tests/btrfs/252

#! /bin/bash
# SPDX-License-Identifier: GPL-2.0
# Copyright (C) 2021 SUSE Linux Products GmbH. All Rights Reserved.
#
# FS QA Test No. 252
#
# Test that send and balance can run in parallel, without failures and producing
# correct results.
#
# Before kernel 5.3 it was possible to run both operations in parallel, however
# it was buggy and caused sporadic failures due to races, so it was disabled in
# kernel 5.3 by commit 9e967495e0e0ae ("Btrfs: prevent send failures and crashes
# due to concurrent relocation"). There is a now a patch that enables both
# operations to safely run in parallel, and it has the following subject:
#
#      "btrfs: make send work with concurrent block group relocation"
#
# This also serves the purpose of testing a succession of incremental send
# operations, where we have a bunch of snapshots of the same subvolume and we
# keep doing an incremental send using the previous snapshot as the parent.
#
. ./common/preamble
_begin_fstest auto send balance stress

_cleanup()
{
	if [ ! -z $balance_pid ]; then
		kill $balance_pid &> /dev/null
		wait $balance_pid
	fi
	cd /
	rm -r -f $tmp.*
}

. ./common/filter


# The size needed is variable as it depends on the specific randomized
# operations from fsstress and on the value of $LOAD_FACTOR. But require
# at least $LOAD_FACTOR * 6G, as we do the receive operations to the same
# filesystem, do relocation and store snapshot checksums from fssum in the
# filesystem as well (can be hundreds of megabytes for $LOAD_FACTOR > 3).
_require_scratch_size $(($LOAD_FACTOR * 6 * 1024 * 1024))
_require_fssum

balance_loop()
{
	trap "wait; exit" SIGTERM

	while true; do
		_run_btrfs_balance_start $SCRATCH_MNT > /dev/null
		[ $? -eq 0 ] || echo "Balance failed: $?"
	done
}

_scratch_mkfs >> $seqres.full 2>&1
_scratch_mount

num_snapshots=$((10 + $LOAD_FACTOR * 2))
avg_ops_per_snapshot=$((1000 * LOAD_FACTOR))
total_fsstress_ops=$((num_snapshots * avg_ops_per_snapshot))

data_subvol="$SCRATCH_MNT/data"
snapshots_dir="$SCRATCH_MNT/snapshots"
dest_dir="$SCRATCH_MNT/received"
fssum_dir="$SCRATCH_MNT/fssum"

mkdir -p "$snapshots_dir"
mkdir -p "$dest_dir"
mkdir -p "$fssum_dir"
$BTRFS_UTIL_PROG subvolume create "$data_subvol" >> $seqres.full

snapshot_cmd="$BTRFS_UTIL_PROG subvolume snapshot -r \"$data_subvol\""
snapshot_cmd="$snapshot_cmd \"$snapshots_dir/snap_\`date +'%s%N'\`\""

# Use a single fsstress process so that in case of a failure we can grab the seed
# number from the .full log file and deterministically reproduce a failure.
# Also disable subvolume and snapshot creation, since send is not recursive, so
# it's pointless to have them.
#
echo "Running fsstress..." >> $seqres.full
$FSSTRESS_PROG $FSSTRESS_AVOID -d "$data_subvol" -p 1 -w \
	       -f subvol_create=0 -f subvol_delete=0 -f snapshot=0 \
	       -x "$snapshot_cmd" -X $num_snapshots \
	       -n $total_fsstress_ops >> $seqres.full

snapshots=(`IFS=$'\n' ls -1 "$snapshots_dir"`)

# Compute the checksums for every snapshot.
for i in "${!snapshots[@]}"; do
	snap="${snapshots_dir}/${snapshots[$i]}"
	echo "Computing checksum for snapshot: ${snapshots[$i]}" >> $seqres.full
	$FSSUM_PROG -A -f -w "${fssum_dir}/${i}.fssum" "$snap"
done

