[PATCH v2] f2fs/011: use random data to avoid file compression

[PATCH v2] f2fs/011: use random data to avoid file compression

[Joanne Chang]

Currently, the created files are filled with 0. When filesystem level
compression is used, they take up much less space than expected. So
the final fallocate does not show an error.

The created files are filled by /dev/urandom instead to ensure they
are not compressed. This way the files take up the same space whether
compression is used or not.

Signed-off-by: Joanne Chang <joannechien@google.com>
---
v2:
- changed dd to $XFS_IO_PROG as suggested by Chao Yu

 tests/f2fs/011 | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tests/f2fs/011 b/tests/f2fs/011
index c21cb586..07c94d8c 100755
--- a/tests/f2fs/011
+++ b/tests/f2fs/011
@@ -36,7 +36,7 @@ pinfile=$SCRATCH_MNT/file
 
 # simulate fragment status in f2fs
 for ((i=0;i<256;i++)) do
-	$XFS_IO_PROG -f -c "pwrite 0 1m" $SCRATCH_MNT/$i >>$seqres.full
+	$XFS_IO_PROG -f -c "pwrite -i /dev/urandom 0 1m" $SCRATCH_MNT/$i >>$seqres.full
 done
 sync
 
-- 
2.51.1.930.gacf6e81ea2-goog

Re: [PATCH v2] f2fs/011: use random data to avoid file compression

[Chao Yu]

On 10/30/25 13:45, Joanne Chang wrote:
> Currently, the created files are filled with 0. When filesystem level
> compression is used, they take up much less space than expected. So
> the final fallocate does not show an error.
> 
> The created files are filled by /dev/urandom instead to ensure they
> are not compressed. This way the files take up the same space whether
> compression is used or not.
> 
> Signed-off-by: Joanne Chang <joannechien@google.com>

Reviewed-by: Chao Yu <chao@kernel.org>

Thanks,