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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id E029EC433EF for ; Tue, 2 Nov 2021 15:25:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C9DA860EB4 for ; Tue, 2 Nov 2021 15:25:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234560AbhKBP2S (ORCPT ); Tue, 2 Nov 2021 11:28:18 -0400 Received: from smtp-out2.suse.de ([195.135.220.29]:50524 "EHLO smtp-out2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233007AbhKBP2J (ORCPT ); Tue, 2 Nov 2021 11:28:09 -0400 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 D8B701FD4C; Tue, 2 Nov 2021 15:25:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1635866732; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=6GiLMiJAnzbcLthSAl63S33g7iKONODGvH3XGxM/R0o=; b=K7gLoMiRyUeZh7HLcZBFrqwMvxbmkkbhXcP91l+wofrlw3wOIWqbqYp06s1OFkz/gOELiT ZX/0NWCxoVh6I//D6I7cIGnkeW5DJFyCzI7fbnugZ94LWWLN7lmNmIeCdZQSdLy6X1dNkU Z6J1vXAhPA9B6P0w6IN+XrrZZeAJPVw= 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 A5B6613D66; Tue, 2 Nov 2021 15:25:32 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id 2cPlJWxYgWExSgAAMHmgww (envelope-from ); Tue, 02 Nov 2021 15:25:32 +0000 Subject: Re: [PATCH 0/3] Balance vs device add fixes To: Josef Bacik Cc: linux-btrfs@vger.kernel.org, Goldwyn Rodrigues References: <20211101115324.374076-1-nborisov@suse.com> From: Nikolay Borisov Message-ID: <516c7eaf-3fb2-fe61-08f8-ac4201752121@suse.com> Date: Tue, 2 Nov 2021 17:25:32 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.13.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org On 2.11.21 г. 16:30, Josef Bacik wrote: > On Mon, Nov 01, 2021 at 01:53:21PM +0200, Nikolay Borisov wrote: >> This series enables adding of a device when balance is paused (i.e an fs is mounted >> with skip_balance options). This is needed to give users a chance to gracefully >> handle an ENOSPC situation in the face of running balance. To achieve this introduce >> a new exclop - BALANCE_PAUSED which is made compatible with device add. More >> details in each patche. >> >> I've tested this with an fstests which I will be posting in a bit. >> >> Nikolay Borisov (3): >> btrfs: introduce BTRFS_EXCLOP_BALANCE_PAUSED exclusive state >> btrfs: make device add compatible with paused balance in >> btrfs_exclop_start_try_lock >> btrfs: allow device add if balance is paused >> >> fs/btrfs/ctree.h | 1 + >> fs/btrfs/ioctl.c | 49 +++++++++++++++++++++++++++++++++++++++------- >> fs/btrfs/volumes.c | 23 ++++++++++++++++++---- >> fs/btrfs/volumes.h | 2 +- >> 4 files changed, 63 insertions(+), 12 deletions(-) >> > > A few things > > 1) Can we integrate the flipping into helpers? Something like > > btrfs_exclop_change_state(PAUSED); > > So the locking and stuff is all with the code that messes with the exclop? Right, I left the code flipping balance->paused opencoded because that's really a special case. By all means I can add a specific helper so that the ASSERT is not lost as well. The reason I didn't do it in the first place is because PAUSED is really "special" in the sense it can be entered only from BALANCE and it's not really generic. If you take a look how btrfs_exclop_start does it for example, it simply checks we don't have a running op and simply sets it to whatever is passed > > 2) The existing helpers do WRITE_ONCE(), is that needed here? I assume not> because we're not actually exiting our exclop state, but still seems wonky. That got me thinking in the first place and actually initially I had a patch which removed it. However, I *think* it might be required since exclusive_operation is accessed without a lock ini the sysfs code i.e. btrfs_exclusive_operation_show so I guess that's why we need it. Goldwyn, what's your take on this? > > 3) Maybe have an __btrfs_exclop_finish(type), so instead of > > if (paused) { > do thing; > } else { > btrfs_exclop_finish(); > } > > you can instead do > > type = BTRFS_EXCLOP_NONE; > if (pause stuff) { > do things; > type = BTRFS_EXCLOP_BALANCE_PAUSED; > } > > /* other stuff. */ > __btrfs_exclop_finish(type); > > then btrfs_exclop_finish just does __btrfs_exclop_finish(NONE); I'm having a hard time seeing how this would increase readability. What should go into the __btrfs_exclop_finish function? > Thanks, > > Josef >