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Subject[PATCH] net: use __GFP_NORETRY for high order allocations
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From: Eric Dumazet <edumazet@google.com>

sock_alloc_send_pskb() & sk_page_frag_refill()
have a loop trying high order allocations to prepare
skb with low number of fragments as this increases performance.

Problem is that under memory pressure/fragmentation, this can
trigger OOM while the intent was only to try the high order
allocations, then fallback to order-0 allocations.

We had various reports from unexpected regressions.

According to David, setting __GFP_NORETRY should be fine,
as the asynchronous compaction is still enabled, and this
will prevent OOM from kicking as in :

CFSClientEventm invoked oom-killer: gfp_mask=0x42d0, order=3, oom_adj=0,
oom_score_adj=0, oom_score_badness=2 (enabled),memcg_scoring=disabled
CFSClientEventm

Call Trace:
[<ffffffff8043766c>] dump_header+0xe1/0x23e
[<ffffffff80437a02>] oom_kill_process+0x6a/0x323
[<ffffffff80438443>] out_of_memory+0x4b3/0x50d
[<ffffffff8043a4a6>] __alloc_pages_may_oom+0xa2/0xc7
[<ffffffff80236f42>] __alloc_pages_nodemask+0x1002/0x17f0
[<ffffffff8024bd23>] alloc_pages_current+0x103/0x2b0
[<ffffffff8028567f>] sk_page_frag_refill+0x8f/0x160
[<ffffffff80295fa0>] tcp_sendmsg+0x560/0xee0
[<ffffffff802a5037>] inet_sendmsg+0x67/0x100
[<ffffffff80283c9c>] __sock_sendmsg_nosec+0x6c/0x90
[<ffffffff80283e85>] sock_sendmsg+0xc5/0xf0
[<ffffffff802847b6>] __sys_sendmsg+0x136/0x430
[<ffffffff80284ec8>] sys_sendmsg+0x88/0x110
[<ffffffff80711472>] system_call_fastpath+0x16/0x1b
Out of Memory: Kill process 2856 (bash) score 9999 or sacrifice child

Signed-off-by: Eric Dumazet <edumazet@google.com>
Acked-by: David Rientjes <rientjes@google.com>
---
net/core/sock.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/net/core/sock.c b/net/core/sock.c
index 0c127dcdf6a8..5b6a9431b017 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -1775,7 +1775,9 @@ struct sk_buff *sock_alloc_send_pskb(struct sock *sk, unsigned long header_len,
while (order) {
if (npages >= 1 << order) {
page = alloc_pages(sk->sk_allocation |
- __GFP_COMP | __GFP_NOWARN,
+ __GFP_COMP |
+ __GFP_NOWARN |
+ __GFP_NORETRY,
order);
if (page)
goto fill_page;
@@ -1845,7 +1847,7 @@ bool skb_page_frag_refill(unsigned int sz, struct page_frag *pfrag, gfp_t prio)
gfp_t gfp = prio;

if (order)
- gfp |= __GFP_COMP | __GFP_NOWARN;
+ gfp |= __GFP_COMP | __GFP_NOWARN | __GFP_NORETRY;
pfrag->page = alloc_pages(gfp, order);
if (likely(pfrag->page)) {
pfrag->offset = 0;



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