check.c

这是一个同样来自贝尔实验室的和UNIX有着渊源的操作系统, 其简洁的设计和实现易于我们学习和理解

	r = nil;
	if(getBit(bm, offset)){
		warn(chk, "multiple references to source: %s -> %d", name, offset);
		goto Err;
	}
	setBit(bm, offset);

	r = sourceOpen(s, offset, OReadOnly);
	if(r == nil){
		warn(chk, "could not open source: %s -> %d: %R", name, offset);
		goto Err;
	}

	if(r->gen != gen){
		warn(chk, "source has been removed: %s -> %d", name, offset);
		goto Err;
	}

	if(r->dir != dir){
		warn(chk, "dir mismatch: %s -> %d", name, offset);
		goto Err;
	}
	return r;
Err:
	chk->clri(chk, name, mb, i, b);
	chk->nclri++;
	if(r)
		sourceClose(r);
	return nil;
}

typedef struct MetaChunk MetaChunk;

struct MetaChunk {
	ushort offset;
	ushort size;
	ushort index;
};

static int
offsetCmp(void *s0, void *s1)
{
	MetaChunk *mc0, *mc1;

	mc0 = s0;
	mc1 = s1;
	if(mc0->offset < mc1->offset)
		return -1;
	if(mc0->offset > mc1->offset)
		return 1;
	return 0;
}

/*
 * Fsck that MetaBlock has reasonable header, sorted entries,
 */
static int
chkMetaBlock(MetaBlock *mb)
{
	MetaChunk *mc;
	int oo, o, n, i;
	uchar *p;

	mc = vtMemAlloc(mb->nindex*sizeof(MetaChunk));
	p = mb->buf + MetaHeaderSize;
	for(i = 0; i<mb->nindex; i++){
		mc[i].offset = (p[0]<<8) | p[1];
		mc[i].size = (p[2]<<8) | p[3];
		mc[i].index = i;
		p += MetaIndexSize;
	}

	qsort(mc, mb->nindex, sizeof(MetaChunk), offsetCmp);

	/* check block looks ok */
	oo = MetaHeaderSize + mb->maxindex*MetaIndexSize;
	o = oo;
	n = 0;
	for(i=0; i<mb->nindex; i++){
		o = mc[i].offset;
		n = mc[i].size;
		if(o < oo)
			goto Err;
		oo += n;
	}
	if(o+n > mb->size)
		goto Err;
	if(mb->size - oo != mb->free)
		goto Err;

	vtMemFree(mc);
	return 1;

Err:
if(0){
	fprint(2, "metaChunks failed!\n");
	oo = MetaHeaderSize + mb->maxindex*MetaIndexSize;
	for(i=0; i<mb->nindex; i++){
		fprint(2, "\t%d: %d %d\n", i, mc[i].offset, mc[i].offset + mc[i].size);
		oo += mc[i].size;
	}
	fprint(2, "\tused=%d size=%d free=%d free2=%d\n", 
		oo, mb->size, mb->free, mb->size - oo);
}
	vtMemFree(mc);
	return 0;
}

static void
scanSource(Fsck *chk, char *name, Source *r)
{
	u32int nb, o;
	Block *b;
	Entry e;
	u32int a;

	if(!chk->useventi && globalToLocal(r->score)==NilBlock)
		return;
	if(!sourceGetEntry(r, &e)){
		error(chk, "could not get entry for %s", name);
		return;
	}
	a = globalToLocal(e.score);
	if(!chk->useventi && a==NilBlock)
		return;
	if(getBit(chk->smap, a))
		return;
	setBit(chk->smap, a);

	nb = (sourceGetSize(r) + r->dsize-1) / r->dsize;
	for(o=0; o<nb; o++){
		b = sourceBlock(r, o, OReadOnly);
		if(b == nil){
			error(chk, "could not read block in data file %s", name);
			continue;
		}
		if(b->addr != NilBlock && getBit(chk->errmap, b->addr)){
			warn(chk, "previously reported error in block %ux is in file %s",
				b->addr, name);
		}
		blockPut(b);
	}
}

/*
 * Walk the source tree making sure that the BtData
 * sources containing directory entries are okay.
 */
static void
chkDir(Fsck *chk, char *name, Source *source, Source *meta)
{
	uchar *bm;
	Block *b, *bb;
	u32int nb, o;
	MetaBlock mb;
	DirEntry de;
	Entry e1, e2;
	MetaEntry me;
	int i;
	char *s, *nn;
	Source *r, *mr;
	u32int a1, a2;

	if(!chk->useventi && globalToLocal(source->score)==NilBlock && globalToLocal(meta->score)==NilBlock)
		return;

	if(!sourceLock2(source, meta, OReadOnly)){
		warn(chk, "could not lock sources for %s: %R", name);
		return;
	}
	if(!sourceGetEntry(source, &e1) || !sourceGetEntry(meta, &e2)){
		warn(chk, "could not load entries for %s: %R", name);
		return;
	}
	a1 = globalToLocal(e1.score);
	a2 = globalToLocal(e2.score);
	if((!chk->useventi && a1==NilBlock && a2==NilBlock)
	|| (getBit(chk->smap, a1) && getBit(chk->smap, a2))){
		sourceUnlock(source);
		sourceUnlock(meta);
		return;
	}
	setBit(chk->smap, a1);
	setBit(chk->smap, a2);

	bm = vtMemAllocZ(sourceGetDirSize(source)/8 + 1);

