Re: [PATCH V2 1/2] mm: avoid marking swap cached page as lazyfree

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



[ups this got stuck in the outgoing queue]

On Tue 26-09-17 15:07:05, Michal Hocko wrote:
> On Fri 22-09-17 11:46:30, Shaohua Li wrote:
> > From: Shaohua Li <shli@xxxxxx>
> > 
> > MADV_FREE clears pte dirty bit and then marks the page lazyfree (clear
> > SwapBacked). There is no lock to prevent the page is added to swap cache
> > between these two steps by page reclaim. If the page is added to swap
> > cache, marking the page lazyfree will confuse page fault if the page is
> > reclaimed and refault.
> 
> Could you be more specific how exactly what kind of the confusion is the
> result? I suspect you are talking about VM_BUG_ON_PAGE in
> __add_to_swap_cache right?

I completely mixed reclaim and the #PF path here

> I am also not sure how that would actually happen to be honest. If we
> raced with the reclaim then the page should have been isolated and so
> PageLRU is no longer true. Or am I missing something?

And here I've completely missed that the swapcache page will go back to
the LRU. Stupid me. Your new changelog [1] explained it all. Thanks and
sorry for these stupid questions.

[1] http://lkml.kernel.org/r/6537ef3814398c0073630b03f176263bc81f0902.1506446061.git.shli@xxxxxx
-- 
Michal Hocko
SUSE Labs

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@xxxxxxxxx.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>



[Index of Archives]     [Linux ARM Kernel]     [Linux ARM]     [Linux Omap]     [Fedora ARM]     [IETF Annouce]     [Bugtraq]     [Linux OMAP]     [Linux MIPS]     [eCos]     [Asterisk Internet PBX]     [Linux API]
  Powered by Linux