		node = node->version_next;
		jffs_free_node(p);
		DJM(no_jffs_node--);
	}
	return 0;
}


/* Free a file and its name.  */
int
jffs_free_file(struct jffs_file *f)
{
	D3(printk("jffs_free_file: f #%u, \"%s\"\n",
		  f->ino, (f->name ? f->name : "")));

	if (f->name) {
		kfree(f->name);
		DJM(no_name--);
	}
	kfree(f);
	no_jffs_file--;
	return 0;
}

long
jffs_get_file_count(void)
{
	return no_jffs_file;
}

/* See if a file is deleted. If so, mark that file's nodes as obsolete.  */
int
jffs_possibly_delete_file(struct jffs_file *f)
{
	struct jffs_node *n;

	D3(printk("jffs_possibly_delete_file(): ino: %u\n",
		  f->ino));

	ASSERT(if (!f) {
		printk(KERN_ERR "jffs_possibly_delete_file(): f == NULL\n");
		return -1;
	});

	if (f->deleted) {
		/* First try to remove all older versions.  Commence with
		   the oldest node.  */
		for (n = f->version_head; n; n = n->version_next) {
			if (!n->fm) {
				continue;
			}
			if (jffs_fmfree(f->c->fmc, n->fm, n) < 0) {
				break;
			}
		}
		/* Unlink the file from the filesystem.  */
		if (!f->c->building_fs) {
			jffs_unlink_file_from_tree(f);
		}
		jffs_unlink_file_from_hash(f);
		jffs_free_node_list(f);
		jffs_free_file(f);
	}
	return 0;
}


/* Used in conjunction with jffs_foreach_file() to count the number
   of files in the file system.  */
int
jffs_file_count(struct jffs_file *f)
{
	return 1;
}


/* Build up a file's range list from scratch by going through the
   version list.  */
int
jffs_build_file(struct jffs_file *f)
{
	struct jffs_node *n;

	D3(printk("jffs_build_file(): ino: %u, name: \"%s\"\n",
		  f->ino, (f->name ? f->name : "")));

	for (n = f->version_head; n; n = n->version_next) {
		jffs_update_file(f, n);
	}
	return 0;
}


/* Remove an amount of data from a file. If this amount of data is
   zero, that could mean that a node should be split in two parts.
   We remove or change the appropriate nodes in the lists.

   Starting offset of area to be removed is node->data_offset,
   and the length of the area is in node->removed_size.   */
static int
jffs_delete_data(struct jffs_file *f, struct jffs_node *node)
{
	struct jffs_node *n;
	__u32 offset = node->data_offset;
	__u32 remove_size = node->removed_size;

	D3(printk("jffs_delete_data(): offset = %u, remove_size = %u\n",
		  offset, remove_size));

	if (remove_size == 0
	    && f->range_tail
	    && f->range_tail->data_offset + f->range_tail->data_size
	       == offset) {
		/* A simple append; nothing to remove or no node to split.  */
		return 0;
	}

	/* Find the node where we should begin the removal.  */
	for (n = f->range_head; n; n = n->range_next) {
		if (n->data_offset + n->data_size > offset) {
			break;
		}
	}
	if (!n) {
		/* If there's no data in the file there's no data to
		   remove either.  */
		return 0;
	}

	if (n->data_offset > offset) {
		/* XXX: Not implemented yet.  */
		printk(KERN_WARNING "JFFS: An unexpected situation "
		       "occurred in jffs_delete_data.\n");
	}
	else if (n->data_offset < offset) {
		/* See if the node has to be split into two parts.  */
		if (n->data_offset + n->data_size > offset + remove_size) {
			/* Do the split.  */
			struct jffs_node *new_node;
			D3(printk("jffs_delete_data(): Split node with "
				  "version number %u.\n", n->version));

			if (!(new_node = jffs_alloc_node())) {
				D(printk("jffs_delete_data(): -ENOMEM\n"));
				return -ENOMEM;
			}
			DJM(no_jffs_node++);

			new_node->ino = n->ino;
			new_node->version = n->version;
			new_node->data_offset = offset;
			new_node->data_size = n->data_size - (remove_size + (offset - n->data_offset));
			new_node->fm_offset = n->fm_offset + (remove_size + (offset - n->data_offset));
			new_node->name_size = n->name_size;
			new_node->fm = n->fm;
			new_node->version_prev = n;
			new_node->version_next = n->version_next;
			if (new_node->version_next) {
				new_node->version_next->version_prev
				= new_node;
			}
			else {
				f->version_tail = new_node;
			}
			n->version_next = new_node;
			new_node->range_prev = n;
			new_node->range_next = n->range_next;
			if (new_node->range_next) {
				new_node->range_next->range_prev = new_node;
			}
			else {
				f->range_tail = new_node;
			}
			/* A very interesting can of worms.  */
			n->range_next = new_node;
			n->data_size = offset - n->data_offset;
			if (new_node->fm)
				jffs_add_node(new_node);
			else {
				D1(printk(KERN_WARNING "jffs_delete_data(): Splitting an empty node (file hold).\n!"));
				D1(printk(KERN_WARNING "FIXME: Did dwmw2 do the right thing here?\n"));
			}
			n = new_node->range_next;
			remove_size = 0;
		}
		else {
			/* No.  No need to split the node.  Just remove
			   the end of the node.  */
			int r = min(n->data_offset + n->data_size
					 - offset, remove_size);
			n->data_size -= r;
			remove_size -= r;
			n = n->range_next;
		}
	}

