new venti library.

1 files changed, 560 insertions, 0 deletions

diff --git a/src/libventi/cache.c b/src/libventi/cache.c
new file mode 100644
index 00000000..ed8a7f2f
--- /dev/null
+++ b/src/libventi/cache.c
@@ -0,0 +1,560 @@
+/*
+ * Memory-only VtBlock cache.
+ *
+ * The cached Venti blocks are in the hash chains.
+ * The cached local blocks are only in the blocks array.
+ * The free blocks are in the heap, which is supposed to
+ * be indexed by second-to-last use but actually
+ * appears to be last use.
+ */
+
+#include <u.h>
+#include <libc.h>
+#include <venti.h>
+
+int nread, ncopy, nwrite;
+
+enum {
+	BioLocal = 1,
+	BioVenti,
+	BioReading,
+	BioWriting,
+	BioEmpty,
+	BioVentiError,
+};
+enum {
+	BadHeap = ~0,
+};
+struct VtCache
+{
+	QLock	lk;
+	VtConn	*z;
+	u32int	blocksize;
+	u32int	now;		/* ticks for usage time stamps */
+	VtBlock	**hash;	/* hash table for finding addresses */
+	int		nhash;
+	VtBlock	**heap;	/* heap for finding victims */
+	int		nheap;
+	VtBlock	*block;	/* all allocated blocks */
+	int		nblock;
+	uchar	*mem;	/* memory for all blocks and data */
+	int		mode;
+};
+
+static void cachecheck(VtCache*);
+
+VtCache*
+vtcachealloc(VtConn *z, int blocksize, ulong nblock, int mode)
+{
+	uchar *p;
+	VtCache *c;
+	int i;
+	VtBlock *b;
+
+	c = vtmallocz(sizeof(VtCache));
+
+	c->z = z;
+	c->blocksize = (blocksize + 127) & ~127;
+	c->nblock = nblock;
+
+	c->nhash = nblock;
+	c->hash = vtmallocz(nblock*sizeof(VtBlock*));
+	c->heap = vtmallocz(nblock*sizeof(VtBlock*));
+	c->block = vtmallocz(nblock*sizeof(VtBlock));
+	c->mem = vtmallocz(nblock*c->blocksize);
+	c->mode = mode;
+
+	p = c->mem;
+	for(i=0; i<nblock; i++){
+		b = &c->block[i];
+		b->addr = NilBlock;
+		b->c = c;
+		b->data = p;
+		b->heap = i;
+		c->heap[i] = b;
+		p += c->blocksize;
+	}
+	c->nheap = nblock;
+	cachecheck(c);
+	return c;
+}
+
+void
+vtcachefree(VtCache *c)
+{
+	int i;
+
+	qlock(&c->lk);
+
+	cachecheck(c);
+	for(i=0; i<c->nblock; i++)
+		assert(c->block[i].ref == 0);
+
+	vtfree(c->hash);
+	vtfree(c->heap);
+	vtfree(c->block);
+	vtfree(c->mem);
+	vtfree(c);
+}
+
+static void
+vtcachedump(VtCache *c)
+{
+	int i;
+	VtBlock *b;
+
+	for(i=0; i<c->nblock; i++){
+		b = &c->block[i];
+		print("cache block %d: type %d score %V iostate %d addr %d ref %d nlock %d\n",
+			i, b->type, b->score, b->iostate, b->addr, b->ref, b->nlock);
+	}
+}
+
+static void
+cachecheck(VtCache *c)
+{
+	u32int size, now;
+	int i, k, refed;
+	VtBlock *b;
+
+	size = c->blocksize;
+	now = c->now;
+
+	for(i = 0; i < c->nheap; i++){
+		if(c->heap[i]->heap != i)
+			sysfatal("mis-heaped at %d: %d", i, c->heap[i]->heap);
+		if(i > 0 && c->heap[(i - 1) >> 1]->used - now > c->heap[i]->used - now)
+			sysfatal("bad heap ordering");
+		k = (i << 1) + 1;
+		if(k < c->nheap && c->heap[i]->used - now > c->heap[k]->used - now)
+			sysfatal("bad heap ordering");
+		k++;
+		if(k < c->nheap && c->heap[i]->used - now > c->heap[k]->used - now)
