readinode.c

这是著名的jffs2嵌入式日志文件系统的源代码

/*
 * JFFS2 -- Journalling Flash File System, Version 2.
 *
 * Copyright (C) 2001 Red Hat, Inc.
 *
 * Created by David Woodhouse <[e-mail]>
 *
 * The original JFFS, from which the design for JFFS2 was derived,
 * was designed and implemented by Axis Communications AB.
 *
 * The contents of this file are subject to the Red Hat eCos Public
 * License Version 1.1 (the "Licence"); you may not use this file
 * except in compliance with the Licence.  You may obtain a copy of
 * the Licence at http://www.redhat.com/
 *
 * Software distributed under the Licence is distributed on an "AS IS"
 * basis, WITHOUT WARRANTY OF ANY KIND, either express or implied.
 * See the Licence for the specific language governing rights and
 * limitations under the Licence.
 *
 * The Original Code is JFFS2 - Journalling Flash File System, version 2
 *
 * Alternatively, the contents of this file may be used under the
 * terms of the GNU General Public License version 2 (the "GPL"), in
 * which case the provisions of the GPL are applicable instead of the
 * above.  If you wish to allow the use of your version of this file
 * only under the terms of the GPL and not to allow others to use your
 * version of this file under the RHEPL, indicate your decision by
 * deleting the provisions above and replace them with the notice and
 * other provisions required by the GPL.  If you do not delete the
 * provisions above, a recipient may use your version of this file
 * under either the RHEPL or the GPL.
 *
 * $Id: readinode.c,v 1.58.2.5 2002/03/05 22:40:03 dwmw2 Exp $
 *
 */

/* Given an inode, probably with existing list of fragments, add the new node
 * to the fragment list.
 */
#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/fs.h>
#include <linux/mtd/mtd.h>
#include <linux/jffs2.h>
#include "nodelist.h"
#include "crc32.h"


D1(void jffs2_print_frag_list(struct jffs2_inode_info *f)
{
	struct jffs2_node_frag *this = f->fraglist;

	while(this) {
		if (this->node)
			printk(KERN_DEBUG "frag %04x-%04x: 0x%08x on flash (*%p->%p)\n", this->ofs, this->ofs+this->size, this->node->raw->flash_offset &~3, this, this->next);
		else 
			printk(KERN_DEBUG "frag %04x-%04x: hole (*%p->%p)\n", this->ofs, this->ofs+this->size, this, this->next);
		this = this->next;
	}
	if (f->metadata) {
		printk(KERN_DEBUG "metadata at 0x%08x\n", f->metadata->raw->flash_offset &~3);
	}
})


int jffs2_add_full_dnode_to_inode(struct jffs2_sb_info *c, struct jffs2_inode_info *f, struct jffs2_full_dnode *fn)
{
	int ret;
	D1(printk(KERN_DEBUG "jffs2_add_full_dnode_to_inode(ino #%u, f %p, fn %p)\n", f->inocache->ino, f, fn));

	ret = jffs2_add_full_dnode_to_fraglist(c, &f->fraglist, fn);

	D2(jffs2_print_frag_list(f));
	return ret;
}

static void jffs2_obsolete_node_frag(struct jffs2_sb_info *c, struct jffs2_node_frag *this)
{
	if (this->node) {
		this->node->frags--;
		if (!this->node->frags) {
			/* The node has no valid frags left. It's totally obsoleted */
			D2(printk(KERN_DEBUG "Marking old node @0x%08x (0x%04x-0x%04x) obsolete\n",
				  this->node->raw->flash_offset &~3, this->node->ofs, this->node->ofs+this->node->size));
			jffs2_mark_node_obsolete(c, this->node->raw);
			jffs2_free_full_dnode(this->node);
		} else {
			D2(printk(KERN_DEBUG "Not marking old node @0x%08x (0x%04x-0x%04x) obsolete. frags is %d\n",
				  this->node->raw->flash_offset &~3, this->node->ofs, this->node->ofs+this->node->size,
				  this->node->frags));
		}
		
	}
	jffs2_free_node_frag(this);
}

/* Doesn't set inode->i_size */
int jffs2_add_full_dnode_to_fraglist(struct jffs2_sb_info *c, struct jffs2_node_frag **list, struct jffs2_full_dnode *fn)
{
	
	struct jffs2_node_frag *this, **prev, *old;
	struct jffs2_node_frag *newfrag, *newfrag2;
	__u32 lastend = 0;


	newfrag = jffs2_alloc_node_frag();
	if (!newfrag) {
		return -ENOMEM;
	}

	D2(if (fn->raw)
		printk(KERN_DEBUG "adding node %04x-%04x @0x%08x on flash, newfrag *%p\n", fn->ofs, fn->ofs+fn->size, fn->raw->flash_offset &~3, newfrag);
	else
		printk(KERN_DEBUG "adding hole node %04x-%04x on flash, newfrag *%p\n", fn->ofs, fn->ofs+fn->size, newfrag));
	
	prev = list;
	this = *list;

	if (!fn->size) {
		jffs2_free_node_frag(newfrag);
		return 0;
	}

	newfrag->ofs = fn->ofs;
	newfrag->size = fn->size;
	newfrag->node = fn;
	newfrag->node->frags = 1;
	newfrag->next = (void *)0xdeadbeef;

