intrep.c

讲述linux的初始化过程

	while (!fm) {

		/* Deadlocks suck. */
		while(fmc->free_size < fmc->min_free_size + total_size + slack) {
			jffs_fm_write_unlock(fmc);
			if (!JFFS_ENOUGH_SPACE(c, total_size + slack))
				return -ENOSPC;
			jffs_fm_write_lock(fmc);
		}

		/* First try to allocate some flash memory.  */
		err = jffs_fmalloc(fmc, total_size, node, &fm);
		
		if (err == -ENOSPC) {
			/* Just out of space. GC and try again */
			if (fmc->dirty_size < fmc->sector_size) {
				D(printk("jffs_write_node(): jffs_fmalloc(0x%p, %u) "
					 "failed, no dirty space to GC\n", fmc,
					 total_size));
				return err;
			}
			
			D1(printk(KERN_INFO "jffs_write_node(): Calling jffs_garbage_collect_now()\n"));
			jffs_fm_write_unlock(fmc);
			if ((err = jffs_garbage_collect_now(c))) {
				D(printk("jffs_write_node(): jffs_garbage_collect_now() failed\n"));
				return err;
			}
			jffs_fm_write_lock(fmc);
			continue;
		} 

		if (err < 0) {
			jffs_fm_write_unlock(fmc);

			D(printk("jffs_write_node(): jffs_fmalloc(0x%p, %u) "
				 "failed!\n", fmc, total_size));
			return err;
		}

		if (!fm->nodes) {
			/* The jffs_fm struct that we got is not good enough.
			   Make that space dirty and try again  */
			if ((err = jffs_write_dummy_node(c, fm)) < 0) {
				kfree(fm);
				DJM(no_jffs_fm--);
				jffs_fm_write_unlock(fmc);
				D(printk("jffs_write_node(): "
					 "jffs_write_dummy_node(): Failed!\n"));
				return err;
			}
			fm = NULL;
		}
	} /* while(!fm) */
	node->fm = fm;

	ASSERT(if (fm->nodes == 0) {
		printk(KERN_ERR "jffs_write_node(): fm->nodes == 0\n");
	});

	pos = node->fm->offset;

	/* Increment the version number here. We can't let the caller
	   set it beforehand, because we might have had to do GC on a node
	   of this file - and we'd end up reusing version numbers.
	*/
	if (f) {
		raw_inode->version = f->highest_version + 1;
		D1(printk (KERN_NOTICE "jffs_write_node(): setting version of %s to %d\n", f->name, raw_inode->version));
	}

	/* Compute the checksum for the data and name chunks.  */
	raw_inode->dchksum = jffs_checksum(data, raw_inode->dsize);
	raw_inode->nchksum = jffs_checksum(name, raw_inode->nsize);

	/* The checksum is calculated without the chksum and accurate
	   fields so set them to zero first.  */
	raw_inode->accurate = 0;
	raw_inode->chksum = 0;
	raw_inode->chksum = jffs_checksum(raw_inode,
					  sizeof(struct jffs_raw_inode));
	raw_inode->accurate = 0xff;

	D3(printk("jffs_write_node(): About to write this raw inode to the "
		  "flash at pos 0x%lx:\n", (long)pos));
	D3(jffs_print_raw_inode(raw_inode));

	/* Step 1: Write the raw jffs inode to the flash.  */
	if ((err = flash_safe_write(fmc->mtd, pos,
				    (u_char *)raw_inode,
				    sizeof(struct jffs_raw_inode))) < 0) {
		jffs_fmfree_partly(fmc, fm,
				   total_name_size + total_data_size);
		jffs_fm_write_unlock(fmc);
		printk(KERN_ERR "JFFS: jffs_write_node: Failed to write "
		       "raw_inode.\n");
		return err;
	}
	pos += sizeof(struct jffs_raw_inode);

	/* Step 2: Write the name, if there is any.  */
	if (raw_inode->nsize) {
		if ((err = flash_safe_write(fmc->mtd, pos,
					    (u_char *)name,
					    raw_inode->nsize)) < 0) {
			jffs_fmfree_partly(fmc, fm, total_data_size);
			jffs_fm_write_unlock(fmc);
			printk(KERN_ERR "JFFS: jffs_write_node: Failed to "
                              "write the name.\n");
			return err;
		}
		pos += total_name_size;
	}

	/* Step 3: Append the actual data, if any.  */
	if (raw_inode->dsize) {
		if ((err = flash_safe_write(fmc->mtd, pos, data,
					    raw_inode->dsize)) < 0) {
			jffs_fmfree_partly(fmc, fm, 0);
			jffs_fm_write_unlock(fmc);
			printk(KERN_ERR "JFFS: jffs_write_node: Failed to "
			       "write the data.\n");
			return err;
		}
	}
	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 = jffs_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 = jffs_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;
		kfree(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);
	DJM(no_jffs_file--);
	return 0;
}


/* 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 = (struct jffs_node *)
					 kmalloc(sizeof(struct jffs_node),
						 GFP_KERNEL))) {
				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 = jffs_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);
			kfree(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