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[2607:7c80:54:e::133]) by mx.google.com with ESMTPS id a3si1727354pff.117.2019.05.15.04.49.59 for (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Wed, 15 May 2019 04:49:59 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of willy@infradead.org designates 2607:7c80:54:e::133 as permitted sender) client-ip=2607:7c80:54:e::133; Authentication-Results: mx.google.com; dkim=pass header.i=@infradead.org header.s=bombadil.20170209 header.b=NJTP+oeO; spf=pass (google.com: best guess record for domain of willy@infradead.org designates 2607:7c80:54:e::133 as permitted sender) smtp.mailfrom=willy@infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Transfer-Encoding :Content-Type:MIME-Version:References:Message-ID:Subject:Cc:To:From:Date: Sender:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id:List-Help: List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=mc63LhWg2+r8G6LyepIMoQgzu86nCTP3tUKDYnTysXo=; b=NJTP+oeOJ2KTSYKFCNvyNdWTdl pkNAYs4PuM9AmwDSp+SRpJ2s5RQMLUOl+KvQeTbeCBBsWXMw//5EKv/S1ECv3NJFKztodOWSY+uLL x6LYCjisteMmKVkA80CIMjyz4BJLmCPomB9t/OOkhdsAJ/bWKo979xjvYWMODNwDryd1NyB1llGar THnvqn8pLDBzW6vZ4tX+ssfHbXZ49/xxkOo0JV+TI5LpknghfuJv6cbIJh7CPO5Lot3bObhMxV3Yt Fxo2c5686rUezL0nFqDfxSaVnWqnD555AqmYQNfVM1IDIDTE/CQfBBHzPVUdAf/CZJirFW1pVKzht Sl5ZZM5w==; Received: from willy by bombadil.infradead.org with local (Exim 4.90_1 #2 (Red Hat Linux)) id 1hQsPy-0000MW-Qa; Wed, 15 May 2019 11:49:54 +0000 Date: Wed, 15 May 2019 04:49:54 -0700 From: Matthew Wilcox To: Michal =?iso-8859-1?Q?Koutn=FD?= Cc: khlebnikov@yandex-team.ru, akpm@linux-foundation.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, oleg@redhat.com Subject: Re: mm: use down_read_killable for locking mmap_sem in access_remote_vm Message-ID: <20190515114954.GB31704@bombadil.infradead.org> References: <155790847881.2798.7160461383704600177.stgit@buzz> <20190515083825.GJ13687@blackbody.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20190515083825.GJ13687@blackbody.suse.cz> User-Agent: Mutt/1.9.2 (2017-12-15) 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 Wed, May 15, 2019 at 10:38:26AM +0200, Michal Koutný wrote: > Hi, > making this holder of mmap_sem killable was for the reasons of /proc/... > diagnostics was an idea I was pondeering too. However, I think the > approach of pretending we read 0 bytes is not correct. The API would IMO > need to be extended to allow pass a result such as EINTR to the end > caller. > Why do you think it's safe to return just 0? _killable_, not _interruptible_. The return value will never be seen by userspace because it's dead.