Messages in this thread | | | Date | Wed, 25 Sep 2013 16:09:04 +0800 | Subject | Re: [BUG REPORT] ZSWAP: theoretical race condition issues | From | Weijie Yang <> |
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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
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.
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