file.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

	f->dir.qidMax = max;
	ret = fileMetaFlush2(f, nil)>=0;
	fileMetaUnlock(f);
	fileUnlock(f);
	return ret;
}


uvlong
fileGetId(File *f)
{
	/* immutable */
	return f->dir.qid;
}

ulong
fileGetMcount(File *f)
{
	ulong mcount;

	fileMetaLock(f);
	mcount = f->dir.mcount;
	fileMetaUnlock(f);
	return mcount;
}

ulong
fileGetMode(File *f)
{
	ulong mode;

	fileMetaLock(f);
	mode = f->dir.mode;
	fileMetaUnlock(f);
	return mode;
}

int
fileIsDir(File *f)
{
	/* immutable */
	return (f->dir.mode & ModeDir) != 0;
}

int
fileIsRoot(File *f)
{
	return f == f->fs->file;
}

int
fileIsRoFs(File *f)
{
	return f->fs->mode == OReadOnly;
}

int
fileGetSize(File *f, uvlong *size)
{
	if(!fileRLock(f))
		return 0;
	if(!sourceLock(f->source, OReadOnly)){
		fileRUnlock(f);
		return 0;
	}
	*size = sourceGetSize(f->source);
	sourceUnlock(f->source);
	fileRUnlock(f);

	return 1;
}

int
fileMetaFlush(File *f, int rec)
{
	File **kids, *p;
	int nkids;
	int i, rv;

	fileMetaLock(f);
	rv = fileMetaFlush2(f, nil);
	fileMetaUnlock(f);

	if(!rec || !fileIsDir(f))
		return rv;

	if(!fileLock(f))
		return rv;
	nkids = 0;
	for(p=f->down; p; p=p->next)
		nkids++;
	kids = vtMemAlloc(nkids*sizeof(File*));
	i = 0;
	for(p=f->down; p; p=p->next){
		kids[i++] = p;
		p->ref++;
	}
	fileUnlock(f);

	for(i=0; i<nkids; i++){
		rv |= fileMetaFlush(kids[i], 1);
		fileDecRef(kids[i]);
	}
	vtMemFree(kids);
	return rv;
}

/* assumes metaLock is held */
static int
fileMetaFlush2(File *f, char *oelem)
{
	File *fp;
	Block *b, *bb;
	MetaBlock mb;
	MetaEntry me, me2;
	int i, n;
	u32int boff;

	if(!f->dirty)
		return 0;

	if(oelem == nil)
		oelem = f->dir.elem;

//print("fileMetaFlush %s->%s\n", oelem, f->dir.elem);

	fp = f->up;

	if(!sourceLock(fp->msource, -1))
		return -1;
	/* can happen if source is clri'ed out from under us */
	if(f->boff == NilBlock)
		goto Err1;
	b = sourceBlock(fp->msource, f->boff, OReadWrite);
	if(b == nil)
		goto Err1;

	if(!mbUnpack(&mb, b->data, fp->msource->dsize))
		goto Err;
	if(!mbSearch(&mb, oelem, &i, &me))
		goto Err;

	n = deSize(&f->dir);
if(0)fprint(2, "old size %d new size %d\n", me.size, n);

	if(mbResize(&mb, &me, n)){
		/* fits in the block */
		mbDelete(&mb, i);
		if(strcmp(f->dir.elem, oelem) != 0)
			mbSearch(&mb, f->dir.elem, &i, &me2);
		dePack(&f->dir, &me);
		mbInsert(&mb, i, &me);
		mbPack(&mb);
		blockDirty(b);
		blockPut(b);
		sourceUnlock(fp->msource);
		f->dirty = 0;

		return 1;
	}

	/*
	 * moving entry to another block
	 * it is feasible for the fs to crash leaving two copies
	 * of the directory entry.  This is just too much work to
	 * fix.  Given that entries are only allocated in a block that
	 * is less than PercentageFull, most modifications of meta data
	 * will fit within the block.  i.e. this code should almost
	 * never be executed.
	 */
	boff = fileMetaAlloc(fp, &f->dir, f->boff+1);
	if(boff == NilBlock){
		/* mbResize might have modified block */
		mbPack(&mb);
		blockDirty(b);
		goto Err;
	}
fprint(2, "fileMetaFlush moving entry from %ud -> %ud\n", f->boff, boff);
	f->boff = boff;

