[PATCH v3 29/50] perf maps: Add remove maps function to remove a map based on callback

[Ian Rogers <irogers@google.com>]

Removing maps wasn't being done under the write lock. Similar to
maps__for_each_map, iterate the entries but in this case remove the
entry based on the result of the callback. If an entry was removed
then maps_by_name also needs updating, so add missed flush.

In dso__load_kcore, the test of map to save would always be false with
REFCNT_CHECKING because of a missing RC_CHK_ACCESS.

Signed-off-by: Ian Rogers <irogers@google.com>
---
 tools/perf/util/maps.c   | 24 ++++++++++++++++++++++++
 tools/perf/util/maps.h   |  6 ++----
 tools/perf/util/symbol.c | 24 ++++++++++++------------
 3 files changed, 38 insertions(+), 16 deletions(-)

diff --git a/tools/perf/util/maps.c b/tools/perf/util/maps.c
index 00e6589bba10..f13fd3a9686b 100644
--- a/tools/perf/util/maps.c
+++ b/tools/perf/util/maps.c
@@ -13,6 +13,10 @@
 #define maps__for_each_entry(maps, map) \
 	for (map = maps__first(maps); map; map = map_rb_node__next(map))
 
+#define maps__for_each_entry_safe(maps, map, next) \
+	for (map = maps__first(maps), next = map_rb_node__next(map); map; \
+	     map = next, next = map_rb_node__next(map))
+
 static void maps__init(struct maps *maps, struct machine *machine)
 {
 	refcount_set(maps__refcnt(maps), 1);
@@ -214,6 +218,26 @@ int maps__for_each_map(struct maps *maps, int (*cb)(struct map *map, void *data)
 	return ret;
 }
 
+void maps__remove_maps(struct maps *maps, bool (*cb)(struct map *map, void *data), void *data)
+{
+	struct map_rb_node *pos, *next;
+	unsigned int start_nr_maps;
+
+	down_write(maps__lock(maps));
+
+	start_nr_maps = maps__nr_maps(maps);
+	maps__for_each_entry_safe(maps, pos, next)	{
+		if (cb(pos->map, data)) {
+			__maps__remove(maps, pos);
+			--RC_CHK_ACCESS(maps)->nr_maps;
+		}
+	}
+	if (maps__maps_by_name(maps) && start_nr_maps != maps__nr_maps(maps))
+		__maps__free_maps_by_name(maps);
+
+	up_write(maps__lock(maps));
+}
+
 struct symbol *maps__find_symbol(struct maps *maps, u64 addr, struct map **mapp)
 {
 	struct map *map = maps__find(maps, addr);
diff --git a/tools/perf/util/maps.h b/tools/perf/util/maps.h
index 8ac30cdaf5bd..b94ad5c8fea7 100644
--- a/tools/perf/util/maps.h
+++ b/tools/perf/util/maps.h
@@ -36,10 +36,6 @@ struct map_rb_node *map_rb_node__next(struct map_rb_node *node);
 struct map_rb_node *maps__find_node(struct maps *maps, struct map *map);
 struct map *maps__find(struct maps *maps, u64 addr);
 
-#define maps__for_each_entry_safe(maps, map, next) \
-	for (map = maps__first(maps), next = map_rb_node__next(map); map; \
-	     map = next, next = map_rb_node__next(map))
-
 DECLARE_RC_STRUCT(maps) {
 	struct rb_root      entries;
 	struct rw_semaphore lock;
@@ -80,6 +76,8 @@ static inline void __maps__zput(struct maps **map)
 
 /* Iterate over map calling cb for each entry. */
 int maps__for_each_map(struct maps *maps, int (*cb)(struct map *map, void *data), void *data);
+/* Iterate over map removing an entry if cb returns true. */
+void maps__remove_maps(struct maps *maps, bool (*cb)(struct map *map, void *data), void *data);
 
 static inline struct rb_root *maps__entries(struct maps *maps)
 {
diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c
index 72f03b875478..30da8a405d11 100644
--- a/tools/perf/util/symbol.c
+++ b/tools/perf/util/symbol.c
@@ -1239,13 +1239,23 @@ static int kcore_mapfn(u64 start, u64 len, u64 pgoff, void *data)
 	return 0;
 }
 
+static bool remove_old_maps(struct map *map, void *data)
+{
+	const struct map *map_to_save = data;
+
+	/*
+	 * We need to preserve eBPF maps even if they are covered by kcore,
+	 * because we need to access eBPF dso for source data.
+	 */
+	return RC_CHK_ACCESS(map) != RC_CHK_ACCESS(map_to_save) && !__map__is_bpf_prog(map);
+}
+
 static int dso__load_kcore(struct dso *dso, struct map *map,
 			   const char *kallsyms_filename)
 {
 	struct maps *kmaps = map__kmaps(map);
 	struct kcore_mapfn_data md;
 	struct map *replacement_map = NULL;
-	struct map_rb_node *old_node, *next;
 	struct machine *machine;
 	bool is_64_bit;
 	int err, fd;
@@ -1292,17 +1302,7 @@ static int dso__load_kcore(struct dso *dso, struct map *map,
 	}
 
 	/* Remove old maps */
-	maps__for_each_entry_safe(kmaps, old_node, next) {
-		struct map *old_map = old_node->map;
-
-		/*
-		 * We need to preserve eBPF maps even if they are
-		 * covered by kcore, because we need to access
-		 * eBPF dso for source data.
-		 */
-		if (old_map != map && !__map__is_bpf_prog(old_map))
-			maps__remove(kmaps, old_map);
-	}
+	maps__remove_maps(kmaps, remove_old_maps, map);
 	machine->trampolines_mapped = false;
 
 	/* Find the kernel map using the '_stext' symbol */
-- 
2.42.0.758.gaed0368e0e-goog