Made IO_CACHE safe for reading big blocks (> 2G)

The reason for adding this was that while testing mysqlbinlog on
a replication event with 3G event output, Linux failed reading
the whole file in memory with one read (only got 2G on first read
even if file had just been written).

- Don't reset info->error on write error in IO_CACHE.
- In case of write_error in IO_CACHE , always return -1
- Fixed wrong result from my_read when using MY_FULL_IO. Also don't give
  an error in case of retry.

1 files changed, 22 insertions, 18 deletions

diff --git a/mysys/my_read.c b/mysys/my_read.c
index 922da5a7e95..89b368e9800 100644
--- a/mysys/my_read.c
+++ b/mysys/my_read.c
@@ -35,11 +35,10 @@
 
 size_t my_read(File Filedes, uchar *Buffer, size_t Count, myf MyFlags)
 {
-  size_t readbytes, save_count;
+  size_t readbytes, save_count= 0;
   DBUG_ENTER("my_read");
   DBUG_PRINT("my",("fd: %d  Buffer: %p  Count: %lu  MyFlags: %lu",
                    Filedes, Buffer, (ulong) Count, MyFlags));
-  save_count= Count;
   if (!(MyFlags & (MY_WME | MY_FAE | MY_FNABP)))
     MyFlags|= my_global_flags;
 
@@ -61,47 +60,52 @@ size_t my_read(File Filedes, uchar *Buffer, size_t Count, myf MyFlags)
 
     if (readbytes != Count)
     {
-      my_errno= errno;
-      if (errno == 0 || (readbytes != (size_t) -1 &&
-                         (MyFlags & (MY_NABP | MY_FNABP))))
-        my_errno= HA_ERR_FILE_TOO_SHORT;
+      int got_errno= my_errno= errno;
       DBUG_PRINT("warning",("Read only %d bytes off %lu from %d, errno: %d",
                             (int) readbytes, (ulong) Count, Filedes,
-                            my_errno));
+                            got_errno));
+
+      if (got_errno == 0 || (readbytes != (size_t) -1 &&
+                         (MyFlags & (MY_NABP | MY_FNABP))))
+        my_errno= HA_ERR_FILE_TOO_SHORT;
 
-      if ((readbytes == 0 || (int) readbytes == -1) && errno == EINTR)
+      if ((readbytes == 0 || (int) readbytes == -1) && got_errno == EINTR)
       {  
         DBUG_PRINT("debug", ("my_read() was interrupted and returned %ld",
                              (long) readbytes));
         continue;                              /* Interrupted */
       }
 
+      /* Do a read retry if we didn't get enough data on first read */
+      if (readbytes != (size_t) -1 && readbytes != 0 &&
+          (MyFlags & MY_FULL_IO))
+      {
+        Buffer+= readbytes;
+        Count-= readbytes;
+        save_count+= readbytes;
+        continue;
+      }
+
       if (MyFlags & (MY_WME | MY_FAE | MY_FNABP))
       {
         if (readbytes == (size_t) -1)
           my_error(EE_READ,
                    MYF(ME_BELL | ME_WAITTANG | (MyFlags & (ME_JUST_INFO | ME_NOREFRESH))),
-                   my_filename(Filedes),my_errno);
+                   my_filename(Filedes), got_errno);
         else if (MyFlags & (MY_NABP | MY_FNABP))
           my_error(EE_EOFERR,
                    MYF(ME_BELL | ME_WAITTANG | (MyFlags & (ME_JUST_INFO | ME_NOREFRESH))),
-                   my_filename(Filedes),my_errno);
+                   my_filename(Filedes), got_errno);
       }
       if (readbytes == (size_t) -1 ||
           ((MyFlags & (MY_FNABP | MY_NABP)) && !(MyFlags & MY_FULL_IO)))
         DBUG_RETURN(MY_FILE_ERROR);	/* Return with error */
-      if (readbytes != (size_t) -1 && (MyFlags & MY_FULL_IO))
-      {
-        Buffer+= readbytes;
-        Count-= readbytes;
-        continue;
-      }
     }
 
     if (MyFlags & (MY_NABP | MY_FNABP))
       readbytes= 0;			/* Ok on read */
-    else if (MyFlags & MY_FULL_IO)
-      readbytes= save_count;
+    else
+      readbytes+= save_count;
     break;
   }
   DBUG_RETURN(readbytes);