	/* make sure deletion goes to disk after new entry */
	bb = sourceBlock(fp->msource, f->boff, OReadWrite);
	mbDelete(&mb, i);
	mbPack(&mb);
	blockDependency(b, bb, -1, nil, nil);
	blockPut(bb);
	blockDirty(b);
	blockPut(b);
	sourceUnlock(fp->msource);

	f->dirty = 0;

	return 1;

Err:
	blockPut(b);
Err1:
	sourceUnlock(fp->msource);
	return -1;
}

static int
fileMetaRemove(File *f, char *uid)
{
	Block *b;
	MetaBlock mb;
	MetaEntry me;
	int i;
	File *up;

	up = f->up;

	fileWAccess(up, uid);

	fileMetaLock(f);

	sourceLock(up->msource, OReadWrite);
	b = sourceBlock(up->msource, f->boff, OReadWrite);
	if(b == nil)
		goto Err;

	if(!mbUnpack(&mb, b->data, up->msource->dsize))
{
fprint(2, "U\n");
		goto Err;
}
	if(!mbSearch(&mb, f->dir.elem, &i, &me))
{
fprint(2, "S\n");
		goto Err;
}
	mbDelete(&mb, i);
	mbPack(&mb);
	sourceUnlock(up->msource);

	blockDirty(b);
	blockPut(b);

	f->removed = 1;
	f->boff = NilBlock;
	f->dirty = 0;

	fileMetaUnlock(f);
	return 1;

Err:
	sourceUnlock(up->msource);
	blockPut(b);
	fileMetaUnlock(f);
	return 0;
}

/* assume file is locked, assume f->msource is locked */
static int
fileCheckEmpty(File *f)
{
	u32int i, n;
	Block *b;
	MetaBlock mb;
	Source *r;

	r = f->msource;
	n = (sourceGetSize(r)+r->dsize-1)/r->dsize;
	for(i=0; i<n; i++){
		b = sourceBlock(r, i, OReadOnly);
		if(b == nil)
			goto Err;
		if(!mbUnpack(&mb, b->data, r->dsize))
			goto Err;
		if(mb.nindex > 0){
			vtSetError(ENotEmpty);
			goto Err;
		}
		blockPut(b);
	}
	return 1;
Err:
	blockPut(b);
	return 0;
}

int
fileRemove(File *f, char *uid)
{
	File *ff;

	/* can not remove the root */
	if(fileIsRoot(f)){
		vtSetError(ERoot);
		return 0;
	}

	if(!fileLock(f))
		return 0;

	if(f->source->mode != OReadWrite){
		vtSetError(EReadOnly);
		goto Err1;
	}
	if(!sourceLock2(f->source, f->msource, -1))
		goto Err1;
	if(fileIsDir(f) && !fileCheckEmpty(f))
		goto Err;

	for(ff=f->down; ff; ff=ff->next)
		assert(ff->removed);

	sourceRemove(f->source);
	f->source = nil;
	if(f->msource){
		sourceRemove(f->msource);
		f->msource = nil;
	}

	fileUnlock(f);

	if(!fileMetaRemove(f, uid))
		return 0;

	return 1;

Err:
	sourceUnlock(f->source);
	if(f->msource)
		sourceUnlock(f->msource);
Err1:
	fileUnlock(f);
	return 0;
}

static int
clri(File *f, char *uid)
{
	int r;

	if(f == nil)
		return 0;
	if(f->up->source->mode != OReadWrite){
		vtSetError(EReadOnly);
		fileDecRef(f);
		return 0;
	}
	r = fileMetaRemove(f, uid);
	fileDecRef(f);
	return r;
}

int
fileClriPath(Fs *fs, char *path, char *uid)
{
	return clri(_fileOpen(fs, path, 1), uid);
}

int
fileClri(File *dir, char *elem, char *uid)
{
	return clri(_fileWalk(dir, elem, 1), uid);
}

