Re: [PATCH v5] generic: add a test for atomic writes

Ritesh Harjani
2025-04-15T13:26:24Z

Catherine Hoang <catherine.hoang@oracle.com> writes:

> Add a test to validate the new atomic writes feature.
>
> Signed-off-by: Catherine Hoang <catherine.hoang@oracle.com>
> Reviewed-by: Nirjhar Roy (IBM) <nirjhar.roy.lists@gmail.com>
> Reviewed-by: John Garry <john.g.garry@oracle.com>
> ---
> common/rc | 51 ++++++++++++
> tests/generic/765 | 188 ++++++++++++++++++++++++++++++++++++++++++
> tests/generic/765.out | 2 +
> 3 files changed, 241 insertions(+)
> create mode 100755 tests/generic/765
> create mode 100644 tests/generic/765.out
>
> diff --git a/common/rc b/common/rc
> index 16d627e1..25e6a1f7 100644
> --- a/common/rc
> +++ b/common/rc
> @@ -2996,6 +2996,10 @@ _require_xfs_io_command()
> opts+=" -d"
> pwrite_opts+="-V 1 -b 4k"
> fi
> + if [ "$param" == "-A" ]; then
> + opts+=" -d"
> + pwrite_opts+="-D -V 1 -b 4k"

It's not strictly required for -A to also have -D in pwrite_opts.
We might need to add tests later where we would like to test data
integrity tests with atomic writes, correct?

So do we really need to add pwrite_opts with -D too? IMO, we can drop
-D, as the test here suggests that -A can only work with the options
specified in pwrite_opts.

> + fi
> testio=`$XFS_IO_PROG -f $opts -c \
> "pwrite $pwrite_opts $param 0 4k" $testfile 2>&1`
> param_checked="$pwrite_opts $param"
> @@ -5443,6 +5447,53 @@ _require_scratch_btime()
> _scratch_unmount
> }
>
> +_get_atomic_write_unit_min()
> +{
> + $XFS_IO_PROG -c "statx -r -m $STATX_WRITE_ATOMIC" $1 | \
> + grep atomic_write_unit_min | grep -o '[0-9]\+'
> +}
> +
> +_get_atomic_write_unit_max()
> +{
> + $XFS_IO_PROG -c "statx -r -m $STATX_WRITE_ATOMIC" $1 | \
> + grep atomic_write_unit_max | grep -o '[0-9]\+'
> +}
> +
> +_get_atomic_write_segments_max()
> +{
> + $XFS_IO_PROG -c "statx -r -m $STATX_WRITE_ATOMIC" $1 | \
> + grep atomic_write_segments_max | grep -o '[0-9]\+'
> +}
> +
> +_require_scratch_write_atomic()
> +{
> + _require_scratch
> +
> + export STATX_WRITE_ATOMIC=0x10000
> +
> + awu_min_bdev=$(_get_atomic_write_unit_min $SCRATCH_DEV)
> + awu_max_bdev=$(_get_atomic_write_unit_max $SCRATCH_DEV)
> +
> + if [ $awu_min_bdev -eq 0 ] && [ $awu_max_bdev -eq 0 ]; then
> + _notrun "write atomic not supported by this block device"
> + fi
> +
> + _scratch_mkfs > /dev/null 2>&1
> + _scratch_mount
> +
> + testfile=$SCRATCH_MNT/testfile
> + touch $testfile
> +
> + awu_min_fs=$(_get_atomic_write_unit_min $testfile)
> + awu_max_fs=$(_get_atomic_write_unit_max $testfile)
> +
> + _scratch_unmount
> +
> + if [ $awu_min_fs -eq 0 ] && [ $awu_max_fs -eq 0 ]; then
> + _notrun "write atomic not supported by this filesystem"
> + fi
> +}
> +
> _require_inode_limits()
> {
> if [ $(_get_free_inode $TEST_DIR) -eq 0 ]; then
> diff --git a/tests/generic/765 b/tests/generic/765
> new file mode 100755
> index 00000000..9bab3b8a
> --- /dev/null
> +++ b/tests/generic/765
> @@ -0,0 +1,188 @@
> +#! /bin/bash
> +# SPDX-License-Identifier: GPL-2.0
> +# Copyright (c) 2025 Oracle. All Rights Reserved.
> +#
> +# FS QA Test 765
> +#
> +# Validate atomic write support
> +#
> +. ./common/preamble
> +_begin_fstest auto quick rw
> +
> +_require_scratch_write_atomic
> +_require_xfs_io_command pwrite -A
> +
> +get_supported_bsize()
> +{
> + case "$FSTYP" in
> + "xfs")
> + min_bsize=1024
> + for ((i = 65536; i >= 1024; i /= 2)); do
> + _scratch_mkfs -b size=$i >> $seqres.full || continue
> + if _try_scratch_mount >> $seqres.full 2>&1; then
> + max_bsize=$i
> + _scratch_unmount
> + break;
> + fi
> + done
> + ;;
> + "ext4")
> + min_bsize=1024
> + max_bsize=4096

