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DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1743730797; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=SPcJbZY/0G2u+L0qrxlZJ2y8LLOHW+AMha0Dw+104jw=; b=wuy3jajnDZ7Ek+Id4OsrZGBafMEeu1h0zfmikYHmWilsNXTfvonHYmMbFo/nxU8AMZYc76 czhi5qcby2jXTDXKb+TzOuNa5D5pZPWarz3OxmUPPjtKJB/8yNmVx8Uj7EyokzG0KDpTLW JU4vIFP6qzSocknGhQBCPM020VjBrm4= From: Shakeel Butt To: Andrew Morton Cc: Johannes Weiner , Michal Hocko , Roman Gushchin , Muchun Song , Vlastimil Babka , Sebastian Andrzej Siewior , linux-mm@kvack.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, Meta kernel team Subject: [PATCH v2 6/9] memcg: do obj_cgroup_put inside drain_obj_stock Date: Thu, 3 Apr 2025 18:39:10 -0700 Message-ID: <20250404013913.1663035-7-shakeel.butt@linux.dev> In-Reply-To: <20250404013913.1663035-1-shakeel.butt@linux.dev> References: <20250404013913.1663035-1-shakeel.butt@linux.dev> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: C12F4C0007 X-Stat-Signature: bdafdii9cdsnxcxp7d1p3sye9df186uz X-Rspam-User: X-HE-Tag: 1743730798-402778 X-HE-Meta: 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 2yD/b0b/ r94YsJxwu450xusnmfBcjDVErOg87YDxFMipyECa2ynyWXZ40JZu5067MJW9/pR2FotgFjABSSVYy1scqn51QnWEUv3YWaWAhzymanV6H7Pe7xK7J2htKF7769LSP48P7/Nsf/x8/0mToVL3eAVuhjdt0BWzcXPP/206rLgeTgf8kIKDsSxLQPkpgBJk593Ivs6hfwZPEX8A01VNG9b1Ize+POasnUV3taQwy X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Previously we could not call obj_cgroup_put() inside the local lock because on the put on the last reference, the release function obj_cgroup_release() may try to re-acquire the local lock. However that chain has been broken. Now simply do obj_cgroup_put() inside drain_obj_stock() instead of returning the old objcg. Reviewed-by: Roman Gushchin Signed-off-by: Shakeel Butt --- mm/memcontrol.c | 37 +++++++++++-------------------------- 1 file changed, 11 insertions(+), 26 deletions(-) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index df52084e90f4..7988a42b29bf 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -1785,7 +1785,7 @@ static DEFINE_PER_CPU(struct memcg_stock_pcp, memcg_stock) = { }; static DEFINE_MUTEX(percpu_charge_mutex); -static struct obj_cgroup *drain_obj_stock(struct memcg_stock_pcp *stock); +static void drain_obj_stock(struct memcg_stock_pcp *stock); static bool obj_stock_flush_required(struct memcg_stock_pcp *stock, struct mem_cgroup *root_memcg); @@ -1859,7 +1859,6 @@ static void drain_stock(struct memcg_stock_pcp *stock) static void drain_local_stock(struct work_struct *dummy) { struct memcg_stock_pcp *stock; - struct obj_cgroup *old = NULL; unsigned long flags; /* @@ -1870,12 +1869,11 @@ static void drain_local_stock(struct work_struct *dummy) local_lock_irqsave(&memcg_stock.stock_lock, flags); stock = this_cpu_ptr(&memcg_stock); - old = drain_obj_stock(stock); + drain_obj_stock(stock); drain_stock(stock); clear_bit(FLUSHING_CACHED_CHARGE, &stock->flags); local_unlock_irqrestore(&memcg_stock.stock_lock, flags); - obj_cgroup_put(old); } static void refill_stock(struct mem_cgroup *memcg, unsigned int nr_pages) @@ -1958,18 +1956,16 @@ void drain_all_stock(struct mem_cgroup *root_memcg) static int memcg_hotplug_cpu_dead(unsigned int cpu) { struct memcg_stock_pcp *stock; - struct obj_cgroup *old; unsigned long flags; stock = &per_cpu(memcg_stock, cpu); /* drain_obj_stock requires stock_lock */ local_lock_irqsave(&memcg_stock.stock_lock, flags); - old = drain_obj_stock(stock); + drain_obj_stock(stock); local_unlock_irqrestore(&memcg_stock.stock_lock, flags); drain_stock(stock); - obj_cgroup_put(old); return 0; } @@ -2766,24 +2762,20 @@ void __memcg_kmem_uncharge_page(struct page *page, int order) } /* Replace the stock objcg with objcg, return the old objcg */ -static struct obj_cgroup *replace_stock_objcg(struct memcg_stock_pcp *stock, - struct obj_cgroup *objcg) +static void replace_stock_objcg(struct memcg_stock_pcp *stock, + struct obj_cgroup *objcg) { - struct obj_cgroup *old = NULL; - - old = drain_obj_stock(stock); + drain_obj_stock(stock); obj_cgroup_get(objcg); stock->nr_bytes = atomic_read(&objcg->nr_charged_bytes) ? atomic_xchg(&objcg->nr_charged_bytes, 0) : 0; WRITE_ONCE(stock->cached_objcg, objcg); - return old; } static void mod_objcg_state(struct obj_cgroup *objcg, struct pglist_data *pgdat, enum node_stat_item idx, int nr) { struct memcg_stock_pcp *stock; - struct obj_cgroup *old = NULL; unsigned long flags; int *bytes; @@ -2796,7 +2788,7 @@ static void mod_objcg_state(struct obj_cgroup *objcg, struct pglist_data *pgdat, * changes. */ if (READ_ONCE(stock->cached_objcg) != objcg) { - old = replace_stock_objcg(stock, objcg); + replace_stock_objcg(stock, objcg); stock->cached_pgdat = pgdat; } else if (stock->cached_pgdat != pgdat) { /* Flush the existing cached vmstat data */ @@ -2837,7 +2829,6 @@ static void mod_objcg_state(struct obj_cgroup *objcg, struct pglist_data *pgdat, __mod_objcg_mlstate(objcg, pgdat, idx, nr); local_unlock_irqrestore(&memcg_stock.stock_lock, flags); - obj_cgroup_put(old); } static bool consume_obj_stock(struct obj_cgroup *objcg, unsigned int nr_bytes) @@ -2859,12 +2850,12 @@ static bool consume_obj_stock(struct obj_cgroup *objcg, unsigned int nr_bytes) return ret; } -static struct obj_cgroup *drain_obj_stock(struct memcg_stock_pcp *stock) +static void drain_obj_stock(struct memcg_stock_pcp *stock) { struct obj_cgroup *old = READ_ONCE(stock->cached_objcg); if (!old) - return NULL; + return; if (stock->nr_bytes) { unsigned int nr_pages = stock->nr_bytes >> PAGE_SHIFT; @@ -2917,11 +2908,7 @@ static struct obj_cgroup *drain_obj_stock(struct memcg_stock_pcp *stock) } WRITE_ONCE(stock->cached_objcg, NULL); - /* - * The `old' objects needs to be released by the caller via - * obj_cgroup_put() outside of memcg_stock_pcp::stock_lock. - */ - return old; + obj_cgroup_put(old); } static bool obj_stock_flush_required(struct memcg_stock_pcp *stock, @@ -2943,7 +2930,6 @@ static void refill_obj_stock(struct obj_cgroup *objcg, unsigned int nr_bytes, bool allow_uncharge) { struct memcg_stock_pcp *stock; - struct obj_cgroup *old = NULL; unsigned long flags; unsigned int nr_pages = 0; @@ -2951,7 +2937,7 @@ static void refill_obj_stock(struct obj_cgroup *objcg, unsigned int nr_bytes, stock = this_cpu_ptr(&memcg_stock); if (READ_ONCE(stock->cached_objcg) != objcg) { /* reset if necessary */ - old = replace_stock_objcg(stock, objcg); + replace_stock_objcg(stock, objcg); allow_uncharge = true; /* Allow uncharge when objcg changes */ } stock->nr_bytes += nr_bytes; @@ -2962,7 +2948,6 @@ static void refill_obj_stock(struct obj_cgroup *objcg, unsigned int nr_bytes, } local_unlock_irqrestore(&memcg_stock.stock_lock, flags); - obj_cgroup_put(old); if (nr_pages) obj_cgroup_uncharge_pages(objcg, nr_pages); -- 2.47.1