On Tue, Jul 18, 2023 at 06:10:47PM -0700, Darrick J. Wong wrote:
> From: Darrick J. Wong <djwong@xxxxxxxxxx>
>
> Mikulas reported that this test became a forkbomb on his system when he
> tested it with bcachefs. Unlike XFS and ext4, which have large inodes
> consuming hundreds of bytes, bcachefs has very tiny ones. Therefore, it
> reports a large number of free inodes on a freshly mounted 1GB fs (~15
> million), which causes this test to try to create 15000 processes.
>
> There's really no reason to do that -- all this test wanted to do was to
> exhaust the number of inodes as quickly as possible using all available
> CPUs, and then it ran xfs_repair to try to reproduce a bug. Set the
> number of subshells to 4x the CPU count and spread the work among them
> instead of forking thousands of processes.
>
> Reported-by: Mikulas Patocka <mpatocka@xxxxxxxxxx>
> Signed-off-by: Darrick J. Wong <djwong@xxxxxxxxxx>
> Tested-by: Mikulas Patocka <mpatocka@xxxxxxxxxx>
> Reviewed-by: Bill O'Donnell <bodonnel@xxxxxxxxxx>
> ---
This version is good to me, will merge it.
Reviewed-by: Zorro Lang <zlang@xxxxxxxxxx>
> tests/generic/558 | 27 ++++++++++++++++++---------
> 1 file changed, 18 insertions(+), 9 deletions(-)
>
>
> diff --git a/tests/generic/558 b/tests/generic/558
> index 4e22ce656b..510b06f281 100755
> --- a/tests/generic/558
> +++ b/tests/generic/558
> @@ -19,9 +19,8 @@ create_file()
> local prefix=$3
> local i=0
>
> - while [ $i -lt $nr_file ]; do
> + for ((i = 0; i < nr_file; i++)); do
> echo -n > $dir/${prefix}_${i}
> - let i=$i+1
> done
> }
>
> @@ -39,15 +38,25 @@ _scratch_mkfs_sized $((1024 * 1024 * 1024)) >>$seqres.full 2>&1
> _scratch_mount
>
> i=0
> -free_inode=`_get_free_inode $SCRATCH_MNT`
> -file_per_dir=1000
> -loop=$((free_inode / file_per_dir + 1))
> +free_inodes=$(_get_free_inode $SCRATCH_MNT)
> +# Round the number of inodes to create up to the nearest 1000, like the old
> +# code did to make sure that we *cannot* allocate any more inodes at all.
> +free_inodes=$(( ( (free_inodes + 999) / 1000) * 1000 ))
> +nr_cpus=$(( $($here/src/feature -o) * 4 * LOAD_FACTOR ))
> +echo "free inodes: $free_inodes nr_cpus: $nr_cpus" >> $seqres.full
> +
> +if ((free_inodes <= nr_cpus)); then
> + nr_cpus=1
> + files_per_dir=$free_inodes
> +else
> + files_per_dir=$(( (free_inodes + nr_cpus - 1) / nr_cpus ))
> +fi
> mkdir -p $SCRATCH_MNT/testdir
> +echo "nr_cpus: $nr_cpus files_per_dir: $files_per_dir" >> $seqres.full
>
> -echo "Create $((loop * file_per_dir)) files in $SCRATCH_MNT/testdir" >>$seqres.full
> -while [ $i -lt $loop ]; do
> - create_file $SCRATCH_MNT/testdir $file_per_dir $i >>$seqres.full 2>&1 &
> - let i=$i+1
> +echo "Create $((nr_cpus * files_per_dir)) files in $SCRATCH_MNT/testdir" >>$seqres.full
> +for ((i = 0; i < nr_cpus; i++)); do
> + create_file $SCRATCH_MNT/testdir $files_per_dir $i >>$seqres.full 2>&1 &
> done
> wait
>
>