+			sysfatal("bad heap ordering");
+	}
+
+	refed = 0;
+	for(i = 0; i < c->nblock; i++){
+		b = &c->block[i];
+		if(b->data != &c->mem[i * size])
+			sysfatal("mis-blocked at %d", i);
+		if(b->ref && b->heap == BadHeap)
+			refed++;
+		else if(b->addr != NilBlock)
+			refed++;
+	}
+if(c->nheap + refed != c->nblock){
+fprint(2, "cachecheck: nheap %d refed %d nblocks %d\n", c->nheap, refed, c->nblock);
+//vtcachedump(c);
+}
+	assert(c->nheap + refed == c->nblock);
+	refed = 0;
+	for(i = 0; i < c->nblock; i++){
+		b = &c->block[i];
+		if(b->ref){
+if(1)fprint(2, "a=%ud %V ref=%d\n", b->addr, b->score, b->ref);
+			refed++;
+		}
+	}
+if(refed > 0)fprint(2, "cachecheck: in used %d\n", refed);
+}
+
+static int
+upheap(int i, VtBlock *b)
+{
+	VtBlock *bb;
+	u32int now;
+	int p;
+	VtCache *c;
+	
+	c = b->c;
+	now = c->now;
+	for(; i != 0; i = p){
+		p = (i - 1) >> 1;
+		bb = c->heap[p];
+		if(b->used - now >= bb->used - now)
+			break;
+		c->heap[i] = bb;
+		bb->heap = i;
+	}
+	c->heap[i] = b;
+	b->heap = i;
+
+	return i;
+}
+
+static int
+downheap(int i, VtBlock *b)
+{
+	VtBlock *bb;
+	u32int now;
+	int k;
+	VtCache *c;
+	
+	c = b->c;
+	now = c->now;
+	for(; ; i = k){
+		k = (i << 1) + 1;
+		if(k >= c->nheap)
+			break;
+		if(k + 1 < c->nheap && c->heap[k]->used - now > c->heap[k + 1]->used - now)
+			k++;
+		bb = c->heap[k];
+		if(b->used - now <= bb->used - now)
+			break;
+		c->heap[i] = bb;
+		bb->heap = i;
+	}
+	c->heap[i] = b;
+	b->heap = i;
+	return i;
+}
+
+/*
+ * Delete a block from the heap.
+ * Called with c->lk held.
+ */
+static void
+heapdel(VtBlock *b)
+{
+	int i, si;
+	VtCache *c;
+
+	c = b->c;
+
+	si = b->heap;
+	if(si == BadHeap)
+		return;
+	b->heap = BadHeap;
+	c->nheap--;
+	if(si == c->nheap)
+		return;
+	b = c->heap[c->nheap];
+	i = upheap(si, b);
+	if(i == si)
+		downheap(i, b);
+}
+
+/*
+ * Insert a block into the heap.
+ * Called with c->lk held.
+ */
+static void
+heapins(VtBlock *b)
+{
+	assert(b->heap == BadHeap);
+	upheap(b->c->nheap++, b);
+}
+
+/*
+ * locate the vtBlock with the oldest second to last use.
+ * remove it from the heap, and fix up the heap.
+ */
+/* called with c->lk held */
+static VtBlock*
+vtcachebumpblock(VtCache *c)
+{
+	VtBlock *b;
+
+	/*
+	 * locate the vtBlock with the oldest second to last use.
+	 * remove it from the heap, and fix up the heap.
+	 */
+	if(c->nheap == 0){
+		vtcachedump(c);
+abort();
+		sysfatal("vtcachebumpblock: no free blocks in vtCache");
+	}
+	b = c->heap[0];
+	heapdel(b);
+
+	assert(b->heap == BadHeap);
+	assert(b->ref == 0);
+
+	/*
+	 * unchain the vtBlock from hash chain if any
+	 */
+	if(b->prev){
+		*(b->prev) = b->next;
+		if(b->next)
+			b->next->prev = b->prev;
+		b->prev = nil;
+	}
+
+ 	
+if(0)fprint(2, "droping %x:%V\n", b->addr, b->score);
+	/* set vtBlock to a reasonable state */
+	b->ref = 1;
+	b->iostate = BioEmpty;
+	return b;
+}
+
+/*
+ * fetch a local block from the memory cache.
