[Fix] AOF rewrite not working.

Fix for issue https://github.com/MSOpenTech/redis/issues/275
An existing fix was not working in Release mode because the compiler
optimization was removing the code that forces the VEH to map the memory page.

src/Win32_Interop/Win32_Common.cpp

@@ -0,0 +1,48 @@
+/*
+* Copyright (c), Microsoft Open Technologies, Inc.
+* All rights reserved.
+* Redistribution and use in source and binary forms, with or without
+* modification, are permitted provided that the following conditions are met:
+*  - Redistributions of source code must retain the above copyright notice,
+*    this list of conditions and the following disclaimer.
+*  - Redistributions in binary form must reproduce the above copyright notice,
+*    this list of conditions and the following disclaimer in the documentation
+*    and/or other materials provided with the distribution.
+* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+*/
+#include "Win32_Common.h"
+
+namespace Globals
+{
+    size_t pageSize = 0;
+}
+
+/* This function is used to force the VEH on the entire size of the buffer length,
+   in the event that the buffer crosses the memory page boundaries */
+void EnsureMemoryIsMapped(const void *buffer, size_t size) {
+    /* Use 'volatile' to make sure the compiler doesn't remove "c = *((char*) (p + offset));" */
+    volatile char c;    
+    char* p = (char*) buffer;
+    char* pStart = p - ((size_t) p % Globals::pageSize);
+    char* pEnd = p + size;
+    if ((size_t) (pEnd - pStart) > Globals::pageSize) {
+        size_t offset = 0;
+        while (offset < size) {
+            if (size < offset) {
+                offset = size;
+            } else {
+                offset += Globals::pageSize;
+            }
+            c = *((char*) (p + offset));
+        }
+    }
+}

src/Win32_Interop/Win32_Common.h

@@ -0,0 +1,33 @@
+/*
+* Copyright (c), Microsoft Open Technologies, Inc.
+* All rights reserved.
+* Redistribution and use in source and binary forms, with or without
+* modification, are permitted provided that the following conditions are met:
+*  - Redistributions of source code must retain the above copyright notice,
+*    this list of conditions and the following disclaimer.
+*  - Redistributions in binary form must reproduce the above copyright notice,
+*    this list of conditions and the following disclaimer in the documentation
+*    and/or other materials provided with the distribution.
+* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+*/
+
+#ifndef WIN32_COMMON_H
+#define WIN32_COMMON_H
+
+void EnsureMemoryIsMapped(const void *buffer, size_t size);
+
+namespace Globals {
+    // forward declarations only
+    extern size_t pageSize;
+}
+
+#endif

src/Win32_Interop/Win32_Interop.vcxproj

@@ -22,6 +22,7 @@
     <ClCompile Include="win32fixes.c" />
     <ClCompile Include="Win32_ANSI.c" />
     <ClCompile Include="Win32_CommandLine.cpp" />
+    <ClCompile Include="Win32_Common.cpp" />
     <ClCompile Include="Win32_dlmalloc.c" />
     <ClCompile Include="Win32_EventLog.cpp" />
     <ClCompile Include="Win32_FDAPI.cpp" />
@@ -45,6 +46,7 @@
     <ClInclude Include="Win32_EventLog.h" />
     <ClInclude Include="Win32_FDAPI.h" />
     <ClInclude Include="Win32_fdapi_crt.h" />
+    <ClInclude Include="Win32_Common.h" />
     <ClInclude Include="Win32_QFork.h" />
     <ClInclude Include="Win32_QFork_impl.h" />
     <ClInclude Include="Win32_RedisLog.h" />

src/Win32_Interop/Win32_QFork.cpp

@@ -22,6 +22,7 @@
 
 #include "win32_types.h"
 #include "Win32_FDAPI.h"
+#include "Win32_Common.h"
 
