Messages in this thread | | | Date | Tue, 9 Jun 2009 20:47:55 +0800 | From | Wu Fengguang <> | Subject | Re: [PATCH] [13/16] HWPOISON: The high level memory error handler in the VM v3 |
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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.
Thanks, Fengguang
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