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Message-ID: <20250828150947.GC8092@frogsfrogsfrogs>
Date: Thu, 28 Aug 2025 08:09:47 -0700
From: "Darrick J. Wong" <djwong@...nel.org>
To: Ojaswin Mujoo <ojaswin@...ux.ibm.com>
Cc: Zorro Lang <zlang@...hat.com>, fstests@...r.kernel.org,
Ritesh Harjani <ritesh.list@...il.com>, john.g.garry@...cle.com,
tytso@....edu, linux-xfs@...r.kernel.org,
linux-kernel@...r.kernel.org, linux-ext4@...r.kernel.org
Subject: Re: [PATCH v5 10/12] ext4: test atomic write and ioend codepaths
with bigalloc
On Fri, Aug 22, 2025 at 01:32:09PM +0530, Ojaswin Mujoo wrote:
> From: "Ritesh Harjani (IBM)" <ritesh.list@...il.com>
>
> This test does a lot of parallel RWF_ATOMIC IO on a preallocated file to
> stress the write and end-io unwritten conversion code paths. We brute
> force this for different blocksize and clustersizes and after each
> iteration we ensure the data was not torn or corrupted using fio crc
> verification.
>
> Note that in this test we use overlapping atomic writes of same io size.
> Although serializing racing writes is not guaranteed for RWF_ATOMIC,
> NVMe and SCSI provide this guarantee as an inseparable feature to
> power-fail atomicity. Keeping the iosize as same also ensures that ext4
> doesn't tear the write due to racing ioend unwritten conversion.
>
> The value of this test is that we make sure the RWF_ATOMIC is handled
> correctly by ext4 as well as test that the block layer doesn't split or
> only generate multiple bios for an atomic write.
>
> Signed-off-by: Ritesh Harjani (IBM) <ritesh.list@...il.com>
> Signed-off-by: Ojaswin Mujoo <ojaswin@...ux.ibm.com>
Looks good to me!
Reviewed-by: "Darrick J. Wong" <djwong@...nel.org>
--D
> ---
> tests/ext4/061 | 155 +++++++++++++++++++++++++++++++++++++++++++++
> tests/ext4/061.out | 2 +
> 2 files changed, 157 insertions(+)
> create mode 100755 tests/ext4/061
> create mode 100644 tests/ext4/061.out
>
> diff --git a/tests/ext4/061 b/tests/ext4/061
> new file mode 100755
> index 00000000..0ccf9f69
> --- /dev/null
> +++ b/tests/ext4/061
> @@ -0,0 +1,155 @@
> +#! /bin/bash
> +# SPDX-License-Identifier: GPL-2.0
> +# Copyright (c) 2025 IBM Corporation. All Rights Reserved.
> +#
> +# FS QA Test 061
> +#
> +# This test does a lot of parallel RWF_ATOMIC IO on a preallocated file to
> +# stress the write and end-io unwritten conversion code paths. We brute force
> +# this for all possible blocksize and clustersizes and after each iteration we
> +# ensure the data was not torn or corrupted using fio crc verification.
> +#
> +# Note that in this test we use overlapping atomic writes of same io size.
> +# Although serializing racing writes is not guaranteed for RWF_ATOMIC, NVMe and
> +# SCSI provide this guarantee as an inseparable feature to power-fail
> +# atomicity. Keeping the iosize as same also ensures that ext4 doesn't tear the
> +# write due to racing ioend unwritten conversion.
> +#
> +# The value of this test is that we make sure the RWF_ATOMIC is handled
> +# correctly by ext4 as well as test that the block layer doesn't split or only
> +# generate multiple bios for an atomic write.
> +
> +. ./common/preamble
> +. ./common/atomicwrites
> +
> +_begin_fstest auto rw stress atomicwrites
> +
> +_require_scratch_write_atomic
> +_require_aiodio
> +_require_fio_version "3.38+"
> +
> +FIO_LOAD=$(($(nproc) * 2 * LOAD_FACTOR))
> +SIZE=$((100*1024*1024))
> +
> +# Calculate fsblocksize as per bdev atomic write units.