+ * if it's not there, load it, bumping some other Block.
+ * if we're out of free blocks, we're screwed.
+ */
+VtBlock*
+vtcachelocal(VtCache *c, u32int addr, int type)
+{
+	VtBlock *b;
+
+	if(addr >= c->nblock)
+		sysfatal("vtcachelocal: asked for block #%ud; only %d blocks\n",
+			addr, c->nblock);
+
+	b = &c->block[addr];
+	if(b->addr == NilBlock || b->iostate != BioLocal)
+{
+abort();
+		sysfatal("vtcachelocal: block is not local");
+}
+
+	if(b->type != type)
+{
+print("%d != %d\n", b->type, type);
+abort();
+		sysfatal("vtcachelocal: block has wrong type %d != %d", b->type, type);
+}
+
+	qlock(&c->lk);
+	b->ref++;
+	qunlock(&c->lk);
+
+	qlock(&b->lk);
+	b->nlock = 1;
+	return b;
+}
+
+VtBlock*
+vtcacheallocblock(VtCache *c, int type)
+{
+	VtBlock *b;
+
+if(type >= VtMaxType)
+	abort();
+
+	qlock(&c->lk);
+	b = vtcachebumpblock(c);
+	b->iostate = BioLocal;
+	b->type = type;
+	b->addr = b - c->block;
+	vtzeroextend(type, b->data, 0, c->blocksize);
+	vtlocaltoglobal(b->addr, b->score);
+	qunlock(&c->lk);
+
+	qlock(&b->lk);
+	b->nlock = 1;
+
+	return b;
+}
+
+/*
+ * fetch a global (Venti) block from the memory cache.
+ * if it's not there, load it, bumping some other block.
+ */
+VtBlock*
+vtcacheglobal(VtCache *c, uchar score[VtScoreSize], int type)
+{
+	VtBlock *b;
+	ulong h;
+	int n;
+	u32int addr;
+
+	addr = vtglobaltolocal(score);
+	if(addr != NilBlock)
+		return vtcachelocal(c, addr, type);
+
+	h = (u32int)(score[0]|(score[1]<<8)|(score[2]<<16)|(score[3]<<24)) % c->nhash;
+
+	/*
+	 * look for the block in the cache
+	 */
+	qlock(&c->lk);
+	for(b = c->hash[h]; b != nil; b = b->next){
+		if(b->addr != NilBlock || memcmp(b->score, score, VtScoreSize) != 0 || b->type != type)
+			continue;
+		heapdel(b);
+		b->ref++;
+		qunlock(&c->lk);
+		qlock(&b->lk);
+		b->nlock = 1;
+		return b;
+	}
+
+	/*
+	 * not found
+	 */
+	b = vtcachebumpblock(c);
+	b->addr = NilBlock;
+	b->type = type;
+	memmove(b->score, score, VtScoreSize);
+	/* chain onto correct hash */
+	b->next = c->hash[h];
+	c->hash[h] = b;
+	if(b->next != nil)
+		b->next->prev = &b->next;
+	b->prev = &c->hash[h];
+
+	/*
+	 * Lock b before unlocking c, so that others wait while we read.
+	 * 
+	 * You might think there is a race between this qlock(b) before qunlock(c)
+	 * and the qlock(c) while holding a qlock(b) in vtblockwrite.  However,
+	 * the block here can never be the block in a vtblockwrite, so we're safe.
+	 * We're certainly living on the edge.
