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 EEF85C00140 for ; Fri, 5 Aug 2022 12:23:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240676AbiHEMXV (ORCPT ); Fri, 5 Aug 2022 08:23:21 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60902 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236449AbiHEMXU (ORCPT ); Fri, 5 Aug 2022 08:23:20 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 02B8D264B for ; Fri, 5 Aug 2022 05:23:18 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1659702197; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=6XfQitbedfzAjVF7NuSHjlQLXbv3BgZJq1rQlqHH/PQ=; b=IlZPTxndxSVA/CizdjUBuWKiIF6lIO08dcp/DDEK7XjDG0Ku4hgJ1iuRLM87A2q4VNjbJr Qe1fBf9Ui4HlYYeKKm3j5M0MRZ9/PrE8sKyKEabKXw5ge+XFnkCnoBHHIh11/Z0iGjwjh4 UqGavuY/cn8yqzx/Jy3T+Aq5Yo1Btsc= Received: from mimecast-mx02.redhat.com (mx3-rdu2.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-367-vEsnCNv3NgqZcY_wQER0ng-1; Fri, 05 Aug 2022 08:23:13 -0400 X-MC-Unique: vEsnCNv3NgqZcY_wQER0ng-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.rdu2.redhat.com [10.11.54.4]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 9C2893C138B3; Fri, 5 Aug 2022 12:23:10 +0000 (UTC) Received: from fedora (unknown [10.40.193.205]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 0F6392026D4C; Fri, 5 Aug 2022 12:23:08 +0000 (UTC) Date: Fri, 5 Aug 2022 14:23:06 +0200 From: Lukas Czerner To: Eric Biggers Cc: linux-ext4@vger.kernel.org, jlayton@kernel.org, tytso@mit.edu, linux-fsdevel@vger.kernel.org, Dave Chinner , Christoph Hellwig , Jan Kara Subject: Re: [PATCH v2 2/3] fs: record I_DIRTY_TIME even if inode already has I_DIRTY_INODE Message-ID: <20220805122306.anavrrmt6lqwd2yt@fedora> References: <20220803105340.17377-1-lczerner@redhat.com> <20220803105340.17377-2-lczerner@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Scanned-By: MIMEDefang 2.78 on 10.11.54.4 Precedence: bulk List-ID: X-Mailing-List: linux-ext4@vger.kernel.org On Fri, Aug 05, 2022 at 01:05:45AM -0700, Eric Biggers wrote: > On Wed, Aug 03, 2022 at 12:53:39PM +0200, Lukas Czerner wrote: > > diff --git a/include/linux/fs.h b/include/linux/fs.h > > index 9ad5e3520fae..2243797badf2 100644 > > --- a/include/linux/fs.h > > +++ b/include/linux/fs.h > > @@ -2245,9 +2245,9 @@ static inline void kiocb_clone(struct kiocb *kiocb, struct kiocb *kiocb_src, > > * The inode itself only has dirty timestamps, and the > > * lazytime mount option is enabled. We keep track of this > > * separately from I_DIRTY_SYNC in order to implement > > * lazytime. This gets cleared if I_DIRTY_INODE > > - * (I_DIRTY_SYNC and/or I_DIRTY_DATASYNC) gets set. I.e. > > - * either I_DIRTY_TIME *or* I_DIRTY_INODE can be set in > > - * i_state, but not both. I_DIRTY_PAGES may still be set. > > + * (I_DIRTY_SYNC and/or I_DIRTY_DATASYNC) gets set. But > > + * I_DIRTY_TIME can still be set if I_DIRTY_SYNC is already > > + * in place. > > I'm still having a hard time understanding the new semantics. The first > sentence above needs to be updated since I_DIRTY_TIME no longer means "the inode > itself only has dirty timestamps", right? The problem is that it was always assumed that I_DIRTY_INODE superseeds I_DIRTY_TIME and so it would get cleared in __mark_inode_dirty() when we have I_DIRTY_INODE. That's true, we call sb->s_op->dirty_inode(), the time update gets pushed into on-disk inode structure, I_DIRTY_TIME cleared and it will get queued for writeback. Any subsequent dirtying with I_DIRTY_TIME gets ignored simply because I_DIRTY_INODE is already set in i_state. But in ext4 this time update will never get pushed into on disk inode and there is no I_DIRTY_TIME so once the writeback is done we've lost all those I_DIRTY_TIME updates in between even if there was a sync. Now, we still clear I_DIRTY_TIME when we get I_DIRTY_INODE, but any subsequent I_DIRTY_TIME only updates won't be ignored and we set it into i_state. After the writeback is done it'll be moved to b_dirty_time list. So I am not sure how would you like it to be re-worded, simply removing the 'only' would be ok? > > Also, have you checked all the places that I_DIRTY_TIME is used and verified > they do the right thing now? What about inode_is_dirtytime_only()? Yes, that's fine, despite the slightly misleading name ;) > > Also what is the precise meaning of the flags argument to ->dirty_inode now? > > sb->s_op->dirty_inode(inode, > flags & (I_DIRTY_INODE | I_DIRTY_TIME)); > > Note that dirty_inode is documented in Documentation/filesystems/vfs.rst. Don't know. It alredy don't mention I_DIRTY_SYNC that can be there as well. Additionaly it can have I_DIRTY_TIME to inform the fs we have a dirty timestamp as well (in case of lazytime). Perhaps we can add: If the inode has dirty timestamp and lazytime is enabled I_DIRTY_TIME will be set in the flags. -Lukas > > - Eric >