New improved IO_CACHE

include/my_global.h:
  Remove dbug_assert()  (One should use DBUG_ASSERT() instead)
mysql-test/mysql-test-run.sh:
  Fixed that xterm works on Solaris 2.8.
  Fixed printing of errors
mysql-test/r/isam.result:
  Removed MyISAM test from ISAM test
mysql-test/t/isam.test:
  Removed MyISAM test from ISAM test
mysys/my_alloc.c:
  Removed warnings
mysys/my_bitmap.c:
  Use DBUG_ASSERT
mysys/my_pthread.c:
  Use DBUG_ASSERT
mysys/my_seek.c:
  More DBUG
sql/ha_berkeley.cc:
  Use DBUG_ASSERT
sql/ha_innobase.cc:
  Use DBUG_ASSERT
sql/log.cc:
  Use DBUG_ASSERT
sql/opt_range.cc:
  Use DBUG_ASSERT
sql/sql_base.cc:
  Use DBUG_ASSERT
sql/sql_handler.cc:
  Use DBUG_ASSERT
sql/sql_load.cc:
  Cleanup
sql/sql_parse.cc:
  Use DBUG_ASSERT
sql/sql_repl.cc:
  Cleanup
sql/sql_select.cc:
  Use DBUG_ASSERT
tools/mysqlmanager.c:
  Cleanup

1 files changed, 322 insertions, 262 deletions

diff --git a/mysys/mf_iocache.c b/mysys/mf_iocache.c
index f29df74b651..b0868851177 100644
--- a/mysys/mf_iocache.c
+++ b/mysys/mf_iocache.c
@@ -1,15 +1,15 @@
 /* Copyright (C) 2000 MySQL AB & MySQL Finland AB & TCX DataKonsult AB
-   
+
    This library is free software; you can redistribute it and/or
    modify it under the terms of the GNU Library General Public
    License as published by the Free Software Foundation; either
    version 2 of the License, or (at your option) any later version.
-   
+
    This library is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
    Library General Public License for more details.
-   
+
    You should have received a copy of the GNU Library General Public
    License along with this library; if not, write to the Free
    Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
@@ -23,12 +23,30 @@
   Possibly use of asyncronic io.
   macros for read and writes for faster io.
   Used instead of FILE when reading or writing whole files.
-  This will make mf_rec_cache obsolete.
+  This code makes mf_rec_cache obsolete (currently only used by ISAM)
   One can change info->pos_in_file to a higher value to skip bytes in file if
-  also info->rc_pos is set to info->rc_end.
+  also info->read_pos is set to info->read_end.
   If called through open_cached_file(), then the temporary file will
   only be created if a write exeeds the file buffer or if one calls
-  flush_io_cache().  
+  flush_io_cache().
+
+  If one uses SEQ_READ_APPEND, then two buffers are allocated, one for
+  reading and another for writing.  Reads are first done from disk and
+  then done from the write buffer.  This is an efficient way to read
+  from a log file when one is writing to it at the same time.
+  For this to work, the file has to be opened in append mode!
+  Note that when one uses SEQ_READ_APPEND, one MUST write using
+  my_b_append !  This is needed because we need to lock the mutex
+  every time we access the write buffer.
+
+TODO:
+  When one SEQ_READ_APPEND and we are reading and writing at the same time,
+  each time the write buffer gets full and it's written to disk, we will
+  always do a disk read to read a part of the buffer from disk to the
+  read buffer.
+  This should be fixed so that when we do a flush_io_cache() and
+  we have been reading the write buffer, we should transfer the rest of the
+  write buffer to the read buffer before we start to reuse it.
 */
 
 #define MAP_TO_USE_RAID
@@ -41,18 +59,20 @@ static void my_aiowait(my_aio_result *result);
 #include <assert.h>
 #include <errno.h>
 
-#ifdef MAIN
-#include <my_dir.h>
+#ifdef THREAD
+#define lock_append_buffer(info) \
+ pthread_mutex_lock(&(info)->append_buffer_lock)
+#define unlock_append_buffer(info) \
+ pthread_mutex_unlock(&(info)->append_buffer_lock)
+#else
+#define lock_append_buffer(info)
+#define unlock_append_buffer(info)
 #endif
 
-static void init_read_function(IO_CACHE* info, enum cache_type type);
-static void init_write_function(IO_CACHE* info, enum cache_type type);
-
-static void init_read_function(IO_CACHE* info, enum cache_type type)
+static void
+init_functions(IO_CACHE* info, enum cache_type type)
 {
-  switch (type)
-  {
-#ifndef MYSQL_CLIENT    
+  switch (type) {
   case READ_NET:
     /* must be initialized by the caller. The problem is that
        _my_b_net_read has to be defined in sql directory because of
@@ -61,24 +81,25 @@ static void init_read_function(IO_CACHE* info, enum cache_type type)
        as myisamchk
     */
     break;
-#endif
   case SEQ_READ_APPEND:
     info->read_function = _my_b_seq_read;
+    info->write_function = 0;			/* Force a core if used */
     break;
   default:
     info->read_function = _my_b_read;
+    info->write_function = _my_b_write;
   }
-}
 
