Stuff

Makefile

@@ -13,8 +13,8 @@ install: make-bcache probe-bcache
 #	install -m0755 bcache-test ${PREFIX}/sbin/
 
 clean:
-	rm -f make-bcache bcache-test *.o
+	rm -f make-bcache probe-bcache bcache-test *.o
 
-bcache-test: LDFLAGS += -lm -lssl -lcrypto
-make-bcache: LDFLAGS += -luuid
-probe-bcache: LDFLAGS += -luuid
+bcache-test: LDLIBS += -lm -lssl -lcrypto
+make-bcache: LDLIBS += -luuid
+probe-bcache: LDLIBS += -luuid

README

@@ -0,0 +1,24 @@
+These are the userspace tools required for bcache.
+
+Bcache is a patch for the Linux kernel to use SSDs to cache other block
+devices. For more information, see http://bcache.evilpiepirate.org.
+Documentation for the run time interface is included in the kernel tree, in
+Documentantion/bcache.txt.
+
+Included tools:
+
+make-bcache
+Formats a block device for use with bcache. A device can be formatted for use
+as a cache or as a backing device (requires yet to be implemented kernel
+support). The most important option is for specifying the bucket size.
+Allocation is done in terms of buckets, and cache hits are counted per bucket;
+thus a smaller bucket size will give better cache utilization, but poorer write
+performance. The bucket size is intended to be equal to the size of your SSD's
+erase blocks, which seems to be 128k-512k for most SSDs; feel free to
+experiment.
+
+probe-bcache
+Only necessary until support for the bcache superblock is included
+in blkid; in the meantime, provides just enough functionality for a udev script
+to create the /dev/disk/by-uuid symlink. The arguments it does support are the
+same as for blkid.

make-bcache.8

@@ -0,0 +1,26 @@
+.TH make-bcache 8
+.SH NAME
+make-bcache \- create a cache device
+.SH  SYNOPSIS
+.B make-bcache
+[\fB \-U\ \fIUUID\fR ]
+[\fB \-b\ \fIbucket-size\fR ]
+.I device
+.SH OPTIONS
+.TP
+.BR \-C
+Create a cache
+.TP
+.BR \-B
+Create a backing device (kernel functionality not yet implemented)
+.TP
+.BR \-U\ \fIUUID
+Create a cache device with the specified UUID
+.TP
+.BR \-b\ \fIbucket-size
+Spcifies the bucket size. Allocation is done in terms of buckets, and cache
+hits are counted per bucket; thus a smaller bucket size will give better cache
+utilization, but poorer write performance. The bucket size is intended to be
+equal to the size of your SSD's erase blocks, which seems to be 128k-512k for
+most SSDs. Must be a power of two; accepts human readable units. Defaults to
+128k.

make-bcache.c

@@ -70,14 +70,14 @@ void usage()
 int main(int argc, char **argv)
 {
 	bool cache = false, backingdev = false;
-	int64_t nblocks, bucketsize = 0, blocksize = 8;
+	int64_t nblocks;
 	int fd, i, c;
-	struct cache_sb sb;
 	char uuid[40];
+	struct cache_sb sb = { .block_size = 8, .bucket_size = 0 };
 
 	uuid_generate(sb.uuid);
 
-	while ((c = getopt(argc, argv, "CBU:b:")) != -1)
+	while ((c = getopt(argc, argv, "CBU:w:b:")) != -1)
 		switch (c) {
 		case 'C':
 			cache = true;
@@ -86,7 +86,10 @@ int main(int argc, char **argv)
 			backingdev = true;
 			break;
 		case 'b':
-			bucketsize = hatoi(optarg) / 512;
+			sb.bucket_size = hatoi(optarg) / 512;
+			break;
+		case 'w':
+			sb.block_size = hatoi(optarg) / 512;
 			break;
 		case 'U':
 			if (uuid_parse(optarg, sb.uuid)) {
@@ -96,8 +99,8 @@ int main(int argc, char **argv)
 			break;
 		}
 
-	if (!bucketsize)
-		bucketsize = cache ? 256 : 8192;
+	if (!sb.bucket_size)
+		sb.bucket_size = cache ? 256 : 8192;
 
 	if (cache == backingdev) {
 		printf("Must specify one of -C or -B\n");
@@ -117,16 +120,14 @@ int main(int argc, char **argv)
 	nblocks = getblocks(fd);
 	printf("device is %li sectors\n", nblocks);
 
-	if (bucketsize < blocksize ||
-	    bucketsize > nblocks / 8) {
-		printf("Bad bucket size %li\n", bucketsize);
+	if (sb.bucket_size < sb.block_size ||
+	    sb.bucket_size > nblocks / 8) {
+		printf("Bad bucket size %i\n", sb.bucket_size);
 		exit(EXIT_FAILURE);
 	}
 
 	memcpy(sb.magic, bcache_magic, 16);
 	sb.version = backingdev ? CACHE_BACKING_DEVICE : 0;
-	sb.block_size = blocksize;
-	sb.bucket_size = bucketsize;
 	sb.nbuckets = nblocks / sb.bucket_size;
 	uuid_unparse(sb.uuid, uuid);