Btrfs-progs: add support for mixed data+metadata block groups

So alot of crazy people (I'm looking at you Meego) want to use btrfs on phones
and such with small devices.  Unfortunately the way we split out metadata/data
chunks it makes space usage inefficient for volumes that are smaller than
1gigabyte.  So add a -M option for mixing metadata+data, and default to this
mixed mode if the filesystem is less than or equal to 1 gigabyte.  I've tested
this with xfstests on a 100mb filesystem and everything is a-ok.

Signed-off-by: Josef Bacik <josef@redhat.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>

btrfs-vol.c

@@ -143,7 +143,9 @@ int main(int ac, char **av)
 		exit(1);
 	}
 	if (cmd == BTRFS_IOC_ADD_DEV) {
-		ret = btrfs_prepare_device(devfd, device, 1, &dev_block_count);
+		int mixed = 0;
+
+		ret = btrfs_prepare_device(devfd, device, 1, &dev_block_count, &mixed);
 		if (ret) {
 			fprintf(stderr, "Unable to init %s\n", device);
 			exit(1);

btrfs_cmds.c

@@ -720,6 +720,7 @@ int do_add_volume(int nargs, char **args)
 		int	devfd, res;
 		u64 dev_block_count = 0;
 		struct stat st;
+		int mixed = 0;
 
 		devfd = open(args[i], O_RDWR);
 		if (!devfd) {
@@ -742,7 +743,7 @@ int do_add_volume(int nargs, char **args)
 			continue;
 		}
 
-		res = btrfs_prepare_device(devfd, args[i], 1, &dev_block_count);
+		res = btrfs_prepare_device(devfd, args[i], 1, &dev_block_count, &mixed);
 		if (res) {
 			fprintf(stderr, "ERROR: Unable to init '%s'\n", args[i]);
 			close(devfd);
@@ -920,8 +921,14 @@ int do_df_filesystem(int nargs, char **argv)
 		memset(description, 0, 80);
 
 		if (flags & BTRFS_BLOCK_GROUP_DATA) {
-			snprintf(description, 5, "%s", "Data");
-			written += 4;
+			if (flags & BTRFS_BLOCK_GROUP_METADATA) {
+				snprintf(description, 15, "%s",
+					 "Data+Metadata");
+				written += 14;
+			} else {
+				snprintf(description, 5, "%s", "Data");
+				written += 4;
+			}
 		} else if (flags & BTRFS_BLOCK_GROUP_SYSTEM) {
 			snprintf(description, 7, "%s", "System");
 			written += 6;

ctree.h

@@ -352,13 +352,15 @@ struct btrfs_super_block {
  * ones specified below then we will fail to mount
  */
 #define BTRFS_FEATURE_INCOMPAT_MIXED_BACKREF	(1ULL << 0)
-#define BTRFS_FEATURE_INCOMPAT_DEFAULT_SUBVOL	(2ULL << 0)
+#define BTRFS_FEATURE_INCOMPAT_DEFAULT_SUBVOL	(1ULL << 1)
+#define BTRFS_FEATURE_INCOMPAT_MIXED_GROUPS	(1ULL << 2)
 
 #define BTRFS_FEATURE_COMPAT_SUPP		0ULL
 #define BTRFS_FEATURE_COMPAT_RO_SUPP		0ULL
-#define BTRFS_FEATURE_INCOMPAT_SUPP		\
-	(BTRFS_FEATURE_INCOMPAT_MIXED_BACKREF |	\
-	 BTRFS_FEATURE_INCOMPAT_DEFAULT_SUBVOL)
+#define BTRFS_FEATURE_INCOMPAT_SUPP			\
+	(BTRFS_FEATURE_INCOMPAT_MIXED_BACKREF |		\
+	 BTRFS_FEATURE_INCOMPAT_DEFAULT_SUBVOL |	\
+	 BTRFS_FEATURE_INCOMPAT_MIXED_GROUPS)
 
