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[70.44.39.90]) by smtp.gmail.com with ESMTPSA id v16sm1825014qkf.80.2020.04.21.07.44.27 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 21 Apr 2020 07:44:27 -0700 (PDT) Date: Tue, 21 Apr 2020 10:44:26 -0400 From: Johannes Weiner To: Andrew Morton Cc: Michal Hocko , Yafang Shao , Matthew Wilcox , Vladimir Davydov , Linux MM Subject: Re: [PATCH v3] mm, memcg: fix error return value of mem_cgroup_css_alloc() Message-ID: <20200421144426.GD341682@cmpxchg.org> References: <20200407064329.GB18914@dhcp22.suse.cz> <20200407111017.GN18914@dhcp22.suse.cz> <20200407181012.GA12461@cmpxchg.org> <20200408182956.0906ebc4f8ec421689ec6df5@linux-foundation.org> <20200409065722.GA18386@dhcp22.suse.cz> <20200409140729.GL18386@dhcp22.suse.cz> <20200420164437.80b7c43dc8962ea9acf0519e@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200420164437.80b7c43dc8962ea9acf0519e@linux-foundation.org> 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: On Mon, Apr 20, 2020 at 04:44:37PM -0700, Andrew Morton wrote: > From: Yafang Shao > Subject: mm, memcg: fix error return value of mem_cgroup_css_alloc() > > When I run my memcg testcase which creates lots of memcgs, I found > there're unexpected out of memory logs while there're still enough > available free memory. The error log is, mkdir: cannot create directory > 'foo.65533': Cannot allocate memory > > The reason is when we try to create more than MEM_CGROUP_ID_MAX memcgs, an > -ENOMEM errno will be set by mem_cgroup_css_alloc(), but the right errno > should be -ENOSPC "No space left on device", which is an appropriate errno > for userspace's failed mkdir. > > As the errno really misled me, we should make it right. After this patch, > the error log will be "mkdir: cannot create directory 'foo.65533': No > space left on device" > > [akpm@linux-foundation.org: s/EBUSY/ENOSPC/, per Michal] > Link: http://lkml.kernel.org/r/20200407063621.GA18914@dhcp22.suse.cz > Link: http://lkml.kernel.org/r/1586192163-20099-1-git-send-email-laoar.shao@gmail.com > Signed-off-by: Yafang Shao > Suggested-by: Matthew Wilcox > Acked-by: Michal Hocko > Cc: Johannes Weiner > Cc: Vladimir Davydov > Signed-off-by: Andrew Morton Fixes: 73f576c04b94 ("mm: memcontrol: fix cgroup creation failure after many small jobs") Acked-by: Johannes Weiner