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 DFF28C433ED for ; Thu, 13 May 2021 19:40:30 +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 178C261358; Thu, 13 May 2021 19:40:30 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 178C261358 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 1lhHC7-0007Y4-OO; Thu, 13 May 2021 19:40:27 +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 1lhHC5-0007Xw-RN for linux-f2fs-devel@lists.sourceforge.net; Thu, 13 May 2021 19:40:25 +0000 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=sourceforge.net; s=x; h=In-Reply-To:Content-Type:MIME-Version:References: 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:List-Id:List-Help:List-Unsubscribe: List-Subscribe:List-Post:List-Owner:List-Archive; bh=O8VUCTzxVSvxa3wVLPh12tovGUEtpcQQ1uxw15XLCZg=; b=Pd7IH2h+3C+0myH6gkQFNKpLdt rSyGPBCOaISAA2cCvyOOMAoqCldgsKvGVz8qeLZYW1PTMOkizWk2rGJzIqTozSCevyOKQ+1cQEHTH EC9JbNZTNzSneUfeb4eORSsB3y8LSQ2/9Wv1cyOaXXKKgSXLUxsHl1AL0ret1sMsi4jc=; DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=sf.net; s=x ; h=In-Reply-To:Content-Type:MIME-Version:References: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:List-Id:List-Help:List-Unsubscribe:List-Subscribe: List-Post:List-Owner:List-Archive; bh=O8VUCTzxVSvxa3wVLPh12tovGUEtpcQQ1uxw15XLCZg=; b=cDl2E/k8gKMRQthu2TjF2EcWXp WemwGpxPCqh4jA2XcvF/ISlj1rjn7CSwk2cc/MNhVEZscMy+/b35FB/MTelEpq3W1cYLV+LJHeZTi CKdCObd7RHD3VJJeAVU1Q5GsxkukAlYX3NxhiLWJSeszpAqPaWpqR8GiS4IgIro5V7eA=; 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 1lhHC1-0005Ka-OH for linux-f2fs-devel@lists.sourceforge.net; Thu, 13 May 2021 19:40:26 +0000 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=O8VUCTzxVSvxa3wVLPh12tovGUEtpcQQ1uxw15XLCZg=; b=S6oimQ+wSggkHbM04qw7qRcCif KxJ6s1XOGzoOpDq2Ik3+iRiwQfDzyBbe0DuWvzC9OR6jXy0kTrw+5iOA+LaoPKGquDRsAkhwtB1fn RAzftQHw1WIHsSHGyasEKCqK6uNc5md/QTdqO/gAX92LY/xjc3aThySb167Hsk1QbFODw0SI99hZD FJ7grq8hsbbFuQNaq3roe74z070sMG/wQF5s2VcKbYsspDgU3/f5jnSJCnX9ybUtPMZoBzeRLnZAR rt44B26yeOFUgC3PP1bOEdl/6GZRpu188I1tXE0mY9mkIB2XhLxPk/VtnEIL19/rPQgwFkGk1TQkJ GlbkDIiw==; Received: from willy by casper.infradead.org with local (Exim 4.94 #2 (Red Hat Linux)) id 1lhHAV-009iZc-F6; Thu, 13 May 2021 19:39:06 +0000 Date: Thu, 13 May 2021 20:38:47 +0100 From: Matthew Wilcox To: Jan Kara Message-ID: References: <20210512101639.22278-1-jack@suse.cz> <20210512134631.4053-3-jack@suse.cz> <20210513190114.GJ2734@quack2.suse.cz> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20210513190114.GJ2734@quack2.suse.cz> X-Headers-End: 1lhHC1-0005Ka-OH Subject: Re: [f2fs-dev] [PATCH 03/11] mm: Protect operations adding pages to page cache with invalidate_lock 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-cifs@vger.kernel.org, Damien Le Moal , linux-ext4@vger.kernel.org, Ted Tso , "Darrick J. Wong" , Jeff Layton , Steve French , Dave Chinner , linux-f2fs-devel@lists.sourceforge.net, Christoph Hellwig , linux-mm@kvack.org, Miklos Szeredi , linux-fsdevel@vger.kernel.org, Jaegeuk Kim , ceph-devel@vger.kernel.org, Johannes Thumshirn , linux-xfs@vger.kernel.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: linux-f2fs-devel-bounces@lists.sourceforge.net On Thu, May 13, 2021 at 09:01:14PM +0200, Jan Kara wrote: > On Wed 12-05-21 15:40:21, Matthew Wilcox wrote: > > Remind me (or, rather, add to the documentation) why we have to hold the > > invalidate_lock during the call to readpage / readahead, and we don't just > > hold it around the call to add_to_page_cache / add_to_page_cache_locked > > / add_to_page_cache_lru ? I appreciate that ->readpages is still going > > to suck, but we're down to just three implementations of ->readpages now > > (9p, cifs & nfs). > > There's a comment in filemap_create_page() trying to explain this. We need > to protect against cases like: Filesystem with 1k blocksize, file F has > page at index 0 with uptodate buffer at 0-1k, rest not uptodate. All blocks > underlying page are allocated. Now let read at offset 1k race with hole > punch at offset 1k, length 1k. > > read() hole punch > ... > filemap_read() > filemap_get_pages() > - page found in the page cache but !Uptodate > filemap_update_page() > locks everything > truncate_inode_pages_range() > lock_page(page) > do_invalidatepage() > unlock_page(page) > locks page > filemap_read_page() Ah, this is the partial_start case, which means that page->mapping is still valid. But that means that do_invalidatepage() was called with (offset 1024, length 1024), immediately after we called zero_user_segment(). So isn't this a bug in the fs do_invalidatepage()? The range from 1k-2k _is_ uptodate. It's been zeroed in memory, and if we were to run after the "free block" below, we'd get that memory zeroed again. > ->readpage() > block underlying offset 1k > still allocated -> map buffer > free block under offset 1k > submit IO -> corrupted data > > If you think I should expand it to explain more details, please tell. > Or maybe I can put more detailed discussion like above into the changelog? > > Why not: > > > > __init_rwsem(&mapping->invalidate_lock, "mapping.invalidate_lock", > > &sb->s_type->invalidate_lock_key); > > I replicated what we do for i_rwsem but you're right, this is better. > Updated. Hmm, there's a few places we should use __init_rwsem() ... something for my "when bored" pile of work. _______________________________________________ Linux-f2fs-devel mailing list Linux-f2fs-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel