1 files changed, 157 insertions, 21 deletions

diff --git a/fs/nfs/super.c b/fs/nfs/super.c
index 3d460527daab..8e0673a0d6aa 100644
--- a/fs/nfs/super.c
+++ b/fs/nfs/super.c
@@ -42,6 +42,8 @@
 #include <linux/smp_lock.h>
 #include <linux/seq_file.h>
 #include <linux/mount.h>
+#include <linux/mnt_namespace.h>
+#include <linux/namei.h>
 #include <linux/nfs_idmap.h>
 #include <linux/vfs.h>
 #include <linux/inet.h>
@@ -272,10 +274,14 @@ static const struct super_operations nfs_sops = {
 #ifdef CONFIG_NFS_V4
 static int nfs4_get_sb(struct file_system_type *fs_type,
         int flags, const char *dev_name, void *raw_data, struct vfsmount *mnt);
+static int nfs4_remote_get_sb(struct file_system_type *fs_type,
+        int flags, const char *dev_name, void *raw_data, struct vfsmount *mnt);
 static int nfs4_xdev_get_sb(struct file_system_type *fs_type,
         int flags, const char *dev_name, void *raw_data, struct vfsmount *mnt);
 static int nfs4_referral_get_sb(struct file_system_type *fs_type,
         int flags, const char *dev_name, void *raw_data, struct vfsmount *mnt);
+static int nfs4_remote_referral_get_sb(struct file_system_type *fs_type,
+        int flags, const char *dev_name, void *raw_data, struct vfsmount *mnt);
 static void nfs4_kill_super(struct super_block *sb);
 
 static struct file_system_type nfs4_fs_type = {
@@ -286,6 +292,14 @@ static struct file_system_type nfs4_fs_type = {
         .fs_flags       = FS_RENAME_DOES_D_MOVE|FS_REVAL_DOT|FS_BINARY_MOUNTDATA,
 };
 
+static struct file_system_type nfs4_remote_fs_type = {
+        .owner          = THIS_MODULE,
+        .name           = "nfs4",
+        .get_sb         = nfs4_remote_get_sb,
+        .kill_sb        = nfs4_kill_super,
+        .fs_flags       = FS_RENAME_DOES_D_MOVE|FS_REVAL_DOT|FS_BINARY_MOUNTDATA,
+};
+
 struct file_system_type nfs4_xdev_fs_type = {
         .owner          = THIS_MODULE,
         .name           = "nfs4",
@@ -294,6 +308,14 @@ struct file_system_type nfs4_xdev_fs_type = {
         .fs_flags       = FS_RENAME_DOES_D_MOVE|FS_REVAL_DOT|FS_BINARY_MOUNTDATA,
 };
 
+static struct file_system_type nfs4_remote_referral_fs_type = {
+        .owner          = THIS_MODULE,
+        .name           = "nfs4",
+        .get_sb         = nfs4_remote_referral_get_sb,
+        .kill_sb        = nfs4_kill_super,
+        .fs_flags       = FS_RENAME_DOES_D_MOVE|FS_REVAL_DOT|FS_BINARY_MOUNTDATA,
+};
+
 struct file_system_type nfs4_referral_fs_type = {
         .owner          = THIS_MODULE,
         .name           = "nfs4",
@@ -2433,12 +2455,12 @@ out_no_client_address:
 }
 
 /*
- * Get the superblock for an NFS4 mountpoint
+ * Get the superblock for the NFS4 root partition
  */
-static int nfs4_get_sb(struct file_system_type *fs_type,
+static int nfs4_remote_get_sb(struct file_system_type *fs_type,
         int flags, const char *dev_name, void *raw_data, struct vfsmount *mnt)
 {
-        struct nfs_parsed_mount_data *data;
+        struct nfs_parsed_mount_data *data = raw_data;
         struct super_block *s;
         struct nfs_server *server;
         struct nfs_fh *mntfh;
@@ -2449,18 +2471,12 @@ static int nfs4_get_sb(struct file_system_type *fs_type,
         };
         int error = -ENOMEM;
 
-        data = kzalloc(sizeof(*data), GFP_KERNEL);
         mntfh = kzalloc(sizeof(*mntfh), GFP_KERNEL);
         if (data == NULL || mntfh == NULL)
                 goto out_free_fh;
 
         security_init_mnt_opts(&data->lsm_opts);
 
-        /* Validate the mount data */
-        error = nfs4_validate_mount_data(raw_data, data, dev_name);
-        if (error < 0)
-                goto out;
-
         /* Get a volume representation */
         server = nfs4_create_server(data, mntfh);
         if (IS_ERR(server)) {
@@ -2473,7 +2489,7 @@ static int nfs4_get_sb(struct file_system_type *fs_type,
                 compare_super = NULL;
 
