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[61.68.212.105]) by smtp.gmail.com with ESMTPSA id z126sm3602084pfc.94.2020.08.21.15.42.45 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 21 Aug 2020 15:42:45 -0700 (PDT) Date: Sat, 22 Aug 2020 08:42:40 +1000 From: Nicholas Piggin Subject: Re: [PATCH v6 01/12] mm/vmalloc: fix vmalloc_to_page for huge vmap mappings To: Andrew Morton References: <20200821151216.1005117-1-npiggin@gmail.com> <20200821151216.1005117-2-npiggin@gmail.com> <20200821130757.289570e4bb491672087d3396@linux-foundation.org> In-Reply-To: <20200821130757.289570e4bb491672087d3396@linux-foundation.org> MIME-Version: 1.0 Message-Id: <1598049375.u9pf1rciw6.astroid@bobo.none> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org, Christoph Hellwig , linux-mm@kvack.org, Zefan Li , Jonathan Cameron , linuxppc-dev@lists.ozlabs.org Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" Excerpts from Andrew Morton's message of August 22, 2020 6:07 am: > On Sat, 22 Aug 2020 01:12:05 +1000 Nicholas Piggin wr= ote: >=20 >> vmalloc_to_page returns NULL for addresses mapped by larger pages[*]. >> Whether or not a vmap is huge depends on the architecture details, >> alignments, boot options, etc., which the caller can not be expected >> to know. Therefore HUGE_VMAP is a regression for vmalloc_to_page. >=20 > I assume this doesn't matter in current mainline? > If wrong, then what are the user-visible effects and why no cc:stable? I haven't heard any reports, but in theory it could cause a prolem. The commit 029c54b095995 from the changelog was made to paper over it. But that was fixed properly afterward I think by 737326aa510b. Not sure of the user visible problems currently. I think generally you wouldn't do vmalloc_to_page() on ioremap() memory, so maybe callilng it a regression is a bit strong. _Technically_ a regression, maybe. Thanks, Nick