mm: clear AS_EIO/AS_ENOSPC when writeback initiation fails

filemap_write_and_wait{_range} will return an error if writeback
initiation fails, but won't clear errors in the address_space. This is
particularly problematic on DAX, as filemap_fdatawrite* is
effectively synchronous there. Ensure that we clear the AS_EIO/AS_ENOSPC
flags when filemap_fdatawrite* returns an error.

Signed-off-by: Jeff Layton <jlayton@redhat.com>

mm/filemap.c

@@ -515,6 +515,9 @@ int filemap_write_and_wait(struct address_space *mapping)
 			int err2 = filemap_fdatawait(mapping);
 			if (!err)
 				err = err2;
+		} else {
+			/* Clear any previously stored errors */
+			filemap_check_errors(mapping);
 		}
 	} else {
 		err = filemap_check_errors(mapping);
@@ -549,6 +552,9 @@ int filemap_write_and_wait_range(struct address_space *mapping,
 						lstart, lend);
 			if (!err)
 				err = err2;
+		} else {
+			/* Clear any previously stored errors */
+			filemap_check_errors(mapping);
 		}
 	} else {
 		err = filemap_check_errors(mapping);