File *
fileIncRef(File *vf)
{
	fileMetaLock(vf);
	assert(vf->ref > 0);
	vf->ref++;
	fileMetaUnlock(vf);
	return vf;
}

int
fileDecRef(File *f)
{
	File *p, *q, **qq;

	if(f->up == nil){
		/* never linked in */
		assert(f->ref == 1);
		fileFree(f);
		return 1;
	}

	fileMetaLock(f);
	f->ref--;
	if(f->ref > 0){
		fileMetaUnlock(f);
		return 0;
	}
	assert(f->ref == 0);
	assert(f->down == nil);

	fileMetaFlush2(f, nil);

	p = f->up;
	qq = &p->down;
	for(q = *qq; q; q = *qq){
		if(q == f)
			break;
		qq = &q->next;
	}
	assert(q != nil);
	*qq = f->next;

	fileMetaUnlock(f);
	fileFree(f);

	fileDecRef(p);
	return 1;
}

File *
fileGetParent(File *f)
{
	if(fileIsRoot(f))
		return fileIncRef(f);
	return fileIncRef(f->up);
}

DirEntryEnum *
deeOpen(File *f)
{
	DirEntryEnum *dee;
	File *p;

	if(!fileIsDir(f)){
		vtSetError(ENotDir);
		fileDecRef(f);
		return nil;
	}

	/* flush out meta data */
	if(!fileLock(f))
		return nil;
	for(p=f->down; p; p=p->next)
		fileMetaFlush2(p, nil);
	fileUnlock(f);

	dee = vtMemAllocZ(sizeof(DirEntryEnum));
	dee->file = fileIncRef(f);

	return dee;
}

static int
dirEntrySize(Source *s, ulong elem, ulong gen, uvlong *size)
{
	Block *b;
	ulong bn;
	Entry e;
	int epb;

	epb = s->dsize/VtEntrySize;
	bn = elem/epb;
	elem -= bn*epb;

	b = sourceBlock(s, bn, OReadOnly);
	if(b == nil)
		goto Err;
	if(!entryUnpack(&e, b->data, elem))
		goto Err;

	/* hanging entries are returned as zero size */
	if(!(e.flags & VtEntryActive) || e.gen != gen)
		*size = 0;
	else
		*size = e.size;
	blockPut(b);
	return 1;

Err:
	blockPut(b);
	return 0;
}

static int
deeFill(DirEntryEnum *dee)
{
	int i, n;
	Source *meta, *source;
	MetaBlock mb;
	MetaEntry me;
	File *f;
	Block *b;
	DirEntry *de;

	/* clean up first */
	for(i=dee->i; i<dee->n; i++)
		deCleanup(dee->buf+i);
	vtMemFree(dee->buf);
	dee->buf = nil;
	dee->i = 0;
	dee->n = 0;

	f = dee->file;

	source = f->source;
	meta = f->msource;

	b = sourceBlock(meta, dee->boff, OReadOnly);
	if(b == nil)
		goto Err;
	if(!mbUnpack(&mb, b->data, meta->dsize))
		goto Err;

	n = mb.nindex;
	dee->buf = vtMemAlloc(n * sizeof(DirEntry));

	for(i=0; i<n; i++){
		de = dee->buf + i;
		meUnpack(&me, &mb, i);
		if(!deUnpack(de, &me))
			goto Err;
		dee->n++;
		if(!(de->mode & ModeDir))
		if(!dirEntrySize(source, de->entry, de->gen, &de->size))
			goto Err;
	}
	dee->boff++;
	blockPut(b);
	return 1;
Err:
	blockPut(b);
	return 0;
}

int
deeRead(DirEntryEnum *dee, DirEntry *de)
{
	int ret, didread;
	File *f;
	u32int nb;

	if(dee == nil){
		vtSetError("cannot happen in deeRead");
		return -1;
	}

	f = dee->file;
	if(!fileRLock(f))
		return -1;

	if(!sourceLock2(f->source, f->msource, OReadOnly)){
		fileRUnlock(f);
		return -1;
	}

	nb = (sourceGetSize(f->msource)+f->msource->dsize-1)/f->msource->dsize;

	didread = 0;
	while(dee->i >= dee->n){
		if(dee->boff >= nb){
			ret = 0;
			goto Return;
		}
		didread = 1;
		if(!deeFill(dee)){
			ret = -1;
			goto Return;
		}
	}

	memmove(de, dee->buf + dee->i, sizeof(DirEntry));
	dee->i++;
	ret = 1;

