From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id AA823ECAAA1 for ; Mon, 12 Sep 2022 04:37:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229569AbiILEhY (ORCPT ); Mon, 12 Sep 2022 00:37:24 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:38986 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229459AbiILEhW (ORCPT ); Mon, 12 Sep 2022 00:37:22 -0400 Received: from mail-pj1-x102c.google.com (mail-pj1-x102c.google.com [IPv6:2607:f8b0:4864:20::102c]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 872601B788 for ; Sun, 11 Sep 2022 21:37:21 -0700 (PDT) Received: by mail-pj1-x102c.google.com with SMTP id m10-20020a17090a730a00b001fa986fd8eeso11187573pjk.0 for ; Sun, 11 Sep 2022 21:37:21 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:from:to:cc:subject:date; bh=cWYgHAq5ny4DLQrfpTw7PtOGqiMCf0iPFjcOwcgSxlU=; b=Crz6FiphaYqTlC2dMlFPl+GwYjNz2ePWhRHPifOOZt/mZkbMeSoz4MuYTmF5cUoQNV Ib2DdBKuxKpN4/oSzh9rMu7CwmDjxWe16386T+j6dS3h7wVp0ozBwsgrxdCGHUnw0Xsh r/dfL1YnFAUl4FJS9gBZ8KLZgjLfg5gVm+e1s= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-message-state:from:to:cc:subject:date; bh=cWYgHAq5ny4DLQrfpTw7PtOGqiMCf0iPFjcOwcgSxlU=; b=cW0cFiEBAKw6aRzZmTMt4Q+RNHflwmXuXO3eTD1uFPo7peDd54t6rwj6cBwsMdP6Rf nlqC77ZwyopUbb3pH7W6z2B5U0RmzLSRiYaaU2eIjKxVxAO2+linIU7GoaFy3oN3Nd1Z R2F5ICNRJGwzGa+GXmPyPbFu/Pqj0mwVh0eSk8aVmhJMmfGH9tfUve81Hzte/59mv3dx ho4mDNlznws/3LhmrlM7Z4liNhrKIL9edaOV7HwsUMIPjuFGV7a1aLDB/LoY8RDlp00l nK4o0iZAFWbjbVRRthzc/VOIT881xSXMGd3lqdSuRYyG0mdfZPwI1qc0mGSdPo28ce/d qa2w== X-Gm-Message-State: ACgBeo2yaxyxN1ZNfFwK9Iu4x1chAxoQU7WZaUDoDCN222PenqvwIVWG S/O8s0JcRUeXqyw0q+HoAMirQw== X-Google-Smtp-Source: AA6agR4KogsmNIRLD4nHdnmzTog+YMrXg3rCn64hzFxSQEP2+xciQ+EsdoGOUp+jKcNUtuqQoUTISg== X-Received: by 2002:a17:902:a388:b0:176:e571:4923 with SMTP id x8-20020a170902a38800b00176e5714923mr24847717pla.6.1662957441064; Sun, 11 Sep 2022 21:37:21 -0700 (PDT) Received: from google.com ([240f:75:7537:3187:7b09:9fce:b16b:c111]) by smtp.gmail.com with ESMTPSA id 11-20020a63040b000000b004347838b12bsm4431251pge.75.2022.09.11.21.37.18 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 11 Sep 2022 21:37:20 -0700 (PDT) Date: Mon, 12 Sep 2022 13:37:15 +0900 From: Sergey Senozhatsky To: Brian Geffon , Minchan Kim Cc: Andrew Morton , Nitin Gupta , linux-kernel@vger.kernel.org, Suleiman Souhlal , Rom Lemarchand , linux-mm@kvack.org, Sergey Senozhatsky Subject: Re: [RESEND RFC] zram: Allow rw_page when page isn't written back. Message-ID: References: <20220908125037.1119114-1-bgeffon@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On (22/09/09 17:30), Sergey Senozhatsky wrote: > > +++ b/drivers/block/zram/zram_drv.h > > @@ -50,6 +50,7 @@ enum zram_pageflags { > > ZRAM_UNDER_WB, /* page is under writeback */ > > ZRAM_HUGE, /* Incompressible page */ > > ZRAM_IDLE, /* not accessed page since last idle marking */ > > + ZRAM_NO_WB, /* Do not allow page to be written back */ > > > > __NR_ZRAM_PAGEFLAGS, > > }; > > Unrelated but somehow related. > > I wonder if it's time for us to introduce a dedicated, say u16, > flags member to struct zram_table_entry. Unless my calculations > are extremely wrong, we are about to run out of spare bits in > zram_table_entry::flags on 32-bit systems. Looking at it more - I wonder why do we define ZRAM_FLAG_SHIFT as 24? This is far more than maximum zram object size. Our max size needs PAGE_SHIFT bits (which is normally 12 bits, can be up to 16 (for 64k arm64 pages)). So we probably can start defining ZRAM_FLAG_SHIFT as (PAGE_SHIFT + 1). Or am I missing something? --- diff --git a/drivers/block/zram/zram_drv.h b/drivers/block/zram/zram_drv.h index b4eecef2a11f..cb8f1f644baf 100644 --- a/drivers/block/zram/zram_drv.h +++ b/drivers/block/zram/zram_drv.h @@ -39,7 +39,7 @@ * The lower ZRAM_FLAG_SHIFT bits is for object size (excluding header), * the higher bits is for zram_pageflags. */ -#define ZRAM_FLAG_SHIFT 24 +#define ZRAM_FLAG_SHIFT (PAGE_SHIFT + 1) /* Flags for zram pages (table[page_no].flags) */ enum zram_pageflags {