Add option to set btree node size, give it sane default

Change-Id: Ic6d0a79b8a33c8c17422e0875d9e8d3fb3ef6d98

bcache.c

@@ -581,24 +581,20 @@ int dev_open(const char *dev, bool wipe_bcache)
 		exit(EXIT_FAILURE);
 }
 
-static unsigned min_bucket_size(int num_bucket_sizes, unsigned *bucket_sizes)
-{
-	int i;
-	unsigned min = bucket_sizes[0];
-
-	for (i = 0; i < num_bucket_sizes; i++)
-		min = bucket_sizes[i] < min ? bucket_sizes[i] : min;
-
-	return min;
-}
-
 void write_cache_sbs(int *fds, struct cache_sb *sb,
 		     unsigned block_size, unsigned *bucket_sizes,
-		     int num_bucket_sizes)
+		     int num_bucket_sizes, unsigned btree_node_size)
 {
 	char uuid_str[40], set_uuid_str[40];
 	size_t i;
-	unsigned min_size = min_bucket_size(num_bucket_sizes, bucket_sizes);
+
+	if (!btree_node_size) {
+		btree_node_size = 512;
+
+		for (i = 0; i < num_bucket_sizes; i++)
+			btree_node_size = min(btree_node_size,
+					      bucket_sizes[i]);
+	}
 
 	sb->offset	= SB_SECTOR;
 	sb->version	= BCACHE_SB_VERSION_CDEV_V3;
@@ -641,7 +637,7 @@ void write_cache_sbs(int *fds, struct cache_sb *sb,
 	for (i = 0; i < sb->nr_in_set; i++) {
 		struct cache_member *m = sb->members + i;
 
-		SET_CACHE_BTREE_NODE_SIZE(sb, min_size);
+		SET_CACHE_BTREE_NODE_SIZE(sb, btree_node_size);
 
 
 		sb->disk_uuid = m->uuid;

bcache.h

@@ -24,6 +24,12 @@ typedef __s64	s64;
 #define MAX_PATH		256
 #define MAX_DEVS		MAX_CACHES_PER_SET
 
+#define min(x, y) ({				\
+	typeof(x) _min1 = (x);			\
+	typeof(y) _min2 = (y);			\
+	(void) (&_min1 == &_min2);		\
+	_min1 < _min2 ? _min1 : _min2; })
+
 #define max(x, y) ({				\
 	typeof(x) _max1 = (x);			\
 	typeof(y) _max2 = (y);			\
@@ -67,7 +73,8 @@ unsigned hatoi_validate(const char *, const char *);
 void write_backingdev_sb(int, unsigned, unsigned *, unsigned, uint64_t,
 			 const char *, uuid_le, uuid_le);
 int dev_open(const char *, bool);
-void write_cache_sbs(int *, struct cache_sb *, unsigned, unsigned *, int);
+void write_cache_sbs(int *, struct cache_sb *, unsigned,
+		     unsigned *, int, unsigned);
 void next_cache_device(struct cache_sb *, unsigned, int, unsigned, bool);
 unsigned get_blocksize(const char *);
 long strtoul_or_die(const char *, size_t, const char *);

bcacheadm.c

@@ -46,6 +46,7 @@ char *backing_devices[MAX_DEVS];
 char *backing_dev_labels[MAX_DEVS];
 size_t i, nr_backing_devices = 0, nr_cache_devices = 0;
 unsigned block_size = 0;
+unsigned btree_node_size = 0;
 unsigned bucket_sizes[MAX_DEVS];
 int num_bucket_sizes = 0;
 int writeback = 0, writearound = 0, discard = 0, wipe_bcache = 0;
@@ -109,6 +110,12 @@ static int set_block_size(NihOption *option, const char *arg)
 	return 0;
 }
 
+static int set_btree_node_size(NihOption *option, const char *arg)
+{
+	btree_node_size = hatoi_validate(arg, "btree node size");
+	return 0;
+}
+
 static int set_cache(NihOption *option, const char *arg)
 {
 	bdev = 0;
@@ -192,6 +199,9 @@ static NihOption make_bcache_options[] = {
 	{'b', "bucket",	N_("bucket size"), NULL, "size", NULL, set_bucket_sizes},
 	//Does the default setter automatically convert strings to an int?
 	{'w', "block",	N_("block size (hard sector size of SSD, often 2k"), NULL, "size", NULL, set_block_size},
+
+	{'n', "btree-node",	N_("Btree node size, default 256k"), NULL, "size", NULL, set_btree_node_size},
+
 	{'t', "tier",	N_("tier of subsequent devices"), NULL,"#", &tier, NULL},
 	{'p', "cache_replacement_policy", N_("one of (lru|fifo|random)"), NULL,"policy", &replacement_policy, NULL},
 	{'o', "data_offset", N_("data offset in sectors"), NULL,"offset", &data_offset, NULL},
@@ -386,7 +396,7 @@ int make_bcache(NihCommand *command, char *const *args)
 		backing_dev_fd[i] = dev_open(backing_devices[i], wipe_bcache);
 
 	write_cache_sbs(cache_dev_fd, cache_set_sb, block_size,
-			bucket_sizes, num_bucket_sizes);
+			bucket_sizes, num_bucket_sizes, btree_node_size);
 
 	if (writeback)
 		cache_mode = CACHE_MODE_WRITEBACK;