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[195.135.220.15]) by mx.google.com with ESMTPS id e129si9092053pgc.333.2019.02.07.11.26.06 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 07 Feb 2019 11:26:06 -0800 (PST) Received-SPF: softfail (google.com: domain of transitioning dave@stgolabs.net does not designate 195.135.220.15 as permitted sender) client-ip=195.135.220.15; Authentication-Results: mx.google.com; spf=softfail (google.com: domain of transitioning dave@stgolabs.net does not designate 195.135.220.15 as permitted sender) smtp.mailfrom=dave@stgolabs.net X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 68F3DAF29; Thu, 7 Feb 2019 19:26:04 +0000 (UTC) Date: Thu, 7 Feb 2019 11:25:55 -0800 From: Davidlohr Bueso To: Paul Burton Cc: "akpm@linux-foundation.org" , "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" , Ralf Baechle , James Hogan , "linux-mips@vger.kernel.org" , Davidlohr Bueso Subject: Re: [PATCH 2/2] MIPS/c-r4k: do no use mmap_sem for gup_fast() Message-ID: <20190207192555.n3qtle4yqmfb2tpo@linux-r8p5> Mail-Followup-To: Paul Burton , "akpm@linux-foundation.org" , "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" , Ralf Baechle , James Hogan , "linux-mips@vger.kernel.org" , Davidlohr Bueso References: <20190207053740.26915-1-dave@stgolabs.net> <20190207053740.26915-3-dave@stgolabs.net> <20190207190007.jz4rz6e6qxwazxm7@pburton-laptop> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Disposition: inline In-Reply-To: <20190207190007.jz4rz6e6qxwazxm7@pburton-laptop> User-Agent: NeoMutt/20180323 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: On Thu, 07 Feb 2019, Paul Burton wrote: >Hi Davidlohr, > >On Wed, Feb 06, 2019 at 09:37:40PM -0800, Davidlohr Bueso wrote: >> It is well known that because the mm can internally >> call the regular gup_unlocked if the lockless approach >> fails and take the sem there, the caller must not hold >> the mmap_sem already. >> >> Fixes: e523f289fe4d (MIPS: c-r4k: Fix sigtramp SMP call to use kmap) >> Cc: Ralf Baechle >> Cc: Paul Burton >> Cc: James Hogan >> Cc: linux-mips@vger.kernel.org >> Signed-off-by: Davidlohr Bueso > >Thanks - this looks good, but: > > 1) The problem it fixes was introduced in v4.8. > > 2) Commit adcc81f148d7 ("MIPS: math-emu: Write-protect delay slot > emulation pages") actually left flush_cache_sigtramp unused, and has > been backported to stable kernels also as far as v4.8. > >Therefore this will just fix code that never gets called, and I'll go >delete the whole thing instead. Even better. Thanks, Davidlohr