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Wed, 10 Jul 2024 14:40:18 -0700 (PDT) X-Google-Smtp-Source: AGHT+IEPTuTQRQE30zFBM0t8+WCUxb2VC4RLEEJeQ4IxECNg0RAHwUr/Q/CjeWUsChjiQaCkqSL2Pg== X-Received: by 2002:a05:6a00:1955:b0:70a:f5c5:135d with SMTP id d2e1a72fcca58-70b43667750mr8053487b3a.32.1720647618108; Wed, 10 Jul 2024 14:40:18 -0700 (PDT) Received: from [10.35.209.243] ([208.115.86.68]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-70b439afda9sm4242396b3a.169.2024.07.10.14.40.17 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 10 Jul 2024 14:40:17 -0700 (PDT) Message-ID: <25a87009-5318-457b-926b-69185767b274@redhat.com> Date: Wed, 10 Jul 2024 23:40:16 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v1] mm/rmap: cleanup partially-mapped handling in __folio_remove_rmap() To: Yosry Ahmed Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org References: <20240618151026.521019-1-david@redhat.com> From: David Hildenbrand Content-Language: en-US Autocrypt: addr=david@redhat.com; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 24.06.24 13:48, Yosry Ahmed wrote: > On Tue, Jun 18, 2024 at 8:10 AM David Hildenbrand wrote: >> >> Let's simplify and reduce code indentation. In the RMAP_LEVEL_PTE case, we >> already check for nr when computing partially_mapped. >> >> For RMAP_LEVEL_PMD, it's a bit more confusing. Likely, we don't need the >> "nr" check, but we could have "nr < nr_pmdmapped" also if we stumbled >> into the "/* Raced ahead of another remove and an add? */" case. So >> let's simply move the nr check in there. >> >> Note that partially_mapped is always false for small folios. >> >> No functional change intended. >> >> Cc: Yosry Ahmed >> Signed-off-by: David Hildenbrand > > Makes sense to me. FWIW: > > Reviewed-by: Yosry Ahmed > >> --- >> mm/rmap.c | 10 ++++------ >> 1 file changed, 4 insertions(+), 6 deletions(-) >> >> diff --git a/mm/rmap.c b/mm/rmap.c >> index afec4b6800caf..aa900e46cdf82 100644 >> --- a/mm/rmap.c >> +++ b/mm/rmap.c >> @@ -1551,11 +1551,12 @@ static __always_inline void __folio_remove_rmap(struct folio *folio, >> } >> } >> >> - partially_mapped = nr < nr_pmdmapped; >> + partially_mapped = nr && nr < nr_pmdmapped; >> break; >> } >> >> - if (nr) { >> + if (partially_mapped && folio_test_anon(folio) && >> + list_empty(&folio->_deferred_list)) >> /* >> * Queue anon large folio for deferred split if at least one >> * page of the folio is unmapped and at least one page >> @@ -1563,10 +1564,7 @@ static __always_inline void __folio_remove_rmap(struct folio *folio, >> * >> * Check partially_mapped first to ensure it is a large folio. >> */ >> - if (folio_test_anon(folio) && partially_mapped && >> - list_empty(&folio->_deferred_list)) >> - deferred_split_folio(folio); >> - } >> + deferred_split_folio(folio); > > FWIW, I prefer moving the comment out of the one-line if block as you > originally suggested in [1]. > > [1]https://lore.kernel.org/lkml/1a408ed1-7e81-457e-a205-db274b4d6b78@redhat.com/ Sorry for the late reply, crazy times here. Let me do that and resend, thanks! -- Cheers, David / dhildenb