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Mon, 14 Jul 2025 07:42:49 -0700 (PDT) Date: Mon, 14 Jul 2025 14:42:48 +0000 From: Wei Yang To: David Hildenbrand Cc: Wei Yang , akpm@linux-foundation.org, lorenzo.stoakes@oracle.com, riel@surriel.com, Liam.Howlett@oracle.com, vbabka@suse.cz, harry.yoo@oracle.com, linux-mm@kvack.org, linux-kselftest@vger.kernel.org Subject: Re: [RFC Patch 2/2] selftests/mm: assert rmap behave as expected Message-ID: <20250714144248.54d4rhboeq2wn6x4@master> Reply-To: Wei Yang References: <20250604082145.13800-1-richard.weiyang@gmail.com> <20250604082145.13800-3-richard.weiyang@gmail.com> <20250604083441.hilkdzlxmxygivvt@master> <2ee1d2ca-94c5-4c27-b2dc-bcea2b710dcf@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <2ee1d2ca-94c5-4c27-b2dc-bcea2b710dcf@redhat.com> User-Agent: NeoMutt/20170113 (1.7.2) X-Rspamd-Queue-Id: 98026100009 X-Stat-Signature: i7rr1i876ob4571qt4uh3r13wicjoagh X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1752504171-781532 X-HE-Meta: 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 /X6nkX6z 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 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: On Fri, Jul 11, 2025 at 05:39:39PM +0200, David Hildenbrand wrote: >On 04.06.25 10:34, Wei Yang wrote: >> On Wed, Jun 04, 2025 at 08:21:45AM +0000, Wei Yang wrote: >> [...] >> > +int try_to_move_page(char *region) >> > +{ >> > + int ret; >> > + int node; >> > + int status = 0; >> > + >> > + ksft_print_msg("worker %d move_pages of content: %.15s\n", getpid(), region); >> >> One thing confused me here. >> >> If I don't access region here, the following move_pages() would report >> -ENOENT occationally. The reason is do_pages_stat_array() -> >> folio_walk_start() returns NULL. > >Right, the pages were not faulted in. The man page mentions that as > >"-ENOENT: The page is not present." > Thanks I see the man page, but from the code point of view, I don't follow it. The move_pages() return -ENOENT in a child process, and the child duplicate it memory space during fork(). dup_mmap() for_each_vma() copy_page_range() ... copy_pte_range() -> copy_present_ptes() __copy_present_ptes() set_ptes() Even we map the range by MAP_SHARED, we don't need to wrprotect it. But we still set_ptes() in the child process page table. So it looks the child has prepared the page table and not need to fault in to setup it. Do I miss something? >-- >Cheers, > >David / dhildenb -- Wei Yang Help you, Help me