On Sun, Nov 15, 2020 at 9:16 PM Dongli Zhang <[email protected]> wrote: > > The ethernet driver may allocate skb (and skb->data) via napi_alloc_skb(). > This ends up to page_frag_alloc() to allocate skb->data from > page_frag_cache->va. > > During the memory pressure, page_frag_cache->va may be allocated as > pfmemalloc page. As a result, the skb->pfmemalloc is always true as > skb->data is from page_frag_cache->va. The skb will be dropped if the > sock (receiver) does not have SOCK_MEMALLOC. This is expected behaviour > under memory pressure. ... > References: > https://lore.kernel.org/lkml/[email protected]/ > References: > https://lore.kernel.org/linux-mm/[email protected]/ > Suggested-by: Matthew Wilcox (Oracle) <[email protected]> > Cc: Aruna Ramakrishna <[email protected]> > Cc: Bert Barbe <[email protected]> > Cc: Rama Nichanamatlu <[email protected]> > Cc: Venkat Venkatsubra <[email protected]> > Cc: Manjunath Patil <[email protected]> > Cc: Joe Jin <[email protected]> > Cc: SRINIVAS <[email protected]> > Cc: [email protected] > Fixes: 79930f5892e ("net: do not deplete pfmemalloc reserve") > Signed-off-by: Dongli Zhang <[email protected]> > Acked-by: Vlastimil Babka <[email protected]> > --- > Changed since v1: > - change author from Matthew to Dongli > - Add references to all prior discussions > - Add more details to commit message > Changed since v2: > - add unlikely (suggested by Eric Dumazet) > > mm/page_alloc.c | 5 +++++ > 1 file changed, 5 insertions(+) > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index 23f5066bd4a5..91129ce75ed4 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -5103,6 +5103,11 @@ void *page_frag_alloc(struct page_frag_cache *nc, > if (!page_ref_sub_and_test(page, nc->pagecnt_bias)) > goto refill; > > + if (unlikely(nc->pfmemalloc)) { > + free_the_page(page, compound_order(page)); > + goto refill; > + } > +
Reviewed-by: Eric Dumazet <[email protected]> Thanks !