	/* Remove as many nodes as necessary.  */
	while (n && remove_size) {
		if (n->data_size <= remove_size) {
			struct jffs_node *p = n;
			remove_size -= n->data_size;
			n = n->range_next;
			D3(printk("jffs_delete_data(): Removing node: "
				  "ino: %u, version: %u%s\n",
				  p->ino, p->version,
				  (p->fm ? "" : " (virtual)")));
			if (p->fm) {
				jffs_fmfree(f->c->fmc, p->fm, p);
			}
			jffs_unlink_node_from_range_list(f, p);
			jffs_unlink_node_from_version_list(f, p);
			jffs_free_node(p);
			DJM(no_jffs_node--);
		}
		else {
			n->data_size -= remove_size;
			n->fm_offset += remove_size;
			n->data_offset -= (node->removed_size - remove_size);
			n = n->range_next;
			break;
		}
	}

	/* Adjust the following nodes' information about offsets etc.  */
	while (n && node->removed_size) {
		n->data_offset -= node->removed_size;
		n = n->range_next;
	}

	if (node->removed_size > (f->size - node->data_offset)) {
		/* It's possible that the removed_size is in fact
		 * greater than the amount of data we actually thought
		 * were present in the first place - some of the nodes 
		 * which this node originally obsoleted may already have
		 * been deleted from the flash by subsequent garbage 
		 * collection.
		 *
		 * If this is the case, don't let f->size go negative.
		 * Bad things would happen :)
		 */
		f->size = node->data_offset;
	} else {
		f->size -= node->removed_size;
	}
	D3(printk("jffs_delete_data(): f->size = %d\n", f->size));
	return 0;
} /* jffs_delete_data()  */


/* Insert some data into a file.  Prior to the call to this function,
   jffs_delete_data should be called.  */
static int
jffs_insert_data(struct jffs_file *f, struct jffs_node *node)
{
	D3(printk("jffs_insert_data(): node->data_offset = %u, "
		  "node->data_size = %u, f->size = %u\n",
		  node->data_offset, node->data_size, f->size));

	/* Find the position where we should insert data.  */
	retry:
	if (node->data_offset == f->size) {
		/* A simple append.  This is the most common operation.  */
		node->range_next = 0;
		node->range_prev = f->range_tail;
		if (node->range_prev) {
			node->range_prev->range_next = node;
		}
		f->range_tail = node;
		f->size += node->data_size;
		if (!f->range_head) {
			f->range_head = node;
		}
	}
	else if (node->data_offset < f->size) {
		/* Trying to insert data into the middle of the file.  This
		   means no problem because jffs_delete_data() has already
		   prepared the range list for us.  */
		struct jffs_node *n;

		/* Find the correct place for the insertion and then insert
		   the node.  */
		for (n = f->range_head; n; n = n->range_next) {
			D2(printk("Cool stuff's happening!\n"));

			if (n->data_offset == node->data_offset) {
				node->range_prev = n->range_prev;
				if (node->range_prev) {
					node->range_prev->range_next = node;
				}
				else {
					f->range_head = node;
				}
				node->range_next = n;
				n->range_prev = node;
				break;
			}
			ASSERT(else if (n->data_offset + n->data_size >
					node->data_offset) {
				printk(KERN_ERR "jffs_insert_data(): "
				       "Couldn't find a place to insert "
				       "the data!\n");
				return -1;
			});
		}

		/* Adjust later nodes' offsets etc.  */
		n = node->range_next;
		while (n) {
			n->data_offset += node->data_size;
			n = n->range_next;
		}
		f->size += node->data_size;
	}
	else if (node->data_offset > f->size) {
		/* Okay.  This is tricky.  This means that we want to insert
		   data at a place that is beyond the limits of the file as
		   it is constructed right now.  This is actually a common
		   event that for instance could occur during the mounting
		   of the file system if a large file have been truncated,
		   rewritten and then only partially garbage collected.  */

		struct jffs_node *n;

		/* We need a place holder for the data that is missing in
		   front of this insertion.  This "virtual node" will not
		   be associated with any space on the flash device.  */
		struct jffs_node *virtual_node;
		if (!(virtual_node = jffs_alloc_node())) {
			re