From 685bcc56351b3e46b69d46118d23268b69052097 Mon Sep 17 00:00:00 2001
From: Ondrej Kozina <okozina@redhat.com>
Date: Tue, 19 Jun 2018 14:07:20 +0200
Subject: [PATCH 1/4] Zero length lseek blockwise i/o should return zero.

Note that both functions perform seek operations aligned to sector
boundary if possible before returning.

Unaligned input offset gets aligned on first preceding sector
boundary.
---
 lib/utils_io.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/lib/utils_io.c b/lib/utils_io.c
index 0f671d6..94c4ef6 100644
--- a/lib/utils_io.c
+++ b/lib/utils_io.c
@@ -199,7 +199,7 @@ ssize_t write_lseek_blockwise(int fd, size_t bsize, size_t alignment,
 	if (lseek(fd, offset - frontHang, SEEK_SET) < 0)
 		return -1;
 
-	if (frontHang) {
+	if (frontHang && length) {
 		if (posix_memalign(&frontPadBuf, alignment, bsize))
 			return -1;
 
@@ -253,7 +253,7 @@ ssize_t read_lseek_blockwise(int fd, size_t bsize, size_t alignment,
 	if (lseek(fd, offset - frontHang, SEEK_SET) < 0)
 		return -1;
 
-	if (frontHang) {
+	if (frontHang && length) {
 		if (posix_memalign(&frontPadBuf, alignment, bsize))
 			return -1;
 
-- 
1.8.3.1