Messages in this thread | | | Date | Thu, 28 May 2009 18:33:00 +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 Thu, May 28, 2009 at 06:11:11PM +0800, Andi Kleen wrote: > On Thu, May 28, 2009 at 05:59:34PM +0800, Wu Fengguang wrote: > > Dirty swap cache page is tricky to handle. The page could live both in page > > cache and swap cache(ie. page is freshly swapped in). So it could be referenced > > concurrently by 2 types of PTEs: one normal PTE and another swap PTE. We try to > > handle them consistently by calling try_to_unmap(TTU_IGNORE_HWPOISON) to convert > > the normal PTEs to swap PTEs, and then > > - clear dirty bit to prevent IO > > - remove from LRU > > - but keep in the swap cache, so that when we return to it on > > a later page fault, we know the application is accessing > > corrupted data and shall be killed (we installed simple > > interception code in do_swap_page to catch it). > > That's a good description. I'll add it as a comment to the code.
OK, thanks.
> > > You haven't waited on writeback here AFAIKS, and have you > > > *really* verified it is safe to call delete_from_swap_cache? > > > > Good catch. I'll soon submit patches for handling the under > > read/write IO pages. In this patchset they are simply ignored. > > Yes, we assume the IO device does something sensible with the poisoned > cache lines and aborts. Later we can likely abort IO requests in a early > stage on the Linux, but that's more advanced. > > The question is if we need to wait on writeback for correctness?
Not necessary. Because I'm going to add a me_writeback() handler.
Then the writeback pages simply won't reach here. And it won't magically go into writeback state, since the page has been locked.
Thanks, Fengguang
> We still don't want to crash if we take a page away that is currently > writebacked. > > My original assumption was that taking the page lock would take > care of that. Is that not true? > > -Andi > -- > ak@linux.intel.com -- Speaking for myself only.
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