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 X-Spam-Level: X-Spam-Status: No, score=-3.6 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 910ADC43460 for ; Thu, 22 Apr 2021 15:48:17 +0000 (UTC) Received: from lists.sourceforge.net (lists.sourceforge.net [216.105.38.7]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 19A25611CD; Thu, 22 Apr 2021 15:48:15 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 19A25611CD Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=linux-f2fs-devel-bounces@lists.sourceforge.net Received: from [127.0.0.1] (helo=sfs-ml-4.v29.lw.sourceforge.com) by sfs-ml-4.v29.lw.sourceforge.com with esmtp (Exim 4.90_1) (envelope-from ) id 1lZbYr-0002mL-Gn; Thu, 22 Apr 2021 15:48:13 +0000 Received: from [172.30.20.202] (helo=mx.sourceforge.net) by sfs-ml-4.v29.lw.sourceforge.com with esmtps (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lZbYp-0002mD-Ff for linux-f2fs-devel@lists.sourceforge.net; Thu, 22 Apr 2021 15:48:11 +0000 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=sourceforge.net; s=x; h=Content-Type:MIME-Version:Message-ID:Subject:Cc:To: From:Date:Sender:Reply-To:Content-Transfer-Encoding:Content-ID: Content-Description:Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc :Resent-Message-ID:In-Reply-To:References:List-Id:List-Help:List-Unsubscribe: List-Subscribe:List-Post:List-Owner:List-Archive; bh=UdV/xsRrw93wPeJQm6RKQW5H8PJQYFUytR36G8I3Ovs=; b=H4Nra5ykUzZ4loK3wbCUwCpHVv BwRJxf/OjMsp73payusJ5uyBtcxRDifdsxsG5KLlq5itfCIo4JIGoTG+C0DVie/bK3miLWQPzi43S g7AThf09zgxzmX4pUmx0lVCVBCTvowMn62bqZinTqKhgW0hVL6DNL38LMm+NWWicbkSE=; DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=sf.net; s=x ; h=Content-Type:MIME-Version:Message-ID:Subject:Cc:To:From:Date:Sender: Reply-To:Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date :Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:In-Reply-To: References:List-Id:List-Help:List-Unsubscribe:List-Subscribe:List-Post: List-Owner:List-Archive; bh=UdV/xsRrw93wPeJQm6RKQW5H8PJQYFUytR36G8I3Ovs=; b=i t+I8w8Sx+mwOlBesGUpnFh/6RbCIHX/TXGyhfxJl0Ty4KjioK6+BTr1CLcMYalIrGvJ6gNMIKrAL9 lprkNXTL4H0KonUThT5yf452avXp7xA52FCIHOBH6zecCZfofb6yKYmUtyG60kmedqyXctHLV/f95 KsmvER6tcetF2QfM=; Received: from casper.infradead.org ([90.155.50.34]) by sfi-mx-2.v28.lw.sourceforge.com with esmtps (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.92.3) id 1lZbYl-0000Fr-9H for linux-f2fs-devel@lists.sourceforge.net; Thu, 22 Apr 2021 15:48:12 +0000 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=Content-Type:MIME-Version:Message-ID: Subject:Cc:To:From:Date:Sender:Reply-To:Content-Transfer-Encoding:Content-ID: Content-Description:In-Reply-To:References; bh=UdV/xsRrw93wPeJQm6RKQW5H8PJQYFUytR36G8I3Ovs=; b=GInvtbQpV+q1DfmdVS3oUS6+UZ oJOQpNnMhVadvMnLboc/BgbyGoaS2y/02q4Dvr5qx00RrWraMLUi6FpXwt/Qdeon62s0vQIQDJOaF j1fHHu/tF67JR3OMAf0DukLYxweRgxgMIHTjK3xuPYX5oy/Knhm5wQaG8Mplvv6MjpnEwQZFRxjrg ffTLs1D2KBaCfaWOTp0rv5HjkS3k+Jo7LxPAneC6YHV7+OjjNQ/aRxi7XbDLSsc0GWStnE1m78AXN Lh8jH79P0t+0OQCsRvHUf0n2RhSrHFvtbjBosTi7TuuejFtDisiTxJMBlpTjhoufpLKH20HcozL2M uVuyaThw==; Received: from willy by casper.infradead.org with local (Exim 4.94 #2 (Red Hat Linux)) id 1lZbXl-000Tl5-4W; Thu, 22 Apr 2021 15:47:29 +0000 Date: Thu, 22 Apr 2021 16:47:05 +0100 From: Matthew Wilcox To: linux-mm@kvack.org, linux-fsdevel@vger.kernel.org Message-ID: <20210422154705.GO3596236@casper.infradead.org> MIME-Version: 1.0 Content-Disposition: inline X-Headers-End: 1lZbYl-0000Fr-9H Subject: [f2fs-dev] [RFC] Reclaiming PG_private X-BeenThere: linux-f2fs-devel@lists.sourceforge.net X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-f2fs-devel@lists.sourceforge.net Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: linux-f2fs-devel-bounces@lists.sourceforge.net We're perenially short of page flags, and I don't really see the need for PG_private to exist. We have 32/64 bits available in page->private, and we don't seem to need the extra bit. Most users store a pointer in page->private, and so PagePrivate() being implemented as page->private != 0 is appropriate. Some users simply SetPagePrivate() and don't touch page->private. Those users could instead set page->private to 1. Do we have any users which want to SetPagePrivate() and want to put a meaningful zero value in page->private? AFS stores a pair of integers in page->private, but the second integer must be greater than the first one, so they can't both be zero. btrfs stores a real or fake pointer. buffer_head filesystems generally store a buffer_head pointer. fscrypt stores a pointer. erofs stores a real or fake pointer. f2fs does set PagePrivate and also set the pointer to NULL, but it's not clear whether that's intentional. iomap stores a pointer. jfs stores a pointer. nfs stores a pointer. ntfs stores a pointer. orangefs stores a pointer. So ... what's going on with f2fs? Does it need to distinguish between a page which has f2fs_set_page_private(page, 0) called on it, and a page which has had f2fs_clear_page_private() called on it? _______________________________________________ Linux-f2fs-devel mailing list Linux-f2fs-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel