From fcab34b433e2c13e333b2f53c4a8409eadc432c7 Mon Sep 17 00:00:00 2001 From: Alex Williamson Date: Wed, 10 Aug 2022 10:53:59 -0600 Subject: mm: re-allow pinning of zero pfns (again) The below referenced commit makes the same error as 1c563432588d ("mm: fix is_pinnable_page against a cma page"), re-interpreting the logic to exclude pinning of the zero page, which breaks device assignment with vfio. To avoid further subtle mistakes, split the logic into discrete tests. [akpm@linux-foundation.org: simplify comment, per John] Link: https://lkml.kernel.org/r/166015037385.760108.16881097713975517242.stgit@omen Link: https://lore.kernel.org/all/165490039431.944052.12458624139225785964.stgit@omen Fixes: f25cbb7a95a2 ("mm: add zone device coherent type memory support") Signed-off-by: Alex Williamson Suggested-by: Matthew Wilcox Suggested-by: Felix Kuehling Tested-by: Slawomir Laba Reviewed-by: John Hubbard Cc: Alex Sierra Cc: Christoph Hellwig Cc: Alistair Popple Signed-off-by: Andrew Morton --- include/linux/mm.h | 13 ++++++++++--- 1 file changed, 10 insertions(+), 3 deletions(-) (limited to 'include/linux') diff --git a/include/linux/mm.h b/include/linux/mm.h index 982f2607180b..21f8b27bd9fd 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -1544,9 +1544,16 @@ static inline bool is_longterm_pinnable_page(struct page *page) if (mt == MIGRATE_CMA || mt == MIGRATE_ISOLATE) return false; #endif - return !(is_device_coherent_page(page) || - is_zone_movable_page(page) || - is_zero_pfn(page_to_pfn(page))); + /* The zero page may always be pinned */ + if (is_zero_pfn(page_to_pfn(page))) + return true; + + /* Coherent device memory must always allow eviction. */ + if (is_device_coherent_page(page)) + return false; + + /* Otherwise, non-movable zone pages can be pinned. */ + return !is_zone_movable_page(page); } #else static inline bool is_longterm_pinnable_page(struct page *page) -- cgit v1.2.3-59-g8ed1b From dbb16df6443c59e8a1ef21c2272fcf387d600ddf Mon Sep 17 00:00:00 2001 From: Shakeel Butt Date: Wed, 17 Aug 2022 17:21:39 +0000 Subject: Revert "memcg: cleanup racy sum avoidance code" MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit This reverts commit 96e51ccf1af33e82f429a0d6baebba29c6448d0f. Recently we started running the kernel with rstat infrastructure on production traffic and begin to see negative memcg stats values. Particularly the 'sock' stat is the one which we observed having negative value. $ grep "sock " /mnt/memory/job/memory.stat sock 253952 total_sock 18446744073708724224 Re-run after couple of seconds $ grep "sock " /mnt/memory/job/memory.stat sock 253952 total_sock 53248 For now we are only seeing this issue on large machines (256 CPUs) and only with 'sock' stat. I think the networking stack increase the stat on one cpu and decrease it on another cpu much more often. So, this negative sock is due to rstat flusher flushing the stats on the CPU that has seen the decrement of sock but missed the CPU that has increments. A typical race condition. For easy stable backport, revert is the most simple solution. For long term solution, I am thinking of two directions. First is just reduce the race window by optimizing the rstat flusher. Second is if the reader sees a negative stat value, force flush and restart the stat collection. Basically retry but limited. Link: https://lkml.kernel.org/r/20220817172139.3141101-1-shakeelb@google.com Fixes: 96e51ccf1af33e8 ("memcg: cleanup racy sum avoidance code") Signed-off-by: Shakeel Butt Cc: "Michal Koutný" Cc: Johannes Weiner Cc: Michal Hocko Cc: Roman Gushchin Cc: Muchun Song Cc: David Hildenbrand Cc: Yosry Ahmed Cc: Greg Thelen Cc: [5.15] Signed-off-by: Andrew Morton --- include/linux/memcontrol.h | 15 +++++++++++++-- 1 file changed, 13 insertions(+), 2 deletions(-) (limited to 'include/linux') diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h index 4d31ce55b1c0..6257867fbf95 100644 --- a/include/linux/memcontrol.h +++ b/include/linux/memcontrol.h @@ -987,19 +987,30 @@ static inline void mod_memcg_page_state(struct page *page, static inline unsigned long memcg_page_state(struct mem_cgroup *memcg, int idx) { - return READ_ONCE(memcg->vmstats.state[idx]); + long x = READ_ONCE(memcg->vmstats.state[idx]); +#ifdef CONFIG_SMP + if (x < 0) + x = 0; +#endif + return x; } static inline unsigned long lruvec_page_state(struct lruvec *lruvec, enum node_stat_item idx) { struct mem_cgroup_per_node *pn; + long x; if (mem_cgroup_disabled()) return node_page_state(lruvec_pgdat(lruvec), idx); pn = container_of(lruvec, struct mem_cgroup_per_node, lruvec); - return READ_ONCE(pn->lruvec_stats.state[idx]); + x = READ_ONCE(pn->lruvec_stats.state[idx]); +#ifdef CONFIG_SMP + if (x < 0) + x = 0; +#endif + return x; } static inline unsigned long lruvec_page_state_local(struct lruvec *lruvec, -- cgit v1.2.3-59-g8ed1b