mdbx: fix mdbx_override_meta() to avoid false-positive assertions.

Fixed https://github.com/erthink/libmdbx/issues/253.

ChangeLog.md

@@ -23,6 +23,7 @@ ChangeLog
 Acknowledgements:
 
  - [gcxfd <i@rmw.link>](https://github.com/gcxfd) for reporting, contributing and testing.
+ - [장세연 (Чан Се Ен)](https://github.com/sasgas) for reporting and testing.
 
 New features, extensions and improvements:
 
@@ -43,6 +44,7 @@ Minors:
  - [Fixed](https://github.com/erthink/libmdbx/issues/248) extra assertion inside `mdbx_cursor_put()` for `MDBX_DUPFIXED` cases.
  - Avoiding extra looping inside `mdbx_env_info_ex()`.
  - Explicitly enabled core dumps from stochastic tests scripts on Linux.
+ - [Fixed](https://github.com/erthink/libmdbx/issues/253) `mdbx_override_meta()` to avoid false-positive assertions.
 
 
 ## v0.11.2 at 2021-12-02

src/core.c

@@ -12319,16 +12319,12 @@ __cold static int __must_check_result mdbx_override_meta(
                     MDBX_SYNC_DATA | MDBX_SYNC_IODQ);
     if (unlikely(rc != MDBX_SUCCESS))
       return rc;
-    MDBX_meta *live = METAPAGE(env, target);
-    mdbx_meta_update_begin(env, live, unaligned_peek_u64(4, model->mm_txnid_a));
+    /* mdbx_override_meta() called only while current process have exclusive
+     * lock of a DB file. So meta-page could be updated directly without
+     * clearing consistency flag by mdbx_meta_update_begin() */
+    memcpy(pgno2page(env, target), page, env->me_psize);
     mdbx_flush_incoherent_cpu_writeback();
-    mdbx_meta_update_begin(env, model,
-                           unaligned_peek_u64(4, model->mm_txnid_a));
-    unaligned_poke_u64(4, model->mm_datasync_sign, MDBX_DATASIGN_WEAK);
-    memcpy((void *)data_page(live), page, env->me_psize);
-    mdbx_meta_update_end(env, live, unaligned_peek_u64(4, model->mm_txnid_b));
-    mdbx_flush_incoherent_cpu_writeback();
-    rc = mdbx_msync(&env->me_dxb_mmap, 0, pgno_align2os_bytes(env, target),
+    rc = mdbx_msync(&env->me_dxb_mmap, 0, pgno_align2os_bytes(env, target + 1),
                     MDBX_SYNC_DATA | MDBX_SYNC_IODQ);
   } else {
     const mdbx_filehandle_t fd = (env->me_dsync_fd != INVALID_HANDLE_VALUE)