Add --discard and --cache_replacement_policy

bcache.h

@@ -15,6 +15,14 @@ static const char bcache_magic[] = {
 	0xc6, 0x85, 0x73, 0xf6, 0x4e, 0x1a, 0x45, 0xca,
 	0x82, 0x65, 0xf5, 0x7f, 0x48, 0xba, 0x6d, 0x81 };
 
+/* Version 1: Backing dev
+ * Version 2: Seed pointer into btree node checksum
+ * Version 3: Backing dev superblock has offset of start of data
+ */
+
+#define BCACHE_SB_BDEV_VERSION	3
+#define BCACHE_SB_MAX_VERSION	3
+
 #define SB_SECTOR		8
 #define SB_LABEL_SIZE		32
 
@@ -51,8 +59,13 @@ struct cache_sb {
 	uint64_t		d[];		/* journal buckets */
 };
 
+BITMASK(SB_BDEV,	struct cache_sb, version, 0, 1);
+
 BITMASK(BDEV_WRITEBACK,	struct cache_sb, flags, 0, 1);
 
+BITMASK(CACHE_DISCARD,	struct cache_sb, flags, 1, 1);
+BITMASK(CACHE_REPLACEMENT, struct cache_sb, flags, 2, 3);
+
 inline uint64_t crc64(const void *_data, size_t len);
 
 #define node(i, j)		((void *) ((i)->d + (j)))

make-bcache.c

@@ -58,6 +58,52 @@ uint64_t hatoi(const char *s)
 	return i;
 }
 
+char *skip_spaces(const char *str)
+{
+	while (isspace(*str))
+		++str;
+	return (char *)str;
+}
+
+char *strim(char *s)
+{
+	size_t size;
+	char *end;
+
+	s = skip_spaces(s);
+	size = strlen(s);
+	if (!size)
+		return s;
+
+	end = s + size - 1;
+	while (end >= s && isspace(*end))
+		end--;
+	*(end + 1) = '\0';
+
+	return s;
+}
+
+ssize_t read_string_list(const char *buf, const char * const list[])
+{
+	size_t i;
+	char *s, *d = strdup(buf);
+	if (!d)
+		return -ENOMEM;
+
+	s = strim(d);
+
+	for (i = 0; list[i]; i++)
+		if (!strcmp(list[i], s))
+			break;
+
+	free(d);
+
+	if (!list[i])
+		return -EINVAL;
+
+	return i;
+}
+
 void usage()
 {
 	printf("Usage: make-bcache [options] device\n"
@@ -67,11 +113,23 @@ void usage()
 	       "	-w, --block		block size (hard sector size of SSD, often 2k)\n"
 	       "	-U			UUID\n"
 	       "	    --writeback		enable writeback\n"
+	       "	    --discard		enable discards\n"
+	       "	    --cache_replacement_policy=(lru|fifo)\n"
 	       "	-h, --help		display this help and exit\n");
 	exit(EXIT_FAILURE);
 }
 
+const char * const cache_replacement_policies[] = {
+	"lru",
+	"fifo",
+	"random",
+	NULL
+};
+
 int writeback;
+int discard;
+unsigned cache_replacement_policy;
+uint64_t data_offset = 16;
 
 struct option opts[] = {
 	{ "cache",		0, NULL,	'C' },
@@ -79,6 +137,9 @@ struct option opts[] = {
 	{ "bucket",		1, NULL,	'b' },
 	{ "block",		1, NULL,	'w' },
 	{ "writeback",		0, &writeback,	1 },
+	{ "discard",		0, &discard,	1 },
+	{ "cache_replacement_policy", 1, NULL, 'p' },
+//	{ "data_offset",	1, NULL,	'o' },
 	{ "help",		0, NULL,	'h' },
 	{ NULL,			0, NULL,	0 },
 };
@@ -88,7 +149,7 @@ void write_sb(char *dev, struct cache_sb *sb)
 	int fd;
 	char uuid[40], set_uuid[40];
 
-	if (sb->version > 1) {
+	if (sb->version > BCACHE_SB_MAX_VERSION) {
 		printf("Must specify one of -C or -B\n");
 		usage();
 	}
@@ -109,11 +170,20 @@ void write_sb(char *dev, struct cache_sb *sb)
 		exit(EXIT_FAILURE);
 	}
 
-	if (sb->version == CACHE_BACKING_DEV &&
-	    writeback)
-		SET_BDEV_WRITEBACK(sb, 1);
-	else
-		SET_BDEV_WRITEBACK(sb, 0);
+	sb->flags = 0;
+
+	if (SB_BDEV(sb)) {
+		SET_BDEV_WRITEBACK(sb, writeback);
+
+		if (data_offset != 16) {
+			sb->version = BCACHE_SB_BDEV_VERSION;
+			sb->keys = 1;
+			sb->d[0] = data_offset;
+		}
+	} else {
+		SET_CACHE_DISCARD(sb, discard);
+		SET_CACHE_REPLACEMENT(sb, cache_replacement_policy);
+	}
 
 	sb->offset		= SB_SECTOR;
 	memcpy(sb->magic, bcache_magic, 16);
@@ -164,7 +234,7 @@ int main(int argc, char **argv)
 	struct cache_sb sb;
 
 	memset(&sb, 0, sizeof(struct cache_sb));
-	sb.version = 2;
+	sb.version = -1;
 	sb.block_size = 8;
 	sb.bucket_size = 1024;
 
@@ -193,6 +263,17 @@ int main(int argc, char **argv)
 				exit(EXIT_FAILURE);
 			}
 			break;
+		case 'p':
+			cache_replacement_policy = read_string_list(optarg,
+						    cache_replacement_policies);
+			break;
+		case 'o':
+			data_offset = atoll(optarg);
+			if (sb.d[0] < 16) {
+				printf("Bad data offset; minimum 16 sectors\n");
+				exit(EXIT_FAILURE);
+			}
+			break;
 		case 'h':
 			usage();
 			break;