Re: [PATCH v2 2/2] xfs: test that zone_gc_low_space writes start gc for rw fses

On Fri, Mar 27, 2026 at 08:22:18AM -0700, Darrick J. Wong wrote:
> On Fri, Mar 27, 2026 at 01:34:29PM +0100, Hans Holmberg wrote:
> > Test that writes to the sysfs attribute zone_gc_low_space triggers
> > garbage collection for rw (but not ro) file systems.
> > 
> > Signed-off-by: Hans Holmberg <[email protected]>
> 
> Looks good to me, given what I saw of the kernel patch.  It probably
> needs a _fixed_by_kernel_commit tag once the patch goes upstream.

Yes, please :) It's helpful for downstream kernel maintainers.

Thanks,
Zorro

> 
> Reviewed-by: "Darrick J. Wong" <[email protected]>
> 
> --D
> 
> > ---
> >  common/xfs        | 17 +++++++++++
> >  tests/xfs/999     | 72 +++++++++++++++++++++++++++++++++++++++++++++++
> >  tests/xfs/999.out |  2 ++
> >  3 files changed, 91 insertions(+)
> >  create mode 100755 tests/xfs/999
> >  create mode 100644 tests/xfs/999.out
> > 
> > diff --git a/common/xfs b/common/xfs
> > index c81f939e68d2..45d7f75d2064 100644
> > --- a/common/xfs
> > +++ b/common/xfs
> > @@ -748,6 +748,23 @@ _xfs_get_scratch_rtdev_bdev()
> >  	fi
> >  }
> >  
> > +# Get a stat from /proc/self/mountstats for a specific mount point
> > +_xfs_get_mountstat() {
> > +	awk -v mount="$1" -v stat="$2" \
> > +		'$0~"mounted on "mount" with fstype xfs"{f=1} f&&index($0,stat){print $NF;exit}' \
> > +		/proc/self/mountstats
> > +}
> > +
> > +# Get the user available blocks for a rt mount
> > +_xfs_get_user_available_rt_blocks() {
> > +	_xfs_get_mountstat "$1" "user available RT blocks:"
> > +}
> > +
> > +# Check if gc is required for a rt mount
> > +_xfs_get_rt_gc_required () {
> > +	_xfs_get_mountstat "$1" "RT GC required:"
> > +}
> > +
> >  # Snapshot the metadata on the scratch device
> >  _scratch_xfs_metadump()
> >  {
> > diff --git a/tests/xfs/999 b/tests/xfs/999
> > new file mode 100755
> > index 000000000000..2c5b54368b6d
> > --- /dev/null
> > +++ b/tests/xfs/999
> > @@ -0,0 +1,72 @@
> > +#! /bin/bash
> > +# SPDX-License-Identifier: GPL-2.0
> > +# Copyright (c) 2026 Western Digital Corporation
> > +#
> > +# FS QA Test No. 999
> > +#
> > +# Tests that writes to zonegc_low_space will trigger start of garbage
> > +# collection for rw (but not ro) file systems
> > +#
> > +. ./common/preamble
> > +_begin_fstest auto rw zone quick
> > +
> > +. ./common/zoned
> > +
> > +_require_scratch
> > +_require_odirect
> > +
> > +zdev="$(_xfs_get_scratch_rtdev_bdev)"
> > +_require_zoned_device "$zdev"
> > +capacity=$(_zone_capacity 0 $zdev)
> > +_scratch_mkfs_sized $(($capacity * 6)) > $seqres.full 2>&1
> > +
> > +# limit max open zones to avoid gc to trigger before we want it to
> > +export MOUNT_OPTIONS="$MOUNT_OPTIONS -o max_open_zones=2"
> > +_try_scratch_mount || _notrun "mount option not supported"
> > +_require_xfs_scratch_zoned
> > +
> > +# create three zone-sized files and invalidate 95% of the data
> > +for i in $(seq 1 3); do
> > +	filename=$SCRATCH_MNT/data_$i
> > +	dd if=/dev/zero of=$filename bs=1M oflag=direct\
> > +		count=$(($capacity / (1024 * 1024))) >> $seqres.full 2>&1
> > +	truncate -s $(($capacity / 20)) $filename
> > +done
> > +
> > +# remount read-only and set the gc limit to free up unused space
> > +_scratch_remount ro
> > +rt_available_pre="$(_xfs_get_user_available_rt_blocks "$SCRATCH_MNT")"
> > +_set_fs_sysfs_attr $SCRATCH_DEV "zoned/zonegc_low_space" 100
> > +
> > +# reclaiming a zone with 5% used blocks should take way less than 1 second
> > +sleep 1
> > +
> > +# gc should not run for read only file systems
> > +rt_available_post="$(_xfs_get_user_available_rt_blocks "$SCRATCH_MNT")"
> > +[ "$rt_available_post" -gt "$rt_available_pre" ] && \
> > +	_fail "gc should not run while read only"
> > +
> > +_set_fs_sysfs_attr $SCRATCH_DEV "zoned/zonegc_low_space" 0
> > +
> > +# remount rw and check that gc starts, frees up blocks and stops after
> > +# the threshold is set to reclaim the unused blocks
> > +_scratch_remount rw
> > +
> > +rt_available_pre="$(_xfs_get_user_available_rt_blocks "$SCRATCH_MNT")"
> > +_set_fs_sysfs_attr $SCRATCH_DEV "zoned/zonegc_low_space" 100
> > +
> > +i=0
> > +while [ $(_xfs_get_rt_gc_required "$SCRATCH_MNT") -eq "1" ]; do
> > +	sleep 1
> > +	let i=$i+1
> > +	[ $i -gt 3 ] && _fail "gc did not complete within a reasonable time"
> > +done
> > +
> > +rt_available_post="$(_xfs_get_user_available_rt_blocks "$SCRATCH_MNT")"
> > +[ "$rt_available_pre" -ge "$rt_available_post" ] && \
> > +	_fail "gc did not free up space"
> > +
> > +echo "Silence is golden"
> > +status=0
> > +
> > +exit
> > diff --git a/tests/xfs/999.out b/tests/xfs/999.out
> > new file mode 100644
> > index 000000000000..3b276ca804fc
> > --- /dev/null
> > +++ b/tests/xfs/999.out
> > @@ -0,0 +1,2 @@
> > +QA output created by 999
> > +Silence is golden
> > -- 
> > 2.34.1
> > 
> > 
>