diff options
| author | Johannes Weiner | 2021-04-29 22:57:04 -0700 |
|---|---|---|
| committer | Linus Torvalds | 2021-04-30 11:20:38 -0700 |
| commit | 9317d0fffeb4c3929069cfc7377cfa2a7cd36d1d (patch) | |
| tree | 8c155926064d116b6949a06b1c0889e55bf8cfb7 /mm | |
| parent | a10e995749a6c65833edd201c55665e5d44d14fc (diff) | |
mm: page_counter: mitigate consequences of a page_counter underflow
When the unsigned page_counter underflows, even just by a few pages, a
cgroup will not be able to run anything afterwards and trigger the OOM
killer in a loop.
Underflows shouldn't happen, but when they do in practice, we may just be
off by a small amount that doesn't interfere with the normal operation -
consequences don't need to be that dire.
Reset the page_counter to 0 upon underflow. We'll issue a warning that
the accounting will be off and then try to keep limping along.
[ We used to do this with the original res_counter, where it was a
more straight-forward correction inside the spinlock section. I
didn't carry it forward into the lockless page counters for
simplicity, but it turns out this is quite useful in practice. ]
Link: https://lkml.kernel.org/r/20210408143155.2679744-1-hannes@cmpxchg.org
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Chris Down <chris@chrisdown.name>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Roman Gushchin <guro@fb.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm')
| -rw-r--r-- | mm/page_counter.c | 8 |
1 files changed, 6 insertions, 2 deletions
diff --git a/mm/page_counter.c b/mm/page_counter.c index c6860f51b6c6..7d83641eb86b 100644 --- a/mm/page_counter.c +++ b/mm/page_counter.c @@ -52,9 +52,13 @@ void page_counter_cancel(struct page_counter *counter, unsigned long nr_pages) long new; new = atomic_long_sub_return(nr_pages, &counter->usage); - propagate_protected_usage(counter, new); /* More uncharges than charges? */ - WARN_ON_ONCE(new < 0); + if (WARN_ONCE(new < 0, "page_counter underflow: %ld nr_pages=%lu\n", + new, nr_pages)) { + new = 0; + atomic_long_set(&counter->usage, new); + } + propagate_protected_usage(counter, new); } /** |