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

#include "stdinc.h"
#include "dat.h"
#include "fns.h"

static void error(Fsck*, char*, ...);
static void setBit(uchar*, u32int);
static int getBit(uchar*, u32int);
static int walkEpoch(Fsck *chk, Block *b, uchar score[VtScoreSize], int type, u32int tag, u32int epoch);
static void warn(Fsck*, char*, ...);
static void checkLeak(Fsck*);
static void clrenop(Fsck*, Block*, int);
static void closenop(Fsck*, Block*, u32int);
static void clrinop(Fsck*, char*, MetaBlock*, int, Block*);
static int printnop(char*, ...);
static void checkEpochs(Fsck*);
static void checkDirs(Fsck*);

#pragma varargck argpos error 2
#pragma varargck argpos warn 2

static Fsck*
checkInit(Fsck *chk)
{
	chk->cache = chk->fs->cache;
	chk->nblocks = cacheLocalSize(chk->cache, PartData);;
	chk->bsize = chk->fs->blockSize;
	chk->walkdepth = 0;
	chk->hint = 0;
	chk->quantum = chk->nblocks/100;
	if(chk->quantum == 0)
		chk->quantum = 1;
	if(chk->print == nil)
		chk->print = printnop;
	if(chk->clre == nil)
		chk->clre = clrenop;
	if(chk->close == nil)
		chk->close = closenop;
	if(chk->clri == nil)
		chk->clri = clrinop;
	return chk;
}

/*
 * BUG: Should merge checkEpochs and checkDirs so that 
 * bad blocks are only reported once, and so that errors in checkEpochs
 * can have the affected file names attached, and so that the file system
 * is only read once.
 * 
 * Also should summarize the errors instead of printing for every one
 * (e.g., XXX bad or unreachable blocks in /active/usr/rsc/foo).
 */

void
fsCheck(Fsck *chk)
{
	Block *b;
	Super super;

	checkInit(chk);
	b = superGet(chk->cache, &super);
	if(b == nil){
		chk->print("could not load super block: %R");
		return;
	}
	blockPut(b);

	chk->hint = super.active;
	checkEpochs(chk);

	chk->smap = vtMemAllocZ(chk->nblocks/8+1);
	checkDirs(chk);
	vtMemFree(chk->smap);
}

static void checkEpoch(Fsck*, u32int);

/*
 * Walk through all the blocks in the write buffer.
 * Then we can look for ones we missed -- those are leaks.
 */
static void
checkEpochs(Fsck *chk)
{
	u32int e;
	uint nb;

	nb = chk->nblocks;
	chk->amap = vtMemAllocZ(nb/8+1);
	chk->emap = vtMemAllocZ(nb/8+1);
	chk->xmap = vtMemAllocZ(nb/8+1);
	chk->errmap = vtMemAllocZ(nb/8+1);

	for(e=chk->fs->ehi; e >= chk->fs->elo; e--){
		memset(chk->emap, 0, chk->nblocks/8+1);
		memset(chk->xmap, 0, chk->nblocks/8+1);
		checkEpoch(chk, e);
	}
	checkLeak(chk);
	vtMemFree(chk->amap);
	vtMemFree(chk->emap);
	vtMemFree(chk->xmap);
	vtMemFree(chk->errmap);
}

static void
checkEpoch(Fsck *chk, u32int epoch)
{
	u32int a;
	Block *b;
	Entry e;
	Label l;
	
	chk->print("checking epoch %ud...\n", epoch);

	for(a=0; a<chk->nblocks; a++){
		if(!readLabel(chk->cache, &l, (a+chk->hint)%chk->nblocks)){
			error(chk, "could not read label for addr %.8#ux", a);
			continue;
		}
		if(l.tag == RootTag && l.epoch == epoch)
			break;
	}

	if(a == chk->nblocks){
		chk->print("could not find root block for epoch %ud", epoch);
		return;
	}

	a = (a+chk->hint)%chk->nblocks;
	b = cacheLocalData(chk->cache, a, BtDir, RootTag, OReadOnly, 0);
	if(b == nil){
		error(chk, "could not read root block %.8#ux: %R", a);
		return;
	}

	/* no one should point at root blocks */
	setBit(chk->amap, a);
	setBit(chk->emap, a);
	setBit(chk->xmap, a);