-static void init_write_function(IO_CACHE* info, enum cache_type type)
-{
-  switch (type)
+  /* Ensure that my_b_tell() and my_b_bytes_in_cache works */
+  if (type == WRITE_CACHE)
   {
-  case SEQ_READ_APPEND:
-    info->write_function = _my_b_append;
-    break;
-  default:
-    info->write_function = _my_b_write;
+    info->current_pos= &info->write_pos;
+    info->current_end= &info->write_end;
+  }
+  else
+  {
+    info->current_pos= &info->read_pos;
+    info->current_end= &info->read_end;
   }
 }
 
@@ -93,62 +114,61 @@ int init_io_cache(IO_CACHE *info, File file, uint cachesize,
 		  pbool use_async_io, myf cache_myflags)
 {
   uint min_cache;
+  my_off_t end_of_file= ~(my_off_t) 0;
   DBUG_ENTER("init_io_cache");
   DBUG_PRINT("enter",("type: %d  pos: %ld",(int) type, (ulong) seek_offset));
 
-  /* There is no file in net_reading */
   info->file= file;
+  info->type=type;
+  info->pos_in_file= seek_offset;
   info->pre_close = info->pre_read = info->post_read = 0;
   info->arg = 0;
+  info->alloced_buffer = 0;
+  info->buffer=0;
+  info->seek_not_done= test(file >= 0);
+
   if (!cachesize)
     if (! (cachesize= my_default_record_cache_size))
       DBUG_RETURN(1);				/* No cache requested */
   min_cache=use_async_io ? IO_SIZE*4 : IO_SIZE*2;
-  info->alloced_buffer = 0;
   if (type == READ_CACHE || type == SEQ_READ_APPEND)
   {						/* Assume file isn't growing */
-    if (cache_myflags & MY_DONT_CHECK_FILESIZE)
+    if (!(cache_myflags & MY_DONT_CHECK_FILESIZE))
     {
-      cache_myflags &= ~MY_DONT_CHECK_FILESIZE;
-    }
-    else
-    {
-      my_off_t file_pos,end_of_file;
-      if ((file_pos=my_tell(file,MYF(0)) == MY_FILEPOS_ERROR))
-	DBUG_RETURN(1);
+      /* Calculate end of file to not allocate to big buffers */
       end_of_file=my_seek(file,0L,MY_SEEK_END,MYF(0));
       if (end_of_file < seek_offset)
 	end_of_file=seek_offset;
-      VOID(my_seek(file,file_pos,MY_SEEK_SET,MYF(0)));
-      /* Trim cache size if the file is very small.
-	 However, we should not do this with SEQ_READ_APPEND cache
-      */
-      if (type != SEQ_READ_APPEND &&
-	  (my_off_t) cachesize > end_of_file-seek_offset+IO_SIZE*2-1)
+      /* Trim cache size if the file is very small */
+      if ((my_off_t) cachesize > end_of_file-seek_offset+IO_SIZE*2-1)
       {
 	cachesize=(uint) (end_of_file-seek_offset)+IO_SIZE*2-1;
 	use_async_io=0;				/* No need to use async */
       }
     }
   }
-  if ((int) type < (int) READ_NET)
+  cache_myflags &= ~MY_DONT_CHECK_FILESIZE;
+  if (type != READ_NET && type != WRITE_NET)
   {
-    uint buffer_block;
+    /* Retry allocating memory in smaller blocks until we get one */
     for (;;)
     {
-      buffer_block = cachesize=(uint) ((ulong) (cachesize + min_cache-1) &
+      uint buffer_block;
+      cachesize=(uint) ((ulong) (cachesize + min_cache-1) &
 			(ulong) ~(min_cache-1));
-      if (type == SEQ_READ_APPEND)
-	buffer_block *= 2;
       if (cachesize < min_cache)
 	cachesize = min_cache;
+      buffer_block = cachesize;
+      if (type == SEQ_READ_APPEND)
+	buffer_block *= 2;
       if ((info->buffer=
 	   (byte*) my_malloc(buffer_block,
 			     MYF((cache_myflags & ~ MY_WME) |
 				 (cachesize == min_cache ? MY_WME : 0)))) != 0)
       {
+	info->write_buffer=info->buffer;
 	if (type == SEQ_READ_APPEND)
-	  info->append_buffer = info->buffer + cachesize;
+	  info->write_buffer = info->buffer + cachesize;
 	info->alloced_buffer=1;
 	break;					/* Enough memory found */
       }
@@ -157,45 +177,30 @@ int init_io_cache(IO_CACHE *info, File file, uint cachesize,
       cachesize= (uint) ((long) cachesize*3/4); /* Try with less memory */
     }
   }
-  else
-    info->buffer=0;
-  
+
   DBUG_PRINT("info",("init_io_cache: cachesize = %u",cachesize));
-  info->pos_in_file= seek_offset;
   info->read_length=info->buffer_length=cachesize;
-  info->seek_not_done= test(file >= 0 && type != READ_FIFO &&
-			    type != READ_NET);
   info->myflags=cache_myflags & ~(MY_NABP | MY_FNABP);
-  info->rc_request_pos=info->rc_pos= info->write_pos = info->buffer;
-  info->write_pos = info->write_end = 0;
+  info->request_pos= info->read_pos= info->write_pos = info->buffer;
   if (type == SEQ_READ_APPEND)
   {
-    info->append_read_pos = info->write_pos = info->append_buffer;
-    info->write_end = info->append_end =
-      info->append_buffer + info->buffer_length;
-#ifdef THREAD    
+    info->append_read_pos = info->write_pos = info->write_buffer;
+    info->write_end = info->write_buffer + info->buffer_length;
+#ifdef THREAD
     pthread_mutex_init(&info->append_buffer_lock,MY_MUTEX_INIT_FAST);
-#endif    
+#endif
   }
 