         /* Get a superblock - note that we may end up sharing one that already exists */
-        s = sget(fs_type, compare_super, nfs_set_super, &sb_mntdata);
+        s = sget(&nfs4_fs_type, compare_super, nfs_set_super, &sb_mntdata);
         if (IS_ERR(s)) {
                 error = PTR_ERR(s);
                 goto out_free;
@@ -2510,14 +2526,9 @@ static int nfs4_get_sb(struct file_system_type *fs_type,
         error = 0;
 
 out:
-        kfree(data->client_address);
-        kfree(data->nfs_server.export_path);
-        kfree(data->nfs_server.hostname);
-        kfree(data->fscache_uniq);
         security_free_mnt_opts(&data->lsm_opts);
 out_free_fh:
         kfree(mntfh);
-        kfree(data);
         return error;
 
 out_free:
@@ -2531,6 +2542,102 @@ error_splat_super:
         goto out;
 }
 
+static struct vfsmount *nfs_do_root_mount(struct file_system_type *fs_type,
+                int flags, void *data, const char *hostname)
+{
+        struct vfsmount *root_mnt;
+        char *root_devname;
+        size_t len;
+
+        len = strlen(hostname) + 3;
+        root_devname = kmalloc(len, GFP_KERNEL);
+        if (root_devname == NULL)
+                return ERR_PTR(-ENOMEM);
+        snprintf(root_devname, len, "%s:/", hostname);
+        root_mnt = vfs_kern_mount(fs_type, flags, root_devname, data);
+        kfree(root_devname);
+        return root_mnt;
+}
+
+static int nfs_follow_remote_path(struct vfsmount *root_mnt,
+                const char *export_path, struct vfsmount *mnt_target)
+{
+        struct mnt_namespace *ns_private;
+        struct nameidata nd;
+        struct super_block *s;
+        int ret;
+
+        ns_private = create_mnt_ns(root_mnt);
+        ret = PTR_ERR(ns_private);
+        if (IS_ERR(ns_private))
+                goto out_mntput;
+
+        ret = vfs_path_lookup(root_mnt->mnt_root, root_mnt,
+                        export_path, LOOKUP_FOLLOW, &nd);
+
+        put_mnt_ns(ns_private);
+
+        if (ret != 0)
+                goto out_err;
+
+        s = nd.path.mnt->mnt_sb;
+        atomic_inc(&s->s_active);
+        mnt_target->mnt_sb = s;
+        mnt_target->mnt_root = dget(nd.path.dentry);
+
+        path_put(&nd.path);
+        down_write(&s->s_umount);
+        return 0;
+out_mntput:
+        mntput(root_mnt);
+out_err:
+        return ret;
+}
+
+/*
+ * Get the superblock for an NFS4 mountpoint
+ */
+static int nfs4_get_sb(struct file_system_type *fs_type,
+        int flags, const char *dev_name, void *raw_data, struct vfsmount *mnt)
+{
+        struct nfs_parsed_mount_data *data;
+        char *export_path;
+        struct vfsmount *root_mnt;
+        int error = -ENOMEM;
+
+        data = kzalloc(sizeof(*data), GFP_KERNEL);
+        if (data == NULL)
+                goto out_free_data;
+
+        /* Validate the mount data */
+        error = nfs4_validate_mount_data(raw_data, data, dev_name);
+        if (error < 0)
+                goto out;
+
+        export_path = data->nfs_server.export_path;
+        data->nfs_server.export_path = "/";
+        root_mnt = nfs_do_root_mount(&nfs4_remote_fs_type, flags, data,
+                        data->nfs_server.hostname);
+        data->nfs_server.export_path = export_path;
+
+        error = PTR_ERR(root_mnt);
+        if (IS_ERR(root_mnt))
+                goto out;
+
+        error = nfs_follow_remote_path(root_mnt, export_path, mnt);
+
+out:
+        kfree(data->client_address);
+        kfree(data->nfs_server.export_path);
+        kfree(data->nfs_server.hostname);
+        kfree(data->fscache_uniq);
+out_free_data:
+        kfree(data);
+        dprintk("<-- nfs4_get_sb() = %d%s\n", error,
+                        error != 0 ? " [error]" : "");
+        return error;
+}
+
 static void nfs4_kill_super(struct super_block *sb)
 {
         struct nfs_server *server = NFS_SB(sb);
@@ -2627,12 +2734,9 @@ error_splat_super:
         return error;
 }
 
-/*
- * Create an NFS4 server record on referral traversal
- */
-static int nfs4_referral_get_sb(struct file_system_type *fs_type, int flags,
-                                const char *dev_name, void *raw_data,
-                                struct vfsmount *mnt)
+static int nfs4_remote_referral_get_sb(struct file_system_type *fs_type,
+                int flags, const char *dev_name, void *raw_data,
+                struct vfsmount *mnt)
 {
         struct nfs_clone_mount *data = raw_data;
         struct super_block *s;
@@ -2711,4 +2815,36 @@ error_splat_super:
         return error;
 }
 
+/*
+ * Create an NFS4 server record on referral traversal
+ */
+static int nfs4_referral_get_sb(struct file_system_type *fs_type,
+                int flags, const char *dev_name, void *raw_data,
+                struct vfsmount *mnt)
+{
+        struct nfs_clone_mount *data = raw_data;
+        char *export_path;
+        struct vfsmount *root_mnt;
+        int error;
+
+        dprintk("--> nfs4_referral_get_sb()\n");
+
+        export_path = data->mnt_path;
+        data->mnt_path = "/";
+
+        root_mnt = nfs_do_root_mount(&nfs4_remote_referral_fs_type,
+                        flags, data, data->hostname);
+        data->mnt_path = export_path;
+
+        error = PTR_ERR(root_mnt);
+        if (IS_ERR(root_mnt))
+                goto out;
+
+        error = nfs_follow_remote_path(root_mnt, export_path, mnt);
+out:
+        dprintk("<-- nfs4_referral_get_sb() = %d%s\n", error,
+                        error != 0 ? " [error]" : "");
+        return error;
+}
+
 #endif /* CONFIG_NFS_V4 */