From: "Serge E. Hallyn" Subject: Re: [PATCH 2/5] VFS: Add VFS helper functions for setting up private namespaces Date: Tue, 23 Jun 2009 15:13:07 -0500 Message-ID: <20090623201307.GA25760@us.ibm.com> References: <20090622190913.27923.31665.stgit@heimdal.trondhjem.org> <20090622190913.27923.61549.stgit@heimdal.trondhjem.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Linus Torvalds , Al Viro , Christoph Hellwig , linux-fsdevel@vger.kernel.org, linux-nfs@vger.kernel.org, linux-kernel@vger.kernel.org To: Trond Myklebust Return-path: Received: from e33.co.us.ibm.com ([32.97.110.151]:38480 "EHLO e33.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753057AbZFWUN0 (ORCPT ); Tue, 23 Jun 2009 16:13:26 -0400 In-Reply-To: <20090622190913.27923.61549.stgit-rJ7iovZKK19ZJLDQqaL3InhyD016LWXt@public.gmane.org> Sender: linux-nfs-owner@vger.kernel.org List-ID: Quoting Trond Myklebust (Trond.Myklebust@netapp.com): > The purpose of this patch is to improve the remote mount path lookup > support for distributed filesystems such as the NFSv4 client. > > When given a mount command of the form "mount server:/foo/bar /mnt", the > NFSv4 client is required to look up the filehandle for "server:/", and > then look up each component of the remote mount path "foo/bar" in order > to find the directory that is actually going to be mounted on /mnt. > Following that remote mount path may involve following symlinks, > crossing server-side mount points and even following referrals to > filesystem volumes on other servers. > > Since the standard VFS path lookup code already supports walking paths > that contain all these features (using in-kernel automounts for > following referrals) we would like to be able to reuse that rather than > duplicate the full path traversal functionality in the NFSv4 client code. > > This patch therefore defines a VFS helper function create_mnt_ns(), that > sets up a temporary filesystem namespace and attaches a root filesystem to > it. It exports the create_mnt_ns() and put_mnt_ns() function for use by > filesystem modules. > > Signed-off-by: Trond Myklebust This looks good, thanks. Though I see no reason not to also switch over init_mount_tree() to the new helper. (Seems plausible that c/r code would use this as well) Reviewed-by: Serge Hallyn thanks, -serge > --- > > fs/namespace.c | 45 ++++++++++++++++++++++++++++++++++------- > include/linux/mnt_namespace.h | 1 + > 2 files changed, 38 insertions(+), 8 deletions(-) > > > diff --git a/fs/namespace.c b/fs/namespace.c > index 2465c05..9b766b0 100644 > --- a/fs/namespace.c > +++ b/fs/namespace.c > @@ -1937,6 +1937,21 @@ dput_out: > return retval; > } > > +static struct mnt_namespace *alloc_mnt_ns(void) > +{ > + struct mnt_namespace *new_ns; > + > + new_ns = kmalloc(sizeof(struct mnt_namespace), GFP_KERNEL); > + if (!new_ns) > + return ERR_PTR(-ENOMEM); > + atomic_set(&new_ns->count, 1); > + new_ns->root = NULL; > + INIT_LIST_HEAD(&new_ns->list); > + init_waitqueue_head(&new_ns->poll); > + new_ns->event = 0; > + return new_ns; > +} > + > /* > * Allocate a new namespace structure and populate it with contents > * copied from the namespace of the passed in task structure. > @@ -1948,14 +1963,9 @@ static struct mnt_namespace *dup_mnt_ns(struct mnt_namespace *mnt_ns, > struct vfsmount *rootmnt = NULL, *pwdmnt = NULL; > struct vfsmount *p, *q; > > - new_ns = kmalloc(sizeof(struct mnt_namespace), GFP_KERNEL); > - if (!new_ns) > - return ERR_PTR(-ENOMEM); > - > - atomic_set(&new_ns->count, 1); > - INIT_LIST_HEAD(&new_ns->list); > - init_waitqueue_head(&new_ns->poll); > - new_ns->event = 0; > + new_ns = alloc_mnt_ns(); > + if (IS_ERR(new_ns)) > + return new_ns; > > down_write(&namespace_sem); > /* First pass: copy the tree topology */ > @@ -2019,6 +2029,24 @@ struct mnt_namespace *copy_mnt_ns(unsigned long flags, struct mnt_namespace *ns, > return new_ns; > } > > +/** > + * create_mnt_ns - creates a private namespace and adds a root filesystem > + * @mnt: pointer to the new root filesystem mountpoint > + */ > +struct mnt_namespace *create_mnt_ns(struct vfsmount *mnt) > +{ > + struct mnt_namespace *new_ns; > + > + new_ns = alloc_mnt_ns(); > + if (!IS_ERR(new_ns)) { > + mnt->mnt_ns = new_ns; > + new_ns->root = mnt; > + list_add(&new_ns->list, &new_ns->root->mnt_list); > + } > + return new_ns; > +} > +EXPORT_SYMBOL(create_mnt_ns); > + > SYSCALL_DEFINE5(mount, char __user *, dev_name, char __user *, dir_name, > char __user *, type, unsigned long, flags, void __user *, data) > { > @@ -2264,3 +2292,4 @@ void put_mnt_ns(struct mnt_namespace *ns) > release_mounts(&umount_list); > kfree(ns); > } > +EXPORT_SYMBOL(put_mnt_ns); > diff --git a/include/linux/mnt_namespace.h b/include/linux/mnt_namespace.h > index 299d11a..3beb259 100644 > --- a/include/linux/mnt_namespace.h > +++ b/include/linux/mnt_namespace.h > @@ -24,6 +24,7 @@ struct proc_mounts { > > struct fs_struct; > > +extern struct mnt_namespace *create_mnt_ns(struct vfsmount *mnt); > extern struct mnt_namespace *copy_mnt_ns(unsigned long, struct mnt_namespace *, > struct fs_struct *); > extern void put_mnt_ns(struct mnt_namespace *ns); > > -- > To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html