On Thu, Aug 10, 2017 at 01:56:05PM +0200, Michal Hocko wrote: > On Wed 09-08-17 14:38:25, Johannes Weiner wrote: > > The issue is that writeback doesn't hold a page reference and the page > > might get freed after PG_writeback is cleared (and the mapping is > > unlocked) in test_clear_page_writeback(). The stat functions looking > > up the page's node or zone are safe, as those attributes are static > > across allocation and free cycles. But page->mem_cgroup is not, and it > > will get cleared if we race with truncation or migration. > > Is there anything that prevents us from holding a reference on a page > under writeback? Hm, I'm hesitant to add redundant life-time management to the page there just for memcg, which is not always configured in. Pinning the memcg instead is slightly more complex, but IMO has the complexity in a preferrable place. Would you agree? -- To unsubscribe from this list: send the line "unsubscribe cgroups" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