> +bdev_awu_min=$(_get_atomic_write_unit_min $SCRATCH_DEV)
> +bdev_awu_max=$(_get_atomic_write_unit_max $SCRATCH_DEV)
> +bs=$(_max 4096 "$bdev_awu_min")
> +
> +function create_fio_configs()
> +{
> + local bsize=$1
> + create_fio_aw_config $bsize
> + create_fio_verify_config $bsize
> +}
> +
> +function create_fio_verify_config()
> +{
> + local bsize=$1
> +cat >$fio_verify_config <<EOF
> + [aio-dio-aw-verify]
> + direct=1
> + ioengine=libaio
> + rw=read
> + bs=$bsize
> + fallocate=native
> + filename=$SCRATCH_MNT/test-file
> + size=$SIZE
> + iodepth=$FIO_LOAD
> + numjobs=$FIO_LOAD
> + atomic=1
> + group_reporting=1
> +
> + verify_only=1
> + verify_state_save=0
> + verify=crc32c
> + verify_fatal=1
> + verify_write_sequence=0
> +EOF
> +}
> +
> +function create_fio_aw_config()
> +{
> + local bsize=$1
> +cat >$fio_aw_config <<EOF
> + [aio-dio-aw]
> + direct=1
> + ioengine=libaio
> + rw=randwrite
> + bs=$bsize
> + fallocate=native
> + filename=$SCRATCH_MNT/test-file
> + size=$SIZE
> + iodepth=$FIO_LOAD
> + numjobs=$FIO_LOAD
> + group_reporting=1
> + atomic=1
> +
> + verify_state_save=0
> + verify=crc32c
> + do_verify=0
> +
> +EOF
> +}
> +
> +run_test_one() {
> + local bs=$1
> + local cs=$2
> + local iosize=$3
> +
> + MKFS_OPTIONS="-O bigalloc -b $bs -C $cs"
> + _scratch_mkfs_ext4 >> $seqres.full 2>&1 || continue
> + if _try_scratch_mount >> $seqres.full 2>&1; then
> + echo "== Testing: bs=$bs cs=$cs iosize=$iosize ==" >> $seqres.full
> +
> + touch $SCRATCH_MNT/f1
> + create_fio_configs $iosize
> +
> + cat $fio_aw_config >> $seqres.full
> + echo >> $seqres.full
> + cat $fio_verify_config >> $seqres.full
> +
> + $FIO_PROG $fio_aw_config >> $seqres.full
> + ret1=$?
> +
> + $FIO_PROG $fio_verify_config >> $seqres.full
> + ret2=$?
> +
> + _scratch_unmount
> +
> + [[ $ret1 -eq 0 && $ret2 -eq 0 ]] || _fail "fio with atomic write failed"
> + fi
> +}
> +
> +run_test() {
> + local bs=$1
> +
> + # cluster sizes above 16 x blocksize are experimental so avoid them
> + # Also, cap cluster size at 128kb to keep it reasonable for large
> + # blocks size
> + max_cs=$(_min $((16 * bs)) "$bdev_awu_max" $((128 * 1024)))
> +
> + # Fuzz for combinations of blocksize, clustersize and
> + # iosize that cover most of the cases
> + run_test_one $bs $bs $bs
> + run_test_one $bs $max_cs $bs
> + run_test_one $bs $max_cs $max_cs
> + run_test_one $bs $max_cs $(_max "$((max_cs/2))" $bs)
> +}
> +
> +# Let's create a sample fio config to check whether fio supports all options.
> +fio_aw_config=$tmp.aw.fio
> +fio_verify_config=$tmp.verify.fio
> +fio_out=$tmp.fio.out
> +
> +create_fio_configs $bs
> +_require_fio $fio_aw_config
> +
> +for ((bs=$bs; bs <= $(_get_page_size); bs = $bs << 1)); do
> + run_test $bs
> +done
> +
> +# success, all done
> +echo Silence is golden
> +status=0
> +exit
> diff --git a/tests/ext4/061.out b/tests/ext4/061.out
> new file mode 100644
> index 00000000..273be9e0
> --- /dev/null
> +++ b/tests/ext4/061.out
> @@ -0,0 +1,2 @@
> +QA output created by 061
> +Silence is golden
> --
> 2.49.0
>
>
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