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a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1770238909; bh=jp2KfloYw+uC2B4Pxh+HiUCTQy7uOAAaMHvJN6AaS6c=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=Vzrnjuj/OhJlTXjtTS+zXd6lBLI3Hiy4cjnZ1JFzAV4OwNr4aBpV5r5gxMCWDXb7W yJZoVMfN6LFBlWkgImX9+f1eXNpte8okcFJ3D3N+5VjQMXdPFA0SUdhXMvaO1/KNYY q621/QIUEvMNKxbMZKdfnR0fpMtFX/bK+sKRFWX0ZOjj/dNfeKn5QT4rb5rc5gjDmE x6xjMVdUETf+K3mbOGTED080SE3lbocDvqPiMVIc5c/ljKPAIso7z0+XVkLqaTYhNU m7wCg7fEA1IdNGDk/yZ7X0lvogdWdcOrE563hP1IUoRgTQC8hjQJySuQznONrj74q9 s7shtKCW4HvEQ== Message-ID: <9206a7c4-bf88-4138-b8af-961625a82439@kernel.org> Date: Wed, 4 Feb 2026 22:01:42 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2] mm: folio_zero_user: open code range computation in folio_zero_user() To: Ankur Arora , linux-kernel@vger.kernel.org, linux-mm@kvack.org, x86@kernel.org Cc: akpm@linux-foundation.org, bp@alien8.de, dave.hansen@linux.intel.com, hpa@zytor.com, mingo@redhat.com, mjguzik@gmail.com, luto@kernel.org, peterz@infradead.org, tglx@linutronix.de, willy@infradead.org, raghavendra.kt@amd.com, chleroy@kernel.org, ioworker0@gmail.com, lizhe.67@bytedance.com, boris.ostrovsky@oracle.com, konrad.wilk@oracle.com, kernel test robot References: <20260107072009.1615991-9-ankur.a.arora@oracle.com> <20260128185943.2397128-1-ankur.a.arora@oracle.com> From: "David Hildenbrand (arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: A6E861A0008 X-Stat-Signature: ess5qapmo5rw35ejshaaybo5n7gmg33z X-HE-Tag: 1770238910-475740 X-HE-Meta: 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 NuZlvJLR EGL9esC+NJSTRpoCm1egM3kQK62tnv5TYcDg7FjItzfvFXSiiIEOJYiXe4zEuzKZ7Kgv+k9JyPnUJe533B+RZnwJTtZ7kvYYO6QDQts/gQhMTItKCHy4RY9n/h3j+NWKcm3P5vSSUFwjen3yh2YIcUaYoZPQb5TcPlXSmAmQLBuJS+Nlh7+qqs9SHT3DG3coXJz63j28z525zAix7ucYnhl7fRTf3Is0dnJlJZgCgNNFtT8CPWkhiQGGNJYE/Q9cYIP2JmHQr+e+cGiy9fEKE/CbMRkoKRF/xR2FKFlH9dgPN34NH8Dn8u1RpfQFvncmSg4/y1Nr6jvrOAqodD7vjLplOvTOYctTDr5FUrNvFRiiRsUdNjOyJqdt1mq72t7Gd3DpB 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 1/28/26 19:59, Ankur Arora wrote: > riscv64-gcc-linux-gnu (v8.5) reports a compile time assert in: > > r[2] = DEFINE_RANGE(clamp_t(s64, fault_idx - radius, pg.start, pg.end), > clamp_t(s64, fault_idx + radius, pg.start, pg.end)); > > where it decides that pg.start > pg.end in: > clamp_t(s64, fault_idx + radius, pg.start, pg.end)); > > where pg comes from: > const struct range pg = DEFINE_RANGE(0, folio_nr_pages(folio) - 1); > > That does not seem like it could be true. Even for pg.start == pg.end, > we would need folio_test_large() to evaluate to false at compile time: > > static inline unsigned long folio_nr_pages(const struct folio *folio) > { > if (!folio_test_large(folio)) > return 1; > return folio_large_nr_pages(folio); > } > > Workaround by open coding the range computation. Also, simplify the type > declarations for the relevant variables. > > Reported-by: kernel test robot > Closes: https://lore.kernel.org/oe-kbuild-all/202601240453.QCjgGdJa-lkp@intel.com/ > Fixes: 93552c9a3350 ("mm: folio_zero_user: cache neighbouring pages") > Signed-off-by: Ankur Arora > --- > > Hi Andrew > > As David pointed out, the previous open coded version makes a few > unnecessary changes. Could you queue this one instead? > I'm late, maybe this is already upstream. > Thanks > Ankur > > > mm/memory.c | 17 ++++++++--------- > 1 file changed, 8 insertions(+), 9 deletions(-) > > diff --git a/mm/memory.c b/mm/memory.c > index ce933ee4a3dd..f5bfc082ab61 100644 > --- a/mm/memory.c > +++ b/mm/memory.c > @@ -7284,7 +7284,7 @@ void folio_zero_user(struct folio *folio, unsigned long addr_hint) > const unsigned long base_addr = ALIGN_DOWN(addr_hint, folio_size(folio)); > const long fault_idx = (addr_hint - base_addr) / PAGE_SIZE; > const struct range pg = DEFINE_RANGE(0, folio_nr_pages(folio) - 1); > - const int radius = FOLIO_ZERO_LOCALITY_RADIUS; > + const long radius = FOLIO_ZERO_LOCALITY_RADIUS; > struct range r[3]; > int i; > > @@ -7292,24 +7292,23 @@ void folio_zero_user(struct folio *folio, unsigned long addr_hint) > * Faulting page and its immediate neighbourhood. Will be cleared at the > * end to keep its cachelines hot. > */ > - r[2] = DEFINE_RANGE(clamp_t(s64, fault_idx - radius, pg.start, pg.end), > - clamp_t(s64, fault_idx + radius, pg.start, pg.end)); > + r[2] = DEFINE_RANGE(fault_idx - radius < (long)pg.start ? pg.start : fault_idx - radius, > + fault_idx + radius > (long)pg.end ? pg.end : fault_idx + radius); > + LGTM, although it could likely be made a bit more readable by using some temporary variables. const long fault_idx_low = fault_idx - radius; const long fault_idx_high = fault_idx + radius; r[2] = DEFINE_RANGE(fault_idx_low < (long)pg.start ? pg.start : fault_idx_low, fault_idx_high > (long)pg.end ? pg.end : fault_idx_high); Well, still a bit unreadable, so ... :) > > /* Region to the left of the fault */ > - r[1] = DEFINE_RANGE(pg.start, > - clamp_t(s64, r[2].start - 1, pg.start - 1, r[2].start)); > + r[1] = DEFINE_RANGE(pg.start, r[2].start - 1); > > /* Region to the right of the fault: always valid for the common fault_idx=0 case. */ > - r[0] = DEFINE_RANGE(clamp_t(s64, r[2].end + 1, r[2].end, pg.end + 1), > - pg.end); > + r[0] = DEFINE_RANGE(r[2].end + 1, pg.end); TBH, without the clamp that looks much more readable here. > > for (i = 0; i < ARRAY_SIZE(r); i++) { > const unsigned long addr = base_addr + r[i].start * PAGE_SIZE; > - const unsigned int nr_pages = range_len(&r[i]); > + const long nr_pages = (long)range_len(&r[i]); > struct page *page = folio_page(folio, r[i].start); > > if (nr_pages > 0) > - clear_contig_highpages(page, addr, nr_pages); > + clear_contig_highpages(page, addr, (unsigned int)nr_pages); Is that cast really required? -- Cheers, David