generic/042: fix stale disk contents check

This test doesn't call fsync or sync to force writeback of the first 60k
of the file, which means that we could end up with a file full of
zeroes or an empty file.  Since this is a regression test that looks for
stale disk contents slipping through, change the test to look for the
stale bytes.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Eryu Guan <guaneryu@gmail.com>
Signed-off-by: Eryu Guan <guaneryu@gmail.com>

diff --git a/tests/generic/042 b/tests/generic/042
index 1aa18f9b82413afb2e4110e04b40b21fe621e843..6c62eb63ba826c13cd679b92ac1ee3d6ae3a6daa 100755 (executable)
--- a/tests/generic/042
+++ b/tests/generic/042
@@ -44,7 +44,7 @@ _crashtest()
 
        # Create an fs on a small, initialized image. The pattern is written to
        # the image to detect stale data exposure.
-       $XFS_IO_PROG -f -c "truncate 0" -c "pwrite 0 25M" $img \
+       $XFS_IO_PROG -f -c "truncate 0" -c "pwrite -S 0xCD 0 25M" $img \
                >> $seqres.full 2>&1
        _mkfs_dev $img >> $seqres.full 2>&1
 
@@ -61,8 +61,12 @@ _crashtest()
        $UMOUNT_PROG $mnt
        _mount $img $mnt
 
-       # we generally expect a zero-sized file (this should be silent)
-       hexdump $file
+       # We should /never/ see 0xCD in the file, because we wrote that pattern
+       # to the filesystem image to expose stale data.
+       if hexdump -v -e '/1 "%02X "' $file | grep -q "CD"; then
+               echo "Saw stale data!!!"
+               hexdump $file
+       fi
 
        $UMOUNT_PROG $mnt
 }