[patch v2 2/2] mm, oom: avoid reaping only for mm's with blockable invalidate callbacks

From: David Rientjes <rientjes@google.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: "Michal Hocko" <mhocko@suse.com>,
	"Andrea Arcangeli" <aarcange@redhat.com>,
	"Benjamin Herrenschmidt" <benh@kernel.crashing.org>,
	"Paul Mackerras" <paulus@samba.org>,
	"Oded Gabbay" <oded.gabbay@gmail.com>,
	"Alex Deucher" <alexander.deucher@amd.com>,
	"Christian König" <christian.koenig@amd.com>,
	"David Airlie" <airlied@linux.ie>,
	"Joerg Roedel" <joro@8bytes.org>,
	"Doug Ledford" <dledford@redhat.com>,
	"Jani Nikula" <jani.nikula@linux.intel.com>,
	"Mike Marciniszyn" <mike.marciniszyn@intel.com>,
	"Sean Hefty" <sean.hefty@intel.com>,
	"Dimitri Sivanich" <sivanich@sgi.com>,
	"Boris Ostrovsky" <boris.ostrovsky@oracle.com>,
	"Jérôme Glisse" <jglisse@redhat.com>,
	"Paolo Bonzini" <pbonzini@redhat.com>,
	"Radim Krčmář" <rkrcmar@redhat.com>,
	linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: [patch v2 2/2] mm, oom: avoid reaping only for mm's with blockable invalidate callbacks
Date: Thu, 14 Dec 2017 13:31:00 -0800 (PST)	[thread overview]
Message-ID: <alpine.DEB.2.10.1712141330120.74052@chino.kir.corp.google.com> (raw)
In-Reply-To: <alpine.DEB.2.10.1712141329500.74052@chino.kir.corp.google.com>

This uses the new annotation to determine if an mm has mmu notifiers with
blockable invalidate range callbacks to avoid oom reaping.  Otherwise, the
callbacks are used around unmap_page_range().

Signed-off-by: David Rientjes <rientjes@google.com>
---
 mm/oom_kill.c | 21 +++++++++++----------
 1 file changed, 11 insertions(+), 10 deletions(-)

diff --git a/mm/oom_kill.c b/mm/oom_kill.c
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -514,15 +514,12 @@ static bool __oom_reap_task_mm(struct task_struct *tsk, struct mm_struct *mm)
 	}
 
 	/*
-	 * If the mm has notifiers then we would need to invalidate them around
-	 * unmap_page_range and that is risky because notifiers can sleep and
-	 * what they do is basically undeterministic.  So let's have a short
+	 * If the mm has invalidate_{start,end}() notifiers that could block,
 	 * sleep to give the oom victim some more time.
 	 * TODO: we really want to get rid of this ugly hack and make sure that
-	 * notifiers cannot block for unbounded amount of time and add
-	 * mmu_notifier_invalidate_range_{start,end} around unmap_page_range
+	 * notifiers cannot block for unbounded amount of time
 	 */
-	if (mm_has_notifiers(mm)) {
+	if (mm_has_blockable_invalidate_notifiers(mm)) {
 		up_read(&mm->mmap_sem);
 		schedule_timeout_idle(HZ);
 		goto unlock_oom;
@@ -565,10 +562,14 @@ static bool __oom_reap_task_mm(struct task_struct *tsk, struct mm_struct *mm)
 		 * count elevated without a good reason.
 		 */
 		if (vma_is_anonymous(vma) || !(vma->vm_flags & VM_SHARED)) {
-			tlb_gather_mmu(&tlb, mm, vma->vm_start, vma->vm_end);
-			unmap_page_range(&tlb, vma, vma->vm_start, vma->vm_end,
-					 NULL);
-			tlb_finish_mmu(&tlb, vma->vm_start, vma->vm_end);
+			const unsigned long start = vma->vm_start;
+			const unsigned long end = vma->vm_end;
+
+			tlb_gather_mmu(&tlb, mm, start, end);
+			mmu_notifier_invalidate_range_start(mm, start, end);
+			unmap_page_range(&tlb, vma, start, end, NULL);
+			mmu_notifier_invalidate_range_end(mm, start, end);
+			tlb_finish_mmu(&tlb, start, end);
 		}
 	}
 	pr_info("oom_reaper: reaped process %d (%s), now anon-rss:%lukB, file-rss:%lukB, shmem-rss:%lukB\n",
