On Fri, Jan 28, 2022 at 08:27:01AM +0800, Qu Wenruo wrote: > There is a long existing bug in btrfs defrag code that it will always > try to defrag compressed extents, even they are already at max capacity. > > This will not reduce the number of extents, but only waste IO/CPU. > > The kernel fix is titled: > > btrfs: defrag: don't defrag extents which is already at its max capacity > > Signed-off-by: Qu Wenruo <wqu@xxxxxxxx> > --- > Changelog: > v2: > - Use fiemap output to compare the difference > Now no need to use _get_file_extent_sector() helper at all. > > - Remove unnecessary mount options > > - Enlarge the write size to 16M > To be future proof > > - Shorten the subject > --- > tests/btrfs/257 | 57 +++++++++++++++++++++++++++++++++++++++++++++ > tests/btrfs/257.out | 2 ++ > 2 files changed, 59 insertions(+) > create mode 100755 tests/btrfs/257 > create mode 100644 tests/btrfs/257.out > > diff --git a/tests/btrfs/257 b/tests/btrfs/257 > new file mode 100755 > index 00000000..bacd0c23 > --- /dev/null > +++ b/tests/btrfs/257 > @@ -0,0 +1,57 @@ > +#! /bin/bash > +# SPDX-License-Identifier: GPL-2.0 > +# Copyright (C) 2022 SUSE Linux Products GmbH. All Rights Reserved. > +# > +# FS QA Test 257 > +# > +# Make sure btrfs defrag ioctl won't defrag compressed extents which are already > +# at their max capacity. > +# > +. ./common/preamble > +_begin_fstest auto quick defrag Still missing the 'compress' group. > + > +# Import common functions. > +. ./common/filter > +. ./common/btrfs > + > +# real QA test starts here > + > +# Modify as appropriate. > +_supported_fs btrfs > +_require_scratch > + > +_scratch_mkfs >> $seqres.full > + > +_scratch_mount -o compress > + > +# Btrfs uses 128K as max extent size for compressed extents, this would result > +# several compressed extents all at their max size > +$XFS_IO_PROG -f -c "pwrite -S 0xee 0 16m" -c sync \ > + $SCRATCH_MNT/foobar >> $seqres.full > + > +old_csum=$(_md5_checksum $SCRATCH_MNT/foobar) > + > +echo "=== File extent layout before defrag ===" >> $seqres.full > +$XFS_IO_PROG -c "fiemap -v" "$SCRATCH_MNT/foobar" >> $seqres.full > +$XFS_IO_PROG -c "fiemap -v" "$SCRATCH_MNT/foobar" > $tmp.before > + > +$BTRFS_UTIL_PROG filesystem defrag "$SCRATCH_MNT/foobar" >> $seqres.full > +sync > + > +new_csum=$(_md5_checksum $SCRATCH_MNT/foobar) > + > +echo "=== File extent layout before defrag ===" >> $seqres.full > +$XFS_IO_PROG -c "fiemap -v" "$SCRATCH_MNT/foobar" >> $seqres.full > +$XFS_IO_PROG -c "fiemap -v" "$SCRATCH_MNT/foobar" > $tmp.after > + > +if [ $new_csum != $old_csum ]; then > + echo "file content changed" > +fi > + > +diff -q $tmp.before $tmp.after || echo "compressed extents get defragged" get -> got Like patch 1/3, it can probably be fixed by Eryu when he picks it. Minor things apart, it looks good, and it fails without the kernel patch and passes with it, as expected. Reviewed-by: Filipe Manana <fdmanana@xxxxxxxx> Thanks. > + > +echo "Silence is golden" > + > +# success, all done > +status=0 > +exit > diff --git a/tests/btrfs/257.out b/tests/btrfs/257.out > new file mode 100644 > index 00000000..cc3693f3 > --- /dev/null > +++ b/tests/btrfs/257.out > @@ -0,0 +1,2 @@ > +QA output created by 257 > +Silence is golden > -- > 2.34.1 >
