From: "Serge E. Hallyn" Subject: Re: [PATCH 2/5] VFS: Add VFS helper functions for setting up private namespaces Date: Tue, 23 Jun 2009 17:32:30 -0500 Message-ID: <20090623223230.GA30173@us.ibm.com> References: <20090622190913.27923.31665.stgit@heimdal.trondhjem.org> <20090622190913.27923.61549.stgit@heimdal.trondhjem.org> <20090623201307.GA25760@us.ibm.com> <1245792589.5133.24.camel@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: In-Reply-To: <1245792589.5133.24.camel@heimdal.trondhjem.org> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: Quoting Trond Myklebust (Trond.Myklebust@netapp.com): > On Tue, 2009-06-23 at 15:13 -0500, Serge E. Hallyn wrote: > > 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 > > Thanks for the review! I missed the code duplication in > init_mount_tree(). Something like the following? Yup. (it keeps bugging me that the order of args to list_add() gets reversed as a result, but clearly with both starting out empty it doesn't matter..) thanks, -serge > Cheers > Trond > -------------------------------------------------------------------- > From: Trond Myklebust > VFS: Switch init_mount_tree() to use the new create_mnt_ns() helper > > Eliminates some duplicated code... > > Signed-off-by: Trond Myklebust > --- > > fs/namespace.c | 11 ++--------- > 1 files changed, 2 insertions(+), 9 deletions(-) > > > diff --git a/fs/namespace.c b/fs/namespace.c > index a7bea8c..4a86b85 100644 > --- a/fs/namespace.c > +++ b/fs/namespace.c > @@ -2222,16 +2222,9 @@ static void __init init_mount_tree(void) > mnt = do_kern_mount("rootfs", 0, "rootfs", NULL); > if (IS_ERR(mnt)) > panic("Can't create rootfs"); > - ns = kmalloc(sizeof(*ns), GFP_KERNEL); > - if (!ns) > + ns = create_mnt_ns(mnt); > + if (IS_ERR(ns)) > panic("Can't allocate initial namespace"); > - atomic_set(&ns->count, 1); > - INIT_LIST_HEAD(&ns->list); > - init_waitqueue_head(&ns->poll); > - ns->event = 0; > - list_add(&mnt->mnt_list, &ns->list); > - ns->root = mnt; > - mnt->mnt_ns = ns; > > init_task.nsproxy->mnt_ns = ns; > get_mnt_ns(ns); > > > -- > Trond Myklebust > Linux NFS client maintainer > > NetApp > Trond.Myklebust@netapp.com > www.netapp.com > -- > 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