Shouldn't we keep max_bsize as system's pagesize? For systems with 64k
pagesize max_bsize can be 64k.

max_bsize=$(_get_page_size)

> + ;;
> + *)
> + _notrun "$FSTYP does not support atomic writes"
> + ;;
> + esac
> +}
> +
> +get_mkfs_opts()
> +{
> + local bsize=$1
> +
> + case "$FSTYP" in
> + "xfs")
> + mkfs_opts="-b size=$bsize"
> + ;;
> + "ext4")
> + mkfs_opts="-b $bsize"
> + ;;
> + *)
> + _notrun "$FSTYP does not support atomic writes"
> + ;;
> + esac
> +}
> +
> +test_atomic_writes()
> +{
> + local bsize=$1
> +
> + get_mkfs_opts $bsize
> + _scratch_mkfs $mkfs_opts >> $seqres.full
> + _scratch_mount
> +
> + test "$FSTYP" = "xfs" && _xfs_force_bdev data $SCRATCH_MNT

Ok, this (_xfs_force_bdev()) clears the rtinherit flag on $SCRATCH_MNT
in case if someone is passing that in MKFS_OPTIONS right? But since we
are using our own mkfs_opts, then do we still need this?

> +
> + testfile=$SCRATCH_MNT/testfile
> + touch $testfile
> +
> + file_min_write=$(_get_atomic_write_unit_min $testfile)
> + file_max_write=$(_get_atomic_write_unit_max $testfile)
> + file_max_segments=$(_get_atomic_write_segments_max $testfile)
> +
> + # Check that atomic min/max = FS block size
> + test $file_min_write -eq $bsize || \
> + echo "atomic write min $file_min_write, should be fs block size $bsize"
> + test $file_min_write -eq $bsize || \

we should check for $file_max_write here ^^

> + echo "atomic write max $file_max_write, should be fs block size $bsize"
> + test $file_max_segments -eq 1 || \
> + echo "atomic write max segments $file_max_segments, should be 1"
> +
> + # Check that we can perform an atomic write of len = FS block size
> + bytes_written=$($XFS_IO_PROG -dc "pwrite -A -D -V1 -b $bsize 0 $bsize" $testfile | \
> + grep wrote | awk -F'[/ ]' '{print $2}')
> + test $bytes_written -eq $bsize || echo "atomic write len=$bsize failed"
> +
> + # Check that we can perform an atomic single-block cow write
> + if [ "$FSTYP" == "xfs" ]; then
> + testfile_cp=$SCRATCH_MNT/testfile_copy
> + if _xfs_has_feature $SCRATCH_MNT reflink; then
> + cp --reflink $testfile $testfile_cp
> + fi
> + bytes_written=$($XFS_IO_PROG -dc "pwrite -A -D -V1 -b $bsize 0 $bsize" $testfile_cp | \
> + grep wrote | awk -F'[/ ]' '{print $2}')
> + test $bytes_written -eq $bsize || echo "atomic write on reflinked file failed"
> + fi
> +
> + # Check that we can perform an atomic write on an unwritten block
> + $XFS_IO_PROG -c "falloc $bsize $bsize" $testfile
> + bytes_written=$($XFS_IO_PROG -dc "pwrite -A -D -V1 -b $bsize $bsize $bsize" $testfile | \
> + grep wrote | awk -F'[/ ]' '{print $2}')
> + test $bytes_written -eq $bsize || echo "atomic write to unwritten block failed"
> +
> + # Check that we can perform an atomic write on a sparse hole
> + $XFS_IO_PROG -c "fpunch 0 $bsize" $testfile
> + bytes_written=$($XFS_IO_PROG -dc "pwrite -A -D -V1 -b $bsize 0 $bsize" $testfile | \
> + grep wrote | awk -F'[/ ]' '{print $2}')
> + test $bytes_written -eq $bsize || echo "atomic write to sparse hole failed"
> +
> + # Check that we can perform an atomic write on a fully mapped block
> + bytes_written=$($XFS_IO_PROG -dc "pwrite -A -D -V1 -b $bsize 0 $bsize" $testfile | \
> + grep wrote | awk -F'[/ ]' '{print $2}')
> + test $bytes_written -eq $bsize || echo "atomic write to mapped block failed"
> +
> + # Reject atomic write if len is out of bounds
> + $XFS_IO_PROG -dc "pwrite -A -D -V1 -b $bsize 0 $((bsize - 1))" $testfile 2>> $seqres.full && \
> + echo "atomic write len=$((bsize - 1)) should fail"
> + $XFS_IO_PROG -dc "pwrite -A -D -V1 -b $bsize 0 $((bsize + 1))" $testfile 2>> $seqres.full && \
> + echo "atomic write len=$((bsize + 1)) should fail"
> +
> + # Reject atomic write when iovecs > 1
> + $XFS_IO_PROG -dc "pwrite -A -D -V2 -b $bsize 0 $bsize" $testfile 2>> $seqres.full && \
> + echo "atomic write only supports iovec count of 1"
> +
> + # Reject atomic write when not using direct I/O
> + $XFS_IO_PROG -c "pwrite -A -V1 -b $bsize 0 $bsize" $testfile 2>> $seqres.full && \
> + echo "atomic write requires direct I/O"
> +
> + # Reject atomic write when offset % bsize != 0
> + $XFS_IO_PROG -dc "pwrite -A -D -V1 -b $bsize 1 $bsize" $testfile 2>> $seqres.full && \
> + echo "atomic write requires offset to be aligned to bsize"
> +
> + _scratch_unmount
> +}
> +
> +test_atomic_write_bounds()
> +{
> + local bsize=$1
> +
> + get_mkfs_opts $bsize
> + _scratch_mkfs $mkfs_opts >> $seqres.full
> + _scratch_mount
> +
> + test "$FSTYP" = "xfs" && _xfs_force_bdev data $SCRATCH_MNT

