1 files changed, 111 insertions, 1 deletions

diff --git a/fs/nfs/namespace.c b/fs/nfs/namespace.c
index 8ca44b7b25c3..19b98ca468eb 100644
--- a/fs/nfs/namespace.c
+++ b/fs/nfs/namespace.c
@@ -15,15 +15,64 @@
 #include <linux/string.h>
 #include <linux/sunrpc/clnt.h>
 #include <linux/vfs.h>
+#include "internal.h"
 
 #define NFSDBG_FACILITY         NFSDBG_VFS
 
-LIST_HEAD(nfs_automount_list);
 static void nfs_expire_automounts(void *list);
+
+LIST_HEAD(nfs_automount_list);
 static DECLARE_WORK(nfs_automount_task, nfs_expire_automounts, &nfs_automount_list);
 int nfs_mountpoint_expiry_timeout = 500 * HZ;
 
 /*
+ * nfs_path - reconstruct the path given an arbitrary dentry
+ * @base - arbitrary string to prepend to the path
+ * @dentry - pointer to dentry
+ * @buffer - result buffer
+ * @buflen - length of buffer
+ *
+ * Helper function for constructing the path from the
+ * root dentry to an arbitrary hashed dentry.
+ *
+ * This is mainly for use in figuring out the path on the
+ * server side when automounting on top of an existing partition.
+ */
+char *nfs_path(const char *base, const struct dentry *dentry,
+               char *buffer, ssize_t buflen)
+{
+        char *end = buffer+buflen;
+        int namelen;
+
+        *--end = '\0';
+        buflen--;
+        spin_lock(&dcache_lock);
+        while (!IS_ROOT(dentry)) {
+                namelen = dentry->d_name.len;
+                buflen -= namelen + 1;
+                if (buflen < 0)
+                        goto Elong;
+                end -= namelen;
+                memcpy(end, dentry->d_name.name, namelen);
+                *--end = '/';
+                dentry = dentry->d_parent;
+        }
+        spin_unlock(&dcache_lock);
+        namelen = strlen(base);
+        /* Strip off excess slashes in base string */
+        while (namelen > 0 && base[namelen - 1] == '/')
+                namelen--;
+        buflen -= namelen;
+        if (buflen < 0)
+                goto Elong;
+        end -= namelen;
+        memcpy(end, base, namelen);
+        return end;
+Elong:
+        return ERR_PTR(-ENAMETOOLONG);
+}
+
+/*
  * nfs_follow_mountpoint - handle crossing a mountpoint on the server
  * @dentry - dentry of mountpoint
  * @nd - nameidata info
@@ -117,3 +166,64 @@ void nfs_release_automount_timer(void)
                 flush_scheduled_work();
         }
 }
+
+/*
+ * Clone a mountpoint of the appropriate type
+ */
+static struct vfsmount *nfs_do_clone_mount(struct nfs_server *server, char *devname,
+                                           struct nfs_clone_mount *mountdata)
+{
+#ifdef CONFIG_NFS_V4
+        struct vfsmount *mnt = NULL;
+        switch (server->rpc_ops->version) {
+                case 2:
+                case 3:
+                        mnt = vfs_kern_mount(&clone_nfs_fs_type, 0, devname, mountdata);
+                        break;
+                case 4:
+                        mnt = vfs_kern_mount(&clone_nfs4_fs_type, 0, devname, mountdata);
+        }
+        return mnt;
+#else
+        return vfs_kern_mount(&clone_nfs_fs_type, 0, devname, mountdata);
+#endif
+}
+
+/**
+ * nfs_do_submount - set up mountpoint when crossing a filesystem boundary
+ * @mnt_parent - mountpoint of parent directory
+ * @dentry - parent directory
+ * @fh - filehandle for new root dentry
+ * @fattr - attributes for new root inode
+ *
+ */
+struct vfsmount *nfs_do_submount(const struct vfsmount *mnt_parent,
+                const struct dentry *dentry, struct nfs_fh *fh,
+                struct nfs_fattr *fattr)
+{
+        struct nfs_clone_mount mountdata = {
+                .sb = mnt_parent->mnt_sb,
+                .dentry = dentry,
+                .fh = fh,
+                .fattr = fattr,
+        };
+        struct vfsmount *mnt = ERR_PTR(-ENOMEM);
+        char *page = (char *) __get_free_page(GFP_USER);
+        char *devname;
+
+        dprintk("%s: submounting on %s/%s\n", __FUNCTION__,
+                        dentry->d_parent->d_name.name,
+                        dentry->d_name.name);
+        if (page == NULL)
+                goto out;
+        devname = nfs_devname(mnt_parent, dentry, page, PAGE_SIZE);
+        mnt = (struct vfsmount *)devname;
+        if (IS_ERR(devname))
+                goto free_page;
+        mnt = nfs_do_clone_mount(NFS_SB(mnt_parent->mnt_sb), devname, &mountdata);
+free_page:
+        free_page((unsigned long)page);
+out:
+        dprintk("%s: done\n", __FUNCTION__);
+        return mnt;
+}