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authorHugh Dickins <hughd@google.com>2022-12-04 17:01:03 -0800
committerAndrew Morton <akpm@linux-foundation.org>2022-12-11 18:12:20 -0800
commitc449deb2b99ff2458214ed4a3526277bc9e40757 (patch)
treeed92c53a9c0438b1810598e7e451b579dfa7e15a /mm/vmscan.c
parent12a5d3955227b0d7e04fb793ccceeb2a1dd275c5 (diff)
downloadlwn-c449deb2b99ff2458214ed4a3526277bc9e40757.tar.gz
lwn-c449deb2b99ff2458214ed4a3526277bc9e40757.zip
mm: memcg: fix swapcached stat accounting
I'd been worried by high "swapcached" counts in memcg OOM reports, thought we had a problem freeing swapcache, but it was just the accounting that was wrong. Two issues: 1. When __remove_mapping() removes swapcache, __delete_from_swap_cache() relies on memcg_data for the right counts to be updated; but that had already been reset by mem_cgroup_swapout(). Swap those calls around - mem_cgroup_swapout() does not require the swapcached flag to be set. 6.1 commit ac35a4902374 ("mm: multi-gen LRU: minimal implementation") already made a similar swap for workingset_eviction(), but not for this. 2. memcg's "swapcached" count was added for memcg v2 stats, but displayed on OOM even for memcg v1: so mem_cgroup_move_account() ought to move it. Link: https://lkml.kernel.org/r/b8b96ee0-1e1e-85f8-df97-c82a11d7cd14@google.com Fixes: b6038942480e ("mm: memcg: add swapcache stat for memcg v2") Signed-off-by: Hugh Dickins <hughd@google.com> Acked-by: Johannes Weiner <hannes@cmpxchg.org> Acked-by: Shakeel Butt <shakeelb@google.com> Cc: Michal Hocko <mhocko@suse.com> Cc: Roman Gushchin <roman.gushchin@linux.dev> Cc: Yu Zhao <yuzhao@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'mm/vmscan.c')
-rw-r--r--mm/vmscan.c3
1 files changed, 1 insertions, 2 deletions
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 2b42ac9ad755..aba991c505f1 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1368,11 +1368,10 @@ static int __remove_mapping(struct address_space *mapping, struct folio *folio,
if (folio_test_swapcache(folio)) {
swp_entry_t swap = folio_swap_entry(folio);
- /* get a shadow entry before mem_cgroup_swapout() clears folio_memcg() */
if (reclaimed && !mapping_exiting(mapping))
shadow = workingset_eviction(folio, target_memcg);
- mem_cgroup_swapout(folio, swap);
__delete_from_swap_cache(folio, swap, shadow);
+ mem_cgroup_swapout(folio, swap);
xa_unlock_irq(&mapping->i_pages);
put_swap_folio(folio, swap);
} else {