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[209.85.208.175]) by smtp.gmail.com with ESMTPSA id j2sm21048ljc.49.2021.07.26.10.15.47 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 26 Jul 2021 10:15:48 -0700 (PDT) Received: by mail-lj1-f175.google.com with SMTP id m9so12151465ljp.7 for ; Mon, 26 Jul 2021 10:15:47 -0700 (PDT) X-Received: by 2002:a2e:3212:: with SMTP id y18mr12834084ljy.220.1627319747365; Mon, 26 Jul 2021 10:15:47 -0700 (PDT) MIME-Version: 1.0 References: <20210723205840.299280-1-agruenba@redhat.com> <20210723205840.299280-2-agruenba@redhat.com> <20210726163326.GK20621@quack2.suse.cz> In-Reply-To: <20210726163326.GK20621@quack2.suse.cz> From: Linus Torvalds Date: Mon, 26 Jul 2021 10:15:31 -0700 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH v3 1/7] iov_iter: Introduce fault_in_iov_iter helper To: Jan Kara Cc: Andreas Gruenbacher , Alexander Viro , Christoph Hellwig , "Darrick J. Wong" , Matthew Wilcox , cluster-devel , linux-fsdevel , Linux Kernel Mailing List , ocfs2-devel@oss.oracle.com Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jul 26, 2021 at 9:33 AM Jan Kara wrote: > > On Fri 23-07-21 22:58:34, Andreas Gruenbacher wrote: > > + gup_flags = FOLL_TOUCH | FOLL_POPULATE; > > I don't think FOLL_POPULATE makes sense here. It makes sense only with > FOLL_MLOCK and determines whether mlock(2) should fault in missing pages or > not. Yeah, it won't hurt, but FOLL_POPULATE doesn't actually do anything unless FOLL_MLOCK is set. It is, as you say, a magic flag just for mlock. The only ones that should matter are FOLL_WRITE (for obvious reasons) and FOLL_TOUCH (to set the accessed and dirty bits, rather than just th protection bits) Linus