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[37.188.158.19]) by smtp.gmail.com with ESMTPSA id z10sm12950424ejb.9.2020.06.17.02.02.39 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 17 Jun 2020 02:02:40 -0700 (PDT) Date: Wed, 17 Jun 2020 11:02:38 +0200 From: Michal Hocko To: Andrew Morton , Johannes Weiner Cc: Alex Shi , Joonsoo Kim , Shakeel Butt , Hugh Dickins , "Kirill A. Shutemov" , Roman Gushchin , linux-mm@kvack.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, kernel-team@fb.com Subject: Re: [PATCH for 5.8] mm: do_swap_page fix up the error code instantiation Message-ID: <20200617090238.GL9499@dhcp22.suse.cz> References: <20200508183105.225460-1-hannes@cmpxchg.org> <20200508183105.225460-17-hannes@cmpxchg.org> <20200611093523.GB20450@dhcp22.suse.cz> <20200617084927.GK9499@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200617084927.GK9499@dhcp22.suse.cz> X-Rspamd-Queue-Id: E013C18038E60 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam04 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: Damn, I forgot to commit my last change (s@err@ret@). Sorry about the noise. >From 50297dd026ebf71fe901e1945a9ce1e8d8aa083b Mon Sep 17 00:00:00 2001 From: Michal Hocko Date: Wed, 17 Jun 2020 10:40:47 +0200 Subject: [PATCH] mm: do_swap_page fix up the error code do_swap_page returns error codes from the VM_FAULT* space. try_charge might return -ENOMEM, though, and then do_swap_page simply returns 0 which means a success. We almost never return ENOMEM for GFP_KERNEL single page charge. Except for async OOM handling (oom_disabled v1). So this needs translation to VM_FAULT_OOM otherwise the the page fault path will not notify the userspace and wait for an action. Fixes: 4c6355b25e8b ("mm: memcontrol: charge swapin pages on instantiation") Signed-off-by: Michal Hocko --- mm/memory.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/mm/memory.c b/mm/memory.c index dc7f3543b1fd..1c632faa2611 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -3140,8 +3140,10 @@ vm_fault_t do_swap_page(struct vm_fault *vmf) err = mem_cgroup_charge(page, vma->vm_mm, GFP_KERNEL); ClearPageSwapCache(page); - if (err) + if (err) { + ret = VM_FAULT_OOM; goto out_page; + } lru_cache_add(page); swap_readpage(page, true); -- 2.26.2 -- Michal Hocko SUSE Labs