-  if (type == READ_CACHE || type == SEQ_READ_APPEND ||
-      type == READ_NET || type == READ_FIFO)
-  {
-    info->rc_end=info->buffer;			/* Nothing in cache */
-  }
-  else /* type == WRITE_CACHE */
-  {
+  if (type == WRITE_CACHE)
     info->write_end=
       info->buffer+info->buffer_length- (seek_offset & (IO_SIZE-1));
-    info->write_pos = info->buffer;
-  }
-  /* end_of_file may be changed by user later */
-  info->end_of_file= ((type == READ_NET || type == READ_FIFO ) ? 0
-		      : ~(my_off_t) 0);
-  info->type=type;
+  else
+    info->read_end=info->buffer;		/* Nothing in cache */
+
+  /* End_of_file may be changed by user later */
+  info->end_of_file= end_of_file;
   info->error=0;
-  init_read_function(info,type);
-  init_write_function(info,type);
+  init_functions(info,type);
 #ifdef HAVE_AIOWAIT
   if (use_async_io && ! my_disable_async_io)
   {
@@ -236,8 +241,13 @@ static void my_aiowait(my_aio_result *result)
 }
 #endif
 
-	/* Use this to reset cache to start or other type */
-	/* Some simple optimizing is done when reinit in current buffer */
+
+/*
+  Use this to reset cache to re-start reading or to change the type
+  between READ_CACHE <-> WRITE_CACHE
+  If we are doing a reinit of a cache where we have the start of the file
+  in the cache, we are reusing this memory without flushing it to disk.
+*/
 
 my_bool reinit_io_cache(IO_CACHE *info, enum cache_type type,
 			my_off_t seek_offset,
@@ -245,33 +255,37 @@ my_bool reinit_io_cache(IO_CACHE *info, enum cache_type type,
 			pbool clear_cache)
 {
   DBUG_ENTER("reinit_io_cache");
+  DBUG_PRINT("enter",("type: %d  seek_offset: %lu  clear_cache: %d",
+		      type, (ulong) seek_offset, (int) clear_cache));
 
-  info->seek_not_done= test(info->file >= 0);	/* Seek not done */
+  /* One can't do reinit with the following types */
+  DBUG_ASSERT(type != READ_NET && info->type != READ_NET &&
+	      type != WRITE_NET && info->type != WRITE_NET &&
+	      type != SEQ_READ_APPEND && info->type != SEQ_READ_APPEND);
 
   /* If the whole file is in memory, avoid flushing to disk */
   if (! clear_cache &&
       seek_offset >= info->pos_in_file &&
-      seek_offset <= info->pos_in_file +
-      (uint) (info->rc_end - info->rc_request_pos))
-  {						/* use current buffer */
+      seek_offset <= my_b_tell(info))
+  {
+    /* Reuse current buffer without flushing it to disk */
+    byte *pos;
     if (info->type == WRITE_CACHE && type == READ_CACHE)
     {
-      info->rc_end=info->write_pos;
+      info->read_end=info->write_pos;
       info->end_of_file=my_b_tell(info);
     }
     else if (type == WRITE_CACHE)
     {
       if (info->type == READ_CACHE)
-      {
-	info->write_end=info->buffer+info->buffer_length;
-	info->write_pos=info->rc_pos;
-      }
+	info->write_end=info->write_buffer+info->buffer_length;
       info->end_of_file = ~(my_off_t) 0;
     }
+    pos=info->request_pos+(seek_offset-info->pos_in_file);
     if (type == WRITE_CACHE)
-      info->write_pos=info->rc_request_pos+(seek_offset-info->pos_in_file);
-    else  
-      info->rc_pos=info->rc_request_pos+(seek_offset-info->pos_in_file);
+      info->write_pos=pos;
+    else
+      info->read_pos= pos;
 #ifdef HAVE_AIOWAIT
     my_aiowait(&info->aio_result);		/* Wait for outstanding req */
 #endif
@@ -284,50 +298,35 @@ my_bool reinit_io_cache(IO_CACHE *info, enum cache_type type,
     */
     if (info->type == WRITE_CACHE && type == READ_CACHE)
       info->end_of_file=my_b_tell(info);
-    /* No need to flush cache if we want to reuse it */
-    if ((type != WRITE_CACHE || !clear_cache) && flush_io_cache(info))
+    /* flush cache if we want to reuse it */
+    if (!clear_cache && flush_io_cache(info))
       DBUG_RETURN(1);
-    if (info->pos_in_file != seek_offset)
-    {
-      info->pos_in_file=seek_offset;
-      info->seek_not_done=1;
-    }
-    info->rc_request_pos=info->rc_pos=info->buffer;
-    if (type == READ_CACHE || type == READ_NET || type == READ_FIFO)
+    info->pos_in_file=seek_offset;
+    /* Better to do always do a seek */
+    info->seek_not_done=1;
+    info->request_pos=info->read_pos=info->write_pos=info->buffer;
+    if (type == READ_CACHE)
     {
-      info->rc_end=info->buffer;		/* Nothing in cache */
+      info->read_end=info->buffer;		/* Nothing in cache */
     }
     else
     {
-      info->rc_end=info->buffer+info->buffer_length-
-	(seek_offset & (IO_SIZE-1));
-      info->end_of_file= ((type == READ_NET || type == READ_FIFO) ? 0 :
-			  ~(my_off_t) 0);
+      info->write_end=(info->buffer + info->buffer_length -
+		       (seek_offset & (IO_SIZE-1)));
+      info->end_of_file= ~(my_off_t) 0;
     }
   }
-  if (info->type == SEQ_READ_APPEND)
-  {
-    info->append_read_pos = info->write_pos = info->append_buffer;
-  }
-  if (!info->write_pos)
-    info->write_pos = info->buffer;
-  if (!info->write_end)
-    info->write_end = info->buffer+info->buffer_length-
-      (seek_offset & (IO_SIZE-1));
   info->type=type;
   info->error=0;
-  init_read_function(info,type);
-  init_write_function(info,type);
+  init_functions(info,type);
+
 #ifdef HAVE_AIOWAIT
-  if (type != READ_NET)
+  if (use_async_io && ! my_disable_async_io &&
+      ((ulong) info->buffer_length <
+       (ulong) (info->end_of_file - seek_offset)))
   {
-    if (use_async_io && ! my_disable_async_io &&
-	((ulong) info->buffer_length <
-	 (ulong) (info->end_of_file - seek_offset)))
-    {
-      info->read_length=info->buffer_length/2;
-      info->read_function=_my_b_async_read;
-    }
+    info->read_length=info->buffer_length/2;
+    info->read_function=_my_b_async_read;
   }
   info->inited=0;
 #endif
@@ -336,28 +335,30 @@ my_bool reinit_io_cache(IO_CACHE *info, enum cache_type type,
 
