[PATCH 4/5] btrfs/282: reduce scrub dataset size

[David Disseldorp <ddiss@suse.de>]

The use of dmdelay means that we can use a smaller dataset while still
achieving a reasonable scrub duration. This also drops the xfs_io pwrite
/dev/urandom input file, instead relying on xfs_io's built-in
pseudorandom pattern generation.

Signed-off-by: David Disseldorp <ddiss@suse.de>
---
 tests/btrfs/282     | 8 +++-----
 tests/btrfs/282.out | 2 +-
 2 files changed, 4 insertions(+), 6 deletions(-)

diff --git a/tests/btrfs/282 b/tests/btrfs/282
index f9e22e12..42d992a6 100755
--- a/tests/btrfs/282
+++ b/tests/btrfs/282
@@ -25,8 +25,7 @@ _supported_fs btrfs
 _wants_kernel_commit eb3b50536642 \
 	"btrfs: scrub: per-device bandwidth control"
 
-# We want at least 5G for the scratch device.
-_require_scratch_size $(( 5 * 1024 * 1024))
+_require_scratch
 _require_dm_target delay
 
 # Make sure we can create scrub progress data file
@@ -49,9 +48,8 @@ if [ ! -f "${devinfo_dir}/scrub_speed_max" ]; then
 	_notrun "No sysfs interface for scrub speed throttle"
 fi
 
-# Create a 2G file for later scrub workload.
-# The 2G size is chosen to fit even DUP on a 5G disk.
-$XFS_IO_PROG -f -c "pwrite -i /dev/urandom 0 2G" $SCRATCH_MNT/file | _filter_xfs_io
+# Create a 100M file for later scrub workload.
+$XFS_IO_PROG -f -c "pwrite 0 100M" $SCRATCH_MNT/file | _filter_xfs_io
 
 # Writeback above data, as scrub only verify the committed data.
 sync
diff --git a/tests/btrfs/282.out b/tests/btrfs/282.out
index 8d53e7eb..840e3826 100644
--- a/tests/btrfs/282.out
+++ b/tests/btrfs/282.out
@@ -1,3 +1,3 @@
 QA output created by 282
-wrote 2147483648/2147483648 bytes at offset 0
+wrote 104857600/104857600 bytes at offset 0
 XXX Bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
-- 
2.35.3