[PATCH 4/4] btrfs: tier-aware free space cacl

[wangyugui <wangyugui@e16-tech.com>]

Detect some case of free space 0 because of tier policy of data.
Full support is yet TODO/FIXME.

Signed-off-by: wangyugui <wangyugui@e16-tech.com>
---
 fs/btrfs/super.c | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index c8dfa89..feb1ae3 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -2105,6 +2105,9 @@ static inline int btrfs_calc_avail_data_space(struct btrfs_fs_info *fs_info,
 	int num_stripes = 1;
 	int i = 0, nr_devices;
 	const struct btrfs_raid_attr *rattr;
+	/* tier-aware */
+	int nr_top_tier = 0;
+	u8 top_tier_score = 0;
 
 	/*
 	 * We aren't under the device list lock, so this is racy-ish, but good
@@ -2176,12 +2179,27 @@ static inline int btrfs_calc_avail_data_space(struct btrfs_fs_info *fs_info,
 		devices_info[i].dev = device;
 		devices_info[i].max_avail = avail_space;
 
+		if (devices_info[i].dev->tier_score > top_tier_score) {
+			top_tier_score = devices_info[i].dev->tier_score;
+			nr_top_tier = 1;
+		}
+		else if (devices_info[i].dev->tier_score == top_tier_score) {
+			nr_top_tier++;
+		}
+
 		i++;
 	}
 	rcu_read_unlock();
 
 	nr_devices = i;
 
+	if (fs_info->data_tier_policy == OTHER_TIER_ONLY &&
+		nr_top_tier != nr_devices && nr_devices - nr_top_tier < rattr->devs_min) {
+		/* FIXME: full support of tier-aware. */
+		*free_bytes = 0;
+		return 0;
+	}
+
 	btrfs_descending_sort_devices(devices_info, nr_devices);
 
 	i = nr_devices - 1;
-- 
2.29.1