mm, memcg: sync allocation and memcg charge gfp flags for THP
memcg currently uses hardcoded GFP_TRANSHUGE gfp flags for all THP charges. THP allocations, however, might be using different flags depending on /sys/kernel/mm/transparent_hugepage/{,khugepaged/}defrag and the current allocation context. The primary difference is that defrag configured to "madvise" value will clear __GFP_WAIT flag from the core gfp mask to make the allocation lighter for all mappings which are not backed by VM_HUGEPAGE vmas. If memcg charge path ignores this fact we will get light allocation but the a potential memcg reclaim would kill the whole point of the configuration. Fix the mismatch by providing the same gfp mask used for the allocation to the charge functions. This is quite easy for all paths except for hugepaged kernel thread with !CONFIG_NUMA which is doing a pre-allocation long before the allocated page is used in collapse_huge_page via khugepaged_alloc_page. To prevent from cluttering the whole code path from khugepaged_do_scan we simply return the current flags as per khugepaged_defrag() value which might have changed since the preallocation. If somebody changed the value of the knob we would charge differently but this shouldn't happen often and it is definitely not critical because it would only lead to a reduced success rate of one-off THP promotion. [akpm@linux-foundation.org: fix weird code layout while we're there] [rientjes@google.com: clean up around alloc_hugepage_gfpmask()] Signed-off-by: NMichal Hocko <mhocko@suse.cz> Acked-by: NVlastimil Babka <vbabka@suse.cz> Cc: Johannes Weiner <hannes@cmpxchg.org> Acked-by: NDavid Rientjes <rientjes@google.com> Signed-off-by: NDavid Rientjes <rientjes@google.com> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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