dedup

commit f91758f2fd077c0288c664572559d01c91ba54fd
parent dfdce10112dbafc512a9b4d69a4f380372532422
Author: sin <sin@2f30.org>
Date:   Thu, 25 Apr 2019 21:36:29 +0100

Store a reference count in the block descriptor

Diffstat:
M
bstorage.c
 | 
22
+++++++++++++++++++---

1 file changed, 19 insertions(+), 3 deletions(-)
diff --git a/bstorage.c b/bstorage.c
@@ -42,7 +42,7 @@
 #define BDTYPE		0x100
 
 #define BHDRSIZE	(NBHDRMAGIC + 8 + 8)
-#define BDSIZE		(8 + 8 + 8 + (MDSIZE))
+#define BDSIZE		(8 + 8 + 8 + 8 + (MDSIZE))
 
 extern int pack(unsigned char *dst, char *fmt, ...);
 extern int unpack(unsigned char *src, char *fmt, ...);
@@ -77,6 +77,7 @@ struct bd {
 	uint64_t type;
 	uint64_t offset;
 	uint64_t size;
+	uint64_t refcnt;
 	unsigned char md[MDSIZE];
 	RB_ENTRY(bd) entry;
 };
@@ -218,11 +219,12 @@ unpackbd(int fd, struct bd *bd)
 	if (xread(fd, buf, sizeof(buf)) != sizeof(buf))
 		return -1;
 
-	snprintf(fmt, sizeof(fmt), "qqq'%d", MDSIZE);
+	snprintf(fmt, sizeof(fmt), "qqqq'%d", MDSIZE);
 	n = unpack(buf, fmt,
 	           &bd->type,
 	           &bd->offset,
 	           &bd->size,
+	           &bd->refcnt,
 	           bd->md);
 
 	assert(n == BDSIZE);
@@ -237,11 +239,12 @@ packbd(int fd, struct bd *bd)
 	char fmt[BUFSIZ];
 	int n;
 
-	snprintf(fmt, sizeof(fmt), "qqq'%d", MDSIZE);
+	snprintf(fmt, sizeof(fmt), "qqqq'%d", MDSIZE);
 	n = pack(buf, fmt,
 	         bd->type,
 	         bd->offset,
 	         bd->size,
+	         bd->refcnt,
 	         bd->md);
 
 	assert(n == BDSIZE);
@@ -457,6 +460,18 @@ bsput(struct bctx *bctx, void *buf, size_t n, unsigned char *md)
 
 	bd = RB_FIND(bdcache, &sctx->bdcache, &key);
 	if (bd != NULL) {
+		off_t bdoffs;
+
+		bdoffs = bd->offset - BDSIZE;
+		if (lseek(sctx->fd, bdoffs, SEEK_SET) < 0)
+			return -1;
+
+		bd->refcnt++;
+		if (packbd(sctx->fd, bd) < 0) {
+			bd->refcnt--;
+			return -1;
+		}
+
 		memcpy(md, bd->md, MDSIZE);
 		return 0;
 	}
@@ -471,6 +486,7 @@ bsput(struct bctx *bctx, void *buf, size_t n, unsigned char *md)
 	bd->type = BDTYPE;
 	bd->offset = offs + BDSIZE;
 	bd->size = n;
+	bd->refcnt = 1;
 	memcpy(bd->md, key.md, MDSIZE);
 
 	if (packbd(sctx->fd, bd) < 0) {