[uClinux-dev] I modified "fs/buffer.c", would you give me some suggestions?

[David Agan]

kernel "2.4.24-uc0(nommu)", 
with USB storage disk.
 
I modified the function "create_buffers()", as :

while ((offset -= size) >= 0) {
 // add
 if (async && (nr_unused_buffer_heads<=NR_RESERVED)) {
  /* try get unused header,
   * before we alloc one.
    */
   run_task_queue(&tq_disk);
   free_more_memory();
  }
  // add end
  bh = get_unused_buffer_head(async);
  if (!bh)
   goto no_grow;
  ...
 } 

All I want to do is to reduce the size of the memory that taken by the buffer cache while writing files. Some times, I can't allocate new memory while writing files, I think it's due to "nommu". The memory allocated by buffer cache would be free by the file system it'self,  is it right?
 
After I modified the code, the IO operates more frequently. I test it on ext2 & ext3, everything seems ok, but on fat32, file system would panic with error message "File without EOF";
 
With the same purpose, I tried the patch "O_STREAM", it would be better, but it seems can't prevent the buffer cache from stealing the memory. I also tried "O_DIRECT", and found it's not implemented.
 
 
Any comments or suggestions will be really appreciated!

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