From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754521AbaBRRP4 (ORCPT ); Tue, 18 Feb 2014 12:15:56 -0500 Received: from mail-wi0-f180.google.com ([209.85.212.180]:54096 "EHLO mail-wi0-f180.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754298AbaBRRPx (ORCPT ); Tue, 18 Feb 2014 12:15:53 -0500 Date: Tue, 18 Feb 2014 18:17:08 +0100 From: Miklos Szeredi To: "Eric W. Biederman" Cc: Al Viro , "Serge E. Hallyn" , Linux-Fsdevel , Kernel Mailing List , Andy Lutomirski , Rob Landley , Linus Torvalds , Christoph Hellwig , Karel Zak , "J. Bruce Fields" Subject: Re: [PATCH 05/11] vfs: Add a function to lazily unmount all mounts from any dentry. Message-ID: <20140218171708.GD4026@tucsk.piliscsaba.szeredi.hu> References: <87a9kkax0j.fsf@xmission.com> <8761v7h2pt.fsf@tw-ebiederman.twitter.com> <87li281wx6.fsf_-_@xmission.com> <87ob28kqks.fsf_-_@xmission.com> <87txc0jbvt.fsf_-_@xmission.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87txc0jbvt.fsf_-_@xmission.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Feb 15, 2014 at 01:37:26PM -0800, Eric W. Biederman wrote: > > v2: Always drop the lock when exiting early. > v3: Make detach_mounts robust about freeing several > mounts on the same mountpoint at one time, and remove > the unneeded mnt_list list test. > v4: Document the purpose of detach_mounts and why new_mountpoint is > safe to call. > > Signed-off-by: Eric W. Biederman > --- > fs/mount.h | 2 ++ > fs/namespace.c | 39 +++++++++++++++++++++++++++++++++++++++ > 2 files changed, 41 insertions(+), 0 deletions(-) > > diff --git a/fs/mount.h b/fs/mount.h > index 50a72d46e7a6..2b470f34e665 100644 > --- a/fs/mount.h > +++ b/fs/mount.h > @@ -84,6 +84,8 @@ extern struct mount *__lookup_mnt_last(struct vfsmount *, struct dentry *); > > extern bool legitimize_mnt(struct vfsmount *, unsigned); > > +extern void detach_mounts(struct dentry *dentry); > + > static inline void get_mnt_ns(struct mnt_namespace *ns) > { > atomic_inc(&ns->count); > diff --git a/fs/namespace.c b/fs/namespace.c > index 33db9e95bd5c..7abbf722ce18 100644 > --- a/fs/namespace.c > +++ b/fs/namespace.c > @@ -1359,6 +1359,45 @@ static int do_umount(struct mount *mnt, int flags) > return retval; > } > > +/* > + * detach_mounts - lazily unmount all mounts on the specified dentry > + * > + * During unlink, rmdir, and d_drop it is possible to loose the path > + * to an existing mountpoint, and wind up leaking the mount. > + * detach_mounts allows lazily unmounting those mounts instead of > + * leaking them. > + * > + * The caller may hold dentry->d_inode->i_mutex. > + */ > +void detach_mounts(struct dentry *dentry) > +{ > + struct mountpoint *mp; > + struct mount *mnt; > + > + namespace_lock(); > + if (!d_mountpoint(dentry)) > + goto out_unlock; > + > + /* > + * The namespace lock and d_mountpoint being set guarantees > + * that new_mountpoint will just be a lookup of the existing > + * mountpoint structure. > + */ > + mp = new_mountpoint(dentry); Howabout a get_mountpoint(dentry) helper, that returns NULL if it turns out to be not a mountpoint? And, as an added bonus, you can drop the comment above as well. > + if (IS_ERR(mp)) > + goto out_unlock; > + > + lock_mount_hash(); > + while (!list_empty(&mp->m_list)) { > + mnt = list_first_entry(&mp->m_list, struct mount, mnt_mp_list); > + umount_tree(mnt, 1); > + } > + unlock_mount_hash(); > + put_mountpoint(mp); > +out_unlock: > + namespace_unlock(); > +} > + > /* > * Is the caller allowed to modify his namespace? > */ > -- > 1.7.5.4 >