From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1794331842; b=WMDLvzMIrja9JzxtanXQjoMpWK91ArgXxibbsANijbrlB4PCQh0tS0mCaSRSwdMRPCC2 VwLKHp4TRIPNj+DDqs/zrM8zBhy6g/4k6+BoQrljPdx2o9XfPfuWp3ortfLJ5jNOsdjnS 3A8CYGoYQZjM527lUb0DjiryjRM73H2sIfrqX7VGV5yENOVnB7Tva+bq8lvc5bTK2otHY UJHS7Rxox7DEGXSSAcRyeka+P3djK63SqdHfjKgCOgWzzhFN3FvQzjNo+63NiJUxgJbfN cCDQQAnM6F7staSNJS4V1FvKBSc3HwCsXxv9XPj2RQTrP3VXdkho1HIGEODZjVqdNtw== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794331842; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:MIME-Version:Content-Transfer-Encoding; bh=kWPMc5MkO6fyRKvhyV3mY4b213zNGSf1COAbedk/OiE=; b=5Ltt4whDnqKeHM1xEUXX49Px4WKOd6f4lmpccX1kn/771jBgPwlJ1h1iqHxj309LxP0C 0IWcM9u/zyReY42XfZ4U6y2dIUUyAu9J3vUzGCrP9Yf5V38WhHDI347gMkNvNWgHdV6iA 077fW/Rah6NZZNkBmOW5NpGe9mgqaf3CmpfD0W1IjA7TvHoD6UEtBDTq24LUlw58BaO4E ExKy5b4svN354Yzxevj04ousdqqPYVAz81smL75Bi/CArag7xgYWC4tgC/L+x/WwuwmOl gnfPJZRw2z60jATUp3s95/g/IUwpUcEIUGQo3nGAZvkaP2/9oQ/x3fGoTr/UHZ0PFfw== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=PSHi9iZU; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id AC875606A320 for ; Tue, 10 Nov 2026 17:30:41 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=PSHi9iZU Received: by smtp.kernel.org (Postfix) with ESMTPSA id 41CCE1F0089F; Tue, 10 Nov 2026 17:30:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794331841; bh=kWPMc5MkO6fyRKvhyV3mY4b213zNGSf1COAbedk/OiE=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=PSHi9iZUFVcaxSnaJmWgAQc83WnLBIdpvhAWH7tO+FGboY0i3kDTOXyYoNart4TSj GMYeW2tXXWXZh67SB1oFJZaXRP/X5b2QH9RXlKxSmDRBP2whOswFoLn4MbeJRfe3k/ 4C9LoYydsHFH46dE/7EhRtP1K94cB0DAJvHkTp9X5ur26lMOSx+wkWAhKWN3fsjuCK I3bZLCyWwvVBgZArlahzTZusoHro9osGDrjUl3488xppYFmPvWDUKxYlHXdUjtK46c 7W8JHQz2cXKc8iqBo8QbjL8PxASSF4TUC5SgxXd1RsTd0OmEMT//lnRmVaUK4oWWL+ iYnTWoIUan3PA== From: Sasha Levin To: stable@vger.kernel.org Cc: Joe Damato , Andrew Morton , Shakeel Butt , Johannes Weiner , Michal Hocko , Muchun Song , Roman Gushchin , Sasha Levin Subject: [PATCH 6.6.y] mm: memcontrol: raise MEMCG_MAX for charges that fail without reclaiming Date: Tue, 10 Nov 2026 12:30:38 -0500 Message-ID: <20261110173025.2913165-1-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20261107053206-failed-6.6-374f65b14819@kernel.org> References: <20261107053206-failed-6.6-374f65b14819@kernel.org> X-Mailing-List: stable@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Joe Damato [ Upstream commit 374f65b1481992eb6b9c6bffd53f3afa5c2e94cf ] Charges that exceed memory.max and return through the nomem label can raise no event and simply return -ENOMEM. A non-blocking charge can hit the limit, get rejected, but is not visible in memory.events. This was noticed in a production setting where bpf_mem_alloc() attempted to refill its per-cpu freelists, which triggered a non-blocking charge while at the limit. Commit d6e103a757fa ("mm: memcontrol: do not miss MEMCG_MAX events for enforced allocations") added raised_max_event to cover charges that are force charged without ever reaching reclaim, but charges that are rejected outright were left out. Getting an allocation failure without the corresponding MEMCG_MAX event is unexpected and makes debugging