tests/btrfs/199

#! /bin/bash
# SPDX-License-Identifier: GPL-2.0
# Copyright (C) 2019 SUSE Linux Products GmbH. All Rights Reserved.
#
# FS QA Test 199
#
# Test if btrfs discard mount option is trimming adjacent extents across
# block groups boundary.
# The test case uses loopback device and file used space to detect trimmed
# bytes.
#
# There is a long existing bug that btrfs doesn't discard all space for
# above mentioned case.
#
. ./common/preamble
_begin_fstest auto quick trim fiemap

# Override the default cleanup function.
_cleanup()
{
	cd /
	umount $loop_mnt &> /dev/null
	_destroy_loop_device $loop_dev &> /dev/null
	rm -rf $tmp.*
}

. ./common/filter

_fixed_by_kernel_commit 6b7faadd985c \
	"btrfs: Ensure we trim ranges across block group boundary"

_require_loop
_require_xfs_io_command "fiemap"

# We need less than 2G data write, consider it 2G and double it just in case
_require_scratch_size	$((4 * 1024 * 1024))

loop_file="$SCRATCH_MNT/image"

# The margin when checking trimmed size.
#
# The margin is for tree blocks, calculated by
# 3 * max_tree_block_size
# |   |- 64K
# |- 3 trees get modified (root tree, extent tree, fs tree)
#
# In reality, there should be no margin at all due to the mount options.
# But who knows what will happen in later kernels.
margin_kb=$(( 3 * 64 ))
trimmed_kb=$(( 768 * 1024 )) # 768M

_scratch_mkfs >> $seqres.full
_scratch_mount

# Create a sparse file as the loopback target.
# 10G size makes sure we have 1G chunk size.
truncate -s 10G "$loop_file"

_mkfs_dev -d SINGLE "$loop_file"

loop_dev=$(_create_loop_device "$loop_file")
loop_mnt=$tmp/loop_mnt

mkdir -p $loop_mnt
# - $(_btrfs_no_v1_cache_opt)
#   Since v1 cache using DATA space, it can break data extent bytenr
#   continuousness.
# - nodatasum
#   As there will be 1.5G data write, generating 1.5M csum.
#   Disabling datasum could reduce the margin caused by metadata to minimal
# - discard
#   What we're testing
_mount $(_btrfs_no_v1_cache_opt) -o nodatasum,discard $loop_dev $loop_mnt

# Craft the following extent layout:
#         |  BG1 |      BG2        |       BG3            |
# Bytenr: X-8M   X      X+512M     X+1G  X+1G+128M 
#         |//////|//////|                |//|
#            V      V           V          V
#            |      |           |          |- file 'tail_padding'
#            |      |           |- file 'cross_boundary'
#            |      |- file 'lead_padding2'
#            |- file 'lead_padding1'
# So that all extents of file 'cross_boundary' are all adjacent and crosses the
# boundary of BG1 and BG2
# File 'lead_padding1' and 'lead_padding2' are all paddings to fill the
# leading gap.
# File 'tail_padding' is to ensure after deleting file 'cross_boundary' we still
# have used extent in BG3, to prevent trimming the whole BG3.
# And since BG1 needs exactly 8M to fill, we need to sync write to ensure
# the write sequence.
_pwrite_byte 0xcd 0 8M $loop_mnt/lead_padding1 > /dev/null
sync

_pwrite_byte 0xcd 0 512M $loop_mnt/lead_padding2 > /dev/null
sync
_pwrite_byte 0xcd 0 $(($trimmed_kb * 1024)) $loop_mnt/cross_boundary \
	> /dev/null
sync

_pwrite_byte 0xcd 0 1M $loop_mnt/tail_padding > /dev/null
sync

$XFS_IO_PROG -c "fiemap" $loop_mnt/cross_boundary >> $seqres.full
# Ensure all extent are continuous
# Btrfs fiemap will merge continuous results, so the output should be only
# 2 lines, 1 line for filename, 1 line for a large merged fiemap result.
if [ $($XFS_IO_PROG -c "fiemap" $loop_mnt/cross_boundary | wc -l) -ne 2 ]; then
	_notrun "Non-continuous extent bytenr detected"
fi

size1_kb=$(du $loop_file| cut -f1)

# Delete the file 'cross_boundary'.
# This will delete $trimmed_kb data extents across the chunk boundary.
rm -f $loop_mnt/cross_boundary

# sync so btrfs will commit transaction and trim the freed extents
sync

size2_kb=$(du $loop_file | cut -f1)

echo "loopback file size before discard: $size1_kb KiB" >> $seqres.full
echo "loopback file size after discard:  $size2_kb KiB" >> $seqres.full
echo "Expect trimmed size:               $trimmed_kb KiB" >> $seqres.full
echo "Have trimmed size:                 $(($size1_kb - $size2_kb)) KiB" >> $seqres.full

if [ $(($size2_kb+ $trimmed_kb)) -gt $(($size1_kb + $margin_kb)) -o \
     $(($size2_kb+ $trimmed_kb)) -lt $(($size1_kb - $margin_kb)) ]; then
	echo "Btrfs doesn't trim the range correctly"
fi

echo "Silence is golden"

# success, all done
status=0
exit