linux-kernel - [PATCH 3.16.y-ckt 041/142] KVM: async_pf: do not warn on page allocation failures

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Message-Id: <1458643271-4227-42-git-send-email-luis.henriques@canonical.com>
Date:	Tue, 22 Mar 2016 10:39:30 +0000
From:	Luis Henriques <luis.henriques@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	Christian Borntraeger <borntraeger@...ibm.com>,
	Paolo Bonzini <pbonzini@...hat.com>,
	Luis Henriques <luis.henriques@...onical.com>
Subject: [PATCH 3.16.y-ckt 041/142] KVM: async_pf: do not warn on page allocation failures

3.16.7-ckt26 -stable review patch.  If anyone has any objections, please let me know.

---8<------------------------------------------------------------

From: Christian Borntraeger <borntraeger@...ibm.com>

commit d7444794a02ff655eda87e3cc54e86b940e7736f upstream.

In async_pf we try to allocate with NOWAIT to get an element quickly
or fail. This code also handle failures gracefully. Lets silence
potential page allocation failures under load.

qemu-system-s39: page allocation failure: order:0,mode:0x2200000
[...]
Call Trace:
([<00000000001146b8>] show_trace+0xf8/0x148)
[<000000000011476a>] show_stack+0x62/0xe8
[<00000000004a36b8>] dump_stack+0x70/0x98
[<0000000000272c3a>] warn_alloc_failed+0xd2/0x148
[<000000000027709e>] __alloc_pages_nodemask+0x94e/0xb38
[<00000000002cd36a>] new_slab+0x382/0x400
[<00000000002cf7ac>] ___slab_alloc.constprop.30+0x2dc/0x378
[<00000000002d03d0>] kmem_cache_alloc+0x160/0x1d0
[<0000000000133db4>] kvm_setup_async_pf+0x6c/0x198
[<000000000013dee8>] kvm_arch_vcpu_ioctl_run+0xd48/0xd58
[<000000000012fcaa>] kvm_vcpu_ioctl+0x372/0x690
[<00000000002f66f6>] do_vfs_ioctl+0x3be/0x510
[<00000000002f68ec>] SyS_ioctl+0xa4/0xb8
[<0000000000781c5e>] system_call+0xd6/0x264
[<000003ffa24fa06a>] 0x3ffa24fa06a

Signed-off-by: Christian Borntraeger <borntraeger@...ibm.com>
Reviewed-by: Dominik Dingel <dingel@...ux.vnet.ibm.com>
Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
Signed-off-by: Luis Henriques <luis.henriques@...onical.com>
---
 virt/kvm/async_pf.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/virt/kvm/async_pf.c b/virt/kvm/async_pf.c
index d6a3d0993d88..965a818dea75 100644
--- a/virt/kvm/async_pf.c
+++ b/virt/kvm/async_pf.c
@@ -171,7 +171,7 @@ int kvm_setup_async_pf(struct kvm_vcpu *vcpu, gva_t gva, unsigned long hva,
 	 * do alloc nowait since if we are going to sleep anyway we
 	 * may as well sleep faulting in page
 	 */
-	work = kmem_cache_zalloc(async_pf_cache, GFP_NOWAIT);
+	work = kmem_cache_zalloc(async_pf_cache, GFP_NOWAIT | __GFP_NOWARN);
 	if (!work)
 		return 0;