1 files changed, 76 insertions, 0 deletions

diff --git a/fs/nfs/super.c b/fs/nfs/super.c
index 614efeed5437..b550e921f661 100644
--- a/fs/nfs/super.c
+++ b/fs/nfs/super.c
@@ -207,6 +207,7 @@ static int nfs_xdev_get_sb(struct file_system_type *fs_type,
                 int flags, const char *dev_name, void *raw_data, struct vfsmount *mnt);
 static void nfs_kill_super(struct super_block *);
 static void nfs_put_super(struct super_block *);
+static int nfs_remount(struct super_block *sb, int *flags, char *raw_data);
 
 static struct file_system_type nfs_fs_type = {
         .owner          = THIS_MODULE,
@@ -234,6 +235,7 @@ static const struct super_operations nfs_sops = {
         .umount_begin   = nfs_umount_begin,
         .show_options   = nfs_show_options,
         .show_stats     = nfs_show_stats,
+        .remount_fs     = nfs_remount,
 };
 
 #ifdef CONFIG_NFS_V4
@@ -278,6 +280,7 @@ static const struct super_operations nfs4_sops = {
         .umount_begin   = nfs_umount_begin,
         .show_options   = nfs_show_options,
         .show_stats     = nfs_show_stats,
+        .remount_fs     = nfs_remount,
 };
 #endif
 
@@ -1396,6 +1399,79 @@ out_invalid_fh:
         return -EINVAL;
 }
 
+static int
+nfs_compare_remount_data(struct nfs_server *nfss,
+                         struct nfs_parsed_mount_data *data)
+{
+        if (data->flags != nfss->flags ||
+            data->rsize != nfss->rsize ||
+            data->wsize != nfss->wsize ||
+            data->retrans != nfss->client->cl_timeout->to_retries ||
+            data->auth_flavors[0] != nfss->client->cl_auth->au_flavor ||
+            data->acregmin != nfss->acregmin / HZ ||
+            data->acregmax != nfss->acregmax / HZ ||
+            data->acdirmin != nfss->acdirmin / HZ ||
+            data->acdirmax != nfss->acdirmax / HZ ||
+            data->timeo != (10U * nfss->client->cl_timeout->to_initval / HZ) ||
+            data->nfs_server.addrlen != nfss->nfs_client->cl_addrlen ||
+            memcmp(&data->nfs_server.address, &nfss->nfs_client->cl_addr,
+                   data->nfs_server.addrlen) != 0)
+                return -EINVAL;
+
+        return 0;
+}
+
+static int
+nfs_remount(struct super_block *sb, int *flags, char *raw_data)
+{
+        int error;
+        struct nfs_server *nfss = sb->s_fs_info;
+        struct nfs_parsed_mount_data *data;
+        struct nfs_mount_data *options = (struct nfs_mount_data *)raw_data;
+        struct nfs4_mount_data *options4 = (struct nfs4_mount_data *)raw_data;
+
+        /*
+         * Userspace mount programs that send binary options generally send
+         * them populated with default values. We have no way to know which
+         * ones were explicitly specified. Fall back to legacy behavior and
+         * just return success.
+         */
+        if ((sb->s_type == &nfs4_fs_type && options4->version == 1) ||
+            (sb->s_type == &nfs_fs_type && options->version >= 1 &&
+             options->version <= 6))
+                return 0;
+
+        data = kzalloc(sizeof(*data), GFP_KERNEL);
+        if (data == NULL)
+                return -ENOMEM;
+
+        /* fill out struct with values from existing mount */
+        data->flags = nfss->flags;
+        data->rsize = nfss->rsize;
+        data->wsize = nfss->wsize;
+        data->retrans = nfss->client->cl_timeout->to_retries;
+        data->auth_flavors[0] = nfss->client->cl_auth->au_flavor;
+        data->acregmin = nfss->acregmin / HZ;
+        data->acregmax = nfss->acregmax / HZ;
+        data->acdirmin = nfss->acdirmin / HZ;
+        data->acdirmax = nfss->acdirmax / HZ;
+        data->timeo = 10U * nfss->client->cl_timeout->to_initval / HZ;
+        data->nfs_server.addrlen = nfss->nfs_client->cl_addrlen;
+        memcpy(&data->nfs_server.address, &nfss->nfs_client->cl_addr,
+                data->nfs_server.addrlen);
+
+        /* overwrite those values with any that were specified */
+        error = nfs_parse_mount_options((char *)options, data);
+        if (error < 0)
+                goto out;
+
+        /* compare new mount options with old ones */
+        error = nfs_compare_remount_data(nfss, data);
+out:
+        kfree(data);
+        return error;
+}
+
 /*
  * Initialise the common bits of the superblock
  */