6.17-stable review patch. If anyone has any objections, please let me know.
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From: Shakeel Butt shakeel.butt@linux.dev
commit fcc0669c5aa681994c507b50f1c706c969d99730 upstream.
Generally memcg charging is allowed from all the contexts including NMI where even spinning on spinlock can cause locking issues. However one call chain was missed during the addition of memcg charging from any context support. That is try_charge_memcg() -> memcg_memory_event() -> cgroup_file_notify().
The possible function call tree under cgroup_file_notify() can acquire many different spin locks in spinning mode. Some of them are cgroup_file_kn_lock, kernfs_notify_lock, pool_workqeue's lock. So, let's just skip cgroup_file_notify() from memcg charging if the context does not allow spinning.
Alternative approach was also explored where instead of skipping cgroup_file_notify(), we defer the memcg event processing to irq_work [1]. However it adds complexity and it was decided to keep things simple until we need more memcg events with !allow_spinning requirement.
Link: https://lore.kernel.org/all/5qi2llyzf7gklncflo6gxoozljbm4h3tpnuv4u4ej4ztysvi... [1] Link: https://lkml.kernel.org/r/20250922220203.261714-1-shakeel.butt@linux.dev Fixes: 3ac4638a734a ("memcg: make memcg_rstat_updated nmi safe") Signed-off-by: Shakeel Butt shakeel.butt@linux.dev Acked-by: Michal Hocko mhocko@suse.com Closes: https://lore.kernel.org/all/20250905061919.439648-1-yepeilin@google.com/ Cc: Alexei Starovoitov ast@kernel.org Cc: Johannes Weiner hannes@cmpxchg.org Cc: Kumar Kartikeya Dwivedi memxor@gmail.com Cc: Muchun Song muchun.song@linux.dev Cc: Peilin Ye yepeilin@google.com Cc: Roman Gushchin roman.gushchin@linux.dev Cc: Tejun Heo tj@kernel.org Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- include/linux/memcontrol.h | 26 +++++++++++++++++++------- mm/memcontrol.c | 7 ++++--- 2 files changed, 23 insertions(+), 10 deletions(-)
--- a/include/linux/memcontrol.h +++ b/include/linux/memcontrol.h @@ -987,22 +987,28 @@ static inline void count_memcg_event_mm( count_memcg_events_mm(mm, idx, 1); }
-static inline void memcg_memory_event(struct mem_cgroup *memcg, - enum memcg_memory_event event) +static inline void __memcg_memory_event(struct mem_cgroup *memcg, + enum memcg_memory_event event, + bool allow_spinning) { bool swap_event = event == MEMCG_SWAP_HIGH || event == MEMCG_SWAP_MAX || event == MEMCG_SWAP_FAIL;
+ /* For now only MEMCG_MAX can happen with !allow_spinning context. */ + VM_WARN_ON_ONCE(!allow_spinning && event != MEMCG_MAX); + atomic_long_inc(&memcg->memory_events_local[event]); - if (!swap_event) + if (!swap_event && allow_spinning) cgroup_file_notify(&memcg->events_local_file);
do { atomic_long_inc(&memcg->memory_events[event]); - if (swap_event) - cgroup_file_notify(&memcg->swap_events_file); - else - cgroup_file_notify(&memcg->events_file); + if (allow_spinning) { + if (swap_event) + cgroup_file_notify(&memcg->swap_events_file); + else + cgroup_file_notify(&memcg->events_file); + }
if (!cgroup_subsys_on_dfl(memory_cgrp_subsys)) break; @@ -1012,6 +1018,12 @@ static inline void memcg_memory_event(st !mem_cgroup_is_root(memcg)); }
+static inline void memcg_memory_event(struct mem_cgroup *memcg, + enum memcg_memory_event event) +{ + __memcg_memory_event(memcg, event, true); +} + static inline void memcg_memory_event_mm(struct mm_struct *mm, enum memcg_memory_event event) { --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -2309,12 +2309,13 @@ static int try_charge_memcg(struct mem_c bool drained = false; bool raised_max_event = false; unsigned long pflags; + bool allow_spinning = gfpflags_allow_spinning(gfp_mask);
retry: if (consume_stock(memcg, nr_pages)) return 0;
- if (!gfpflags_allow_spinning(gfp_mask)) + if (!allow_spinning) /* Avoid the refill and flush of the older stock */ batch = nr_pages;
@@ -2350,7 +2351,7 @@ retry: if (!gfpflags_allow_blocking(gfp_mask)) goto nomem;
- memcg_memory_event(mem_over_limit, MEMCG_MAX); + __memcg_memory_event(mem_over_limit, MEMCG_MAX, allow_spinning); raised_max_event = true;
psi_memstall_enter(&pflags); @@ -2417,7 +2418,7 @@ force: * a MEMCG_MAX event. */ if (!raised_max_event) - memcg_memory_event(mem_over_limit, MEMCG_MAX); + __memcg_memory_event(mem_over_limit, MEMCG_MAX, allow_spinning);
/* * The allocation either can't fail or will lead to more memory