NFS: Remove unnecessary check in nfs_read_folio()

All the callers are expected to supply a valid struct file argument, so
there is no need for the NULL check.

Reported-by: kernel test robot <lkp@intel.com>
Reported-by: Dan Carpenter <error27@gmail.com>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

Author: Trond Myklebust

fs/nfs/read.c

@@ -355,13 +355,7 @@ int nfs_read_folio(struct file *file, struct folio *folio)
 	if (NFS_STALE(inode))
 		goto out_unlock;
 
-	if (file == NULL) {
-		ret = -EBADF;
-		desc.ctx = nfs_find_open_context(inode, NULL, FMODE_READ);
-		if (desc.ctx == NULL)
-			goto out_unlock;
-	} else
-		desc.ctx = get_nfs_open_context(nfs_file_open_context(file));
+	desc.ctx = get_nfs_open_context(nfs_file_open_context(file));
 
 	xchg(&desc.ctx->error, 0);
 	nfs_pageio_init_read(&desc.pgio, inode, false,