staging: lustre: llite: ll_write_begin/end not passing on errors

Because of a implementation of generic_perform_write(), write(2)
may return 0 with no errno even if EDQUOT or ENOSPC actually
happened in it. This patch fixes the issue with setting a proper
errno to ci_result.
Signed-off-by: Hiroya Nozaki <nozaki.hiroya@jp.fujitsu.com>
Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-6732
Reviewed-on: http://review.whamcloud.com/15302Reviewed-by: Bobi Jam <bobijam@hotmail.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>
Signed-off-by: James Simmons <jsimmons@infradead.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/lustre/lustre/llite/rw26.c

@@ -478,6 +478,7 @@ static int ll_write_begin(struct file *file, struct address_space *mapping,
 
 	lcc = ll_cl_find(file);
 	if (!lcc) {
+		io = NULL;
 		result = -EIO;
 		goto out;
 	}
@@ -558,6 +559,8 @@ static int ll_write_begin(struct file *file, struct address_space *mapping,
 			lu_ref_del(&page->cp_reference, "cl_io", io);
 			cl_page_put(env, page);
 		}
+		if (io)
+			io->ci_result = result;
 	} else {
 		*pagep = vmpage;
 		*fsdata = lcc;
@@ -627,6 +630,8 @@ static int ll_write_end(struct file *file, struct address_space *mapping,
 	    file->f_flags & O_SYNC || IS_SYNC(file_inode(file)))
 		result = vvp_io_write_commit(env, io);
 
+	if (result < 0)
+		io->ci_result = result;
 	return result >= 0 ? copied : result;
 }