Re: O_DIRECT foolish question

[Andrew Morton <akpm@digeo.com>]

Bruno Diniz de Paula <diniz@cs.rutgers.edu> wrote:
>
> Thanks, Andrew. So, no chances of getting this working correctly on 2.4
> kernel for now (I mean, reading files with size != n*block_size), and
> I'd better give up on this... Is it the case, or you think there is
> still something to do to get this working on ext2 and 2.4 kernel?
> 

Oh I think we can probably fix this up.  Can you test this diff?


diff -puN fs/buffer.c~o_direct-length-fix fs/buffer.c
--- 24/fs/buffer.c~o_direct-length-fix	2003-02-13 09:23:34.000000000 -0800
+++ 24-akpm/fs/buffer.c	2003-02-13 09:24:39.000000000 -0800
@@ -2107,7 +2107,7 @@ int generic_direct_IO(int rw, struct ino
 	int length;
 
 	length = iobuf->length;
-	nr_blocks = length / blocksize;
+	nr_blocks = (length + blocksize - 1) / blocksize;
 	/* build the blocklist */
 	for (i = 0; i < nr_blocks; i++, blocknr++) {
 		struct buffer_head bh;
@@ -2148,6 +2148,10 @@ int generic_direct_IO(int rw, struct ino
 	retval = brw_kiovec(rw, 1, &iobuf, inode->i_dev, iobuf->blocks, blocksize);
 	/* restore orig length */
 	iobuf->length = length;
+
+	/* Return correct value for reads at eof */
+	if (retval > 0 && retval > length)
+		retval = length;
  out:
 
 	return retval;

_