	/*
	 * First entry is the rest of the file system.
	 * Second entry is link to previous epoch root,
	 * just a convenience to help the search.
	 */
	if(!entryUnpack(&e, b->data, 0)){
		error(chk, "could not unpack root block %.8#ux: %R", a);
		blockPut(b);
		return;
	}
	walkEpoch(chk, b, e.score, BtDir, e.tag, epoch);
	if(entryUnpack(&e, b->data, 1))
		chk->hint = globalToLocal(e.score);
	blockPut(b);
}

/*
 * When b points at bb, need to check:
 *
 * (i) b.e in [bb.e, bb.eClose)
 * (ii) if b.e==bb.e,  then no other b' in e points at bb.
 * (iii) if !(b.state&Copied) and b.e==bb.e then no other b' points at bb.
 * (iv) if b is active then no other active b' points at bb.
 * (v) if b is a past life of b' then only one of b and b' is active (too hard to check)
 */
static int
walkEpoch(Fsck *chk, Block *b, uchar score[VtScoreSize], int type, u32int tag, u32int epoch)
{
	int i, ret;
	u32int addr, ep;
	Block *bb;
	Entry e;

	if(b && chk->walkdepth == 0 && chk->printblocks)
		chk->print("%V %d %#.8ux %#.8ux\n", b->score, b->l.type, b->l.tag, b->l.epoch);

	if(!chk->useventi && globalToLocal(score) == NilBlock)
		return 1;

	chk->walkdepth++;

	bb = cacheGlobal(chk->cache, score, type, tag, OReadOnly);
	if(bb == nil){
		error(chk, "could not load block %V type %d tag %ux: %R", score, type, tag);
		chk->walkdepth--;
		return 0;
	}
	if(chk->printblocks)
		chk->print("%*s%V %d %#.8ux %#.8ux\n", chk->walkdepth*2, "", score, type, tag, bb->l.epoch);

	ret = 0;
	addr = globalToLocal(score);
	if(addr == NilBlock){
		ret = 1;
		goto Exit;
	}

	if(b){
		/* (i) */
		if(b->l.epoch < bb->l.epoch || bb->l.epochClose <= b->l.epoch){
			error(chk, "walk: block %#ux [%ud, %ud) points at %#ux [%ud, %ud)",
				b->addr, b->l.epoch, b->l.epochClose,
				bb->addr, bb->l.epoch, bb->l.epochClose);
			goto Exit;
		}
	
		/* (ii) */
		if(b->l.epoch == epoch && bb->l.epoch == epoch){
			if(getBit(chk->emap, addr)){
				error(chk, "walk: epoch join detected: addr %#ux %L", bb->addr, &bb->l);
				goto Exit;
			}
			setBit(chk->emap, addr);
		}
	
		/* (iii) */
		if(!(b->l.state&BsCopied) && b->l.epoch == bb->l.epoch){
			if(getBit(chk->xmap, addr)){
				error(chk, "walk: copy join detected; addr %#ux %L", bb->addr, &bb->l);
				goto Exit;
			}
			setBit(chk->xmap, addr);
		}
	}

	/* (iv) */
	if(epoch == chk->fs->ehi){
		/* since epoch==fs->ehi is first, amap is same as ``have seen active'' */
		if(getBit(chk->amap, addr)){
			error(chk, "walk: active join detected: addr %#ux %L", bb->addr, &bb->l);
			goto Exit;
		}
		if(bb->l.state&BsClosed)
			error(chk, "walk: addr %#ux: block is in active tree but is closed", addr);
	}else{
		if(!getBit(chk->amap, addr)){
			if(!(bb->l.state&BsClosed)){
				// error(chk, "walk: addr %#ux: block is not in active tree, not closed (%d)", addr, bb->l.epochClose);
				chk->close(chk, bb, epoch+1);
				chk->nclose++;
			}
		}
	}

	if(getBit(chk->amap, addr)){
		ret = 1;
		goto Exit;
	}
	setBit(chk->amap, addr);

	if(chk->nseen++%chk->quantum == 0)
		chk->print("check: visited %d/%d blocks (%.0f%%)\n",
			chk->nseen, chk->nblocks, chk->nseen*100./chk->nblocks);

	b = nil;		/* make sure no more refs to parent */
	USED(b);

