nfs: keep server info for remounts

With newer kernels that use fs_context for nfs mounts, remounts fail with
-EINVAL.

$ mount -t nfs -o nolock 10.0.0.1:/tmp/test /mnt/test/
$ mount -t nfs -o remount /mnt/test/
mount: mounting 10.0.0.1:/tmp/test on /mnt/test failed: Invalid argument

For remounts, the nfs server address and port are populated by
nfs_init_fs_context and later overwritten with 0x00 bytes by
nfs23_parse_monolithic. The remount then fails as the server address is
invalid.

Fix this by not overwriting nfs server info in nfs23_parse_monolithic if
we're doing a remount.

Fixes: f2aedb713c28 ("NFS: Add fs_context support.")
Signed-off-by: Martin Kaiser <martin@kaiser.cx>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

diff --git a/fs/nfs/fs_context.c b/fs/nfs/fs_context.c
index ec93306b7e79d4d0503b4e6a2e1d5d6a1a0a2067..6c9f3f6645dd51759dd5e7e1a61abb868e038c51 100644 (file)
--- a/fs/nfs/fs_context.c
+++ b/fs/nfs/fs_context.c
@@ -1114,9 +1114,12 @@ static int nfs23_parse_monolithic(struct fs_context *fc,
                ctx->acdirmax   = data->acdirmax;
                ctx->need_mount = false;
 
-               memcpy(sap, &data->addr, sizeof(data->addr));
-               ctx->nfs_server.addrlen = sizeof(data->addr);
-               ctx->nfs_server.port = ntohs(data->addr.sin_port);
+               if (!is_remount_fc(fc)) {
+                       memcpy(sap, &data->addr, sizeof(data->addr));
+                       ctx->nfs_server.addrlen = sizeof(data->addr);
+                       ctx->nfs_server.port = ntohs(data->addr.sin_port);
+               }
+
                if (sap->ss_family != AF_INET ||
                    !nfs_verify_server_address(sap))
                        goto out_no_address;