From c1ad75d8107d9ff4e5e89df8058c65161d43a188 Mon Sep 17 00:00:00 2001
From: Leo Yuriev <leo@yuriev.ru>
Date: Fri, 21 Apr 2017 19:00:33 +0300
Subject: [PATCH] mdbx: check env-flags while opening live db.

---
 src/bits.h |  2 ++
 src/mdbx.c | 15 ++++++++++++---
 2 files changed, 14 insertions(+), 3 deletions(-)

diff --git a/src/bits.h b/src/bits.h
index 7b89604d..ca6dc06c 100644
--- a/src/bits.h
+++ b/src/bits.h
@@ -360,6 +360,8 @@ typedef struct MDBX_lockinfo {
   uint64_t mti_magic;
   /* Format of this lock file. Must be set to MDB_LOCK_FORMAT. */
   uint64_t mti_format;
+  /* Flags which environment was opened. */
+  uint64_t mti_envmode;
 
 #ifdef MDBX_OSAL_LOCK
   MDBX_OSAL_LOCK mti_wmutex;
diff --git a/src/mdbx.c b/src/mdbx.c
index 655c0534..fc7db92b 100644
--- a/src/mdbx.c
+++ b/src/mdbx.c
@@ -3994,6 +3994,7 @@ int __cold mdbx_env_open_ex(MDB_env *env, const char *path, unsigned flags,
   if (rc == MDB_SUCCESS) {
     mdbx_debug("opened dbenv %p", (void *)env);
     if (excl > 0) {
+      env->me_txns->mti_envmode = env->me_flags;
       if (exclusive == NULL || *exclusive < 2) {
         /* LY: downgrade lock only if exclusive access not requested.
          *     in case exclusive==1, just leave value as is. */
@@ -4002,9 +4003,17 @@ int __cold mdbx_env_open_ex(MDB_env *env, const char *path, unsigned flags,
           goto bailout;
         excl = 0;
       }
-    } else if (exclusive) {
-      /* LY: just indicate that is not an exclusive access. */
-      *exclusive = 0;
+    } else {
+      if (exclusive) {
+        /* LY: just indicate that is not an exclusive access. */
+        *exclusive = 0;
+      }
+      if ((env->me_txns->mti_envmode ^ env->me_flags) &
+          (MDB_WRITEMAP | MDB_NOSYNC | MDB_NOMETASYNC | MDB_MAPASYNC)) {
+        /* LY: Current mode/flags incompatible with requested. */
+        rc = MDB_INCOMPATIBLE;
+        goto bailout;
+      }
     }
     if (!(flags & MDB_RDONLY)) {
       MDB_txn *txn;