btrfs: extend balance filter usage to take minimum and maximum

Similar to the 'limit' filter, we can enhance the 'usage' filter to
accept a range. The change is backward compatible, the range is applied
only in connection with the BTRFS_BALANCE_ARGS_USAGE_RANGE flag.

We don't have a usecase yet, the current syntax has been sufficient. The
enhancement should provide parity with other range-like filters.
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Chris Mason <clm@fb.com>

fs/btrfs/ctree.h

@@ -823,8 +823,18 @@ struct btrfs_disk_balance_args {
 	 */
 	__le64 profiles;
 
-	/* usage filter */
+	/*
+	 * usage filter
+	 * BTRFS_BALANCE_ARGS_USAGE with a single value means '0..N'
+	 * BTRFS_BALANCE_ARGS_USAGE_RANGE - range syntax, min..max
+	 */
+	union {
 		__le64 usage;
+		struct {
+			__le32 usage_min;
+			__le32 usage_max;
+		};
+	};
 
 	/* devid filter */
 	__le64 devid;

fs/btrfs/volumes.c

@@ -3059,16 +3059,19 @@ static void update_balance_args(struct btrfs_balance_control *bctl)
 	 * (albeit full) chunks.
 	 */
 	if (!(bctl->data.flags & BTRFS_BALANCE_ARGS_USAGE) &&
+	    !(bctl->data.flags & BTRFS_BALANCE_ARGS_USAGE_RANGE) &&
 	    !(bctl->data.flags & BTRFS_BALANCE_ARGS_CONVERT)) {
 		bctl->data.flags |= BTRFS_BALANCE_ARGS_USAGE;
 		bctl->data.usage = 90;
 	}
 	if (!(bctl->sys.flags & BTRFS_BALANCE_ARGS_USAGE) &&
+	    !(bctl->sys.flags & BTRFS_BALANCE_ARGS_USAGE_RANGE) &&
 	    !(bctl->sys.flags & BTRFS_BALANCE_ARGS_CONVERT)) {
 		bctl->sys.flags |= BTRFS_BALANCE_ARGS_USAGE;
 		bctl->sys.usage = 90;
 	}
 	if (!(bctl->meta.flags & BTRFS_BALANCE_ARGS_USAGE) &&
+	    !(bctl->meta.flags & BTRFS_BALANCE_ARGS_USAGE_RANGE) &&
 	    !(bctl->meta.flags & BTRFS_BALANCE_ARGS_CONVERT)) {
 		bctl->meta.flags |= BTRFS_BALANCE_ARGS_USAGE;
 		bctl->meta.usage = 90;
@@ -3122,6 +3125,39 @@ static int chunk_profiles_filter(u64 chunk_type,
 
 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;
+	u64 user_thresh_min;
+	u64 user_thresh_max;
+	int ret = 1;
+
+	cache = btrfs_lookup_block_group(fs_info, chunk_offset);
+	chunk_used = btrfs_block_group_used(&cache->item);
+
+	if (bargs->usage_min == 0)
+		user_thresh_min = 0;
+	else
+		user_thresh_min = div_factor_fine(cache->key.offset,
+					bargs->usage_min);
+
+	if (bargs->usage_max == 0)
+		user_thresh_max = 1;
+	else if (bargs->usage_max > 100)
+		user_thresh_max = cache->key.offset;
+	else
+		user_thresh_max = div_factor_fine(cache->key.offset,
+					bargs->usage_max);
+
+	if (user_thresh_min <= chunk_used && chunk_used < user_thresh_max)
+		ret = 0;
+
+	btrfs_put_block_group(cache);
+	return ret;
+}
+
+static int chunk_usage_range_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;
@@ -3130,7 +3166,7 @@ static int chunk_usage_filter(struct btrfs_fs_info *fs_info, u64 chunk_offset,
 	cache = btrfs_lookup_block_group(fs_info, chunk_offset);
 	chunk_used = btrfs_block_group_used(&cache->item);
 
-	if (bargs->usage == 0)
+	if (bargs->usage_min == 0)
 		user_thresh = 1;
 	else if (bargs->usage > 100)
 		user_thresh = cache->key.offset;
@@ -3279,6 +3315,9 @@ static int should_balance_chunk(struct btrfs_root *root,
 	if ((bargs->flags & BTRFS_BALANCE_ARGS_USAGE) &&
 	    chunk_usage_filter(bctl->fs_info, chunk_offset, bargs)) {
 		return 0;
+	} else if ((bargs->flags & BTRFS_BALANCE_ARGS_USAGE_RANGE) &&
+	    chunk_usage_range_filter(bctl->fs_info, chunk_offset, bargs)) {
+		return 0;
 	}
 
 	/* devid filter */

fs/btrfs/volumes.h

@@ -382,6 +382,7 @@ struct map_lookup {
 #define BTRFS_BALANCE_ARGS_LIMIT	(1ULL << 5)
 #define BTRFS_BALANCE_ARGS_LIMIT_RANGE	(1ULL << 6)
 #define BTRFS_BALANCE_ARGS_STRIPES_RANGE (1ULL << 7)
+#define BTRFS_BALANCE_ARGS_USAGE_RANGE	(1ULL << 8)
 
 #define BTRFS_BALANCE_ARGS_MASK			\
 	(BTRFS_BALANCE_ARGS_PROFILES |		\

include/uapi/linux/btrfs.h

@@ -206,7 +206,13 @@ struct btrfs_ioctl_feature_flags {
  */
 struct btrfs_balance_args {
 	__u64 profiles;
-	__u64 usage;
+	union {
+		__le64 usage;
+		struct {
+			__le32 usage_min;
+			__le32 usage_max;
+		};
+	};
 	__u64 devid;
 	__u64 pstart;
 	__u64 pend;