From: Vladimír Čunát <vladimir.cunat@nic.cz>
Date: Wed, 19 Aug 2020 08:23:04 +0000 (+0200)
Subject: lib/cache check_health(): also detect size changes
X-Git-Tag: v5.1.3~1^2~16
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=cd845d5f7c3664db0089cd00e2130f16cf96378c;p=thirdparty%2Fknot-resolver.git

lib/cache check_health(): also detect size changes

This is important for GC - otherwise the usage computation would be
wrong after another process changed size (without replacing the file).
---

diff --git a/lib/cache/cdb_lmdb.c b/lib/cache/cdb_lmdb.c
index 81708ee5c..c955b3bfb 100644
--- a/lib/cache/cdb_lmdb.c
+++ b/lib/cache/cdb_lmdb.c
@@ -48,6 +48,7 @@ struct lmdb_env
 	/* Cached part of struct stat for data.mdb. */
 	dev_t st_dev;
 	ino_t st_ino;
+	off_t st_size;
 	const char *mdb_data_path; /**< path to data.mdb, for convenience */
 };
 
@@ -309,6 +310,10 @@ static int cdb_open_env(struct lmdb_env *env, const char *path, size_t mapsize,
 	}
 	env->st_dev = st.st_dev;
 	env->st_ino = st.st_ino;
+	env->st_size = st.st_size;
+	if (env->st_size != env->mapsize)
+		kr_log_verbose("[cache] suspicious size of cache file: %zu != %zu\n",
+				(size_t)env->st_size, env->mapsize);
 
 	/* Open the database. */
 	MDB_txn *txn = NULL;
@@ -436,7 +441,15 @@ static int cdb_check_health(knot_db_t *db, struct kr_cdb_stats *stats)
 		// FIXME: if the file doesn't exist?
 	}
 	if (st.st_dev == env->st_dev && st.st_ino == env->st_ino) {
-		return kr_ok();
+		if (st.st_size == env->st_size)
+			return kr_ok();
+		kr_log_info("[cache] detected size change by another process: %zu -> %zu\n",
+				(size_t)env->st_size, (size_t)st.st_size);
+		int ret = cdb_commit(db, stats);
+		if (!ret) ret = lmdb_error(mdb_env_set_mapsize(env->env, st.st_size));
+		if (!ret) env->mapsize = st.st_size;
+		env->st_size = st.st_size; // avoid retrying in cycle even if it failed
+		return kr_error(ret);
 	}
 	kr_log_verbose("[cache] cache file has been replaced, reopening\n");
 	int ret = reopen_env(env, stats);
diff --git a/utils/cache_gc/db.h b/utils/cache_gc/db.h
index 74d876359..44cfbec29 100644
--- a/utils/cache_gc/db.h
+++ b/utils/cache_gc/db.h
@@ -9,6 +9,8 @@
 int kr_gc_cache_open(const char *cache_path, struct kr_cache *kres_db,
 		     knot_db_t ** libknot_db);
 
+/** A wrapper around kr_cdb_api::check_health that keeps libknot_db up to date.
+ * \return zero or negative error code. */
 int kr_gc_cache_check_health(struct kr_cache *kres_db, knot_db_t ** libknot_db);
 
 void kr_gc_cache_close(struct kr_cache *kres_db, knot_db_t * knot_db);
diff --git a/utils/cache_gc/main.c b/utils/cache_gc/main.c
index a2c05489f..736ade321 100644
--- a/utils/cache_gc/main.c
+++ b/utils/cache_gc/main.c
@@ -8,6 +8,7 @@
 #include "lib/defines.h"
 #include "lib/utils.h"
 #include <libknot/libknot.h>
+#include <lmdb.h>
 
 #include "kresconfig.h"
 #include "kr_cache_gc.h"
@@ -148,7 +149,8 @@ int main(int argc, char *argv[])
 		}
 
 		// ENOENT: kresd may not be started yet or cleared the cache now
-		if (ret && ret != KNOT_ENOENT) {
+		// MDB_MAP_RESIZED: GC bailed out but on next iteration it should be OK
+		if (ret && ret != KNOT_ENOENT && ret != kr_error(MDB_MAP_RESIZED)) {
 			printf("Error (%s)\n", knot_strerror(ret));
 			exit_code = 10;
 			break;