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[79.242.61.236]) by smtp.gmail.com with ESMTPSA id s7sm3255500wra.75.2021.08.26.07.09.24 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 26 Aug 2021 07:09:25 -0700 (PDT) To: SeongJae Park , akpm@linux-foundation.org Cc: SeongJae Park , Jonathan.Cameron@Huawei.com, acme@kernel.org, alexander.shishkin@linux.intel.com, amit@kernel.org, benh@kernel.crashing.org, brendanhiggins@google.com, corbet@lwn.net, dwmw@amazon.com, elver@google.com, fan.du@intel.com, foersleo@amazon.de, greg@kroah.com, gthelen@google.com, guoju.fgj@alibaba-inc.com, jgowans@amazon.com, joe@perches.com, mgorman@suse.de, mheyne@amazon.de, minchan@kernel.org, mingo@redhat.com, namhyung@kernel.org, peterz@infradead.org, riel@surriel.com, rientjes@google.com, rostedt@goodmis.org, rppt@kernel.org, shakeelb@google.com, shuah@kernel.org, sieberf@amazon.com, snu@zelle79.org, vbabka@suse.cz, vdavydov.dev@gmail.com, zgf574564920@gmail.com, linux-damon@amazon.com, linux-mm@kvack.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org References: <20210716081449.22187-1-sj38.park@gmail.com> <20210716081449.22187-6-sj38.park@gmail.com> From: David Hildenbrand Organization: Red Hat Subject: Re: [PATCH v34 05/13] mm/damon: Implement primitives for the virtual memory address spaces Message-ID: <358fa060-7702-d523-5169-f25a3de0c22e@redhat.com> Date: Thu, 26 Aug 2021 16:09:23 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 MIME-Version: 1.0 In-Reply-To: <20210716081449.22187-6-sj38.park@gmail.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > +static void damon_va_mkold(struct mm_struct *mm, unsigned long addr) > +{ > + pte_t *pte = NULL; > + pmd_t *pmd = NULL; > + spinlock_t *ptl; > + I just stumbled over this, sorry for the dumb questions: a) What do we know about that region we are messing with? AFAIU, just like follow_pte() and follow_pfn(), follow_invalidate_pte() should only be called on VM_IO and raw VM_PFNMAP mappings in general (see the doc of follow_pte()). Do you even know that it's within a single VMA and that there are no concurrent modifications? b) Which locks are we holding? I hope we're holding the mmap lock in read mode at least. Or how are you making sure there are no concurrent modifications to page tables / VMA layout ... ? > + if (follow_invalidate_pte(mm, addr, NULL, &pte, &pmd, &ptl)) -- Thanks, David / dhildenb