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Date: Thu, 22 Aug 2013 23:21:27 -0400
From: Dave Jones <davej@redhat.com>
To: Hillf Danton <dhillf@gmail.com>
Cc: Linux-MM <linux-mm@kvack.org>, Linux Kernel <linux-kernel@vger.kernel.org>
Subject: Re: unused swap offset / bad page map.
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On Thu, Aug 22, 2013 at 11:21:28AM +0800, Hillf Danton wrote:
 > On Thu, Aug 22, 2013 at 4:49 AM, Dave Jones <davej@redhat.com> wrote:
 > >
 > > didn't hit the bug_on, but got a bunch of
 > >
 > > [  424.077993] swap_free: Unused swap offset entry 000187d5
 > > [  439.377194] swap_free: Unused swap offset entry 000187e7
 > > [  441.998411] swap_free: Unused swap offset entry 000187ee
 > > [  446.956551] swap_free: Unused swap offset entry 0000245f
 > >
 > If page is reused, its swap entry is freed.
 > 
 > reuse_swap_page()
 >   delete_from_swap_cache()
 >     swapcache_free()
 >       count = swap_entry_free(p, entry, SWAP_HAS_CACHE);
 > 
 > If count drops to zero, then swap_free() gives warning.
 > 
 > 
 > --- a/mm/memory.c Wed Aug  7 16:29:34 2013
 > +++ b/mm/memory.c Thu Aug 22 10:44:32 2013
 > @@ -3123,6 +3123,7 @@ static int do_swap_page(struct mm_struct
 >   /* It's better to call commit-charge after rmap is established */
 >   mem_cgroup_commit_charge_swapin(page, ptr);
 > 
 > + if (!exclusive)
 >   swap_free(entry);
 >   if (vm_swap_full() || (vma->vm_flags & VM_LOCKED) || PageMlocked(page))
 >   try_to_free_swap(page);
 > --

I still see the swap_free messages with this applied.

	Dave