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[198.145.29.99]) by mx.google.com with ESMTPS id c11si81263pgk.383.2019.07.02.15.24.10 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 02 Jul 2019 15:24:10 -0700 (PDT) Received-SPF: pass (google.com: domain of akpm@linux-foundation.org designates 198.145.29.99 as permitted sender) client-ip=198.145.29.99; Authentication-Results: mx.google.com; dkim=pass header.i=@kernel.org header.s=default header.b="W75jKD/r"; spf=pass (google.com: domain of akpm@linux-foundation.org designates 198.145.29.99 as permitted sender) smtp.mailfrom=akpm@linux-foundation.org Received: from akpm3.svl.corp.google.com (unknown [104.133.8.65]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 9E41A218E0; Tue, 2 Jul 2019 22:24:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1562106249; bh=paq3rBGRhLW2Qpm44+MevTEqQRAXrHYmPUYx69zxz/M=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=W75jKD/rNzq2PuPQpltd8H0MgbE9WV7KUI0OFTUGJiv4fPwyzhUtfkvdxeVlqOkFL 4b4xWxBzPXNyswEVKmLNwRI3tbXoIQnWMp3m/zqn80P3dgemCD1FV6iQddz/Pfn4vq yEgltIRFEizLLcYCPK78BUk8j0MPX6sFGN8Y+qYk= Date: Tue, 2 Jul 2019 15:24:09 -0700 From: Andrew Morton To: Henry Burns Cc: Shakeel Butt , Vitaly Wool , Vitaly Vul , Mike Rapoport , Xidong Wang , Jonathan Adams , Linux MM , LKML Subject: Re: [PATCH v2] mm/z3fold.c: Lock z3fold page before __SetPageMovable() Message-Id: <20190702152409.21c6c3787d125d61fb47840a@linux-foundation.org> In-Reply-To: References: <20190702005122.41036-1-henryburns@google.com> <20190702141930.e31bf1c07a77514d976ef6e2@linux-foundation.org> X-Mailer: Sylpheed 3.7.0 (GTK+ 2.24.32; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit 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 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? Also, pr_err(...)+WARN_ON(1) can basically be replaced with WARN(1, ...)? > > > > > + } > > > > > + }