	/* Skip all the nodes which are completed before this one starts */
	while(this && fn->ofs >= this->ofs+this->size) {
		lastend = this->ofs + this->size;

		D2(printk(KERN_DEBUG "j_a_f_d_t_f: skipping frag 0x%04x-0x%04x; phys 0x%08x (*%p->%p)\n", 
			  this->ofs, this->ofs+this->size, this->node?(this->node->raw->flash_offset &~3):0xffffffff, this, this->next));
		prev = &this->next;
		this = this->next;
	}

	/* See if we ran off the end of the list */
	if (!this) {
		/* We did */
		if (lastend < fn->ofs) {
			/* ... and we need to put a hole in before the new node */
			struct jffs2_node_frag *holefrag = jffs2_alloc_node_frag();
			if (!holefrag)
				return -ENOMEM;
			holefrag->ofs = lastend;
			holefrag->size = fn->ofs - lastend;
			holefrag->next = NULL;
			holefrag->node = NULL;
			*prev = holefrag;
			prev = &holefrag->next;
		}
		newfrag->next = NULL;
		*prev = newfrag;
		return 0;
	}

	D2(printk(KERN_DEBUG "j_a_f_d_t_f: dealing with frag 0x%04x-0x%04x; phys 0x%08x (*%p->%p)\n", 
		  this->ofs, this->ofs+this->size, this->node?(this->node->raw->flash_offset &~3):0xffffffff, this, this->next));

	/* OK. 'this' is pointing at the first frag that fn->ofs at least partially obsoletes,
	 * - i.e. fn->ofs < this->ofs+this->size && fn->ofs >= this->ofs  
	 */
	if (fn->ofs > this->ofs) {
		/* This node isn't completely obsoleted. The start of it remains valid */
		if (this->ofs + this->size > fn->ofs + fn->size) {
			/* The new node splits 'this' frag into two */
			newfrag2 = jffs2_alloc_node_frag();
			if (!newfrag2) {
				jffs2_free_node_frag(newfrag);
				return -ENOMEM;
			}
			D1(printk(KERN_DEBUG "split old frag 0x%04x-0x%04x -->", this->ofs, this->ofs+this->size);
			if (this->node)
				printk("phys 0x%08x\n", this->node->raw->flash_offset &~3);
			else 
				printk("hole\n");
			   )
			newfrag2->ofs = fn->ofs + fn->size;
			newfrag2->size = (this->ofs+this->size) - newfrag2->ofs;
			newfrag2->next = this->next;
			newfrag2->node = this->node;
			if (this->node)
				this->node->frags++;
			newfrag->next = newfrag2;
			this->next = newfrag;
			this->size = newfrag->ofs - this->ofs;
			return 0;
		}
		/* New node just reduces 'this' frag in size, doesn't split it */
		this->size = fn->ofs - this->ofs;
		newfrag->next = this->next;
		this->next = newfrag;
		this = newfrag->next;
	} else {
		D2(printk(KERN_DEBUG "Inserting newfrag (*%p) in before 'this' (*%p)\n", newfrag, this));
		*prev = newfrag;
	        newfrag->next = this;
	}
	/* OK, now we have newfrag added in the correct place in the list, but
	   newfrag->next points to a fragment which may be overlapping it
	*/
	while (this && newfrag->ofs + newfrag->size >= this->ofs + this->size) {
		/* 'this' frag is obsoleted. */
		old = this;
		this = old->next;
		jffs2_obsolete_node_frag(c, old);
	}
	/* Now we're pointing at the first frag which isn't totally obsoleted by 
	   the new frag */
	newfrag->next = this;

	if (!this || newfrag->ofs + newfrag->size == this->ofs) {
		return 0;
	}
	/* Still some overlap */
	this->size = (this->ofs + this->size) - (newfrag->ofs + newfrag->size);
	this->ofs = newfrag->ofs + newfrag->size;
	return 0;
}

void jffs2_truncate_fraglist (struct jffs2_sb_info *c, struct jffs2_node_frag **list, __u32 size)
{
	D1(printk(KERN_DEBUG "Truncating fraglist to 0x%08x bytes\n", size));

	while (*list) {
		if ((*list)->ofs >= size) {
			struct jffs2_node_frag *this = *list;
			*list = this->next;
			D1(printk(KERN_DEBUG "Removing frag 0x%08x-0x%08x\n", this->ofs, this->ofs+this->size));
			jffs2_obsolete_node_frag(c, this);
			continue;
		} else if ((*list)->ofs + (*list)->size > size) {
			D1(printk(KERN_DEBUG "Truncating frag 0x%08x-0x%08x\n", (*list)->ofs, (*list)->ofs + (*list)->size));
			(*list)->size = size - (*list)->ofs;
		}
		list = &(*list)->next;
	}
}

/* Scan the list of all nodes present for this ino, build map of versions, etc. */

void jffs2_read_inode (struct inode *inode)
{
	struct jffs2_tmp_dnode_info *tn_list, *tn;
	struct jffs2_full_dirent *fd_list;
	struct jffs2_inode_info *f;
	struct jffs2_full_dnode *fn = NULL;
	struct jffs2_sb_info *c;
	struct jffs2_raw_inode latest_node;
	__u32 latest_mctime, mctime_ver;