btrfs-progs: extend balance args to take min/max usage filter

Add the overlapping usage and [usage_min, usage_max] members to the
balance args. The min/max values are interpreted iff the corresponding
flag BTRFS_BALANCE_ARGS_USAGE_RANGE is set.

The minimum boundary is inclusive, maximum is exclusive:
* usage_min <= chunk_usage < usage_max

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

4 files changed, 25 insertions, 1 deletions

diff --git a/Documentation/btrfs-balance.asciidoc b/Documentation/btrfs-balance.asciidoc
index 9adf7784..92a37784 100644
--- a/Documentation/btrfs-balance.asciidoc
+++ b/Documentation/btrfs-balance.asciidoc
@@ -106,6 +106,12 @@ Balances only block groups with usage under the given percentage. The
 value of 0 is allowed and will clean up completely unused block groups, this
 should not require any new space allocated. You may want to use 'usage=0' in
 case balance is returnin ENOSPC and your filesystem is not too full.
++
+The argument may be a single value or a range. The single value *N* means *at
+most N percent used*, equivalent to *..N* range syntax. Kernels prior to 4.4
+accept only the single value format.
++
+The minimum boundary is inclusive, maximum is exclusive.
 
 *devid=<id>*::
 Balances only block groups which have at least one chunk on the given
diff --git a/cmds-balance.c b/cmds-balance.c
index 2453101a..2c5d2eb1 100644
--- a/cmds-balance.c
+++ b/cmds-balance.c
@@ -355,6 +355,10 @@ static void dump_balance_args(struct btrfs_balance_args *args)
 		printf(", profiles=%llu", (unsigned long long)args->profiles);
 	if (args->flags & BTRFS_BALANCE_ARGS_USAGE)
 		printf(", usage=%llu", (unsigned long long)args->usage);
+	if (args->flags & BTRFS_BALANCE_ARGS_USAGE_RANGE) {
+		printf(", usage=");
+		print_range_u32(args->usage_min, args->usage_max);
+	}
 	if (args->flags & BTRFS_BALANCE_ARGS_DEVID)
 		printf(", devid=%llu", (unsigned long long)args->devid);
 	if (args->flags & BTRFS_BALANCE_ARGS_DRANGE)
diff --git a/ioctl.h b/ioctl.h
index 0df2444c..771da231 100644
--- a/ioctl.h
+++ b/ioctl.h
@@ -216,7 +216,20 @@ struct btrfs_ioctl_feature_flags {
  */
 struct btrfs_balance_args {
 	__u64 profiles;
-	__u64 usage;
+
+	/*
+	 * usage filter
+	 * BTRFS_BALANCE_ARGS_USAGE with a single value means '0..N'
+	 * BTRFS_BALANCE_ARGS_USAGE_RANGE - range syntax, min..max
+	 */
+	union {
+		__u64 usage;
+		struct {
+			__u32 usage_min;
+			__u32 usage_max;
+		};
+	};
+
 	__u64 devid;
 	__u64 pstart;
 	__u64 pend;
diff --git a/volumes.h b/volumes.h
index f5064304..c0007adc 100644
--- a/volumes.h
+++ b/volumes.h
@@ -138,6 +138,7 @@ 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 << 10)
 
 /*
  * Profile changing flags.  When SOFT is set we won't relocate chunk if