memcg, thp: do not invoke oom killer on thp charges

A THP memcg charge can trigger the oom killer since 2516035 ("mm,
thp: remove __GFP_NORETRY from khugepaged and madvised allocations").
We have used an explicit __GFP_NORETRY previously which ruled the OOM
killer automagically.

Memcg charge path should be semantically compliant with the allocation
path and that means that if we do not trigger the OOM killer for costly
orders which should do the same in the memcg charge path as well.
Otherwise we are forcing callers to distinguish the two and use
different gfp masks which is both non-intuitive and bug prone.  As soon
as we get a costly high order kmalloc user we even do not have any means
to tell the memcg specific gfp mask to prevent from OOM because the
charging is deep within guts of the slab allocator.

The unexpected memcg OOM on THP has already been fixed upstream by
9d3c335 ("mm, thp: do not cause memcg oom for thp") but this is a
one-off fix rather than a generic solution.  Teach mem_cgroup_oom to
bail out on costly order requests to fix the THP issue as well as any
other costly OOM eligible allocations to be added in future.

Also revert 9d3c335 because special gfp for THP is no longer
needed.

Link: http://lkml.kernel.org/r/[email protected]
Fixes: 2516035 ("mm, thp: remove __GFP_NORETRY from khugepaged and madvised allocations")
Signed-off-by: Michal Hocko <[email protected]>
Acked-by: Johannes Weiner <[email protected]>
Cc: "Kirill A. Shutemov" <[email protected]>
Cc: Vlastimil Babka <[email protected]>
Cc: David Rientjes <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

mm/huge_memory.c

@@ -555,8 +555,7 @@ static int __do_huge_pmd_anonymous_page(struct vm_fault *vmf, struct page *page,
 
 	VM_BUG_ON_PAGE(!PageCompound(page), page);
 
-	if (mem_cgroup_try_charge(page, vma->vm_mm, gfp | __GFP_NORETRY, &memcg,
-				  true)) {
+	if (mem_cgroup_try_charge(page, vma->vm_mm, gfp, &memcg, true)) {
 		put_page(page);
 		count_vm_event(THP_FAULT_FALLBACK);
 		return VM_FAULT_FALLBACK;
@@ -1317,7 +1316,7 @@ int do_huge_pmd_wp_page(struct vm_fault *vmf, pmd_t orig_pmd)
 	}
 
 	if (unlikely(mem_cgroup_try_charge(new_page, vma->vm_mm,
-				huge_gfp | __GFP_NORETRY, &memcg, true))) {
+					huge_gfp, &memcg, true))) {
 		put_page(new_page);
 		split_huge_pmd(vma, vmf->pmd, vmf->address);
 		if (page)

mm/khugepaged.c

@@ -965,9 +965,7 @@ static void collapse_huge_page(struct mm_struct *mm,
 		goto out_nolock;
 	}
 
-	/* Do not oom kill for khugepaged charges */
-	if (unlikely(mem_cgroup_try_charge(new_page, mm, gfp | __GFP_NORETRY,
-					   &memcg, true))) {
+	if (unlikely(mem_cgroup_try_charge(new_page, mm, gfp, &memcg, true))) {
 		result = SCAN_CGROUP_CHARGE_FAIL;
 		goto out_nolock;
 	}
@@ -1326,9 +1324,7 @@ static void collapse_shmem(struct mm_struct *mm,
 		goto out;
 	}
 
-	/* Do not oom kill for khugepaged charges */
-	if (unlikely(mem_cgroup_try_charge(new_page, mm, gfp | __GFP_NORETRY,
-					   &memcg, true))) {
+	if (unlikely(mem_cgroup_try_charge(new_page, mm, gfp, &memcg, true))) {
 		result = SCAN_CGROUP_CHARGE_FAIL;
 		goto out;
 	}

mm/memcontrol.c

@@ -1485,7 +1485,7 @@ static void memcg_oom_recover(struct mem_cgroup *memcg)
 
 static void mem_cgroup_oom(struct mem_cgroup *memcg, gfp_t mask, int order)
 {
-	if (!current->memcg_may_oom)
+	if (!current->memcg_may_oom || order > PAGE_ALLOC_COSTLY_ORDER)
 		return;
 	/*
 	 * We are in the middle of the charge context here, so we