 
 
-	/*
-	  Read buffered. Returns 1 if can't read requested characters
-	  This function is only called from the my_b_read() macro
-	  when there isn't enough characters in the buffer to
-	  satisfy the request.
-	  Returns 0 we succeeded in reading all data
-	*/
+/*
+  Read buffered. Returns 1 if can't read requested characters
+  This function is only called from the my_b_read() macro
+  when there isn't enough characters in the buffer to
+  satisfy the request.
+  Returns 0 we succeeded in reading all data
+*/
 
 int _my_b_read(register IO_CACHE *info, byte *Buffer, uint Count)
 {
   uint length,diff_length,left_length;
   my_off_t max_length, pos_in_file;
-  
-  if ((left_length=(uint) (info->rc_end-info->rc_pos)))
+  DBUG_ENTER("_my_b_read");
+
+  if ((left_length=(uint) (info->read_end-info->read_pos)))
   {
-    dbug_assert(Count >= left_length);	/* User is not using my_b_read() */
-    memcpy(Buffer,info->rc_pos, (size_t) (left_length));
+    DBUG_ASSERT(Count >= left_length);	/* User is not using my_b_read() */
+    memcpy(Buffer,info->read_pos, (size_t) (left_length));
     Buffer+=left_length;
     Count-=left_length;
   }
+
   /* pos_in_file always point on where info->buffer was read */
-  pos_in_file=info->pos_in_file+(uint) (info->rc_end - info->buffer);
+  pos_in_file=info->pos_in_file+(uint) (info->read_end - info->buffer);
   if (info->seek_not_done)
   {					/* File touched, do seek */
     VOID(my_seek(info->file,pos_in_file,MY_SEEK_SET,MYF(0)));
@@ -370,7 +371,7 @@ int _my_b_read(register IO_CACHE *info, byte *Buffer, uint Count)
     if (info->end_of_file == pos_in_file)
     {					/* End of file */
       info->error=(int) left_length;
-      return 1;
+      DBUG_RETURN(1);
     }
     length=(Count & (uint) ~(IO_SIZE-1))-diff_length;
     if ((read_length=my_read(info->file,Buffer,(uint) length,info->myflags))
@@ -378,7 +379,7 @@ int _my_b_read(register IO_CACHE *info, byte *Buffer, uint Count)
     {
       info->error= read_length == (uint) -1 ? -1 :
 	(int) (read_length+left_length);
-      return 1;
+      DBUG_RETURN(1);
     }
     Count-=length;
     Buffer+=length;
@@ -386,16 +387,17 @@ int _my_b_read(register IO_CACHE *info, byte *Buffer, uint Count)
     left_length+=length;
     diff_length=0;
   }
+
   max_length=info->read_length-diff_length;
   if (info->type != READ_FIFO &&
-      (info->end_of_file - pos_in_file) < max_length)
+      max_length > (info->end_of_file - pos_in_file))
     max_length = info->end_of_file - pos_in_file;
   if (!max_length)
   {
     if (Count)
     {
       info->error= left_length;		/* We only got this many char */
-      return 1;
+      DBUG_RETURN(1);
     }
     length=0;				/* Didn't read any chars */
   }
@@ -406,20 +408,22 @@ int _my_b_read(register IO_CACHE *info, byte *Buffer, uint Count)
     if (length != (uint) -1)
       memcpy(Buffer,info->buffer,(size_t) length);
     info->error= length == (uint) -1 ? -1 : (int) (length+left_length);
-    return 1;
+    info->read_pos=info->read_end=info->buffer;
+    DBUG_RETURN(1);
   }
-  info->rc_pos=info->buffer+Count;
-  info->rc_end=info->buffer+length;
+  info->read_pos=info->buffer+Count;
+  info->read_end=info->buffer+length;
   info->pos_in_file=pos_in_file;
   memcpy(Buffer,info->buffer,(size_t) Count);
-  return 0;
+  DBUG_RETURN(0);
 }
 
