always use my_b_pread() instead of mysql_file_pread()

when working with IO_CACHE's, don't access IO_CACHE::file directly

include/my_sys.h

@@ -610,6 +610,7 @@ static inline size_t my_b_bytes_in_cache(const IO_CACHE *info)
 int      my_b_copy_to_file(IO_CACHE *cache, FILE *file);
 my_off_t my_b_append_tell(IO_CACHE* info);
 my_off_t my_b_safe_tell(IO_CACHE* info); /* picks the correct tell() */
+int my_b_pread(IO_CACHE *info, uchar *Buffer, size_t Count, my_off_t pos);
 
 typedef uint32 ha_checksum;
 extern ulong my_crc_dbug_check;

mysys/mf_iocache2.c

@@ -180,6 +180,12 @@ void my_b_seek(IO_CACHE *info,my_off_t pos)
   DBUG_VOID_RETURN;
 }
 
+int my_b_pread(IO_CACHE *info, uchar *Buffer, size_t Count, my_off_t pos)
+{
+  if (mysql_file_pread(info->file, Buffer, Count, pos, info->myflags | MY_NABP))
+    return info->error= -1;
+  return 0;
+}
 
 /*
   Read a string ended by '\n' into a buffer of 'max_length' size.

sql/filesort.cc

@@ -1483,10 +1483,9 @@ uint read_to_buffer(IO_CACHE *fromfile, BUFFPEK *buffpek,
 
   if ((count=(uint) MY_MIN((ha_rows) buffpek->max_keys,buffpek->count)))
   {
-    if (mysql_file_pread(fromfile->file, (uchar*) buffpek->base,
-                         (length= rec_length*count),
-                         buffpek->file_pos, MYF_RW))
-      return((uint) -1);			/* purecov: inspected */
+    if (my_b_pread(fromfile, (uchar*) buffpek->base,
+                   (length= rec_length*count), buffpek->file_pos))
+      return ((uint) -1);
     buffpek->key=buffpek->base;
     buffpek->file_pos+= length;			/* New filepos */
     buffpek->count-=	count;

storage/maria/ma_sort.c

@@ -929,9 +929,8 @@ static my_off_t read_to_buffer(IO_CACHE *fromfile, BUFFPEK *buffpek,
 
   if ((count= (ha_keys) MY_MIN((ha_rows) buffpek->max_keys,buffpek->count)))
   {
-    if (mysql_file_pread(fromfile->file, (uchar*) buffpek->base,
-                         (length= sort_length * count),
-                         buffpek->file_pos, MYF_RW))
+    if (my_b_pread(fromfile, (uchar*) buffpek->base,
+                   (length= sort_length * count), buffpek->file_pos))
       return(HA_OFFSET_ERROR);               /* purecov: inspected */
     buffpek->key=buffpek->base;
     buffpek->file_pos+= length;                 /* New filepos */
@@ -956,12 +955,12 @@ static my_off_t read_to_buffer_varlen(IO_CACHE *fromfile, BUFFPEK *buffpek,
     for (idx=1;idx<=count;idx++)
     {
       uint16 length_of_key;
-      if (mysql_file_pread(fromfile->file,(uchar*)&length_of_key,sizeof(length_of_key),
-                   buffpek->file_pos,MYF_RW))
+      if (my_b_pread(fromfile, (uchar*)&length_of_key,
+                     sizeof(length_of_key), buffpek->file_pos))
         return(HA_OFFSET_ERROR);
       buffpek->file_pos+=sizeof(length_of_key);
-      if (mysql_file_pread(fromfile->file, buffp, length_of_key,
-                   buffpek->file_pos,MYF_RW))
+      if (my_b_pread(fromfile, (uchar*) buffp,
+                     length_of_key, buffpek->file_pos))
         return((uint) -1);
       buffpek->file_pos+=length_of_key;
       buffp = buffp + sort_length;

storage/myisam/sort.c

@@ -876,10 +876,9 @@ static my_off_t read_to_buffer(IO_CACHE *fromfile, BUFFPEK *buffpek,
 
   if ((count= (ha_keys) MY_MIN((ha_rows) buffpek->max_keys,buffpek->count)))
   {
-    if (mysql_file_pread(fromfile->file, (uchar*) buffpek->base,
-                         (length= sort_length * count),
-                         buffpek->file_pos, MYF_RW))
-      return(HA_OFFSET_ERROR);               /* purecov: inspected */
+    if (my_b_pread(fromfile, (uchar*) buffpek->base,
+                   (length= sort_length * count), buffpek->file_pos))
+      return(HA_OFFSET_ERROR);
     buffpek->key=buffpek->base;
     buffpek->file_pos+= length;               /* New filepos */
     buffpek->count-=    count;
@@ -903,12 +902,12 @@ static my_off_t read_to_buffer_varlen(IO_CACHE *fromfile, BUFFPEK *buffpek,
 
     for (idx=1;idx<=count;idx++)
     {
-      if (mysql_file_pread(fromfile->file, (uchar*)&length_of_key,
-                           sizeof(length_of_key), buffpek->file_pos, MYF_RW))
+      if (my_b_pread(fromfile, (uchar*)&length_of_key,
+                     sizeof(length_of_key), buffpek->file_pos))
         return(HA_OFFSET_ERROR);
       buffpek->file_pos+=sizeof(length_of_key);
-      if (mysql_file_pread(fromfile->file, (uchar*) buffp,
-                           length_of_key, buffpek->file_pos, MYF_RW))
+      if (my_b_pread(fromfile, (uchar*) buffp,
+                     length_of_key, buffpek->file_pos))
         return(HA_OFFSET_ERROR);
       buffpek->file_pos+=length_of_key;
       buffp = buffp + sort_length;