and monitoring harder. Raise the event on the way out for rejected charges as well, by routing the -ENOMEM return through the same exit path that already covers forced charges. The existing behavior of raising a MEMCG_MAX event on every charge/reclaim/retry iteration is left unchanged. Tested with a module that performs accounted GFP_NOWAIT page allocations from a task in a cgroup at its memory.max, and measures the resulting memory.events:max delta. Without this patch the rejected charges raise no event at all; with it the delta matches the number of rejected charges exactly. A GFP_KERNEL|__GFP_NORETRY control, which reaches reclaim, raises the same two events per failed charge before and after, confirming the existing charge/reclaim/retry accounting is unchanged. Link: https://lore.kernel.org/20260831174836.3102406-1-joe@dama.to Fixes: d6e103a757fa ("mm: memcontrol: do not miss MEMCG_MAX events for enforced allocations") Signed-off-by: Joe Damato Signed-off-by: Andrew Morton Suggested-by: Shakeel Butt Acked-by: Shakeel Butt Cc: Johannes Weiner Cc: Michal Hocko Cc: Muchun Song Cc: Roman Gushchin Cc: [ sashal: Changed __memcg_memory_event(..., allow_spinning) to memcg_memory_event(...) to match the existing API. ] Signed-off-by: Sasha Levin --- mm/memcontrol.c | 28 ++++++++++++++++------------ 1 file changed, 16 insertions(+), 12 deletions(-) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 852fa93efe1be..34920b31e456c 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -2682,10 +2682,11 @@ static int try_charge_memcg(struct mem_cgroup *memcg, gfp_t gfp_mask, bool drained = false; bool raised_max_event = false; unsigned long pflags; + int ret = 0; retry: if (consume_stock(memcg, nr_pages)) - return 0; + return ret; if (!do_memsw_account() || page_counter_try_charge(&memcg->memsw, batch, &counter)) { @@ -2797,16 +2798,11 @@ static int try_charge_memcg(struct mem_cgroup *memcg, gfp_t gfp_mask, * put the burden of reclaim on regular allocation requests * and let these go through as privileged allocations. */ - if (!(gfp_mask & (__GFP_NOFAIL | __GFP_HIGH))) - return -ENOMEM; + if (!(gfp_mask & (__GFP_NOFAIL | __GFP_HIGH))) { + ret = -ENOMEM; + goto out; + } force: - /* - * If the allocation has to be enforced, don't forget to raise - * a MEMCG_MAX event. - */ - if (!raised_max_event) - memcg_memory_event(mem_over_limit, MEMCG_MAX); - /* * The allocation either can't fail or will lead to more memory * being freed very soon. Allow memory usage go over the limit @@ -2816,7 +2812,15 @@ static int try_charge_memcg(struct mem_cgroup *memcg, gfp_t gfp_mask, if (do_memsw_account()) page_counter_charge(&memcg->memsw, nr_pages); - return 0; +out: + /* + * Don't forget to raise a MEMCG_MAX event for forced or rejected + * requests. + */ + if (!raised_max_event) + memcg_memory_event(mem_over_limit, MEMCG_MAX); + + return ret; done_restock: if (batch > nr_pages) @@ -2869,7 +2873,7 @@ static int try_charge_memcg(struct mem_cgroup *memcg, gfp_t gfp_mask, gfpflags_allow_blocking(gfp_mask)) { mem_cgroup_handle_over_high(gfp_mask); } - return 0; + return ret; } static inline int try_charge(struct mem_cgroup *memcg, gfp_t gfp_mask, -- 2.53.0