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    SubjectRe: [PATCH 1/4] mm/page_alloc: fix non cma alloc context
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    On 7/17/20 9:29 AM, Joonsoo Kim wrote:
    > 2020년 7월 16일 (목) 오후 4:45, Vlastimil Babka <vbabka@suse.cz>님이 작성:
    >>
    >> On 7/16/20 9:27 AM, Joonsoo Kim wrote:
    >> > 2020년 7월 15일 (수) 오후 5:24, Vlastimil Babka <vbabka@suse.cz>님이 작성:
    >> >> > /*
    >> >> > * get_page_from_freelist goes through the zonelist trying to allocate
    >> >> > * a page.
    >> >> > @@ -3706,6 +3714,8 @@ get_page_from_freelist(gfp_t gfp_mask, unsigned int order, int alloc_flags,
    >> >> > struct pglist_data *last_pgdat_dirty_limit = NULL;
    >> >> > bool no_fallback;
    >> >> >
    >> >> > + current_alloc_flags(gfp_mask, &alloc_flags);
    >> >>
    >> >> I don't see why to move the test here? It will still be executed in the
    >> >> fastpath, if that's what you wanted to avoid.
    >> >
    >> > I want to execute it on the fastpath, too. Reason that I moved it here
    >> > is that alloc_flags could be reset on slowpath. See the code where
    >> > __gfp_pfmemalloc_flags() is on. This is the only place that I can apply
    >> > this option to all the allocation paths at once.
    >>
    >> But get_page_from_freelist() might be called multiple times in the slowpath, and
    >> also anyone looking for gfp and alloc flags setup will likely not examine this
    >> function. I don't see a problem in having it in two places that already deal
    >> with alloc_flags setup, as it is now.
    >
    > I agree that anyone looking alloc flags will miss that function easily. Okay.
    > I will place it on its original place, although we now need to add one
    > more place.
    > *Three places* are gfp_to_alloc_flags(), prepare_alloc_pages() and
    > __gfp_pfmemalloc_flags().

    Hm the check below should also work for ALLOC_OOM|ALLOC_NOCMA then.

    /* Avoid allocations with no watermarks from looping endlessly */
    if (tsk_is_oom_victim(current) &&
    (alloc_flags == ALLOC_OOM ||
    (gfp_mask & __GFP_NOMEMALLOC)))
    goto nopage;

    Maybe it's simpler to change get_page_from_freelist() then. But document well.

    > Thanks.
    >

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