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Mon, 07 Apr 2025 05:09:48 -0700 (PDT) Date: Mon, 7 Apr 2025 12:09:48 +0000 From: Wei Yang To: Lorenzo Stoakes Cc: Wei Yang , Andrew Morton , Vlastimil Babka , Jann Horn , "Liam R . Howlett" , Suren Baghdasaryan , David Hildenbrand , Matthew Wilcox , Rik van Riel , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 3/3] tools/testing/selftests: assert that anon merge cases behave as expected Message-ID: <20250407120948.zb5th45e6ehxpmrm@master> Reply-To: Wei Yang References: <20250407025455.67nhchndedotn57g@master> <4a8a1163-a7f9-4368-98e1-f79b0411aac4@lucifer.local> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4a8a1163-a7f9-4368-98e1-f79b0411aac4@lucifer.local> User-Agent: NeoMutt/20170113 (1.7.2) X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: C731D1C000D X-Stat-Signature: 5pwdx8tz98wjxs3mkmstj5af9p7y6xid X-Rspam-User: X-HE-Tag: 1744027790-229178 X-HE-Meta: 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 Gj4VYNdS 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.002578, 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 Mon, Apr 07, 2025 at 12:02:00PM +0100, Lorenzo Stoakes wrote: >I know you mean well Wei, > >But drive-by extremely pedantic review on minor details isn't really >useful. I can't tell you not to do this, but I can at least ask. I don't >think this is a great use of either of our time. > >Thanks. > [...] >> >+ >> >+ /* unCOWing everything does not cause the AVC to go away. */ >> ^^^ >> >> Before ptr[i] = 'x', we have unCOWed pages in vma. What we are doing here is >> COWing, right? > >Nope, it's the other way round, as commented. A 'CoW' page is one marked >for copy-on-write right? we now make it just a normal mapping by writing to >it. > Oh, I misunderstand the meaning of 'CoW' page. It is the page before copy. I thought it is the page after. Sorry for bothering. >> >> >+ for (i = 0; i < 5 * page_size; i += page_size) >> >+ ptr[i] = 'x'; >> >+ >> >+ /* >> >+ * Map in adjacent VMA in child. >> >+ * >> >+ * forked >> >+ * |-----------|-----------| >> >+ * | faulted | unfaulted | >> >+ * |-----------|-----------| >> >+ * ptr ptr2 >> >+ */ >> >+ ptr2 = mmap(&ptr[5 * page_size], 5 * page_size, PROT_READ | PROT_WRITE, >> >+ MAP_ANON | MAP_PRIVATE | MAP_FIXED, -1, 0); >> >+ ASSERT_NE(ptr2, MAP_FAILED); >> >+ >> >+ /* Make sure not merged. */ >> >+ ASSERT_TRUE(find_vma_procmap(procmap, ptr)); >> >+ ASSERT_EQ(procmap->query.vma_start, (unsigned long)ptr); >> >+ ASSERT_EQ(procmap->query.vma_end, (unsigned long)ptr + 5 * page_size); >> >+} >> >+ >> >+TEST_F(merge, forked_source_vma) >> >+{ >> >+ unsigned int page_size = self->page_size; >> >+ char *carveout = self->carveout; >> >+ struct procmap_fd *procmap = &self->procmap; >> >+ pid_t pid; >> >+ char *ptr, *ptr2; >> >+ int i; >> >+ >> >+ /* >> >+ * |............|-----------| >> >+ * | | unfaulted | >> >+ * |............|-----------| >> >> I am not sure "unmapped" is correct here. The range has already been mapped by >> FIXTURE_SETUP(merge). > >This is pointless and actually misleading pedantry. > >For the purposes of what we are doing here, this is unmapped. Do you truly >think mentioning a PROT_NONE mapping here would be useful, meaningful, or >add anything but noise? > >> >> >+ */ >> >+ ptr = mmap(&carveout[page_size], 5 * page_size, PROT_READ | PROT_WRITE, >> >+ MAP_ANON | MAP_PRIVATE | MAP_FIXED | MAP_NORESERVE, -1, 0); >> >+ ASSERT_NE(ptr, MAP_FAILED); >> >+ >> >+ /* >> >+ * Fault in process. >> >+ * >> >+ * |............||-----------| >> >+ * | || faulted | >> >+ * |............||-----------| >> ^ >> >> Extra line here? > >Eh? I don't understand what you mean... you mean an extra '-'? This is to >fit both unfaulted/faulted in the same size SACII 'VMA', a convention I've >kept (hopefully) consistently... > Sounds the character format is corrupted. The extra line I meant is "||" between unmapped and faulted area. Well it is trivial, just forget it. -- Wei Yang Help you, Help me