NFS: Error when mounting the same filesystem with different options

Unless the user sets the NFS_MOUNT_NOSHAREDCACHE mount flag, we should
return EBUSY if the filesystem is already mounted on a superblock that
has set conflicting mount options.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

diff --git a/fs/nfs/super.c b/fs/nfs/super.c
index 1b555cd41e3bae9ea5524cbdd3b3e9b1fda63099..a2b1af89ca1af331763a35f3b90f83864edd66d7 100644 (file)
--- a/fs/nfs/super.c
+++ b/fs/nfs/super.c
@@ -1317,7 +1317,9 @@ static int nfs_compare_super(struct super_block *sb, void *data)
 {
        struct nfs_server *server = data, *old = NFS_SB(sb);
 
-       if (old->nfs_client != server->nfs_client)
+       if (memcmp(&old->nfs_client->cl_addr,
+                               &server->nfs_client->cl_addr,
+                               sizeof(old->nfs_client->cl_addr)) != 0)
                return 0;
        /* Note: NFS_MOUNT_UNSHARED == NFS4_MOUNT_UNSHARED */
        if (old->flags & NFS_MOUNT_UNSHARED)
@@ -1327,6 +1329,39 @@ static int nfs_compare_super(struct super_block *sb, void *data)
        return 1;
 }
 
+#define NFS_MS_MASK (MS_RDONLY|MS_NOSUID|MS_NODEV|MS_NOEXEC|MS_SYNCHRONOUS)
+
+static int nfs_compare_mount_options(const struct super_block *s, const struct nfs_server *b, int flags)
+{
+       const struct nfs_server *a = s->s_fs_info;
+       const struct rpc_clnt *clnt_a = a->client;
+       const struct rpc_clnt *clnt_b = b->client;
+
+       if ((s->s_flags & NFS_MS_MASK) != (flags & NFS_MS_MASK))
+               goto Ebusy;
+       if (a->nfs_client != b->nfs_client)
+               goto Ebusy;
+       if (a->flags != b->flags)
+               goto Ebusy;
+       if (a->wsize != b->wsize)
+               goto Ebusy;
+       if (a->rsize != b->rsize)
+               goto Ebusy;
+       if (a->acregmin != b->acregmin)
+               goto Ebusy;
+       if (a->acregmax != b->acregmax)
+               goto Ebusy;
+       if (a->acdirmin != b->acdirmin)
+               goto Ebusy;
+       if (a->acdirmax != b->acdirmax)
+               goto Ebusy;
+       if (clnt_a->cl_auth->au_flavor != clnt_b->cl_auth->au_flavor)
+               goto Ebusy;
+       return 0;
+Ebusy:
+       return -EBUSY;
+}
+
 static int nfs_get_sb(struct file_system_type *fs_type,
        int flags, const char *dev_name, void *raw_data, struct vfsmount *mnt)
 {
@@ -1361,8 +1396,11 @@ static int nfs_get_sb(struct file_system_type *fs_type,
        }
 
        if (s->s_fs_info != server) {
+               error = nfs_compare_mount_options(s, server, flags);
                nfs_free_server(server);
                server = NULL;
+               if (error < 0)
+                       goto error_splat_super;
        }
 
        if (!s->s_root) {
@@ -1442,8 +1480,11 @@ static int nfs_xdev_get_sb(struct file_system_type *fs_type, int flags,
        }
 
        if (s->s_fs_info != server) {
+               error = nfs_compare_mount_options(s, server, flags);
                nfs_free_server(server);
                server = NULL;
+               if (error < 0)
+                       goto error_splat_super;
        }
 
        if (!s->s_root) {