Read-ahead code

["Luciano A. Stertz" <luciano@tteng.com.br>]

	I guess I found a bug in the readahead code, kernel 2.6.7.
	In filemap_nopage, if the memory area is not marked as sequential 
(VM_SEQ_READ isn't set) and the page is not in the page cache, the 
following code is executed:

1                ra_pages = max_sane_readahead(file->f_ra.ra_pages);
2                if (ra_pages) {
3                        long start;
4
5                        start = pgoff - ra_pages / 2;
6                        if (pgoff < 0)
7                                pgoff = 0;
8                        do_page_cache_readahead(mapping, file, pgoff, 
ra_pages);
9                }

	Seems that the author wanted to read ra_pages around pgoff. Shouldn't 
it be using 'start' instead of 'pgoff' in lines 6 to 8?!? Start is 
calculated and never used. Instead of reading pages from start to pgoff 
+ ra_pages/2, it's reading ra_pages from pgoff.

	Luciano

-- 
Luciano A. Stertz
luciano@tteng.com.br
T&T Engenheiros Associados Ltda
http://www.tteng.com.br-
Fone/Fax (51) 3224 8425
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