Messages in this thread | | | Date | Tue, 2 Jun 2009 15:24:41 +0200 | From | Nick Piggin <> | 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 03:25:38PM +0200, Andi Kleen wrote: > 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.
Can't kill what? The page is gone from pagecache. It may remain other kernel references, but I don't see why this code will consider this as a failure (and not, for example, a raised error count).
> > > 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 ...
+static int me_pagecache_clean(struct page *p) +{ + if (!isolate_lru_page(p)) + page_cache_release(p); + + if (page_has_private(p)) + do_invalidatepage(p, 0); + if (page_has_private(p) && !try_to_release_page(p, GFP_NOIO)) + Dprintk(KERN_ERR "MCE %#lx: failed to release buffers\n", + page_to_pfn(p)); + + /* + * remove_from_page_cache assumes (mapping && !mapped) + */ + if (page_mapping(p) && !page_mapped(p)) { ^^^^^^^^^^^^^^^
+ remove_from_page_cache(p); + page_cache_release(p); + } + + return RECOVERED;
> > > 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 it's that bad, then I'll be happy to rewrite it for you.
> > > > 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.
So I just don't know why you argue the point that you have lots of large holes left.
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