From patchwork Thu Oct 18 13:17:08 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jan Kara X-Patchwork-Id: 985899 Return-Path: X-Original-To: patchwork-incoming@ozlabs.org Delivered-To: patchwork-incoming@ozlabs.org Authentication-Results: ozlabs.org; spf=none (mailfrom) smtp.mailfrom=vger.kernel.org (client-ip=209.132.180.67; helo=vger.kernel.org; envelope-from=linux-ext4-owner@vger.kernel.org; receiver=) Authentication-Results: ozlabs.org; dmarc=none (p=none dis=none) header.from=suse.cz Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by ozlabs.org (Postfix) with ESMTP id 42bV2W1sY1z9s9J for ; Fri, 19 Oct 2018 00:17:23 +1100 (AEDT) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728150AbeJRVSS (ORCPT ); Thu, 18 Oct 2018 17:18:18 -0400 Received: from mx2.suse.de ([195.135.220.15]:59834 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1727633AbeJRVSS (ORCPT ); Thu, 18 Oct 2018 17:18:18 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay1.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id E0D99AD83; Thu, 18 Oct 2018 13:17:16 +0000 (UTC) Received: by quack2.suse.cz (Postfix, from userid 1000) id 5B9131E050D; Thu, 18 Oct 2018 15:17:16 +0200 (CEST) From: Jan Kara To: Al Viro Cc: Ted Tso , , , , Jan Kara Subject: [PATCH 1/2] vfs: Provide function to grab superblock reference Date: Thu, 18 Oct 2018 15:17:08 +0200 Message-Id: <20181018131709.11976-2-jack@suse.cz> X-Mailer: git-send-email 2.16.4 In-Reply-To: <20181018131709.11976-1-jack@suse.cz> References: <20181018131709.11976-1-jack@suse.cz> Sender: linux-ext4-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-ext4@vger.kernel.org Provide function to hold superblock reference when we are sure the superblock is active. This function will get used by code reading /proc/mounts and friends. Signed-off-by: Jan Kara --- fs/internal.h | 1 + fs/super.c | 16 ++++++++++++++++ 2 files changed, 17 insertions(+) diff --git a/fs/internal.h b/fs/internal.h index d410186bc369..608f4f276ba5 100644 --- a/fs/internal.h +++ b/fs/internal.h @@ -104,6 +104,7 @@ extern bool trylock_super(struct super_block *sb); extern struct dentry *mount_fs(struct file_system_type *, int, const char *, void *); extern struct super_block *user_get_super(dev_t); +extern void hold_sb(struct super_block *sb); /* * open.c diff --git a/fs/super.c b/fs/super.c index f3a8c008e164..f60a07f794cc 100644 --- a/fs/super.c +++ b/fs/super.c @@ -775,6 +775,22 @@ struct super_block *get_super_exclusive_thawed(struct block_device *bdev) } EXPORT_SYMBOL(get_super_exclusive_thawed); +/** + * hold_sb - get superblock reference for active superblock + * @sb: superblock to get reference for + * + * Get reference to superblock. The caller must make sure the superblock + * is currently active by other means (e.g. holding an active reference + * itself or holding namespace_sem preventing unmount). + */ +void hold_sb(struct super_block *sb) +{ + spin_lock(&sb_lock); + WARN_ON_ONCE(!atomic_read(&sb->s_active)); + sb->s_count++; + spin_unlock(&sb_lock); +} + /** * get_active_super - get an active reference to the superblock of a device * @bdev: device to get the superblock for