From patchwork Tue Aug 18 07:21:59 2015 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Kinglong Mee X-Patchwork-Id: 7028781 Return-Path: X-Original-To: patchwork-linux-fsdevel@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork1.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.136]) by patchwork1.web.kernel.org (Postfix) with ESMTP id D524C9F344 for ; Tue, 18 Aug 2015 07:22:18 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 0F5DB205DB for ; Tue, 18 Aug 2015 07:22:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1A89320788 for ; Tue, 18 Aug 2015 07:22:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750962AbbHRHWP (ORCPT ); Tue, 18 Aug 2015 03:22:15 -0400 Received: from mail-pa0-f41.google.com ([209.85.220.41]:33806 "EHLO mail-pa0-f41.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750855AbbHRHWN (ORCPT ); Tue, 18 Aug 2015 03:22:13 -0400 Received: by paccq16 with SMTP id cq16so82896030pac.1; Tue, 18 Aug 2015 00:22:13 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=subject:to:references:cc:from:message-id:date:user-agent :mime-version:in-reply-to:content-type:content-transfer-encoding; bh=Ukhtd0q3v5LMmizsIHlpWj6DrMd1hczX9dSSDifMEgo=; b=rc6TUr9Ci/8kSFq6R/4PWL0wQRCCGYeZ4MHxoHRhikZ/9ouB8UhMiA+pTGn9iY24is e9byt6OBEod2g6orkreDVdg+Vcb4t3qvtounJU55Zj6HbUtzqbHMAz1TwrdUgeOB5UXN qK0M7rfXb7TLTjL3BhXWOeqV0iCRj5DhsX6DQj2KZ4RGK2ILjOMXEXhUi8n1kTdXFv/M BP1p48yZ6NtKSQzy/N5+qeepqtMZMU9AvUG+Ohp8lKx2yLnfvn/kMK8WI20zW9bP5rWN STHbmV89iIXaavr0uhvctfTqS87LUefP9mI0s+tFBhEbvGg+WbjhntYFcpAGe4e2MumX 23zg== X-Received: by 10.66.231.69 with SMTP id te5mr10335664pac.98.1439882533553; Tue, 18 Aug 2015 00:22:13 -0700 (PDT) Received: from [192.168.99.18] ([104.143.41.79]) by smtp.googlemail.com with ESMTPSA id w11sm16905963pbs.55.2015.08.18.00.22.05 (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 18 Aug 2015 00:22:13 -0700 (PDT) Subject: [PATCH 4/6 v9] fs: New helper legitimize_mntget() for getting a legitimize mnt To: "J. Bruce Fields" , Al Viro References: <55D2DBF6.3010406@gmail.com> Cc: "linux-nfs@vger.kernel.org" , linux-fsdevel@vger.kernel.org, NeilBrown , Trond Myklebust , kinglongmee@gmail.com From: Kinglong Mee Message-ID: <55D2DD17.7050504@gmail.com> Date: Tue, 18 Aug 2015 15:21:59 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:38.0) Gecko/20100101 Thunderbird/38.1.0 MIME-Version: 1.0 In-Reply-To: <55D2DBF6.3010406@gmail.com> Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org X-Spam-Status: No, score=-7.2 required=5.0 tests=BAYES_00, DKIM_ADSP_CUSTOM_MED, DKIM_SIGNED, FREEMAIL_FROM, RCVD_IN_DNSWL_HI, RP_MATCHES_RCVD, T_DKIM_INVALID, UNPARSEABLE_RELAY autolearn=unavailable version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP New helper legitimize_mntget for getting a mnt without setting MNT_SYNC_UMOUNT | MNT_UMOUNT | MNT_DOOMED, otherwise return NULL. v9, Update using read_seqbegin_or_lock instead read_seqlock_excl Signed-off-by: Kinglong Mee --- fs/namespace.c | 30 ++++++++++++++++++++++++++++++ include/linux/mount.h | 1 + 2 files changed, 31 insertions(+) diff --git a/fs/namespace.c b/fs/namespace.c index 2b8aa15..bf4a9f5 100644 --- a/fs/namespace.c +++ b/fs/namespace.c @@ -1153,6 +1153,36 @@ struct vfsmount *mntget(struct vfsmount *mnt) } EXPORT_SYMBOL(mntget); +struct vfsmount *legitimize_mntget(struct vfsmount *vfsmnt) +{ + struct mount *mnt; + unsigned seq = 0; + + if (vfsmnt == NULL) + return NULL; +retry: + read_seqbegin_or_lock(&mount_lock, &seq); + + if (vfsmnt->mnt_flags & (MNT_SYNC_UMOUNT | MNT_UMOUNT | MNT_DOOMED)) + vfsmnt = NULL; + else if (need_seqretry(&mount_lock, seq)) + goto retry; + else { + mnt = real_mount(vfsmnt); + mnt_add_count(mnt, 1); + if (need_seqretry(&mount_lock, seq) || + vfsmnt->mnt_flags & (MNT_SYNC_UMOUNT | MNT_UMOUNT | + MNT_DOOMED)) { + mnt_add_count(mnt, -1); + goto retry; + } + } + + done_seqretry(&mount_lock, seq); + return vfsmnt; +} +EXPORT_SYMBOL(legitimize_mntget); + struct vfsmount *mnt_clone_internal(struct path *path) { struct mount *p; diff --git a/include/linux/mount.h b/include/linux/mount.h index f822c3c..8ae9dc0 100644 --- a/include/linux/mount.h +++ b/include/linux/mount.h @@ -79,6 +79,7 @@ extern void mnt_drop_write(struct vfsmount *mnt); extern void mnt_drop_write_file(struct file *file); extern void mntput(struct vfsmount *mnt); extern struct vfsmount *mntget(struct vfsmount *mnt); +extern struct vfsmount *legitimize_mntget(struct vfsmount *vfsmnt); extern struct vfsmount *mnt_clone_internal(struct path *path); extern int __mnt_is_readonly(struct vfsmount *mnt);