Re: [PATCH] [13/16] HWPOISON: The high level memory error handlerin the VM v3
From: Wu Fengguang
Date: Tue Jun 09 2009 - 08:48:42 EST
On Tue, Jun 09, 2009 at 08:17:22PM +0800, Nick Piggin wrote:
> On Tue, Jun 09, 2009 at 08:15:10PM +0800, Wu Fengguang wrote:
> > On Tue, Jun 09, 2009 at 06:48:25PM +0800, Nick Piggin wrote:
> > > On Tue, Jun 09, 2009 at 02:48:55PM +0800, Wu Fengguang wrote:
> > > > On Mon, Jun 08, 2009 at 10:46:53PM +0800, Nai Xia wrote:
> > > > > I meant PG_writeback stops writers to index---->struct page mapping.
> > > >
> > > > It's protected by the radix tree RCU locks. Period.
> > > >
> > > > If you are referring to the reverse mapping: page->mapping is procted
> > > > by PG_lock. No one should make assumption that it won't change under
> > > > page writeback.
> > >
> > > Well... I think probably PG_writeback should be enough. Phrased another
> > > way: I think it is a very bad idea to truncate PG_writeback pages out of
> > > pagecache. Does anything actually do that?
> > There shall be no one. OK I will follow that convention..
> > But as I stated it is only safe do rely on the fact "no one truncates
> > PG_writeback pages" in end_writeback_io handlers. And I suspect if
> > there does exist such a handler, it could be trivially converted to
> > take the page lock.
> Well, the writeback submitter first sets writeback, then unlocks
> the page. I don't think he wants a truncate coming in at that point.
OK. I think we've mostly agreed on the consequences of PG_writeback vs
truncation. I'll follow the least surprise principle and stop here, hehe.
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/