 /*
  * A leaf is full of items. offset and size tell us where to find

mkfs.c

@@ -69,7 +69,7 @@ static u64 parse_size(char *s)
 	return atol(s) * mult;
 }
 
-static int make_root_dir(struct btrfs_root *root)
+static int make_root_dir(struct btrfs_root *root, int mixed)
 {
 	struct btrfs_trans_handle *trans;
 	struct btrfs_key location;
@@ -88,30 +88,47 @@ static int make_root_dir(struct btrfs_root *root)
 				     0, BTRFS_MKFS_SYSTEM_GROUP_SIZE);
 	BUG_ON(ret);
 
-	ret = btrfs_alloc_chunk(trans, root->fs_info->extent_root,
-				&chunk_start, &chunk_size,
-				BTRFS_BLOCK_GROUP_METADATA);
-	BUG_ON(ret);
-	ret = btrfs_make_block_group(trans, root, 0,
-				     BTRFS_BLOCK_GROUP_METADATA,
-				     BTRFS_FIRST_CHUNK_TREE_OBJECTID,
-				     chunk_start, chunk_size);
-	BUG_ON(ret);
+	if (mixed) {
+		ret = btrfs_alloc_chunk(trans, root->fs_info->extent_root,
+					&chunk_start, &chunk_size,
+					BTRFS_BLOCK_GROUP_METADATA |
+					BTRFS_BLOCK_GROUP_DATA);
+		BUG_ON(ret);
+		ret = btrfs_make_block_group(trans, root, 0,
+					     BTRFS_BLOCK_GROUP_METADATA |
+					     BTRFS_BLOCK_GROUP_DATA,
+					     BTRFS_FIRST_CHUNK_TREE_OBJECTID,
+					     chunk_start, chunk_size);
+		BUG_ON(ret);
+		printf("Created a data/metadata chunk of size %llu\n", chunk_size);
+	} else {
+		ret = btrfs_alloc_chunk(trans, root->fs_info->extent_root,
+					&chunk_start, &chunk_size,
+					BTRFS_BLOCK_GROUP_METADATA);
+		BUG_ON(ret);
+		ret = btrfs_make_block_group(trans, root, 0,
+					     BTRFS_BLOCK_GROUP_METADATA,
+					     BTRFS_FIRST_CHUNK_TREE_OBJECTID,
+					     chunk_start, chunk_size);
+		BUG_ON(ret);
+	}
 
 	root->fs_info->system_allocs = 0;
 	btrfs_commit_transaction(trans, root);
 	trans = btrfs_start_transaction(root, 1);
 	BUG_ON(!trans);
 
-	ret = btrfs_alloc_chunk(trans, root->fs_info->extent_root,
-				&chunk_start, &chunk_size,
-				BTRFS_BLOCK_GROUP_DATA);
-	BUG_ON(ret);
-	ret = btrfs_make_block_group(trans, root, 0,
-				     BTRFS_BLOCK_GROUP_DATA,
-				     BTRFS_FIRST_CHUNK_TREE_OBJECTID,
-				     chunk_start, chunk_size);
-	BUG_ON(ret);
+	if (!mixed) {
+		ret = btrfs_alloc_chunk(trans, root->fs_info->extent_root,
+					&chunk_start, &chunk_size,
+					BTRFS_BLOCK_GROUP_DATA);
+		BUG_ON(ret);
+		ret = btrfs_make_block_group(trans, root, 0,
+					     BTRFS_BLOCK_GROUP_DATA,
+					     BTRFS_FIRST_CHUNK_TREE_OBJECTID,
+					     chunk_start, chunk_size);
+		BUG_ON(ret);
+	}
 
 	ret = btrfs_make_root_dir(trans, root->fs_info->tree_root,
 			      BTRFS_ROOT_TREE_DIR_OBJECTID);
@@ -200,7 +217,7 @@ static int create_one_raid_group(struct btrfs_trans_handle *trans,
 
 static int create_raid_groups(struct btrfs_trans_handle *trans,
 			      struct btrfs_root *root, u64 data_profile,
-			      u64 metadata_profile)
+			      u64 metadata_profile, int mixed)
 {
 	u64 num_devices = btrfs_super_num_devices(&root->fs_info->super_copy);
 	u64 allowed;
@@ -215,20 +232,24 @@ static int create_raid_groups(struct btrfs_trans_handle *trans,
 		allowed = BTRFS_BLOCK_GROUP_RAID0 | BTRFS_BLOCK_GROUP_RAID1;
 
 	if (allowed & metadata_profile) {
+		u64 meta_flags = BTRFS_BLOCK_GROUP_METADATA;
+
 		ret = create_one_raid_group(trans, root,
 					    BTRFS_BLOCK_GROUP_SYSTEM |
 					    (allowed & metadata_profile));
 		BUG_ON(ret);
 
