Messages in this thread | | | Date | Wed, 25 Sep 2013 16:31:08 +0800 | Subject | Re: [BUG REPORT] ZSWAP: theoretical race condition issues | From | Bob Liu <> |
| |
On Wed, Sep 25, 2013 at 4:09 PM, Weijie Yang <weijie.yang.kh@gmail.com> wrote: > I think I find a new issue, for integrity of this mail thread, I reply > to this mail. > > It is a concurrence issue either, when duplicate store and reclaim > concurrentlly. > > zswap entry x with offset A is already stored in zswap backend. > Consider the following scenario: > > thread 0: reclaim entry x (get refcount, but not call zswap_get_swap_cache_page) > > thread 1: store new page with the same offset A, alloc a new zswap entry y. > store finished. shrink_page_list() call __remove_mapping(), and now > it is not in swap_cache >
But I don't think swap layer will call zswap with the same offset A.
> thread 0: zswap_get_swap_cache_page called. old page data is added to swap_cache > > Now, swap cache has old data rather than new data for offset A. > error will happen If do_swap_page() get page from swap_cache. >
-- Regards, --Bob
| |