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[94.245.46.61]) by smtp.gmail.com with ESMTPSA id u17sm2215456ljj.2.2021.01.28.10.07.02 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 28 Jan 2021 10:07:08 -0800 (PST) From: Uladzislau Rezki X-Google-Original-From: Uladzislau Rezki Date: Thu, 28 Jan 2021 19:06:58 +0100 To: "Paul E . McKenney" Cc: LKML , RCU , "Paul E . McKenney" , Michael Ellerman , Andrew Morton , Daniel Axtens , Frederic Weisbecker , Neeraj Upadhyay , Joel Fernandes , Peter Zijlstra , Michal Hocko , Thomas Gleixner , "Theodore Y . Ts'o" , Sebastian Andrzej Siewior , Oleksiy Avramchenko Subject: Re: [PATCH 2/3] kvfree_rcu: Use __GFP_NOMEMALLOC for single-argument kvfree_rcu() Message-ID: <20210128180658.GB5144@pc638.lan> References: <20210120162148.1973-1-urezki@gmail.com> <20210120162148.1973-2-urezki@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210120162148.1973-2-urezki@gmail.com> User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jan 20, 2021 at 05:21:47PM +0100, Uladzislau Rezki (Sony) wrote: > From: "Paul E. McKenney" > > This commit applies the __GFP_NOMEMALLOC gfp flag to memory allocations > carried out by the single-argument variant of kvfree_rcu(), thus avoiding > this can-sleep code path from dipping into the emergency reserves. > > Acked-by: Michal Hocko > Suggested-by: Michal Hocko > Signed-off-by: Paul E. McKenney > Signed-off-by: Uladzislau Rezki (Sony) > --- > kernel/rcu/tree.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c > index 2014fb22644d..454809514c91 100644 > --- a/kernel/rcu/tree.c > +++ b/kernel/rcu/tree.c > @@ -3491,7 +3491,7 @@ add_ptr_to_bulk_krc_lock(struct kfree_rcu_cpu **krcp, > if (!bnode && can_alloc) { > krc_this_cpu_unlock(*krcp, *flags); > bnode = (struct kvfree_rcu_bulk_data *) > - __get_free_page(GFP_KERNEL | __GFP_RETRY_MAYFAIL | __GFP_NOWARN); > + __get_free_page(GFP_KERNEL | __GFP_RETRY_MAYFAIL | __GFP_NOMEMALLOC | __GFP_NOWARN); > *krcp = krc_this_cpu_lock(flags); > } > > -- > 2.20.1 > Please see below a V2: V1 -> V2: - rebase on [PATCH v2 1/1] kvfree_rcu: Directly allocate page for single-argument - add a comment about __GFP_NOMEMALLOC usage. >From 1427698cdbdced53d9b5eee60aa5d22bc223056d Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Wed, 20 Jan 2021 17:21:47 +0100 Subject: [PATCH v2 1/1] kvfree_rcu: Use __GFP_NOMEMALLOC for single-argument kvfree_rcu() This commit applies the __GFP_NOMEMALLOC gfp flag to memory allocations carried out by the single-argument variant of kvfree_rcu(), thus avoiding this can-sleep code path from dipping into the emergency reserves. Acked-by: Michal Hocko Suggested-by: Michal Hocko Signed-off-by: Paul E. McKenney Signed-off-by: Uladzislau Rezki (Sony) Signed-off-by: Paul E. McKenney --- kernel/rcu/tree.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index e450c17a06b2..e7b705155c92 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -3496,11 +3496,14 @@ add_ptr_to_bulk_krc_lock(struct kfree_rcu_cpu **krcp, // view. Apart of that it forbids any OOM invoking what is // also beneficial since we are about to release memory soon. // + // __GFP_NOMEMALLOC - prevents from consuming of all the + // memory reserves. Please note we have a fallback path. + // // __GFP_NOWARN - it is supposed that an allocation can // be failed under low memory or high memory pressure // scenarios. bnode = (struct kvfree_rcu_bulk_data *) - __get_free_page(GFP_KERNEL | __GFP_NORETRY | __GFP_NOWARN); + __get_free_page(GFP_KERNEL | __GFP_NORETRY | __GFP_NOMEMALLOC | __GFP_NOWARN); *krcp = krc_this_cpu_lock(flags); } -- 2.20.1 Thanks! -- Vlad Rezki