libdm: allow regions with histograms in dm_stats_create_group()

Allow regions with histograms to be grouped if all histograms have
the same number of bins and matching bounds.

diff --git a/libdm/libdm-stats.c b/libdm/libdm-stats.c
index 0aca622d5050653bdacb50b32aadbd7fa5486295..55f10104b949adfa421665fe9033b2f5979b6056 100644 (file)
--- a/libdm/libdm-stats.c
+++ b/libdm/libdm-stats.c
@@ -3860,6 +3860,39 @@ merge:
        return overlap;
 }
 
+static void _stats_copy_histogram_bounds(struct dm_histogram *to,
+                                        struct dm_histogram *from)
+{
+       uint64_t i;
+
+       to->nr_bins = from->nr_bins;
+
+       for (i = 0; i < to->nr_bins; i++)
+               to->bins[i].upper = from->bins[i].upper;
+}
+
+/*
+ * Compare histogram bounds h1 and h2, and return 1 if they match (i.e.
+ * have the same number of bins and identical bin boundary values), or 0
+ * otherwise.
+ */
+static int _stats_check_histogram_bounds(struct dm_histogram *h1,
+                                        struct dm_histogram *h2)
+{
+       uint64_t i;
+
+       if (!h1 || !h2)
+               return 0;
+
+       if (h1->nr_bins != h2->nr_bins)
+               return 0;
+
+       for (i = 0; i < h1->nr_bins; i++)
+               if (h1->bins[i].upper != h2->bins[i].upper)
+                       return 0;
+       return 1;
+}
+
 /*
  * Create a new group in stats handle dms from the group description
  * passed in group.
@@ -3867,6 +3900,7 @@ merge:
 int dm_stats_create_group(struct dm_stats *dms, const char *members,
                          const char *alias, uint64_t *group_id)
 {
+       struct dm_histogram *check = NULL, *bounds;
        int i, count = 0, precise = 0;
        dm_bitset_t regions;
 
@@ -3877,6 +3911,11 @@ int dm_stats_create_group(struct dm_stats *dms, const char *members,
 
        if (!(regions = dm_bitset_parse_list(members, NULL))) {
                log_error("Could not parse list: '%s'", members);
+               return 0;
+       }
+
+       if (!(check = dm_pool_zalloc(dms->hist_mem, sizeof(*check)))) {
+               log_error("Could not allocate memory for bounds check");
                goto bad;
        }
 
@@ -3902,14 +3941,20 @@ int dm_stats_create_group(struct dm_stats *dms, const char *members,
                                  FMTu64, i, dms->regions[i].group_id);
                        goto bad;
                }
-               if (dms->regions[i].bounds) {
-                       log_error("Region ID %d: grouping regions with "
-                                 "histograms is not yet supported", i);
-                       goto bad;
-               }
                if (dms->regions[i].timescale == 1)
                        precise++;
 
+               /* check for matching histogram bounds */
+               bounds = dms->regions[i].bounds;
+               if (bounds && !check->nr_bins)
+                       _stats_copy_histogram_bounds(check, bounds);
+               else if (bounds) {
+                       if (!_stats_check_histogram_bounds(check, bounds)) {
+                               log_error("All region histogram bounds "
+                                         "must match exactly");
+                               goto bad;
+                       }
+               }
                count++;
        }
 
@@ -3923,8 +3968,11 @@ int dm_stats_create_group(struct dm_stats *dms, const char *members,
        if (!_stats_create_group(dms, regions, alias, group_id))
                goto bad;
 
+       dm_pool_free(dms->hist_mem, check);
        return 1;
+
 bad:
+       dm_pool_free(dms->hist_mem, check);
        dm_bitset_destroy(regions);
        return 0;
 }