ditto

-ritesh

> +
> + testfile=$SCRATCH_MNT/testfile
> + touch $testfile
> +
> + $XFS_IO_PROG -dc "pwrite -A -D -V1 -b $bsize 0 $bsize" $testfile 2>> $seqres.full && \
> + echo "atomic write should fail when bsize is out of bounds"
> +
> + _scratch_unmount
> +}
> +
> +sys_min_write=$(cat "/sys/block/$(_short_dev $SCRATCH_DEV)/queue/atomic_write_unit_min_bytes")
> +sys_max_write=$(cat "/sys/block/$(_short_dev $SCRATCH_DEV)/queue/atomic_write_unit_max_bytes")
> +
> +bdev_min_write=$(_get_atomic_write_unit_min $SCRATCH_DEV)
> +bdev_max_write=$(_get_atomic_write_unit_max $SCRATCH_DEV)
> +
> +# Test that statx atomic values are the same as sysfs values
> +if [ "$sys_min_write" -ne "$bdev_min_write" ]; then
> + echo "bdev min write != sys min write"
> +fi
> +if [ "$sys_max_write" -ne "$bdev_max_write" ]; then
> + echo "bdev max write != sys max write"
> +fi
> +
> +get_supported_bsize
> +
> +# Test all supported block sizes between bdev min and max
> +for ((bsize=$bdev_min_write; bsize<=bdev_max_write; bsize*=2)); do
> + if [ "$bsize" -ge "$min_bsize" ] && [ "$bsize" -le "$max_bsize" ]; then
> + test_atomic_writes $bsize
> + fi
> +done;
> +
> +# Check that atomic write fails if bsize < bdev min or bsize > bdev max
> +if [ $((bdev_min_write / 2)) -ge "$min_bsize" ]; then
> + test_atomic_write_bounds $((bdev_min_write / 2))
> +fi
> +if [ $((bdev_max_write * 2)) -le "$max_bsize" ]; then
> + test_atomic_write_bounds $((bdev_max_write * 2))
> +fi
> +
> +# success, all done
> +echo Silence is golden
> +status=0
> +exit
> diff --git a/tests/generic/765.out b/tests/generic/765.out
> new file mode 100644
> index 00000000..39c254ae
> --- /dev/null
> +++ b/tests/generic/765.out
> @@ -0,0 +1,2 @@
> +QA output created by 765
> +Silence is golden
> --
> 2.34.1