-/* Do sequential read from the SEQ_READ_APPEND cache
-   we do this in three stages:
-    - first read from info->buffer
-    - then if there are still data to read, try the file descriptor
-    - afterwards, if there are still data to read, try append buffer
+/*
+  Do sequential read from the SEQ_READ_APPEND cache
+  we do this in three stages:
+   - first read from info->buffer
+   - then if there are still data to read, try the file descriptor
+   - afterwards, if there are still data to read, try append buffer
 */
 
 int _my_b_seq_read(register IO_CACHE *info, byte *Buffer, uint Count)
@@ -427,97 +431,127 @@ int _my_b_seq_read(register IO_CACHE *info, byte *Buffer, uint Count)
   uint length,diff_length,left_length,save_count;
   my_off_t max_length, pos_in_file;
   save_count=Count;
+
   /* first, read the regular buffer */
-  if ((left_length=(uint) (info->rc_end-info->rc_pos)))
+  if ((left_length=(uint) (info->read_end-info->read_pos)))
   {
-    dbug_assert(Count >= left_length);	/* User is not using my_b_read() */
-    memcpy(Buffer,info->rc_pos, (size_t) (left_length));
+    DBUG_ASSERT(Count > left_length);	/* User is not using my_b_read() */
+    memcpy(Buffer,info->read_pos, (size_t) (left_length));
     Buffer+=left_length;
     Count-=left_length;
   }
+  lock_append_buffer(info);
+
   /* pos_in_file always point on where info->buffer was read */
-  if ((pos_in_file=info->pos_in_file+(uint) (info->rc_end - info->buffer)) >=
+  if ((pos_in_file=info->pos_in_file+(uint) (info->read_end - info->buffer)) >=
       info->end_of_file)
-  {
-    info->pos_in_file=pos_in_file;
     goto read_append_buffer;
+
+  if (info->seek_not_done)
+  {					/* File touched, do seek */
+    VOID(my_seek(info->file,pos_in_file,MY_SEEK_SET,MYF(0)));
+    info->seek_not_done=0;
   }
-  /* no need to seek since the read is guaranteed to be sequential */
   diff_length=(uint) (pos_in_file & (IO_SIZE-1));
-  
+
   /* now the second stage begins - read from file descriptor */
   if (Count >= (uint) (IO_SIZE+(IO_SIZE-diff_length)))
   {					/* Fill first intern buffer */
     uint read_length;
-    if (info->end_of_file == pos_in_file)
-    {					/* End of file */
-      goto read_append_buffer;
-    }
+
     length=(Count & (uint) ~(IO_SIZE-1))-diff_length;
-    if ((read_length=my_read(info->file,Buffer,(uint) length,info->myflags))
-	!= (uint) length)
+    if ((read_length=my_read(info->file,Buffer,(uint) length,info->myflags)) ==
+	(uint)-1)
     {
-      if (read_length != (uint)-1)
-      {
-	Count -= read_length;
-	Buffer += read_length;
-      }
+      info->error= -1;
+      unlock_append_buffer(info);
+      return 1;
+    }
+    Count-=read_length;
+    Buffer+=read_length;
+    pos_in_file+=read_length;
+
+    if (read_length != (uint) length)
+    {
+      /*
+	We only got part of data;  Read the rest of the data from the
+	write buffer
+      */
       goto read_append_buffer;
     }
-    Count-=length;
-    Buffer+=length;
-    pos_in_file+=length;
     left_length+=length;
     diff_length=0;
   }
+
   max_length=info->read_length-diff_length;
-  if ((info->end_of_file - pos_in_file) < max_length)
+  if (max_length > (info->end_of_file - pos_in_file))
     max_length = info->end_of_file - pos_in_file;
   if (!max_length)
   {
     if (Count)
-    {
       goto read_append_buffer;
-    }
-    length=0;				/* Didn't read any chars */
+    length=0;				/* Didn't read any more chars */
   }
-  else if ((length=my_read(info->file,info->buffer,(uint) max_length,
-			   info->myflags)) < Count ||
-	   length == (uint) -1)
+  else
   {
-    if (length != (uint) -1)
+    length=my_read(info->file,info->buffer,(uint) max_length,
+		   info->myflags);
+    if (length == (uint) -1)
+    {
+      info->error= -1;
+      unlock_append_buffer(info);
+      return 1;
+    }
+    if (length < Count)
     {
       memcpy(Buffer,info->buffer,(size_t) length);
       Count -= length;
       Buffer += length;
+      goto read_append_buffer;
     }
-    goto read_append_buffer;
   }
-  info->rc_pos=info->buffer+Count;
-  info->rc_end=info->buffer+length;
+  unlock_append_buffer(info);
+  info->read_pos=info->buffer+Count;
+  info->read_end=info->buffer+length;
   info->pos_in_file=pos_in_file;
   memcpy(Buffer,info->buffer,(size_t) Count);
   return 0;
+
 read_append_buffer:
-  lock_append_buffer(info);
-  if (!Count) return 0;
+
+  /*
+     Read data from the current write buffer.
+     Count should never be == 0 here (The code will work even if count is 0)
+  */
+
   {
-    uint copy_len = (uint)(info->append_read_pos -
-			   info->write_pos);
-    dbug_assert(info->append_read_pos <= info->write_pos);
-    if (copy_len > Count)
-      copy_len = Count;
-    memcpy(Buffer, info->append_read_pos,
-	 copy_len);
+    /* First copy the data to Count */
+    uint len_in_buff = (uint) (info->write_pos - info->append_read_pos);
+    uint copy_len;
+
+    DBUG_ASSERT(info->append_read_pos <= info->write_pos);
+    DBUG_ASSERT(pos_in_file == info->end_of_file);
+
+    copy_len=min(Count, len_in_buff);
+    memcpy(Buffer, info->append_read_pos, copy_len);
     info->append_read_pos += copy_len;
     Count -= copy_len;
     if (Count)
-      info->error = save_count - Count; 
+      info->error = save_count - Count;
+
+    /* Fill read buffer with data from write buffer */
+    memcpy(info->buffer, info->append_read_pos,
+	   (size_t) (len_in_buff - copy_len));
+    info->read_pos= info->buffer;
+    info->read_end= info->buffer+(len_in_buff - copy_len);
+    info->append_read_pos=info->write_pos;
+    info->pos_in_file+=len_in_buff;
   }
   unlock_append_buffer(info);
   return Count ? 1 : 0;
 }
 