Return:
	sourceUnlock(f->source);
	sourceUnlock(f->msource);
	fileRUnlock(f);

	if(didread)
		fileRAccess(f);
	return ret;
}

void
deeClose(DirEntryEnum *dee)
{
	int i;
	if(dee == nil)
		return;
	for(i=dee->i; i<dee->n; i++)
		deCleanup(dee->buf+i);
	vtMemFree(dee->buf);
	fileDecRef(dee->file);
	vtMemFree(dee);
}

/*
 * caller must lock f->source and f->msource
 * caller must NOT lock the source and msource
 * referenced by dir.
 */
static u32int
fileMetaAlloc(File *f, DirEntry *dir, u32int start)
{
	u32int nb, bo;
	Block *b, *bb;
	MetaBlock mb;
	int nn;
	uchar *p;
	int i, n, epb;
	MetaEntry me;
	Source *s, *ms;

	s = f->source;
	ms = f->msource;

	n = deSize(dir);
	nb = (sourceGetSize(ms)+ms->dsize-1)/ms->dsize;
	b = nil;
	if(start > nb)
		start = nb;
	for(bo=start; bo<nb; bo++){
		b = sourceBlock(ms, bo, OReadWrite);
		if(b == nil)
			goto Err;
		if(!mbUnpack(&mb, b->data, ms->dsize))
			goto Err;
		nn = (mb.maxsize*FullPercentage/100) - mb.size + mb.free;
		if(n <= nn && mb.nindex < mb.maxindex)
			break;
		blockPut(b);
		b = nil;
	}

	/* add block to meta file */
	if(b == nil){
		b = sourceBlock(ms, bo, OReadWrite);
		if(b == nil)
			goto Err;
		sourceSetSize(ms, (nb+1)*ms->dsize);
		mbInit(&mb, b->data, ms->dsize, ms->dsize/BytesPerEntry);
	}

	p = mbAlloc(&mb, n);
	if(p == nil){
		/* mbAlloc might have changed block */
		mbPack(&mb);
		blockDirty(b);
		vtSetError(EBadMeta);
		goto Err;
	}

	mbSearch(&mb, dir->elem, &i, &me);
	assert(me.p == nil);
	me.p = p;
	me.size = n;
	dePack(dir, &me);
	mbInsert(&mb, i, &me);
	mbPack(&mb);

	/* meta block depends on super block for qid ... */
	bb = cacheLocal(b->c, PartSuper, 0, OReadOnly);
	blockDependency(b, bb, -1, nil, nil);
	blockPut(bb);

	/* ... and one or two dir entries */
	epb = s->dsize/VtEntrySize;
	bb = sourceBlock(s, dir->entry/epb, OReadOnly);
	blockDependency(b, bb, -1, nil, nil);
	blockPut(bb);
	if(dir->mode & ModeDir){
		bb = sourceBlock(s, dir->mentry/epb, OReadOnly);
		blockDependency(b, bb, -1, nil, nil);
		blockPut(bb);
	}

	blockDirty(b);
	blockPut(b);
	return bo;
Err:
	blockPut(b);
	return NilBlock;
}

static int
chkSource(File *f)
{
	if(f->partial)
		return 1;

	if(f->source == nil || (f->dir.mode & ModeDir) && f->msource == nil){
		vtSetError(ERemoved);
		return 0;
	}
	return 1;
}

static int
fileRLock(File *f)
{
	assert(!vtCanLock(f->fs->elk));
	vtRLock(f->lk);
	if(!chkSource(f)){
		fileRUnlock(f);
		return 0;
	}
	return 1;
}

static void
fileRUnlock(File *f)
{
	vtRUnlock(f->lk);
}

static int
fileLock(File *f)
{
	assert(!vtCanLock(f->fs->elk));
	vtLock(f->lk);
	if(!chkSource(f)){
		fileUnlock(f);
		return 0;
	}
	return 1;
}

static void
fileUnlock(File *f)
{
	vtUnlock(f->lk);
}

/*
 * f->source and f->msource must NOT be locked.
 * fileMetaFlush locks the fileMeta and then the source (in fileMetaFlush2).
 * We have to respect that ordering.
 */
static void
fileMetaLock(File *f)
{
if(f->up == nil)
fprint(2, "f->elem = %s\n", f->dir.elem);
	assert(f->up != nil);
	assert(!vtCanLock(f->fs->elk));
	vtLock(f->up->lk);
}

