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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2B730C77B7C for ; Thu, 4 May 2023 15:55:59 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 495DA900004; Thu, 4 May 2023 11:55:58 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 41F20900002; Thu, 4 May 2023 11:55:58 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 2C114900004; Thu, 4 May 2023 11:55:58 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from smtp-out2.suse.de (smtp-out2.suse.de [195.135.220.29]) by kanga.kvack.org (Postfix) with ESMTP id 0999C900002 for ; Thu, 4 May 2023 11:55:58 -0400 (EDT) Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by smtp-out2.suse.de (Postfix) with ESMTPS id 1BF7D1FD7E; Thu, 4 May 2023 15:55:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_rsa; t=1683215757; h=from:from:reply-to: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=Hs+BLfN/0kNjEK2oUqlUv453FE71ldsqaBdWU5OoWZo=; b=IULcFMzhZk2/u3IGIBLKjmfecbiZdNWFBMDe21BltjDT2hKk2qpnRs+9+Z2i50HzOG3uWY rIvlC54YVJaa5/G9wtDByFpEctWCEmOkiHzbUxK+fwxid4hJmwFcm1wS8hyRRh/O3GJAz9 mcvGKcqtv+zjLI+tOZmzXQnOqUWkmnk= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_ed25519; t=1683215757; h=from:from:reply-to: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=Hs+BLfN/0kNjEK2oUqlUv453FE71ldsqaBdWU5OoWZo=; b=PJBKliX3YTxaHWg2wjYFrF5cfHLpLkaeDlTEYUJakGRbqJW16QM61U/JfUF6Fdm6xoQ6Df Tqs1ezMWlP87uTDw== Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by imap2.suse-dmz.suse.de (Postfix) with ESMTPS id 0D44813444; Thu, 4 May 2023 15:55:57 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id f3YpA43VU2RHMgAAMHmgww (envelope-from ); Thu, 04 May 2023 15:55:57 +0000 Received: by quack3.suse.cz (Postfix, from userid 1000) id 5E8FFA0722; Thu, 4 May 2023 17:55:56 +0200 (CEST) Date: Thu, 4 May 2023 17:55:56 +0200 From: Jan Kara To: Matthew Wilcox Cc: Christoph Hellwig , Ilya Dryomov , Jan Kara , Johannes Thumshirn , Jens Axboe , linux-block@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm: always respect QUEUE_FLAG_STABLE_WRITES on the block device Message-ID: <20230504155556.t6byee6shgb27pw5@quack3> References: <20230504105624.9789-1-idryomov@gmail.com> <20230504135515.GA17048@lst.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: 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 Thu 04-05-23 15:16:39, Matthew Wilcox wrote: > On Thu, May 04, 2023 at 03:55:15PM +0200, Christoph Hellwig wrote: > > On Thu, May 04, 2023 at 12:56:24PM +0200, Ilya Dryomov wrote: > > > Commit 1cb039f3dc16 ("bdi: replace BDI_CAP_STABLE_WRITES with a queue > > > and a sb flag") introduced a regression for the raw block device use > > > case. Capturing QUEUE_FLAG_STABLE_WRITES flag in set_bdev_super() has > > > the effect of respecting it only when there is a filesystem mounted on > > > top of the block device. If a filesystem is not mounted, block devices > > > that do integrity checking return sporadic checksum errors. > > > > With "If a file system is not mounted" you want to say "when accessing > > a block device directly" here, right? The two are not exclusive.. > > > > > Additionally, this commit made the corresponding sysfs knob writeable > > > for debugging purposes. However, because QUEUE_FLAG_STABLE_WRITES flag > > > is captured when the filesystem is mounted and isn't consulted after > > > that anywhere outside of swap code, changing it doesn't take immediate > > > effect even though dumping the knob shows the new value. With no way > > > to dump SB_I_STABLE_WRITES flag, this is needlessly confusing. > > > > But very much intentional. s_bdev often is not the only device > > in a file system, and we should never reference if from core > > helpers. > > > > So I think we should go with something like this: > > > > diff --git a/mm/page-writeback.c b/mm/page-writeback.c > > index db794399900734..aa36cc2a4530c1 100644 > > --- a/mm/page-writeback.c > > +++ b/mm/page-writeback.c > > @@ -3129,7 +3129,11 @@ EXPORT_SYMBOL_GPL(folio_wait_writeback_killable); > > */ > > void folio_wait_stable(struct folio *folio) > > { > > - if (folio_inode(folio)->i_sb->s_iflags & SB_I_STABLE_WRITES) > > + struct inode *inode = folio_inode(folio); > > + struct super_block *sb = inode->i_sb; > > + > > + if ((sb->s_iflags & SB_I_STABLE_WRITES) || > > + (sb_is_blkdev_sb(sb) && bdev_stable_writes(I_BDEV(inode)))) > > folio_wait_writeback(folio); > > } > > EXPORT_SYMBOL_GPL(folio_wait_stable); > > I hate both of these patches ;-) What we should do is add > AS_STABLE_WRITES, have the appropriate places call > mapping_set_stable_writes() and then folio_wait_stable() becomes > > if (mapping_test_stable_writes(folio->mapping)) > folio_wait_writeback(folio); > > and we remove all the dereferences (mapping->host->i_sb->s_iflags, plus > whatever else is going on there) For bdev address_space that's easy but what Ilya also mentioned is a problem when 'stable_write' flag gets toggled on the device and in that case having to propagate the flag update to all the address_space structures is a nightmare... Honza -- Jan Kara SUSE Labs, CR