[PATCH] mkfs.xfs: fix fd validity check in get_topology

[Christoph Hellwig]

Only negatie return values from open mean we failed to open the device.
Without this check we do not print the usage message when no device is
specified.  This leads to a weird failure in xfstests 122.

Signed-off-by: Christoph Hellwig <hch at lst.de>

Index: xfsprogs-dev/mkfs/xfs_mkfs.c
===================================================================
--- xfsprogs-dev.orig/mkfs/xfs_mkfs.c	2010-01-30 20:44:03.505255109 +0100
+++ xfsprogs-dev/mkfs/xfs_mkfs.c	2010-01-30 20:44:20.579255807 +0100
@@ -455,7 +455,7 @@ static void get_topology(libxfs_init_t *
 				&ft->dsunit, &ft->dswidth, &ft->sectoralign);
 		fd = open(dfile, O_RDONLY);
 		/* If this fails we just fall back to BBSIZE */
-		if (fd) {
+		if (fd >= 0) {
 			platform_findsizes(dfile, fd, &dummy, &bsz);
 			close(fd);
 		}