Messages in this thread | | | Date | Tue, 2 Jun 2009 15:25:38 +0200 | From | Andi Kleen <> | Subject | Re: [PATCH] [13/16] HWPOISON: The high level memory error handler in the VM v3 |
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On Tue, Jun 02, 2009 at 02:57:13PM +0200, Nick Piggin wrote: > > > not a big deal and just avoids duplicating code. I attached an > > > (untested) patch. > > > > Thanks. But the function in the patch is not doing the same what > > the me_pagecache_clean/dirty are doing. For once there is no error > > checking, as in the second try_to_release_page() > > > > Then it doesn't do all the IO error and missing mapping handling. > > Obviously I don't mean just use that single call for the entire > handler. You can set the EIO bit or whatever you like. The > "error handling" you have there also seems strange. You could > retain it, but the page is assured to be removed from pagecache.
The reason this code double checks is that someone could have a reference (remember we can come in any time) we cannot kill immediately.
> > The page_mapped() check is useless because the pages are not > > mapped here etc. > > That's OK, it is a core part of the protocol to prevent > truncated pages from being mapped, so I like it to be in > that function. > > (you are also doing extraneous page_mapped tests in your handler, > so surely your concern isn't from the perspective of this > error handler code)
We do page_mapping() checks, not page_mapped checks.
I know details, but ...
> > > > We could probably call truncate_complete_page(), but then > > we would also need to duplicate most of the checking outside > > the function anyways and there wouldn't be any possibility > > to share the clean/dirty variants. If you insist I can > > do it, but I think it would be significantly worse code > > than before and I'm reluctant to do that. > > I can write you the patch for that too if you like.
Ok I will write it, but I will add a comment saying that Nick forced me to make the code worse @)
It'll be fairly redundant at least.
> > > if you already have other large ones. > > > > That's unclear too. > > You can't do much about most kernel pages, and dirty metadata pages > are both going to cause big problems. User pagetable pages. Lots of > stuff.
User page tables was on the todo list, these are actually relatively easy. The biggest issue is to detect them.
Metadata would likely need file system callbacks, which I would like to avoid at this point.
-Andi
-- ak@linux.intel.com -- Speaking for myself only.
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