+	 */
+	qlock(&b->lk);
+	b->nlock = 1;
+	qunlock(&c->lk);
+
+	n = vtread(c->z, score, type, b->data, c->blocksize);
+	if(n < 0){
+fprint(2, "vtread: %r\n");
+		b->iostate = BioVentiError;
+		vtblockput(b);
+		return nil;
+	}
+	vtzeroextend(type, b->data, n, c->blocksize);
+	b->iostate = BioVenti;
+	b->nlock = 1;
+	b->decrypted = 0;
+	return b;
+}
+
+/*
+ * The thread that has locked b may refer to it by
+ * multiple names.  Nlock counts the number of
+ * references the locking thread holds.  It will call
+ * vtblockput once per reference.
+ */
+void
+vtblockduplock(VtBlock *b)
+{
+	assert(b->nlock > 0);
+	b->nlock++;
+}
+
+/*
+ * we're done with the block.
+ * unlock it.  can't use it after calling this.
+ */
+void
+vtblockput(VtBlock* b)
+{
+	VtCache *c;
+
+	if(b == nil)
+		return;
+
+if(0)fprint(2, "vtblockput: %d: %x %d %d\n", getpid(), b->addr, c->nheap, b->iostate);
+
+	if(--b->nlock > 0)
+		return;
+
+	/*
+	 * b->nlock should probably stay at zero while
+	 * the vtBlock is unlocked, but diskThread and vtSleep
+	 * conspire to assume that they can just qlock(&b->lk); vtblockput(b),
+	 * so we have to keep b->nlock set to 1 even 
+	 * when the vtBlock is unlocked.
+	 */
+	assert(b->nlock == 0);
+	b->nlock = 1;
+
+	qunlock(&b->lk);
+	c = b->c;
+	qlock(&c->lk);
+
+	if(--b->ref > 0){
+		qunlock(&c->lk);
+		return;
+	}
+
+	assert(b->ref == 0);
+	switch(b->iostate){
+	case BioVenti:
+//if(b->addr != NilBlock) print("blockput %d\n", b->addr);
+		b->used = c->now++;
+	case BioVentiError:
+		heapins(b);
+		break;
+	case BioLocal:
+		break;
+	}
+	qunlock(&c->lk);
+}
+
+int
+vtblockwrite(VtBlock *b)
+{
+	uchar score[VtScoreSize];
+	VtCache *c;
+	uint h;
+	int n;
+
+	if(b->iostate != BioLocal){
+		abort();
+		sysfatal("vtBlockWrite: not a local block");
+	}
+
+	c = b->c;
+	n = vtzerotruncate(b->type, b->data, c->blocksize);
+	if(vtwrite(c->z, score, b->type, b->data, n) < 0)
+		return -1;
+
+	memmove(b->score, score, VtScoreSize);
+
+	qlock(&c->lk);
+	b->iostate = BioVenti;
+	h = (u32int)(score[0]|(score[1]<<8)|(score[2]<<16)|(score[3]<<24)) % c->nhash;
+	b->next = c->hash[h];
+	c->hash[h] = b;
+	if(b->next != nil)
+		b->next->prev = &b->next;
+	b->prev = &c->hash[h];
+	qunlock(&c->lk);
+	return 0;
+}
+
+uint
+vtcacheblocksize(VtCache *c)
+{
+	return c->blocksize;
+}
+
+VtBlock*
+vtblockcopy(VtBlock *b)
+{
+	VtBlock *bb;
+
+ncopy++;
+	bb = vtcacheallocblock(b->c, b->type);
+	if(bb == nil){
+		vtblockput(b);
+		return nil;
+	}
+	memmove(bb->data, b->data, b->c->blocksize);
+	vtblockput(b);
+	return bb;
+}
+
+void
+vtlocaltoglobal(u32int addr, uchar score[VtScoreSize])
+{
+	memset(score, 0, 16);
+	score[16] = addr>>24;
+	score[17] = addr>>16;
+	score[18] = addr>>8;
+	score[19] = addr;
+}
+
+
+u32int
+vtglobaltolocal(uchar score[VtScoreSize])
+{
+	static uchar zero[16];
+	if(memcmp(score, zero, 16) != 0)
+		return NilBlock;
+	return (score[16]<<24)|(score[17]<<16)|(score[18]<<8)|score[19];
+}