nfs: nfs_file_write() should check for writeback errors

The NFS_CONTEXT_ERROR_WRITE flag (as well as the check of said flag) was
removed by commit 6fbda89.  The absence of an error check allows
writes to be continually queued up for a server that may no longer be
able to handle them.  Fix it by adding an error check using the generic
error reporting functions.

Fixes: 6fbda89 ("NFS: Replace custom error reporting mechanism with generic one")
Signed-off-by: Scott Mayhew <smayhew@redhat.com>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

fs/nfs/file.c

@@ -591,12 +591,14 @@ static const struct vm_operations_struct nfs_file_vm_ops = {
 	.page_mkwrite = nfs_vm_page_mkwrite,
 };
 
-static int nfs_need_check_write(struct file *filp, struct inode *inode)
+static int nfs_need_check_write(struct file *filp, struct inode *inode,
+				int error)
 {
 	struct nfs_open_context *ctx;
 
 	ctx = nfs_file_open_context(filp);
-	if (nfs_ctx_key_to_expire(ctx, inode))
+	if (nfs_error_is_fatal_on_server(error) ||
+	    nfs_ctx_key_to_expire(ctx, inode))
 		return 1;
 	return 0;
 }
@@ -607,6 +609,8 @@ ssize_t nfs_file_write(struct kiocb *iocb, struct iov_iter *from)
 	struct inode *inode = file_inode(file);
 	unsigned long written = 0;
 	ssize_t result;
+	errseq_t since;
+	int error;
 
 	result = nfs_key_timeout_notify(file, inode);
 	if (result)
@@ -631,6 +635,7 @@ ssize_t nfs_file_write(struct kiocb *iocb, struct iov_iter *from)
 	if (iocb->ki_pos > i_size_read(inode))
 		nfs_revalidate_mapping(inode, file->f_mapping);
 
+	since = filemap_sample_wb_err(file->f_mapping);
 	nfs_start_io_write(inode);
 	result = generic_write_checks(iocb, from);
 	if (result > 0) {
@@ -649,7 +654,8 @@ ssize_t nfs_file_write(struct kiocb *iocb, struct iov_iter *from)
 		goto out;
 
 	/* Return error values */
-	if (nfs_need_check_write(file, inode)) {
+	error = filemap_check_wb_err(file->f_mapping, since);
+	if (nfs_need_check_write(file, inode, error)) {
 		int err = nfs_wb_all(inode);
 		if (err < 0)
 			result = err;