+
 #ifdef HAVE_AIOWAIT
 
 int _my_b_async_read(register IO_CACHE *info, byte *Buffer, uint Count)
@@ -527,8 +561,8 @@ int _my_b_async_read(register IO_CACHE *info, byte *Buffer, uint Count)
   my_off_t next_pos_in_file;
   byte *read_buffer;
 
-  memcpy(Buffer,info->rc_pos,
-	 (size_t) (left_length=(uint) (info->rc_end-info->rc_pos)));
+  memcpy(Buffer,info->read_pos,
+	 (size_t) (left_length=(uint) (info->read_end-info->read_pos)));
   Buffer+=left_length;
   org_Count=Count;
   Count-=left_length;
@@ -555,13 +589,13 @@ int _my_b_async_read(register IO_CACHE *info, byte *Buffer, uint Count)
 		    (int) (read_length+left_length));
       return(1);
     }
-    info->pos_in_file+=(uint) (info->rc_end - info->rc_request_pos);
+    info->pos_in_file+=(uint) (info->read_end - info->request_pos);
 
-    if (info->rc_request_pos != info->buffer)
-      info->rc_request_pos=info->buffer;
+    if (info->request_pos != info->buffer)
+      info->request_pos=info->buffer;
     else
-      info->rc_request_pos=info->buffer+info->read_length;
-    info->rc_pos=info->rc_request_pos;
+      info->request_pos=info->buffer+info->read_length;
+    info->read_pos=info->request_pos;
     next_pos_in_file=info->aio_read_pos+read_length;
 
 	/* Check if pos_in_file is changed
@@ -578,8 +612,8 @@ int _my_b_async_read(register IO_CACHE *info, byte *Buffer, uint Count)
       {
 	my_off_t offset= (info->pos_in_file - info->aio_read_pos);
 	info->pos_in_file=info->aio_read_pos; /* Whe are here */
-	info->rc_pos=info->rc_request_pos+offset;
-	read_length-=offset;			/* Bytes left from rc_pos */
+	info->read_pos=info->request_pos+offset;
+	read_length-=offset;			/* Bytes left from read_pos */
       }
     }
 #ifndef DBUG_OFF
@@ -591,16 +625,16 @@ int _my_b_async_read(register IO_CACHE *info, byte *Buffer, uint Count)
 #endif
 	/* Copy found bytes to buffer */
     length=min(Count,read_length);
-    memcpy(Buffer,info->rc_pos,(size_t) length);
+    memcpy(Buffer,info->read_pos,(size_t) length);
     Buffer+=length;
     Count-=length;
     left_length+=length;
-    info->rc_end=info->rc_pos+read_length;
-    info->rc_pos+=length;
+    info->read_end=info->rc_pos+read_length;
+    info->read_pos+=length;
   }
   else
     next_pos_in_file=(info->pos_in_file+ (uint)
-		      (info->rc_end - info->rc_request_pos));
+		      (info->read_end - info->request_pos));
 
 	/* If reading large blocks, or first read or read with skipp */
   if (Count)
@@ -614,13 +648,13 @@ int _my_b_async_read(register IO_CACHE *info, byte *Buffer, uint Count)
     read_length=IO_SIZE*2- (uint) (next_pos_in_file & (IO_SIZE-1));
     if (Count < read_length)
     {					/* Small block, read to cache */
-      if ((read_length=my_read(info->file,info->rc_request_pos,
+      if ((read_length=my_read(info->file,info->request_pos,
 			       read_length, info->myflags)) == (uint) -1)
 	return info->error= -1;
       use_length=min(Count,read_length);
-      memcpy(Buffer,info->rc_request_pos,(size_t) use_length);
-      info->rc_pos=info->rc_request_pos+Count;
-      info->rc_end=info->rc_request_pos+read_length;
+      memcpy(Buffer,info->request_pos,(size_t) use_length);
+      info->read_pos=info->request_pos+Count;
+      info->read_end=info->request_pos+read_length;
       info->pos_in_file=next_pos_in_file;	/* Start of block in cache */
       next_pos_in_file+=read_length;
 
