issue 126: fwrite() failure with buffers straddling page boundaries during background AOF save

src/Win32_Interop/Win32_FDAPI.cpp

@@ -45,6 +45,7 @@ redis_WSACleanup WSACleanup = NULL;
 redis_WSAGetOverlappedResult WSAGetOverlappedResult = NULL;
 
 // other API forwards
+redis_fwrite fdapi_fwrite = NULL;
 redis_setmode fdapi_setmode = NULL;
 redis_select select = NULL;
 redis_ntohl ntohl = NULL;
@@ -906,6 +907,10 @@ int redis_setmode_impl(int fd,int mode) {
     return crtsetmode(fd,mode);
 }
 
+size_t redis_fwrite_impl(const void * _Str, size_t _Size, size_t _Count, FILE * _File) {
+    return crtfwrite(_Str, _Size, _Count, _File);
+}
+
 auto f_select = dllfunctor_stdcall<int, int, fd_set*, fd_set*, fd_set*, const struct timeval*>("ws2_32.dll", "select");
 int redis_select_impl(int nfds, fd_set *readfds, fd_set *writefds,fd_set *exceptfds, struct timeval *timeout) {
    try { 
@@ -1053,6 +1058,7 @@ private:
         inet_addr = redis_inet_addr_impl;
         gethostbyname = redis_gethostbyname_impl;
         inet_ntoa = redis_inet_ntoa_impl; 
+        fdapi_fwrite = redis_fwrite_impl;
         fdapi_setmode = redis_setmode_impl;
         WSASetLastError = redis_WSASetLastError_impl;
         WSAGetLastError = redis_WSAGetLastError_impl;

src/Win32_Interop/Win32_FDAPI.h

@@ -40,6 +40,7 @@ typedef int ssize_t;
 #define INCL_WINSOCK_API_PROTOTYPES 0 // Important! Do not include Winsock API definitions to avoid conflicts with API entry points defnied below.
 #include <WinSock2.h>
 #include <fcntl.h>
+#include <stdio.h>
 
 // the following are required to be defined before WS2tcpip is included.
 typedef void (*redis_WSASetLastError)(int iError);
@@ -149,6 +150,7 @@ typedef BOOL (*redis_WSAGetOverlappedResult)(int rfd,LPWSAOVERLAPPED lpOverlappe
 
 // other API forwards
 typedef int (*redis_setmode)(int fd,int mode);
+typedef size_t (*redis_fwrite)(const void * _Str, size_t _Size, size_t _Count, FILE * _File);
 
 // API prototypes must match the unix implementation
 typedef int (*redis_socket)(int af,int type,int protocol);
@@ -227,6 +229,7 @@ extern redis_getpeername getpeername;
 extern redis_getsockname getsockname;
 extern redis_ntohs ntohs;
 extern redis_setmode fdapi_setmode;
+extern redis_fwrite fdapi_fwrite;
 
 extern redis_select select;
 extern redis_ntohl ntohl;
@@ -250,6 +253,7 @@ int FDAPI_UpdateAcceptContext( int fd );
 #ifndef FDAPI_NOCRTREDEFS
 #define close(fd) fdapi_close(fd)
 #define setmode(fd,mode) fdapi_setmode(fd,mode)
+#define fwrite(Str, Size, Count, File) fdapi_fwrite(Str,Size,Count,File)
 #define _get_osfhandle(fd) fdapi_get_osfhandle(fd)
 
 #define _INC_STAT_INL

src/Win32_Interop/Win32_fdapi_crt.cpp

@@ -19,6 +19,7 @@
 * 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_fdapi_crt.h"
 #include <io.h>
 #include <stdlib.h>
@@ -47,6 +48,25 @@ int crtsetmode(int fd, int mode) {
 	return ::_setmode(fd, mode);
 }
 
+size_t crtfwrite(const void * _Str, 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);
+        }
+    }
+
+    return ::fwrite(_Str, _Size, _Count, _File);
+}
+
+
 int crt_isatty(int fd) {
 	return _isatty(fd);
 }

src/Win32_Interop/Win32_fdapi_crt.h

@@ -21,6 +21,7 @@
 */
 #pragma once
 #include <cstdint>
+#include <stdio.h>
 
 int crt_close(int fd);
 int crt_read(int fd, void *buffer, unsigned int count);
@@ -28,6 +29,7 @@ int crt_write(int fd, const void *buffer, unsigned int count);
 int crt_open(const char *filename, int oflag, int pmode);
 intptr_t crtget_osfhandle(int fd);
 int crtsetmode(int fd, int mode);
+size_t crtfwrite(const void * _Str, size_t _Size, size_t _Count, FILE * _File);
 int crt_isatty(int fd);
 int crt_access(const char *pathname, int mode);
 __int64 crt_lseek64(int fd, __int64 offset, int origin);

src/rio.c

@@ -54,7 +54,7 @@
 #include "rio.h"
 #include "util.h"
 #ifdef _WIN32
-//#include "win32fixes.h"
+#include "Win32_Interop\Win32_FDAPI.h"
 #endif
 #include "config.h"
 #include "redis.h"
@@ -86,7 +86,6 @@ static off_t rioBufferTell(rio *r) {
 /* Returns 1 or 0 for success/failure. */
 static size_t rioFileWrite(rio *r, const void *buf, size_t len) {
     size_t retval;
-
     retval = fwrite(buf,len,1,r->io.file.fp);
     r->io.file.buffered += (off_t)len;
 

src/ziplist.c

@@ -112,6 +112,10 @@
 #include "endianconv.h"
 #include "redisassert.h"
 
+#ifdef _WIN32
+#include "Win32_Interop\Win32_FDAPI.h"
+#endif
+
 #define ZIP_END 255
 #define ZIP_BIGLEN 254