Backport Fix for Bug#24509 - 2048 file descriptor limit on windows needs increasing.

The patch replaces the use of the POSIX I/O interfaces in mysys on Windows with 
the Win32 API calls (CreateFile, WriteFile, etc). The Windows HANDLE for the open
 file is stored in the my_file_info struct, along with a flag for append mode 
(because the Windows API does not support opening files in append mode in all cases)
The default max open files has been increased to 16384 and can be increased further
by setting --max-open-files=<value> during the server start.

Noteworthy benefit of this patch is that it removes limits from the table_cache size - 
allowing for more simultaneus users

1 files changed, 34 insertions, 47 deletions

diff --git a/mysys/my_pread.c b/mysys/my_pread.c
index 836f5a92963..6421a2da601 100644
--- a/mysys/my_pread.c
+++ b/mysys/my_pread.c
@@ -18,7 +18,7 @@
 #include "my_base.h"
 #include <m_string.h>
 #include <errno.h>
-#ifdef HAVE_PREAD
+#ifndef _WIN32
 #include <unistd.h>
 #endif
 
@@ -48,9 +48,7 @@ size_t my_pread(File Filedes, uchar *Buffer, size_t Count, my_off_t offset,
 {
   size_t readbytes;
   int error= 0;
-#ifndef HAVE_PREAD
-  int save_errno;
-#endif
+
 #ifndef DBUG_OFF
   char llbuf[22];
   DBUG_ENTER("my_pread");
@@ -61,20 +59,15 @@ size_t my_pread(File Filedes, uchar *Buffer, size_t Count, my_off_t offset,
   for (;;)
   {
     errno= 0;    /* Linux, Windows don't reset this on EOF/success */
-#ifndef HAVE_PREAD
-    pthread_mutex_lock(&my_file_info[Filedes].mutex);
-    readbytes= (uint) -1;
-    error= (lseek(Filedes, offset, MY_SEEK_SET) == (my_off_t) -1 ||
-	    (readbytes= read(Filedes, Buffer, (uint) Count)) != Count);
-    save_errno= errno;
-    pthread_mutex_unlock(&my_file_info[Filedes].mutex);
-    if (error)
-    {
-      errno= save_errno;
+#ifdef _WIN32
+    readbytes= my_win_pread(Filedes, Buffer, Count, offset);
 #else
-    if ((error= ((readbytes= pread(Filedes, Buffer, Count, offset)) != Count)))
-    {
+    readbytes= pread(Filedes, Buffer, Count, offset);
 #endif
+    error = (readbytes != Count);
+
+    if (error)
+    {
       my_errno= errno ? errno : -1;
       if (errno == 0 || (readbytes != (size_t) -1 &&
                          (MyFlags & (MY_NABP | MY_FNABP))))
@@ -91,19 +84,19 @@ size_t my_pread(File Filedes, uchar *Buffer, size_t Count, my_off_t offset,
 #endif
       if (MyFlags & (MY_WME | MY_FAE | MY_FNABP))
       {
-	if (readbytes == (size_t) -1)
-	  my_error(EE_READ, MYF(ME_BELL+ME_WAITTANG),
-		   my_filename(Filedes),my_errno);
-	else if (MyFlags & (MY_NABP | MY_FNABP))
-	  my_error(EE_EOFERR, MYF(ME_BELL+ME_WAITTANG),
-		   my_filename(Filedes),my_errno);
+        if (readbytes == (size_t) -1)
+          my_error(EE_READ, MYF(ME_BELL+ME_WAITTANG),
+                   my_filename(Filedes),my_errno);
+        else if (MyFlags & (MY_NABP | MY_FNABP))
+          my_error(EE_EOFERR, MYF(ME_BELL+ME_WAITTANG),
+                   my_filename(Filedes),my_errno);
       }
       if (readbytes == (size_t) -1 || (MyFlags & (MY_FNABP | MY_NABP)))
-	DBUG_RETURN(MY_FILE_ERROR);		/* Return with error */
+        DBUG_RETURN(MY_FILE_ERROR);         /* Return with error */
     }
     if (MyFlags & (MY_NABP | MY_FNABP))
-      DBUG_RETURN(0);				/* Read went ok; Return 0 */
-    DBUG_RETURN(readbytes);			/* purecov: inspected */
+      DBUG_RETURN(0);                      /* Read went ok; Return 0 */
+    DBUG_RETURN(readbytes);                /* purecov: inspected */
   }
 } /* my_pread */
 
