Re: [PATCH linux-2.6.0-test10-mm1] filemap_fdatawait.patch

[Janet Morgan]

Daniel McNeil wrote:

> On Tue, 2003-12-16 at 18:03, Andrew Morton wrote:
>
> > Daniel McNeil <daniel@xxxxxxxx> wrote:
> >
> > > I have found something else that might be causing the problem.
> > > filemap_fdatawait() skips pages that are not marked PG_writeback.
> > > However, when a page is going to be written, PG_dirty is cleared
> > > before PG_writeback is set (while the PG_locked is set).  So it
> > > looks like filemap_fdatawait() can see a page just before it is
> > > going to be written and not wait for it.  Here is a patch that
> > > makes filemap_fdatawait() wait for locked pages as well to make
> > > sure it does not missed any pages.
> > This filemap_fdatawait() behaviour is as-designed.  That function is only
> > responsible for waiting on I/O which was initiated prior to it being
> > invoked.  Because it is designed for fsync(), fdatasync(), O_SYNC, msync(),
> > sync(), etc.
> >
> > Now, it could be that this behaviour is not appropriate for the O_DIRECT
> > sync function - the result of your testing will be interesting.
>
> My tests still failed overnight.  I was thinking that maybe a
> non-blocking do_writepages() was happening at the same time as
> the filemap_fdatawrite()/filemap_fdatawait(), so even though the
> page was dirty before the filemap_fdatawrite(), it was missed.
>
> Daniel
I'm wondering if processing in generic_file_direct_IO() shouldn't look 
more like
sys_fsync()?  When I add to generic_file_direct_IO() a call to 
f_op->fsync() between the calls to filemap_fdatawrite() and 
filemap_fdatawait(), the test Daniel and I have been running no longer 
fails for me.  This change would also seem consistent with 2.4, but I 
could be way off base.

-Janet

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/