Btrfs: usage filter

Select chunks that are less than X percent full.

Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

1 files changed, 36 insertions, 0 deletions

diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 447bd422d867..b858242374db 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -2120,6 +2120,36 @@ static int chunk_profiles_filter(u64 chunk_profile,
         return 1;
 }
 
+static u64 div_factor_fine(u64 num, int factor)
+{
+        if (factor <= 0)
+                return 0;
+        if (factor >= 100)
+                return num;
+
+        num *= factor;
+        do_div(num, 100);
+        return num;
+}
+
+static int chunk_usage_filter(struct btrfs_fs_info *fs_info, u64 chunk_offset,
+                              struct btrfs_balance_args *bargs)
+{
+        struct btrfs_block_group_cache *cache;
+        u64 chunk_used, user_thresh;
+        int ret = 1;
+
+        cache = btrfs_lookup_block_group(fs_info, chunk_offset);
+        chunk_used = btrfs_block_group_used(&cache->item);
+
+        user_thresh = div_factor_fine(cache->key.offset, bargs->usage);
+        if (chunk_used < user_thresh)
+                ret = 0;
+
+        btrfs_put_block_group(cache);
+        return ret;
+}
+
 static int should_balance_chunk(struct btrfs_root *root,
                                 struct extent_buffer *leaf,
                                 struct btrfs_chunk *chunk, u64 chunk_offset)
@@ -2147,6 +2177,12 @@ static int should_balance_chunk(struct btrfs_root *root,
                 return 0;
         }
 
+        /* usage filter */
+        if ((bargs->flags & BTRFS_BALANCE_ARGS_USAGE) &&
+            chunk_usage_filter(bctl->fs_info, chunk_offset, bargs)) {
+                return 0;
+        }
+
         return 1;
 }