From 261f697d8c033771ccc2c1027b93ee89d4b51ac2 Mon Sep 17 00:00:00 2001
From: Leonid Yuriev <leo@yuriev.ru>
Date: Mon, 19 Aug 2019 21:31:05 +0300
Subject: [PATCH] mdbx: skip msync(MS_ASYNC) on Linux > 2.6.19.

Change-Id: Ic1f631ef856a09cf62353c2b0092b0341ecf4fa2
---
 src/osal.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/src/osal.c b/src/osal.c
index e0858733..03d4c86f 100644
--- a/src/osal.c
+++ b/src/osal.c
@@ -784,6 +784,13 @@ int mdbx_msync(mdbx_mmap_t *map, size_t offset, size_t length, int async) {
     return MDBX_SUCCESS;
   return GetLastError();
 #else
+#ifdef __linux__
+  if (async && linux_kernel_version > 0x02061300)
+    /* Since Linux 2.6.19, MS_ASYNC is in fact a no-op,
+       since the kernel properly tracks dirty pages and flushes them to storage
+       as necessary. */
+    return MDBX_SUCCESS;
+#endif /* Linux */
   const int mode = async ? MS_ASYNC : MS_SYNC;
   return (msync(ptr, length, mode) == 0) ? MDBX_SUCCESS : errno;
 #endif