# Now leave a process constantly running balance.
balance_loop &
balance_pid=$!

# Now send and receive all snapshots to our destination directory.
# We send and receive from/to the same same filesystem using a pipe, because
# this is the most stressful scenario and it could lead (and has lead to during
# development) to deadlocks - the sending task blocking on a full pipe while
# holding some lock, while the receiving side was not reading from the pipe
# because it was waiting for a transaction commit, which could not happen due
# to the lock held by the sending task.
#
for i in "${!snapshots[@]}"; do
	snap="${snapshots_dir}/${snapshots[$i]}"
	prev_snap="${snapshots_dir}/${snapshots[$i - 1]}"

	# For the first snapshot we do a full incremental send, for all the
	# others we do an incremental send, using the previous snapshot as the
	# parent.
	#
	# We redirect stderr of the send command because the commands prints to
	# stderr a message like "At subvol ...", and the number of snapshots and
	# snapshot names we have depends on LOAD_FACTOR and timestamps, so we
	# don't use them in the golden output. Recent versions of btrfs-progs
	# have the --quiet option to eliminate these messages.
	#
	# We also redirect stderr and stdout of the receive command. Note that
	# when receiving a full stream, the command prints a message like
	# "At subvol ..." to stderr, but when receiving an incremental stream it
	# prints a message to stdout like "At snapshot ...". Just like for the
	# send command, new versions of btrfs-progs have the --quiet option to
	# eliminate these messages.
	#
	# Further the send command prints the messages with a full snapshot path,
	# while receive prints only the snapshot name.
	#
	# We redirect all these messages to $seqres.full and then manually check
	# if the commands succeeded. This is just so that the test is able to
	# run with older versions of btrfs-progs.
	#
	if [ $i -eq 0 ]; then
		echo "Full send of the snapshot at: $snap" >>$seqres.full
		$BTRFS_UTIL_PROG send "$snap" 2>>$seqres.full | \
			$BTRFS_UTIL_PROG receive "$dest_dir" 2>>$seqres.full
	else
		echo "Incremental send of the snapshot at: $snap" >>$seqres.full
		$BTRFS_UTIL_PROG send -p "$prev_snap" "$snap" 2>>$seqres.full | \
			$BTRFS_UTIL_PROG receive "$dest_dir" >>$seqres.full
	fi

	retvals=( "${PIPESTATUS[@]}" )

	[ ${retvals[0]} -eq 0 ] || \
		echo "Send of snapshot $snap failed: ${retvals[0]}"
	[ ${retvals[1]} -eq 0 ] || \
		echo "Receive of snapshot $snap failed: ${retvals[1]}"

	if [ $i -gt 0 ]; then
		# We don't need the previous snapshot anymore, so delete it.
		# This makes balance not so slow and triggers the cleaner kthread
		# to run and delete the snapshot tree in parallel, while we are
		# also running balance and send/receive, adding additional test
		# coverage and stress.
		$BTRFS_UTIL_PROG subvolume delete "$prev_snap" >> $seqres.full
	fi
done

# We are done with send/receive, send a signal to the balance job and verify
# the snapshot checksums while it terminates. We do the wait at _cleanup() so
# that we do some useful work while it terminates.
kill $balance_pid

# Now verify that received snapshots have the expected checksums.
for i in "${!snapshots[@]}"; do
	snap_csum="${fssum_dir}/${i}.fssum"
	snap_copy="${dest_dir}/${snapshots[$i]}"

	echo "Verifying checksum for snapshot at: $snap_copy" >> $seqres.full
	# On success, fssum outputs only a single line with "OK" to stdout, and
	# on error it outputs several lines to stdout. Since the number of
	# snapshots in the test depends on $LOAD_FACTOR, filter out the success
	# case, so we don't have a mismatch with the golden output in case we
	# run with a non default $LOAD_FACTOR (default is 1). We only want the
	# mismatch with the golden output in case there's a checksum failure.
	$FSSUM_PROG -r "$snap_csum" "$snap_copy" | grep -E -v '^OK$'
done

echo "Silence is golden"

# success, all done
status=0
exit