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[209.85.220.65]) by mx.google.com with SMTPS id r23sor493343lja.30.2019.07.02.22.54.30 for (Google Transport Security); Tue, 02 Jul 2019 22:54:31 -0700 (PDT) Received-SPF: pass (google.com: domain of vitalywool@gmail.com designates 209.85.220.65 as permitted sender) client-ip=209.85.220.65; Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b=AHbczLFR; spf=pass (google.com: domain of vitalywool@gmail.com designates 209.85.220.65 as permitted sender) smtp.mailfrom=vitalywool@gmail.com; dmarc=pass (p=NONE sp=QUARANTINE dis=NONE) header.from=gmail.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=fodI9RBCNqef8mpe31lNAJ/C8aPx3qCPQdaIULFPQEE=; b=AHbczLFRfqjuasmjmf30Hp49qfV0kAllz4rzpXWdPTIk4/ZlCNK3n/2EkaNRwYdgbz X+cN1RcUD9z36Tgkn2j1xJtIDZYR8Fht7jHZ/tMm4ZcIxsyU60SOhe/boS6RwAnsXUJo X5J8ToDtvEIH/qsrWau/X0ci+4WSMh89blfdBk66hBhOxobWrJ2qD8o9ZcEQGbqHbRBp x98npKojErQCAkBd65rFWVqeJfetB9Eo8/8KJ8O3sa4sy2+ZAFvp8qNadLIbuyNccfhf cp+k5AgU1VUR+Tk6JLRN/QSawNvIrPCeZdT/pV2Yk23NdGrbnxVXdeUMAsgH+KKqWd8L 5NUQ== X-Google-Smtp-Source: APXvYqwQEFSscdGA01+RoCapFWC3y9tcFL0+T1GOAo2m1WR3EkamuBGmQ24dndljkFKzDHi1wqKgkanBahuRl8HlrgY= X-Received: by 2002:a2e:80c8:: with SMTP id r8mr5330522ljg.168.1562133270780; Tue, 02 Jul 2019 22:54:30 -0700 (PDT) MIME-Version: 1.0 References: <20190702005122.41036-1-henryburns@google.com> <20190702141930.e31bf1c07a77514d976ef6e2@linux-foundation.org> <20190702152409.21c6c3787d125d61fb47840a@linux-foundation.org> In-Reply-To: <20190702152409.21c6c3787d125d61fb47840a@linux-foundation.org> From: Vitaly Wool Date: Wed, 3 Jul 2019 07:53:32 +0200 Message-ID: Subject: Re: [PATCH v2] mm/z3fold.c: Lock z3fold page before __SetPageMovable() To: Andrew Morton Cc: Henry Burns , Shakeel Butt , Vitaly Vul , Mike Rapoport , Xidong Wang , Jonathan Adams , Linux MM , LKML Content-Type: text/plain; charset="UTF-8" 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, Jul 3, 2019 at 12:24 AM Andrew Morton wrote: > > On Tue, 2 Jul 2019 15:17:47 -0700 Henry Burns wrote: > > > > > > > + if (can_sleep) { > > > > > > + lock_page(page); > > > > > > + __SetPageMovable(page, pool->inode->i_mapping); > > > > > > + unlock_page(page); > > > > > > + } else { > > > > > > + if (!WARN_ON(!trylock_page(page))) { > > > > > > + __SetPageMovable(page, pool->inode->i_mapping); > > > > > > + unlock_page(page); > > > > > > + } else { > > > > > > + pr_err("Newly allocated z3fold page is locked\n"); > > > > > > + WARN_ON(1); > > The WARN_ON will have already warned in this case. > > But the whole idea of warning in this case may be undesirable. We KNOW > that the warning will sometimes trigger (yes?). So what's the point in > scaring users? Well, normally a newly allocated page that we own should not be locked by someone else so this is worth a warning IMO. With that said, the else branch here appears to be redundant. ~Vitaly