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+#! /bin/bash
+# SPDX-License-Identifier: GPL-2.0
+# Copyright (C) 2022 SUSE Linux Products GmbH. All Rights Reserved.
+#
+# FS QA Test 262
+#
+# Make sure btrfs autodefrag only defrag writes smaller than 64KiB
+# (which is considered as small writes)
+# This behavior will be introduced to v5.17 and backported to v5.16
+#
+# While older kernels (v5.15 and older) will not obey the threshold
+# but always use default threshold (256K) instead.
+#
+. ./common/preamble
+_begin_fstest defrag quick
+
+# Override the default cleanup function.
+# _cleanup()
+# {
+# cd /
+# rm -r -f $tmp.*
+# }
+
+# Import common functions.
+. ./common/filter
+
+# real QA test starts here
+
+# Modify as appropriate.
+_supported_fs btrfs
+_require_scratch
+_require_xfs_io_command "fiemap" "ranged"
+
+# Needs 4K sectorsize, for larger sectorsize like 64K, no write will be
+# considered as small writes then.
+_require_btrfs_support_sectorsize 4096
+
+_scratch_mkfs -s 4k >> $seqres.full 2>&1
+
+# Need datacow to make the defragged extents to have different bytenr
+_scratch_mount -o datacow,autodefrag
+
+# Create the following file layout
+# 0 32K 64K 96K 128K 160K 192K
+# | Ext 1 | Ext 2 | Ext 3 | Ext 4 |
+#
+# Ext 1 and Ext 2 will be defragged as they are smaller than the 64K threshold
+# But Ext 3 and Ext 4 should not be defragged.
+$XFS_IO_PROG -f -s -c "pwrite -b 32K 0 64k" -c "pwrite -b 64K 64K 128K" \
+ "$SCRATCH_MNT/foobar" >> $seqres.full
+
+# Get the logical bytenr of Ext 1 and Ext 3
+old_ext1=$(_get_file_extent_sector "$SCRATCH_MNT/foobar" 0)
+old_ext3=$(_get_file_extent_sector "$SCRATCH_MNT/foobar" 65536)
+
+old_csum=$(_md5_checksum $SCRATCH_MNT/foobar)
+echo "=== File extent layout before autodefrag ===" >> $seqres.full
+$XFS_IO_PROG -c "fiemap -v" "$SCRATCH_MNT/foobar" >> $seqres.full
+echo "old md5=$old_csum" >> $seqres.full
+
+# Now trigger autodefrag, autodefrag is triggered in the cleaner thread,
+# which will be woken up by commit thread
+_scratch_remount commit=1
+sleep 3
+
+# At remount time we may already trigger autodefrag, but if it didn't get
+# triggered, that sleep 3 will trigger autodefrag, and only mark the
+# target range dirty. We need to write back those ranges to reflect the
+# extent logical bytenr change.
+sync
+
+
+new_csum=$(_md5_checksum $SCRATCH_MNT/foobar)
+new_ext1=$(_get_file_extent_sector "$SCRATCH_MNT/foobar" 0)
+new_ext3=$(_get_file_extent_sector "$SCRATCH_MNT/foobar" 65536)
+
+echo "=== File extent layout after autodefrag ===" >> $seqres.full
+$XFS_IO_PROG -c "fiemap -v" "$SCRATCH_MNT/foobar" >> $seqres.full
+echo "new md5=$new_csum" >> $seqres.full
+
+# Ext 1 should be defragged on all kernels
+if [ "$new_ext1" == "$old_ext1" ]; then
+ echo "The extent at offset 0 didn't get defragged"
+fi
+
+# Ext 3 should not be defragged on v5.17 and backported v5.16.
+# But older kernels (v5.15 and older) will not respect the small write
+# extent size threshold, and defrag them.
+if [ "$new_ext3" != "$old_ext3" ]; then
+ echo "The extent at offset 64K get defragged"
+fi
+
+# Defrag should not change file content
+if [ "$new_csum" != "$old_csum" ]; then
+ echo "file content changed"
+fi
+
+echo "Silence is golden"
+
+# success, all done
+status=0
+exit
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+QA output created by 262
+Silence is golden
Btrfs autodefrag used to only use default defrag extent size threshold, which is not the same as the threshold to trigger autodefrag. (The autodefrag triggering threshold is 64K for uncompressed write and 16K for compressed write, while the default defrag extent threshold is 256K). This can lead to unexpected high IO. This behavior is fixed by the upcoming patch, titled "btrfs: reduce extent threshold for autodefrag". This patch will add test case to verify the behavior by: - Creating a file with mixed extent size. File offset 0 ~ 64K will be filled with two 32K extents, which should be defragged. While file offset 64K ~ 196K will be filled with two 64K extent, which should not be defragged. - Trigger autodefrag - Check if extent at offset 0 and offset 64K get defragged. - Verify the checksum Signed-off-by: Qu Wenruo <wqu@suse.com> --- tests/btrfs/262 | 102 ++++++++++++++++++++++++++++++++++++++++++++ tests/btrfs/262.out | 2 + 2 files changed, 104 insertions(+) create mode 100755 tests/btrfs/262 create mode 100644 tests/btrfs/262.out