[bug report] NFS: Convert to the netfs API and nfs_readpage to use netfs_readpage

[Dan Carpenter <dan.carpenter@oracle.com>]

Hello Dave Wysochanski,

This is a semi-automatic email about new static checker warnings.

The patch bc6d7b12e4ea: "NFS: Convert to the netfs API and
nfs_readpage to use netfs_readpage" from Nov 14, 2020, leads to the
following Smatch complaint:

    fs/nfs/read.c:365 nfs_readpage()
    error: we previously assumed 'file' could be null (see line 356)

fs/nfs/read.c
   355	
   356		if (file == NULL) {
                    ^^^^^^^^^^^^
"file" is NULL here

   357			ret = -EBADF;
   358			desc.ctx = nfs_find_open_context(inode, NULL, FMODE_READ);
   359			if (desc.ctx == NULL)
   360				goto out_unlock;
   361		} else
   362			desc.ctx = get_nfs_open_context(nfs_file_open_context(file));
   363	
   364		if (!IS_SYNC(inode)) {
   365			ret = nfs_readpage_from_fscache(file, page, &desc);
                                                        ^^^^
Unchecked dereference inside function call.

   366			if (ret == 0)
   367				goto out;

regards,
dan carpenter