	nb = (sourceGetSize(meta) + meta->dsize - 1)/meta->dsize;
	for(o=0; o<nb; o++){
		b = sourceBlock(meta, o, OReadOnly);
		if(b == nil){
			error(chk, "could not read block in meta file: %s[%ud]: %R", name, o);
			continue;
		}
if(0)fprint(2, "source %V:%d block %d addr %d\n", source->score, source->offset, o, b->addr);
		if(b->addr != NilBlock && getBit(chk->errmap, b->addr))
			warn(chk, "previously reported error in block %ux is in %s",
				b->addr, name);

		if(!mbUnpack(&mb, b->data, meta->dsize)){
			error(chk, "could not unpack meta block: %s[%ud]: %R", name, o);
			blockPut(b);
			continue;
		}
		if(!chkMetaBlock(&mb)){
			error(chk, "bad meta block: %s[%ud]: %R", name, o);
			blockPut(b);
			continue;
		}
		s = nil;
		for(i=mb.nindex-1; i>=0; i--){
			meUnpack(&me, &mb, i);
			if(!deUnpack(&de, &me)){
				error(chk, "cound not unpack dir entry: %s[%ud][%d]: %R", name, o, i);
				continue;
			}
			if(s && strcmp(s, de.elem) <= 0)
				error(chk, "dir entry out of order: %s[%ud][%d] = %s last = %s", name, o, i,
					de.elem, s);
			vtMemFree(s);
			s = vtStrDup(de.elem);
			nn = smprint("%s/%s", name, de.elem);
			if(nn == nil){
				error(chk, "out of memory");
				continue;
			}
			if(chk->printdirs){
				if(de.mode&ModeDir)
					chk->print("%s/\n", nn);
			}
			if(chk->printfiles){
				if(!(de.mode&ModeDir))
					chk->print("%s\n", nn);
			}
			if(!(de.mode & ModeDir)){
				r = openSource(chk, source, nn, bm, de.entry, de.gen, 0, &mb, i, b);
				if(r != nil){
					if(sourceLock(r, OReadOnly)){
						scanSource(chk, nn, r);
						sourceUnlock(r);
					}
					sourceClose(r);
				}
				deCleanup(&de);
				free(nn);
				continue;
			}

			r = openSource(chk, source, nn, bm, de.entry, de.gen, 1, &mb, i, b);
			if(r == nil){
				deCleanup(&de);
				free(nn);
				continue;
			}

			mr = openSource(chk, source, nn, bm, de.mentry, de.mgen, 0, &mb, i, b);
			if(mr == nil){
				sourceClose(r);
				deCleanup(&de);
				free(nn);
				continue;
			}

			if(!(de.mode&ModeSnapshot) || chk->walksnapshots)
				chkDir(chk, nn, r, mr);

			sourceClose(mr);
			sourceClose(r);
			deCleanup(&de);
			free(nn);
			deCleanup(&de);

		}
		vtMemFree(s);
		blockPut(b);
	}

	nb = sourceGetDirSize(source);
	for(o=0; o<nb; o++){
		if(getBit(bm, o))
			continue;
		r = sourceOpen(source, o, OReadOnly);
		if(r == nil)
			continue;
		warn(chk, "non referenced entry in source %s[%d]", name, o);
		if((bb = sourceBlock(source, o/(source->dsize/VtEntrySize), OReadOnly)) != nil){
			if(bb->addr != NilBlock){
				setBit(chk->errmap, bb->addr);
				chk->clre(chk, bb, o%(source->dsize/VtEntrySize));
				chk->nclre++;
			}
			blockPut(bb);
		}
		sourceClose(r);
	}

	sourceUnlock(source);
	sourceUnlock(meta);
	vtMemFree(bm);
}

static void
checkDirs(Fsck *chk)
{
	Source *r, *mr;

	sourceLock(chk->fs->source, OReadOnly);
	r = sourceOpen(chk->fs->source, 0, OReadOnly);
	mr = sourceOpen(chk->fs->source, 1, OReadOnly);
	sourceUnlock(chk->fs->source);
	chkDir(chk, "", r, mr);

	sourceClose(r);
	sourceClose(mr);
}

static void
setBit(uchar *bmap, u32int addr)
{
	if(addr == NilBlock)
		return;

	bmap[addr>>3] |= 1 << (addr & 7);
}

static int
getBit(uchar *bmap, u32int addr)
{
	if(addr == NilBlock)
		return 0;

	return (bmap[addr>>3] >> (addr & 7)) & 1;
}

static void
error(Fsck *chk, char *fmt, ...)
{
	static nerr;
	va_list arg;
	char buf[128];

	va_start(arg, fmt);
	vseprint(buf, buf+sizeof(buf), fmt, arg);
	va_end(arg);

	chk->print("error: %s\n", buf);

//	if(nerr++ > 20)
//		vtFatal("too many errors");
}

static void
warn(Fsck *chk, char *fmt, ...)
{
	static nerr;
	va_list arg;
	char buf[128];


	va_start(arg, fmt);
	vseprint(buf, buf+sizeof(buf), fmt, arg);
	va_end(arg);

	chk->print("error: %s\n", buf);
}

static void
clrenop(Fsck*, Block*, int)
{
}

static void
closenop(Fsck*, Block*, u32int)
{
}

static void
clrinop(Fsck*, char*, MetaBlock*, int, Block*)
{
}

static int
printnop(char*, ...)
{
	return 0;
}