Re: writeback fixes for 3.2-rc5

[Wu Fengguang <fengguang.wu@intel.com>]

On Tue, Dec 13, 2011 at 06:57:11PM +0800, Jan Kara wrote:
> On Tue 13-12-11 09:44:56, Wu Fengguang wrote:
> > On Tue, Dec 13, 2011 at 04:46:34AM +0800, Jan Kara wrote:
> > >   Hi Fengguang,
> > > 
> > > On Mon 12-12-11 18:29:48, Wu Fengguang wrote:
> > > > May I ask if you see any problems pushing these patches to Linus?
> > >   Sorry, this somehow escaped my attention. Patches 1, 2, 3, and 5 are
> > > fine. I'm not sure about patch 4 - I'm not against it but e.g. on
> > > single-cpu machine, bdi_stat_error() is 1 so there the patch won't help
> > 
> > As the comment said, actually 1 is enough to let the tasks go through.
> > It may sound terrible to write 1 page at a time, however it's already
> > much better than being blocked there forever. The user experience is
> > totally different according to my tests, because most tasks are not IO
> > intensive at all, they are blocked simply on writing some small file.
> > 
> > > much. Enconding fixed constant like you had in the first version of the
> > > patch doesn't look nice either. But I don't have a better solution...
> > 
> > My typical need on the global exceeded case is "please at least let me
> > ssh in and kill some task or raise the dirty limit to break out of the
> > error condition". IMHO the patch is good enough for that need.
>   Yes, I understand it's better than nothing. That's why I think it's an
> acceptable solution at least for now. I just don't feel completely
> satisfied with it :). So please go ahead and merge the fixes with Linus.

OK, thanks! :)

Fengguang