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    Subject[PATCH 3.14 04/92] net: do not deplete pfmemalloc reserve
    Date
    3.14-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Eric Dumazet <edumazet@google.com>

    [ Upstream commit 79930f5892e134c6da1254389577fffb8bd72c66 ]

    build_skb() should look at the page pfmemalloc status.
    If set, this means page allocator allocated this page in the
    expectation it would help to free other pages. Networking
    stack can do that only if skb->pfmemalloc is also set.

    Also, we must refrain using high order pages from the pfmemalloc
    reserve, so __page_frag_refill() must also use __GFP_NOMEMALLOC for
    them. Under memory pressure, using order-0 pages is probably the best
    strategy.

    Signed-off-by: Eric Dumazet <edumazet@google.com>
    Signed-off-by: David S. Miller <davem@davemloft.net>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    net/core/skbuff.c | 9 +++++++--
    1 file changed, 7 insertions(+), 2 deletions(-)

    --- a/net/core/skbuff.c
    +++ b/net/core/skbuff.c
    @@ -309,7 +309,11 @@ struct sk_buff *build_skb(void *data, un

    memset(skb, 0, offsetof(struct sk_buff, tail));
    skb->truesize = SKB_TRUESIZE(size);
    - skb->head_frag = frag_size != 0;
    + if (frag_size) {
    + skb->head_frag = 1;
    + if (virt_to_head_page(data)->pfmemalloc)
    + skb->pfmemalloc = 1;
    + }
    atomic_set(&skb->users, 1);
    skb->head = data;
    skb->data = data;
    @@ -352,7 +356,8 @@ refill:
    gfp_t gfp = gfp_mask;

    if (order)
    - gfp |= __GFP_COMP | __GFP_NOWARN;
    + gfp |= __GFP_COMP | __GFP_NOWARN |
    + __GFP_NOMEMALLOC;
    nc->frag.page = alloc_pages(gfp, order);
    if (likely(nc->frag.page))
    break;



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