@@ -132,7 +125,7 @@ size_t my_pread(File Filedes, uchar *Buffer, size_t Count, my_off_t offset,
 size_t my_pwrite(int Filedes, const uchar *Buffer, size_t Count,
                  my_off_t offset, myf MyFlags)
 {
-  size_t writenbytes, written;
+  size_t writtenbytes, written;
   uint errors;
 #ifndef DBUG_OFF
   char llbuf[22];
@@ -146,28 +139,22 @@ size_t my_pwrite(int Filedes, const uchar *Buffer, size_t Count,
 
   for (;;)
   {
-#ifndef HAVE_PREAD
-    int error;
-    writenbytes= (size_t) -1;
-    pthread_mutex_lock(&my_file_info[Filedes].mutex);
-    error= (lseek(Filedes, offset, MY_SEEK_SET) != (my_off_t) -1 &&
-            (writenbytes = write(Filedes, Buffer, (uint) Count)) == Count);
-    pthread_mutex_unlock(&my_file_info[Filedes].mutex);
-    if (error)
-      break;
+#ifdef _WIN32
+    writtenbytes= my_win_pwrite(Filedes, Buffer, Count,offset);
 #else
-    if ((writenbytes= pwrite(Filedes, Buffer, Count,offset)) == Count)
+    writtenbytes= pwrite(Filedes, Buffer, Count, offset);
+#endif
+    if (writtenbytes == Count)
       break;
     my_errno= errno;
-#endif
-    if (writenbytes != (size_t) -1)
+    if (writtenbytes != (size_t) -1)
     {					/* Safegueard */
-      written+=writenbytes;
-      Buffer+=writenbytes;
-      Count-=writenbytes;
-      offset+=writenbytes;
+      written+=writtenbytes;
+      Buffer+=writtenbytes;
+      Count-=writtenbytes;
+      offset+=writtenbytes;
     }
-    DBUG_PRINT("error",("Write only %u bytes", (uint) writenbytes));
+    DBUG_PRINT("error",("Write only %u bytes", (uint) writtenbytes));
 #ifndef NO_BACKGROUND
 #ifdef THREAD
     if (my_thread_var->abort)
@@ -180,15 +167,15 @@ size_t my_pwrite(int Filedes, const uchar *Buffer, size_t Count,
       errors++;
       continue;
     }
-    if ((writenbytes && writenbytes != (size_t) -1) || my_errno == EINTR)
+    if ((writtenbytes && writtenbytes != (size_t) -1) || my_errno == EINTR)
       continue;					/* Retry */
 #endif
     if (MyFlags & (MY_NABP | MY_FNABP))
     {
       if (MyFlags & (MY_WME | MY_FAE | MY_FNABP))
       {
-	my_error(EE_WRITE, MYF(ME_BELL | ME_WAITTANG),
-		 my_filename(Filedes),my_errno);
+        my_error(EE_WRITE, MYF(ME_BELL | ME_WAITTANG),
+                 my_filename(Filedes),my_errno);
       }
       DBUG_RETURN(MY_FILE_ERROR);		/* Error on read */
     }
@@ -198,5 +185,5 @@ size_t my_pwrite(int Filedes, const uchar *Buffer, size_t Count,
   DBUG_EXECUTE_IF("check", my_seek(Filedes, -1, SEEK_SET, MYF(0)););
   if (MyFlags & (MY_NABP | MY_FNABP))
     DBUG_RETURN(0);			/* Want only errors */
-  DBUG_RETURN(writenbytes+written); /* purecov: inspected */
+  DBUG_RETURN(writtenbytes+written); /* purecov: inspected */
 } /* my_pwrite */