static void
fileMetaUnlock(File *f)
{
	vtUnlock(f->up->lk);
}

/*
 * f->source and f->msource must NOT be locked.
 * see fileMetaLock.
 */
static void
fileRAccess(File* f)
{
	if(f->mode == OReadOnly)
		return;

	fileMetaLock(f);
	f->dir.atime = time(0L);
	f->dirty = 1;
	fileMetaUnlock(f);
}

/*
 * f->source and f->msource must NOT be locked.
 * see fileMetaLock.
 */
static void
fileWAccess(File* f, char *mid)
{
	if(f->mode == OReadOnly)
		return;

	fileMetaLock(f);
	f->dir.atime = f->dir.mtime = time(0L);
	if(strcmp(f->dir.mid, mid) != 0){
		vtMemFree(f->dir.mid);
		f->dir.mid = vtStrDup(mid);
	}
	f->dir.mcount++;
	f->dirty = 1;
	fileMetaUnlock(f);

/*RSC: let's try this */
/*presotto - lets not
	if(f->up)
		fileWAccess(f->up, mid);
*/
}

static int
getEntry(Source *r, Entry *e, int checkepoch)
{
	u32int epoch;
	Block *b;

	if(r == nil){
		memset(&e, 0, sizeof e);
		return 1;
	}

	b = cacheGlobal(r->fs->cache, r->score, BtDir, r->tag, OReadOnly);
	if(b == nil)
		return 0;
	if(!entryUnpack(e, b->data, r->offset % r->epb)){
		blockPut(b);
		return 0;
	}
	epoch = b->l.epoch;
	blockPut(b);

	if(checkepoch){
		b = cacheGlobal(r->fs->cache, e->score, entryType(e), e->tag, OReadOnly);
		if(b){
			if(b->l.epoch >= epoch)
				fprint(2, "warning: entry %p epoch not older %#.8ux/%d %V/%d in getEntry\n",
					r, b->addr, b->l.epoch, r->score, epoch);
			blockPut(b);
		}
	}

	return 1;
}

static int
setEntry(Source *r, Entry *e)
{
	Block *b;
	Entry oe;

	b = cacheGlobal(r->fs->cache, r->score, BtDir, r->tag, OReadWrite);
	if(0) fprint(2, "setEntry: b %#ux %d score=%V\n", b->addr, r->offset % r->epb, e->score);
	if(b == nil)
		return 0;
	if(!entryUnpack(&oe, b->data, r->offset % r->epb)){
		blockPut(b);
		return 0;
	}
	e->gen = oe.gen;
	entryPack(e, b->data, r->offset % r->epb);

	/* BUG b should depend on the entry pointer */

	blockDirty(b);
	blockPut(b);
	return 1;
}

/* assumes hold elk */
int
fileSnapshot(File *dst, File *src, u32int epoch, int doarchive)
{
	Entry e, ee;

	/* add link to snapshot */
	if(!getEntry(src->source, &e, 1) || !getEntry(src->msource, &ee, 1))
		return 0;

	e.snap = epoch;
	e.archive = doarchive;
	ee.snap = epoch;
	ee.archive = doarchive;

	if(!setEntry(dst->source, &e) || !setEntry(dst->msource, &ee))
		return 0;
	return 1;
}

int
fileGetSources(File *f, Entry *e, Entry *ee)
{
	if(!getEntry(f->source, e, 0)
	|| !getEntry(f->msource, ee, 0))
		return 0;
	return 1;
}	

/*
 * Walk down to the block(s) containing the Entries
 * for f->source and f->msource, copying as we go.
 */
int
fileWalkSources(File *f)
{
	if(f->mode == OReadOnly){
		fprint(2, "readonly in fileWalkSources\n");
		return 1;
	}
	if(!sourceLock2(f->source, f->msource, OReadWrite)){
		fprint(2, "sourceLock2 failed in fileWalkSources\n");
		return 0;
	}
	sourceUnlock(f->source);
	sourceUnlock(f->msource);
	return 1;
}