From patchwork Tue May 3 08:36:36 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Nikolay Borisov X-Patchwork-Id: 12835278 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 486D4C433F5 for ; Tue, 3 May 2022 08:36:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229938AbiECIkO (ORCPT ); Tue, 3 May 2022 04:40:14 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53242 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232840AbiECIkM (ORCPT ); Tue, 3 May 2022 04:40:12 -0400 Received: from smtp-out1.suse.de (smtp-out1.suse.de [195.135.220.28]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 63037340F0 for ; Tue, 3 May 2022 01:36:41 -0700 (PDT) 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-out1.suse.de (Postfix) with ESMTPS id 176F4210EA; Tue, 3 May 2022 08:36:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1651567000; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=Kj4sB7GY1v9BtXZqfU2Vq/eUw/5wtc7IXEhC7fep08c=; b=Be91MW39k+BtBbm3oxuLiULBOLUwKxHfWMaE59/J4ZqlycdYjfy98wbU/ARyPlF0p1nv2o usp1ZaGffb0qoW3ARVijV4zRtQAy2RI39gshZUIJC7hQpjlJKO7sEJfEhnAPRH31EWDclN 7D3f/YG5ditoOhKjercapajxhWTX+rc= 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 D7F9C13ABE; Tue, 3 May 2022 08:36:39 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id OMoMMpfpcGIQPgAAMHmgww (envelope-from ); Tue, 03 May 2022 08:36:39 +0000 From: Nikolay Borisov To: linux-btrfs@vger.kernel.org Cc: Nikolay Borisov Subject: [PATCH 1/2] btrfs: Introduce btrfs_try_lock_balance Date: Tue, 3 May 2022 11:36:36 +0300 Message-Id: <20220503083637.1051023-2-nborisov@suse.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20220503083637.1051023-1-nborisov@suse.com> References: <20220503083637.1051023-1-nborisov@suse.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org This function contains the factored out locking sequence btrfs_ioctl_balance. Having this piece of code separate helps to simplify btrfs_ioctl_balance which has turned into a boiling pile of spaghetti. This will be used in the next patch to streamline the logic in btrfs_ioctl_balance. Signed-off-by: Nikolay Borisov Reported-by: kernel test robot --- fs/btrfs/ioctl.c | 66 ++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 66 insertions(+) diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c index 9d8e46815ee4..8e0cc17d5f81 100644 --- a/fs/btrfs/ioctl.c +++ b/fs/btrfs/ioctl.c @@ -4334,6 +4334,72 @@ void btrfs_update_ioctl_balance_args(struct btrfs_fs_info *fs_info, spin_unlock(&fs_info->balance_lock); } +/** + * Try to acquire fs_info::balance_Mutex as well as set BTRFS_EXLCOP_BALANCE as + * required. + * + * @fs_info: context of the filesystem + * @excl_acquired: ptr to boolean value which is set to 'false' in case balance + * is being resumed. + * + * Returns 0 on success in which case both fs_info::balance is acquired as well + * as exclusive ops are blocked. In case of failure returns an error code. + * + */ +static int btrfs_try_lock_balance(struct btrfs_fs_info *fs_info, bool *excl_acquired) +{ + int ret; + /* + * mut. excl. ops lock is locked. Three possibilities: + * (1) some other op is running + * (2) balance is running + * (3) balance is paused -- special case (think resume) + */ + while (1) { + if (btrfs_exclop_start(fs_info, BTRFS_EXCLOP_BALANCE)) { + *excl_acquired = true; + mutex_lock(&fs_info->balance_mutex); + return 0; + } + + mutex_lock(&fs_info->balance_mutex); + if (fs_info->balance_ctl) { + /* this is either (2) or (3) */ + if (test_bit(BTRFS_FS_BALANCE_RUNNING, &fs_info->flags)) { + /* this is (2) */ + ret = -EINPROGRESS; + goto out_failure; + + } else { + mutex_unlock(&fs_info->balance_mutex); + /* + * Lock released to allow other waiters to continue, + * we'll reexamine the status again. + */ + mutex_lock(&fs_info->balance_mutex); + + if (fs_info->balance_ctl && + !test_bit(BTRFS_FS_BALANCE_RUNNING, &fs_info->flags)) { + /* this is (3) */ + *excl_acquired = false; + return 0; + } + } + } else { + /* this is (1) */ + ret = BTRFS_ERROR_DEV_EXCL_RUN_IN_PROGRESS; + goto out_failure; + } + + mutex_unlock(&fs_info->balance_mutex); + } + +out_failure: + mutex_unlock(&fs_info->balance_mutex); + *excl_acquired = false; + return ret; +} + static long btrfs_ioctl_balance(struct file *file, void __user *arg) { struct btrfs_root *root = BTRFS_I(file_inode(file))->root;