 #include <Windows.h>
 #include <WinNT.h>
@@ -161,7 +162,6 @@ const SIZE_T cAllocationGranularity = 1 << 18;                    // 256KB per h
 const int cMaxBlocks = 1 << 24;                                   // 256KB * 16M heap blocks = 4TB. 4TB is the largest memory config Windows supports at present.
 const char* cMapFileBaseName = "RedisQFork";
 const int cDeadForkWait = 30000;
-size_t pageSize = 0;
 
 #ifndef _WIN64
 size_t cDefaultmaxHeap32Bit = 1 << 29;                          // 512MB
@@ -693,7 +693,7 @@ StartupStatus QForkStartup(int argc, char** argv) {
         ::redisLog(REDIS_WARNING, "Failing startup.\n");
         return StartupStatus::ssFAILED;
     }
-    pageSize = perfinfo.PageSize;
+    Globals::pageSize = perfinfo.PageSize;
 
     /*
     Not specifying the maxmemory or maxheap flags will result in the default behavior of: new key generation not 
@@ -740,7 +740,7 @@ StartupStatus QForkStartup(int argc, char** argv) {
             maxheapBytes = cSentinelHeapSize;
         } else {
 #ifdef _WIN64
-            maxheapBytes = perfinfo.PhysicalTotal * pageSize;
+            maxheapBytes = perfinfo.PhysicalTotal * Globals::pageSize;
 #else
             maxheapBytes = cDefaultmaxHeap32Bit;
 #endif

src/Win32_Interop/Win32_fdapi_crt.cpp

@@ -21,6 +21,7 @@
 */
 
 #include "Win32_fdapi_crt.h"
+#include "Win32_Common.h"
 #include <io.h>
 #include <stdlib.h>
 
@@ -56,22 +57,14 @@ int crtsetmode(int fd, int mode) {
 	return ::_setmode(fd, mode);
 }
 
-size_t crt_fwrite(const void * _Str, size_t _Size, size_t _Count, FILE * _File) {
+size_t crt_fwrite(const void *buffer, size_t size, size_t count, FILE *file) {
     // fwrite() somehow locks its view of the buffer. If during a fork operation the buffer has not been loaded into the forkee's process space,
     // the VEH will be called to load the missing pages. Although the page gets loaded, fwrite() will not see the loaded page. The result is
     // that fwrite will fail with errno set to ERROR_INVALID_USER_BUFFER. The fix is to force the buffer into memory before fwrite(). This only
-    // impacts wirites that straddle page boundaries.
-    const intptr_t pageSize = 4096;
-    char* p = (char*)_Str;
-    char* pageStart = p - ((intptr_t)p % pageSize);
-    char* pEnd = p + _Size;
-    if ((intptr_t)(pEnd - pageStart) > pageSize)  {
-        for (size_t n = 0; n < _Size; n++) {
-            char x = *((char*)_Str + n);
-        }
-    }
+    // impacts writes that straddle page boundaries.
+    EnsureMemoryIsMapped(buffer, size);
+    return ::fwrite(buffer, size, count, file);
 
-    return ::fwrite(_Str, _Size, _Count, _File);
 }
 
 int crt_fclose(FILE* file) {
@@ -93,4 +86,3 @@ int crt_access(const char *pathname, int mode) {
 __int64 crt_lseek64(int fd, __int64 offset, int origin) {
 	return _lseeki64(fd, offset, origin);
 }
-

src/Win32_Interop/Win32_fdapi_crt.h

@@ -32,7 +32,7 @@ int crt_open(const char *filename, int oflag, int pmode);
 int crt_open_osfhandle(intptr_t osfhandle, int flags);
 intptr_t crtget_osfhandle(int fd);
 int crtsetmode(int fd, int mode);
-size_t crt_fwrite(const void * _Str, size_t _Size, size_t _Count, FILE * _File);
+size_t crt_fwrite(const void *buffer, size_t size, size_t count, FILE *file);
 int crt_fclose(FILE* file);
 int crt_fileno(FILE* file);