btrfs-progs: mkfs: introduce quota runtime feature

Add support for enabling quotas at mkfs time. The qgroup accounting will
be consistent, ie. works with --rootdir.

Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

Documentation/mkfs.btrfs.asciidoc

@@ -244,6 +244,12 @@ option or by an ioctl. Some of them can be enabled early, at mkfs time.  This
 applies to features that need to be enabled once and then the status is
 permanent, this does not replace mount options.
 
+*quota*::
+(kernel support since 3.4)
++
+Enable quota support (qgroups). The qgroup accounting will be consistent,
+can be used together with '--rootdir'.  See also `btrfs-quota`(8).
+
 BLOCK GROUPS, CHUNKS, RAID
 --------------------------
 

common/fsfeatures.c

@@ -104,6 +104,9 @@ static const struct btrfs_feature mkfs_features[] = {
 };
 
 static const struct btrfs_feature runtime_features[] = {
+	{ "quota", BTRFS_RUNTIME_FEATURE_QUOTA, NULL,
+		VERSION_TO_STRING2(3, 4), NULL, 0, NULL, 0,
+		"quota support (qgroups)" },
 	/* Keep this one last */
 	{ "list-all", BTRFS_FEATURE_LIST_ALL, NULL }
 };

common/fsfeatures.h

@@ -39,6 +39,8 @@
 
 #define BTRFS_FEATURE_LIST_ALL		(1ULL << 63)
 
+#define BTRFS_RUNTIME_FEATURE_QUOTA	(1ULL << 0)
+
 void btrfs_list_all_fs_features(u64 mask_disallowed);
 void btrfs_list_all_runtime_features(u64 mask_disallowed);
 char *btrfs_parse_fs_features(char *namelist, u64 *flags);

mkfs/main.c

@@ -1484,6 +1484,13 @@ raid_groups:
 		}
 	}
 
+	if (runtime_features & BTRFS_RUNTIME_FEATURE_QUOTA) {
+		ret = setup_quota_root(fs_info);
+		if (ret < 0) {
+			error("failed to initialize quota: %d (%m)", ret);
+			goto out;
+		}
+	}
 	if (verbose) {
 		char features_buf[64];