linux-kernel - Re: unused swap offset / bad page map.

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Date:	Tue, 20 Aug 2013 12:39:05 +0800
From:	Hillf Danton <dhillf@...il.com>
To:	Dave Jones <davej@...hat.com>, Hillf Danton <dhillf@...il.com>,
	Linux-MM <linux-mm@...ck.org>,
	Linux Kernel <linux-kernel@...r.kernel.org>
Subject: Re: unused swap offset / bad page map.

On Tue, Aug 20, 2013 at 7:18 AM, Dave Jones <davej@...hat.com> wrote:
>
> btw, anyone have thoughts on a patch something like below ?

And another(sorry if message is reformatted by the mail agent,
and it took my an hour to get the agent back to the correct format but failed,
and thanks a lot for any howto send plain text message).

Hillf

--- a/mm/memory.c Wed Aug  7 16:29:34 2013
+++ b/mm/memory.c Tue Aug 20 11:13:06 2013
@@ -933,8 +933,10 @@ again:
  if (progress >= 32) {
  progress = 0;
  if (need_resched() ||
-    spin_needbreak(src_ptl) || spin_needbreak(dst_ptl))
+    spin_needbreak(src_ptl) || spin_needbreak(dst_ptl)) {
+     BUG_ON(entry.val);
  break;
+ }
  }
  if (pte_none(*src_pte)) {
  progress++;
--


> It's really annoying to debug stuff like this and have to walk
> over to the machine and reboot it by hand after it wedges during swapoff.
>
>         Dave
>
> diff --git a/mm/swapfile.c b/mm/swapfile.c
> index 6cf2e60..bbb1192 100644
> --- a/mm/swapfile.c
> +++ b/mm/swapfile.c
> @@ -1587,6 +1587,10 @@ SYSCALL_DEFINE1(swapoff, const char __user *, specialfile)
>         if (!capable(CAP_SYS_ADMIN))
>                 return -EPERM;
>
> +       /* If we have hit memory corruption, we could hang during swapoff, so don't even try. */
> +       if (test_taint(TAINT_BAD_PAGE))
> +               return -EINVAL;
> +
>         BUG_ON(!current->mm);
>
>         pathname = getname(specialfile);
--
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