@@ -641,7 +675,7 @@ int _my_b_async_read(register IO_CACHE *info, byte *Buffer, uint Count)
 	info->error= read_length == (uint)  -1 ? -1 : read_length+left_length;
 	return 1;
       }
-      info->rc_pos=info->rc_end=info->rc_request_pos;
+      info->read_pos=info->read_end=info->request_pos;
       info->pos_in_file=(next_pos_in_file+=Count);
     }
   }
@@ -652,7 +686,7 @@ int _my_b_async_read(register IO_CACHE *info, byte *Buffer, uint Count)
 
   if (max_length > (my_off_t) info->read_length - diff_length)
     max_length= (my_off_t) info->read_length - diff_length;
-  if (info->rc_request_pos != info->buffer)
+  if (info->request_pos != info->buffer)
     read_buffer=info->buffer;
   else
     read_buffer=info->buffer+info->read_length;
@@ -669,13 +703,13 @@ int _my_b_async_read(register IO_CACHE *info, byte *Buffer, uint Count)
       my_errno=errno;
       DBUG_PRINT("error",("got error: %d, aio_result: %d from aioread, async skipped",
 			  errno, info->aio_result.result.aio_errno));
-      if (info->rc_request_pos != info->buffer)
+      if (info->request_pos != info->buffer)
       {
-	bmove(info->buffer,info->rc_request_pos,
-	      (uint) (info->rc_end - info->rc_pos));
-	info->rc_request_pos=info->buffer;
-	info->rc_pos-=info->read_length;
-	info->rc_end-=info->read_length;
+	bmove(info->buffer,info->request_pos,
+	      (uint) (info->read_end - info->read_pos));
+	info->request_pos=info->buffer;
+	info->read_pos-=info->read_length;
+	info->read_end-=info->read_length;
       }
       info->read_length=info->buffer_length;	/* Use hole buffer */
       info->read_function=_my_b_read;		/* Use normal IO_READ next */
@@ -709,16 +743,17 @@ int _my_b_write(register IO_CACHE *info, const byte *Buffer, uint Count)
 {
   uint rest_length,length;
 
+  if (info->pos_in_file+info->buffer_length > info->end_of_file)
+  {
+    my_errno=errno=EFBIG;
+    return info->error = -1;
+  }
+
   rest_length=(uint) (info->write_end - info->write_pos);
   memcpy(info->write_pos,Buffer,(size_t) rest_length);
   Buffer+=rest_length;
   Count-=rest_length;
   info->write_pos+=rest_length;
-  if (info->pos_in_file+info->buffer_length > info->end_of_file)
-  {
-    my_errno=errno=EFBIG;
-    return info->error = -1;
-  }    
   if (flush_io_cache(info))
     return 1;
   if (Count >= IO_SIZE)
@@ -740,12 +775,21 @@ int _my_b_write(register IO_CACHE *info, const byte *Buffer, uint Count)
   return 0;
 }
 
-int _my_b_append(register IO_CACHE *info, const byte *Buffer, uint Count)
+
+/*
+  Append a block to the write buffer.
+  This is done with the buffer locked to ensure that we don't read from
+  the write buffer before we are ready with it.
+*/
+
+int my_b_append(register IO_CACHE *info, const byte *Buffer, uint Count)
 {
   uint rest_length,length;
 
-  rest_length=(uint) (info->append_end -
-		      info->write_pos);
+  lock_append_buffer(info);
+  rest_length=(uint) (info->write_end - info->write_pos);
+  if (Count <= rest_length)
+    goto end;
   memcpy(info->write_pos,Buffer,(size_t) rest_length);
   Buffer+=rest_length;
   Count-=rest_length;
@@ -760,8 +804,11 @@ int _my_b_append(register IO_CACHE *info, const byte *Buffer, uint Count)
     Count-=length;
     Buffer+=length;
   }
+
+end:
   memcpy(info->write_pos,Buffer,(size_t) Count);
   info->write_pos+=Count;
+  unlock_append_buffer(info);
   return 0;
 }
 
@@ -791,10 +838,13 @@ int my_block_write(register IO_CACHE *info, const byte *Buffer, uint Count,
     Buffer+=length;
     pos+=  length;
     Count-= length;
+#ifndef HAVE_PREAD
+    info->seek_not_done=1;
+#endif
   }
 
   /* Check if we want to write inside the used part of the buffer.*/
-  length= (uint) (info->rc_end - info->buffer);
+  length= (uint) (info->write_end - info->buffer);
   if (pos < info->pos_in_file + length)
   {
     uint offset= (uint) (pos - info->pos_in_file);
@@ -816,20 +866,16 @@ int my_block_write(register IO_CACHE *info, const byte *Buffer, uint Count,
   return error;
 }
 
-/* avoid warning about empty if body */
-#ifdef THREAD
-#define IF_APPEND_CACHE if (append_cache)
-#else
-#define IF_APPEND_CACHE
-#endif
 