-		ret = create_one_raid_group(trans, root,
-					    BTRFS_BLOCK_GROUP_METADATA |
+		if (mixed)
+			meta_flags |= BTRFS_BLOCK_GROUP_DATA;
+
+		ret = create_one_raid_group(trans, root, meta_flags |
 					    (allowed & metadata_profile));
 		BUG_ON(ret);
 
 		ret = recow_roots(trans, root);
 		BUG_ON(ret);
 	}
-	if (num_devices > 1 && (allowed & data_profile)) {
+	if (!mixed && num_devices > 1 && (allowed & data_profile)) {
 		ret = create_one_raid_group(trans, root,
 					    BTRFS_BLOCK_GROUP_DATA |
 					    (allowed & data_profile));
@@ -274,6 +295,7 @@ static void print_usage(void)
 	fprintf(stderr, "\t -l --leafsize size of btree leaves\n");
 	fprintf(stderr, "\t -L --label set a label\n");
 	fprintf(stderr, "\t -m --metadata metadata profile, values like data profile\n");
+	fprintf(stderr, "\t -M --mixed mix metadata and data together\n");
 	fprintf(stderr, "\t -n --nodesize size of btree nodes\n");
 	fprintf(stderr, "\t -s --sectorsize min block allocation\n");
 	fprintf(stderr, "%s\n", BTRFS_BUILD_VERSION);
@@ -328,6 +350,7 @@ static struct option long_options[] = {
 	{ "leafsize", 1, NULL, 'l' },
 	{ "label", 1, NULL, 'L'},
 	{ "metadata", 1, NULL, 'm' },
+	{ "mixed", 0, NULL, 'M' },
 	{ "nodesize", 1, NULL, 'n' },
 	{ "sectorsize", 1, NULL, 's' },
 	{ "data", 1, NULL, 'd' },
@@ -358,10 +381,13 @@ int main(int ac, char **av)
 	int first_fd;
 	int ret;
 	int i;
+	int mixed = 0;
+	int data_profile_opt = 0;
+	int metadata_profile_opt = 0;
 
 	while(1) {
 		int c;
-		c = getopt_long(ac, av, "A:b:l:n:s:m:d:L:V", long_options,
+		c = getopt_long(ac, av, "A:b:l:n:s:m:d:L:VM", long_options,
 				&option_index);
 		if (c < 0)
 			break;
@@ -371,6 +397,7 @@ int main(int ac, char **av)
 				break;
 			case 'd':
 				data_profile = parse_profile(optarg);
+				data_profile_opt = 1;
 				break;
 			case 'l':
 				leafsize = parse_size(optarg);
@@ -380,6 +407,10 @@ int main(int ac, char **av)
 				break;
 			case 'm':
 				metadata_profile = parse_profile(optarg);
+				metadata_profile_opt = 1;
+				break;
+			case 'M':
+				mixed = 1;
 				break;
 			case 'n':
 				nodesize = parse_size(optarg);
@@ -389,12 +420,10 @@ int main(int ac, char **av)
 				break;
 			case 'b':
 				block_count = parse_size(optarg);
-				if (block_count < 256*1024*1024) {
-					fprintf(stderr, "File system size "
-						"%llu bytes is too small, "
-						"256M is required at least\n",
-						(unsigned long long)block_count);
-					exit(1);
+				if (block_count <= 1024*1024*1024) {
+					printf("SMALL VOLUME: forcing mixed "
+					       "metadata/data groups\n");
+					mixed = 1;
 				}
 				zero_end = 0;
 				break;
@@ -439,9 +468,22 @@ int main(int ac, char **av)
 	}
 	first_fd = fd;
 	first_file = file;
-	ret = btrfs_prepare_device(fd, file, zero_end, &dev_block_count);
+	ret = btrfs_prepare_device(fd, file, zero_end, &dev_block_count,
+				   &mixed);
 	if (block_count == 0)
 		block_count = dev_block_count;
+	if (mixed) {
+		if (!metadata_profile_opt)
+			metadata_profile = 0;
+		if (!data_profile_opt)
+			data_profile = 0;
+
+		if (metadata_profile != data_profile) {
+			fprintf(stderr, "With mixed block groups data and metadata "
+				"profiles must be the same\n");
+			exit(1);
+		}
+	}
 
