Commit 9a137153 authored Oct 13, 2020 by Ralph Campbell Committed by Linus Torvalds Oct 13, 2020

mm/memcg: fix device private memcg accounting



The code in mc_handle_swap_pte() checks for non_swap_entry() and returns
NULL before checking is_device_private_entry() so device private pages are
never handled.  Fix this by checking for non_swap_entry() after handling
device private swap PTEs.

I assume the memory cgroup accounting would be off somehow when moving
a process to another memory cgroup.  Currently, the device private page
is charged like a normal anonymous page when allocated and is uncharged
when the page is freed so I think that path is OK.

Signed-off-by: Ralph Campbell <rcampbell@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: Jerome Glisse <jglisse@redhat.com>
Cc: Balbir Singh <bsingharora@gmail.com>
Cc: Ira Weiny <ira.weiny@intel.com>
Link: https://lkml.kernel.org/r/20201009215952.2726-1-rcampbell@nvidia.com


xFixes: c733a828 ("mm/memcontrol: support MEMORY_DEVICE_PRIVATE")
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent d1b2cf6c

mm/memcontrol.c

+4 −1

Original line number	Diff line number	Diff line
		@@ -5516,7 +5516,7 @@ static struct page mc_handle_swap_pte(struct vm_area_struct vma,
		struct page *page = NULL;
		swp_entry_t ent = pte_to_swp_entry(ptent);

		if (!(mc.flags & MOVE_ANON) \|\| non_swap_entry(ent))
		if (!(mc.flags & MOVE_ANON))
		return NULL;

		/*
		@@ -5535,6 +5535,9 @@ static struct page mc_handle_swap_pte(struct vm_area_struct vma,
		return page;
		}

		if (non_swap_entry(ent))
		return NULL;

		/*
		* Because lookup_swap_cache() updates some statistics counter,
		* we call find_get_page() with swapper_space directly.

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