From 98f842e675f96ffac96e6c50315790912b2812be Mon Sep 17 00:00:00 2001 From: "Eric W. Biederman" Date: Wed, 15 Jun 2011 10:21:48 -0700 Subject: proc: Usable inode numbers for the namespace file descriptors. Assign a unique proc inode to each namespace, and use that inode number to ensure we only allocate at most one proc inode for every namespace in proc. A single proc inode per namespace allows userspace to test to see if two processes are in the same namespace. This has been a long requested feature and only blocked because a naive implementation would put the id in a global space and would ultimately require having a namespace for the names of namespaces, making migration and certain virtualization tricks impossible. We still don't have per superblock inode numbers for proc, which appears necessary for application unaware checkpoint/restart and migrations (if the application is using namespace file descriptors) but that is now allowd by the design if it becomes important. I have preallocated the ipc and uts initial proc inode numbers so their structures can be statically initialized. Signed-off-by: Eric W. Biederman --- fs/proc/namespaces.c | 24 ++++++++++++++---------- 1 file changed, 14 insertions(+), 10 deletions(-) (limited to 'fs/proc/namespaces.c') diff --git a/fs/proc/namespaces.c b/fs/proc/namespaces.c index 7a6d8d6..b7a4719 100644 --- a/fs/proc/namespaces.c +++ b/fs/proc/namespaces.c @@ -82,7 +82,7 @@ static struct dentry *proc_ns_get_dentry(struct super_block *sb, return ERR_PTR(-ENOMEM); } - inode = new_inode(sb); + inode = iget_locked(sb, ns_ops->inum(ns)); if (!inode) { dput(dentry); ns_ops->put(ns); @@ -90,13 +90,17 @@ static struct dentry *proc_ns_get_dentry(struct super_block *sb, } ei = PROC_I(inode); - inode->i_ino = get_next_ino(); - inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME; - inode->i_op = &ns_inode_operations; - inode->i_mode = S_IFREG | S_IRUGO; - inode->i_fop = &ns_file_operations; - ei->ns_ops = ns_ops; - ei->ns = ns; + if (inode->i_state & I_NEW) { + inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME; + inode->i_op = &ns_inode_operations; + inode->i_mode = S_IFREG | S_IRUGO; + inode->i_fop = &ns_file_operations; + ei->ns_ops = ns_ops; + ei->ns = ns; + unlock_new_inode(inode); + } else { + ns_ops->put(ns); + } d_set_d_op(dentry, &ns_dentry_operations); result = d_instantiate_unique(dentry, inode); @@ -162,12 +166,12 @@ static int proc_ns_readlink(struct dentry *dentry, char __user *buffer, int bufl if (!ns) goto out_put_task; - snprintf(name, sizeof(name), "%s", ns_ops->name); + snprintf(name, sizeof(name), "%s:[%u]", ns_ops->name, ns_ops->inum(ns)); len = strlen(name); if (len > buflen) len = buflen; - if (copy_to_user(buffer, ns_ops->name, len)) + if (copy_to_user(buffer, name, len)) len = -EFAULT; ns_ops->put(ns); -- cgit v1.1