On Tue, 6 Feb 2001, Rasmus Andersen wrote:

On Tue, Feb 06, 2001 at 10:51:05AM -0200, Rik van Riel wrote:

quoted

On Tue, 6 Feb 2001, Rasmus Andersen wrote:

[...]

quoted

I guess the writeout_one_page schedules the dirty pages for IO
and puts them on the list of locked pages. The last call then
waits on those same pages until they've been flushed to disk.

Your change would wait on the pages but never submit them for
IO (again, a guess, I haven't looked at the code in too much
detail).

The total function (generic_buffer_fdatasync) (with my patch):

        /* writeout dirty buffers on pages from both clean and dirty lists */
        retval = do_buffer_fdatasync(&inode->i_mapping->dirty_pages, start_idx, 
end_idx, writeout_one_page);
        retval |= do_buffer_fdatasync(&inode->i_mapping->clean_pages, start_idx,
 end_idx, writeout_one_page);
        retval |= do_buffer_fdatasync(&inode->i_mapping->locked_pages, start_idx
, end_idx, writeout_one_page);

        /* now wait for locked buffers on pages from both clean and dirty lists 
*/
        retval |= do_buffer_fdatasync(&inode->i_mapping->dirty_pages, start_idx,
 end_idx, waitfor_one_page);
        retval |= do_buffer_fdatasync(&inode->i_mapping->clean_pages, start_idx,
 end_idx, waitfor_one_page);
        retval |= do_buffer_fdatasync(&inode->i_mapping->locked_pages, start_idx
, end_idx, waitfor_one_page);


So we start the writeout in the three first lines and wait for them in
the last three. Without my patch we write dirty_pages out again in the
second run.

Pages written in the first run will be moved to the locked list. 

No big deal, but its not a critical bug right now.



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