Btrfs: add support for mixed data+metadata block groups

There are just a few things that need to be fixed in the kernel to support mixed
data+metadata block groups.  Mostly we just need to make sure that if we are
using mixed block groups that we continue to allocate mixed block groups as we
need them.  Also we need to make sure __find_space_info will find our space info
if we search for DATA or METADATA only.  Tested this with xfstests and it works
nicely.  Thanks,

Signed-off-by: Josef Bacik <josef@redhat.com>

fs/btrfs/ctree.h

@@ -397,12 +397,14 @@ struct btrfs_super_block {
  */
 #define BTRFS_FEATURE_INCOMPAT_MIXED_BACKREF	(1ULL << 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)
+	 BTRFS_FEATURE_INCOMPAT_DEFAULT_SUBVOL |	\
+	 BTRFS_FEATURE_INCOMPAT_MIXED_GROUPS)
 
 /*
  * A leaf is full of items. offset and size tell us where to find
@@ -2046,6 +2048,12 @@ static inline struct dentry *fdentry(struct file *file)
 	return file->f_path.dentry;
 }
 
+static inline bool btrfs_mixed_space_info(struct btrfs_space_info *space_info)
+{
+	return ((space_info->flags & BTRFS_BLOCK_GROUP_METADATA) &&
+		(space_info->flags & BTRFS_BLOCK_GROUP_DATA));
+}
+
 /* extent-tree.c */
 void btrfs_put_block_group(struct btrfs_block_group_cache *cache);
 int btrfs_run_delayed_refs(struct btrfs_trans_handle *trans,

fs/btrfs/extent-tree.c

@@ -547,7 +547,7 @@ static struct btrfs_space_info *__find_space_info(struct btrfs_fs_info *info,
 
 	rcu_read_lock();
 	list_for_each_entry_rcu(found, head, list) {
-		if (found->flags == flags) {
+		if (found->flags & flags) {
 			rcu_read_unlock();
 			return found;
 		}
@@ -3266,6 +3266,13 @@ static int do_chunk_alloc(struct btrfs_trans_handle *trans,
 	}
 	spin_unlock(&space_info->lock);
 
+	/*
+	 * If we have mixed data/metadata chunks we want to make sure we keep
+	 * allocating mixed chunks instead of individual chunks.
+	 */
+	if (btrfs_mixed_space_info(space_info))
+		flags |= (BTRFS_BLOCK_GROUP_DATA | BTRFS_BLOCK_GROUP_METADATA);
+
 	/*
 	 * if we're doing a data chunk, go ahead and make sure that
 	 * we keep a reasonable number of metadata chunks allocated in the
@@ -4787,6 +4794,7 @@ static noinline int find_free_extent(struct btrfs_trans_handle *trans,
 	bool found_uncached_bg = false;
 	bool failed_cluster_refill = false;
 	bool failed_alloc = false;
+	bool use_cluster = true;
 	u64 ideal_cache_percent = 0;
 	u64 ideal_cache_offset = 0;
 
@@ -4801,16 +4809,24 @@ static noinline int find_free_extent(struct btrfs_trans_handle *trans,
 		return -ENOSPC;
 	}
 
+	/*
+	 * If the space info is for both data and metadata it means we have a
+	 * small filesystem and we can't use the clustering stuff.
+	 */
+	if (btrfs_mixed_space_info(space_info))
+		use_cluster = false;
+
 	if (orig_root->ref_cows || empty_size)
 		allowed_chunk_alloc = 1;
 
-	if (data & BTRFS_BLOCK_GROUP_METADATA) {
+	if (data & BTRFS_BLOCK_GROUP_METADATA && use_cluster) {
 		last_ptr = &root->fs_info->meta_alloc_cluster;
 		if (!btrfs_test_opt(root, SSD))
 			empty_cluster = 64 * 1024;
 	}
 
-	if ((data & BTRFS_BLOCK_GROUP_DATA) && btrfs_test_opt(root, SSD)) {
+	if ((data & BTRFS_BLOCK_GROUP_DATA) && use_cluster &&
+	    btrfs_test_opt(root, SSD)) {
 		last_ptr = &root->fs_info->data_alloc_cluster;
 	}