	switch(type){
	default:
		/* pointer block */
		for(i=0; i<chk->bsize/VtScoreSize; i++)
			if(!walkEpoch(chk, bb, bb->data + i*VtScoreSize, type-1, tag, epoch)){
				setBit(chk->errmap, bb->addr);
				chk->clrp(chk, bb, i);
				chk->nclrp++;
			}
		break;
	case BtData:
		break;
	case BtDir:
		for(i=0; i<chk->bsize/VtEntrySize; i++){
			if(!entryUnpack(&e, bb->data, i)){
				// error(chk, "walk: could not unpack entry: %ux[%d]: %R", addr, i);
				setBit(chk->errmap, bb->addr);
				chk->clre(chk, bb, i);
				chk->nclre++;
				continue;
			}
			if(!(e.flags & VtEntryActive))
				continue;
//fprint(2, "%x[%d] tag=%x snap=%d score=%V\n", addr, i, e.tag, e.snap, e.score);
			ep = epoch;
			if(e.snap != 0){
				if(e.snap >= epoch){
					// error(chk, "bad snap in entry: %ux[%d] snap = %ud: epoch = %ud",
					//	addr, i, e.snap, epoch);
					setBit(chk->errmap, bb->addr);
					chk->clre(chk, bb, i);
					chk->nclre++;
					continue;
				}
				continue;
			}
			if(e.flags & VtEntryLocal){
				if(e.tag < UserTag)
				if(e.tag != RootTag || tag != RootTag || i != 1){
					// error(chk, "bad tag in entry: %ux[%d] tag = %ux", addr, i, e.tag);
					setBit(chk->errmap, bb->addr);
					chk->clre(chk, bb, i);
					chk->nclre++;
					continue;
				}
			}else{
				if(e.tag != 0){
					// error(chk, "bad tag in entry: %ux[%d] tag = %ux", addr, i, e.tag);
					setBit(chk->errmap, bb->addr);
					chk->clre(chk, bb, i);
					chk->nclre++;
					continue;
				}
			}
			if(!walkEpoch(chk, bb, e.score, entryType(&e), e.tag, ep)){
				setBit(chk->errmap, bb->addr);
				chk->clre(chk, bb, i);
				chk->nclre++;
			}
		}
		break;
	}

	ret = 1;

Exit:
	chk->walkdepth--;
	blockPut(bb);
	return ret;
}

/*
 * We've just walked the whole write buffer.  Notice blocks that
 * aren't marked available but that we didn't visit.  They are lost.
 */
static void
checkLeak(Fsck *chk)
{
	u32int a;
	Label l;
	u32int nfree;
	u32int nlost;
	Block *b;

	nfree = 0;
	nlost = 0;

	for(a=0; a<chk->nblocks; a++){
		if(!readLabel(chk->cache, &l, a)){
			error(chk, "could not read label: addr %ux %d %d: %R",
				a, l.type, l.state);
			continue;
		}
		if(getBit(chk->amap, a))
			continue;
		if(l.state == BsFree || l.epochClose <= chk->fs->elo || l.epochClose == l.epoch){
			nfree++;
			setBit(chk->amap, a);
			continue;
		}
		if(l.state&BsClosed)
			continue;
		nlost++;
		// warn(chk, "unreachable block: addr %ux type %d tag %ux state %s epoch %ud close %ud",
		// 	a, l.type, l.tag, bsStr(l.state), l.epoch, l.epochClose);
		b = cacheLocal(chk->cache, PartData, a, OReadOnly);
		if(b == nil){
			error(chk, "could not read block %#.8ux", a);
			continue;
		}
		chk->close(chk, b, 0);
		chk->nclose++;
		setBit(chk->amap, a);
		blockPut(b);
	}
	chk->print("fsys blocks: total=%ud used=%ud(%.1f%%) free=%ud(%.1f%%) lost=%ud(%.1f%%)\n",
		chk->nblocks, 
		chk->nblocks-nfree-nlost, 
		100.*(chk->nblocks-nfree-nlost)/chk->nblocks,
		nfree, 100.*nfree/chk->nblocks,
		nlost, 100.*nlost/chk->nblocks);
}


/*
 * Check that all sources in the tree are accessible.
 */
static Source *
openSource(Fsck *chk, Source *s, char *name, uchar *bm, u32int offset, u32int gen, int dir, MetaBlock *mb, int i, Block *b)
{
	Source *r;