 	blocks[0] = BTRFS_SUPER_INFO_OFFSET;
 	for (i = 1; i < 7; i++) {
@@ -459,7 +501,7 @@ int main(int ac, char **av)
 	root = open_ctree(file, 0, O_RDWR);
 	root->fs_info->alloc_start = alloc_start;
 
-	ret = make_root_dir(root);
+	ret = make_root_dir(root, mixed);
 	if (ret) {
 		fprintf(stderr, "failed to setup the root directory\n");
 		exit(1);
@@ -478,6 +520,8 @@ int main(int ac, char **av)
 
 	zero_end = 1;
 	while(ac-- > 0) {
+		int old_mixed = mixed;
+
 		file = av[optind++];
 		ret = check_mounted(file);
 		if (ret < 0) {
@@ -503,8 +547,8 @@ int main(int ac, char **av)
 			continue;
 		}
 		ret = btrfs_prepare_device(fd, file, zero_end,
-					   &dev_block_count);
-
+					   &dev_block_count, &mixed);
+		mixed = old_mixed;
 		BUG_ON(ret);
 
 		ret = btrfs_add_to_fsid(trans, root, fd, file, dev_block_count,
@@ -515,12 +559,20 @@ int main(int ac, char **av)
 
 raid_groups:
 	ret = create_raid_groups(trans, root, data_profile,
-				 metadata_profile);
+				 metadata_profile, mixed);
 	BUG_ON(ret);
 
 	ret = create_data_reloc_tree(trans, root);
 	BUG_ON(ret);
 
+	if (mixed) {
+		struct btrfs_super_block *super = &root->fs_info->super_copy;
+		u64 flags = btrfs_super_incompat_flags(super);
+
+		flags |= BTRFS_FEATURE_INCOMPAT_MIXED_GROUPS;
+		btrfs_set_super_incompat_flags(super, flags);
+	}
+
 	printf("fs created label %s on %s\n\tnodesize %u leafsize %u "
 	    "sectorsize %u size %s\n",
 	    label, first_file, nodesize, leafsize, sectorsize,

utils.c

@@ -512,7 +512,8 @@ int btrfs_add_to_fsid(struct btrfs_trans_handle *trans,
 	return 0;
 }
 
-int btrfs_prepare_device(int fd, char *file, int zero_end, u64 *block_count_ret)
+int btrfs_prepare_device(int fd, char *file, int zero_end, u64 *block_count_ret,
+			 int *mixed)
 {
 	u64 block_count;
 	u64 bytenr;
@@ -532,10 +533,9 @@ int btrfs_prepare_device(int fd, char *file, int zero_end, u64 *block_count_ret)
 	}
 	zero_end = 1;
 
-	if (block_count < 256 * 1024 * 1024) {
-		fprintf(stderr, "device %s is too small "
-		        "(must be at least 256 MB)\n", file);
-		exit(1);
+	if (block_count < 1024 * 1024 * 1024 && !(*mixed)) {
+		printf("SMALL VOLUME: forcing mixed metadata/data groups\n");
+		*mixed = 1;
 	}
 	ret = zero_dev_start(fd);
 	if (ret) {

utils.h

@@ -27,7 +27,7 @@ int make_btrfs(int fd, const char *device, const char *label,
 int btrfs_make_root_dir(struct btrfs_trans_handle *trans,
 			struct btrfs_root *root, u64 objectid);
 int btrfs_prepare_device(int fd, char *file, int zero_end,
-			 u64 *block_count_ret);
+			 u64 *block_count_ret, int *mixed);
 int btrfs_add_to_fsid(struct btrfs_trans_handle *trans,
 		      struct btrfs_root *root, int fd, char *path,
 		      u64 block_count, u32 io_width, u32 io_align,