 	/* Flush write cache */
 
 int flush_io_cache(IO_CACHE *info)
 {
   uint length;
-  int append_cache;
+  my_bool append_cache;
+  my_off_t pos_in_file;
   DBUG_ENTER("flush_io_cache");
+
   append_cache = (info->type == SEQ_READ_APPEND);
   if (info->type == WRITE_CACHE || append_cache)
   {
@@ -838,44 +884,45 @@ int flush_io_cache(IO_CACHE *info)
       if (real_open_cached_file(info))
 	DBUG_RETURN((info->error= -1));
     }
-    IF_APPEND_CACHE
-      lock_append_buffer(info);
-    if (info->write_pos != info->buffer)
+    if ((length=(uint) (info->write_pos - info->write_buffer)))
     {
-      length=(uint) (info->write_pos - info->buffer);
+      pos_in_file=info->pos_in_file;
+      if (append_cache)
+      {
+	pos_in_file=info->end_of_file;
+	info->seek_not_done=1;
+      }
       if (info->seek_not_done)
       {					/* File touched, do seek */
-	if (my_seek(info->file,info->pos_in_file,MY_SEEK_SET,MYF(0)) ==
+	if (my_seek(info->file,pos_in_file,MY_SEEK_SET,MYF(0)) ==
 	    MY_FILEPOS_ERROR)
 	{
-	  IF_APPEND_CACHE
-	    unlock_append_buffer(info);
 	  DBUG_RETURN((info->error= -1));
 	}
-	info->seek_not_done=0;
-      }
-      info->write_pos=info->buffer;
-      info->pos_in_file+=length;
-      info->write_end=(info->buffer+info->buffer_length-
-		    (info->pos_in_file & (IO_SIZE-1)));
-      if (append_cache)
-      {
-	info->append_read_pos = info->buffer;
-	info->append_end = info->write_end;
+	if (!append_cache)
+	  info->seek_not_done=0;
       }
-      if (my_write(info->file,info->buffer,length,info->myflags | MY_NABP))
-        info->error= -1;
+      info->write_pos= info->write_buffer;
+      if (!append_cache)
+	info->pos_in_file+=length;
+      info->write_end= (info->write_buffer+info->buffer_length-
+			((pos_in_file+length) & (IO_SIZE-1)));
+
+      /* Set this to be used if we are using SEQ_READ_APPEND */
+      info->append_read_pos = info->write_buffer;
+      if (my_write(info->file,info->write_buffer,length,
+		   info->myflags | MY_NABP))
+	info->error= -1;
       else
 	info->error= 0;
-      IF_APPEND_CACHE
-        unlock_append_buffer(info);
+      set_if_bigger(info->end_of_file,(pos_in_file+length));
       DBUG_RETURN(info->error);
     }
   }
 #ifdef HAVE_AIOWAIT
   else if (info->type != READ_NET)
   {
-    my_aiowait(&info->aio_result);	/* Wait for outstanding req */
+    my_aiowait(&info->aio_result);		/* Wait for outstanding req */
     info->inited=0;
   }
 #endif
@@ -888,7 +935,8 @@ int end_io_cache(IO_CACHE *info)
   int error=0;
   IO_CACHE_CALLBACK pre_close;
   DBUG_ENTER("end_io_cache");
-  if((pre_close=info->pre_close))
+
+  if ((pre_close=info->pre_close))
     (*pre_close)(info);
   if (info->alloced_buffer)
   {
@@ -896,13 +944,28 @@ int end_io_cache(IO_CACHE *info)
     if (info->file != -1)			/* File doesn't exist */
       error=flush_io_cache(info);
     my_free((gptr) info->buffer,MYF(MY_WME));
-    info->buffer=info->rc_pos=(byte*) 0;
-    info->alloced_buffer = 0;
+    info->buffer=info->read_pos=(byte*) 0;
+  }
+  if (info->type == SEQ_READ_APPEND)
+  {
+    /* Destroy allocated mutex */
+    info->type=0;
+#ifdef THREAD
+    pthread_mutex_destroy(&info->append_buffer_lock);
+#endif
   }
   DBUG_RETURN(error);
 } /* end_io_cache */
 
+
+/**********************************************************************
+ Testing of MF_IOCACHE
+**********************************************************************/
+
 #ifdef MAIN
+
+#include <my_dir.h>
+
 void die(const char* fmt, ...)
 {
   va_list va_args;
@@ -916,7 +979,7 @@ void die(const char* fmt, ...)
 int open_file(const char* fname, IO_CACHE* info, int cache_size)
 {
   int fd;
-  if ((fd=my_open(fname,O_CREAT|O_APPEND|O_RDWR,MYF(MY_WME))) < 0)
+  if ((fd=my_open(fname,O_CREAT | O_RDWR,MYF(MY_WME))) < 0)
     die("Could not open %s", fname);
   if (init_io_cache(info, fd, cache_size, SEQ_READ_APPEND, 0,0,MYF(MY_WME)))
     die("failed in init_io_cache()");
@@ -960,8 +1023,8 @@ int main(int argc, char** argv)
     char buf[4];
     int block_size = abs(rand() % max_block);
     int4store(buf, block_size);
-    if (my_b_write(&sra_cache,buf,4) ||
-	my_b_write(&sra_cache, block, block_size))
+    if (my_b_append(&sra_cache,buf,4) ||
+	my_b_append(&sra_cache, block, block_size))
       die("write failed");
     total_bytes += 4+block_size;
   }
@@ -985,6 +1048,3 @@ supposedly written\n");
   return 0;
 }
 #endif
-
-
-