[PATCH v2 2/6] btrfs: qgroup: Introduce helpers to update and access new qgroup rsv

[Qu Wenruo]

Introduce helpers to:

1) Get total reserved space
   For limit calculation
2) Add/release reserved space for given type
   With underflow detection and warning
3) Add/release reserved space according to child qgroup

Signed-off-by: Qu Wenruo <w...@suse.com>
---
 fs/btrfs/qgroup.c | 68 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 68 insertions(+)

diff --git a/fs/btrfs/qgroup.c b/fs/btrfs/qgroup.c
index fe3adb996883..161f16c40264 100644
--- a/fs/btrfs/qgroup.c
+++ b/fs/btrfs/qgroup.c
@@ -47,6 +47,74 @@
  *  - check all ioctl parameters
  */
 
+/*
+ * Helpers to access qgroup reservation
+ *
+ * Callers should ensure the lock context and type are valid
+ */
+
+static u64 qgroup_rsv_total(const struct btrfs_qgroup *qgroup)
+{
+       u64 ret = 0;
+       int i;
+
+       for (i = 0; i < BTRFS_QGROUP_RSV_LAST; i++)
+               ret += qgroup->rsv.values[i];
+
+       return ret;
+}
+
+#ifdef CONFIG_BTRFS_DEBUG
+static const char *qgroup_rsv_type_str(enum btrfs_qgroup_rsv_type type)
+{
+       if (type == BTRFS_QGROUP_RSV_DATA)
+               return "data";
+       if (type == BTRFS_QGROUP_RSV_META)
+               return "meta";
+       return NULL;
+}
+#endif
+
+static void qgroup_rsv_add(struct btrfs_qgroup *qgroup, u64 num_bytes,
+                          enum btrfs_qgroup_rsv_type type)
+{
+       qgroup->rsv.values[type] += num_bytes;
+}
+
+static void qgroup_rsv_release(struct btrfs_qgroup *qgroup, u64 num_bytes,
+                              enum btrfs_qgroup_rsv_type type)
+{
+       if (qgroup->rsv.values[type] >= num_bytes) {
+               qgroup->rsv.values[type] -= num_bytes;
+               return;
+       }
+#ifdef CONFIG_BTRFS_DEBUG
+       WARN_RATELIMIT(1,
+               "qgroup %llu %s reserved space underflow, have %llu to free 
%llu",
+               qgroup->qgroupid, qgroup_rsv_type_str(type),
+               qgroup->rsv.values[type], num_bytes);
+#endif
+       qgroup->rsv.values[type] = 0;
+}
+
+static void qgroup_rsv_add_by_qgroup(struct btrfs_qgroup *dest,
+                                         struct btrfs_qgroup *src)
+{
+       int i;
+
+       for (i = 0; i < BTRFS_QGROUP_RSV_LAST; i++)
+               qgroup_rsv_add(dest, src->rsv.values[i], i);
+}
+
+static void qgroup_rsv_release_by_qgroup(struct btrfs_qgroup *dest,
+                                         struct btrfs_qgroup *src)
+{
+       int i;
+
+       for (i = 0; i < BTRFS_QGROUP_RSV_LAST; i++)
+               qgroup_rsv_release(dest, src->rsv.values[i], i);
+}
+
 static void btrfs_qgroup_update_old_refcnt(struct btrfs_qgroup *qg, u64 seq,
                                           int mod)
 {
-- 
2.14.2

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