btrfs-progs: Fix a clang dead-judgement warning in disk-io.c.

When compiled with clang, the following warning is outputted.

disk-io.c:1017:15: warning: comparison of unsigned expression < 0 is
always false [-Wtautological-compare]
        if (dev_size < 0)
            ~~~~~~~~ ^ ~
1 warning generated.

This is because dev_size is defined as unsigned type, but lseek() will
return singed valued.
So the judgement will always to false.

Use temporary off_t return value to solve it.

Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
Reviewed-by: Satoru Takeuchi <takeuchi_satoru@jp.fujitsu.com>
Signed-off-by: David Sterba <dsterba@suse.cz>

1 files changed, 6 insertions, 3 deletions

diff --git a/disk-io.c b/disk-io.c
index 03edf8ef..2bf85869 100644
--- a/disk-io.c
+++ b/disk-io.c
@@ -1009,13 +1009,16 @@ int btrfs_scan_fs_devices(int fd, const char *path,
 {
 	u64 total_devs;
 	u64 dev_size;
+	off_t seek_ret;
 	int ret;
 	if (!sb_bytenr)
 		sb_bytenr = BTRFS_SUPER_INFO_OFFSET;
 
-	dev_size = lseek(fd, 0, SEEK_END);
-	if (dev_size < 0)
-		return (int)(dev_size);
+	seek_ret = lseek(fd, 0, SEEK_END);
+	if (seek_ret < 0)
+		return -errno;
+
+	dev_size = seek_ret;
 	lseek(fd, 0, SEEK_SET);
 	if (sb_bytenr > dev_size) {
 		fprintf(stderr, "Superblock bytenr is larger than device size\n");