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

[Andrew Morton]

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.


-
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/