#!/bin/bash

# remove_updatelogs: emergency remove MDT updatelog files from server.
#
# This is emergency tool to cleanup updatelogs in server if llog records
# cannot be removed by regular means, e.g. due to llog corruptions
#
# Tool goes the following:
# - goes through update_log catlist to find per-MDT update llog catalog
# - process llog catalog to delete all plain llogs in it
# - truncate or remove related llog catalog after all
# - truncates update_llogs itself if all catalogs were removed
#
# Script required parameter is mount point of server FS mounted locally
# it accepts also optional options as described below in usage()
#
# Steps to cleanup problematic llogs:
#
# 1. mount MDT filesystem locally on server as ldiskfs mount
# 2. run script first in dry-run mode to make sure it parses llogs as needed:
#    # bash remove_updatelog -n <ldiskfs_mount>
# 3. save all llogs for analysis:
#    # bash remove_updatelog -n -z /tmp/llogs_saved <ldiskfs_mount>
# 4. check that /tmp/llogs_saved.tar.gz exists and has all llogs inside:
#    # ls -ali /tmp/llogs_saved.tar.gz
#    # tar -tf /tmp/llog_saved.tar.gz
# 5. finally run script to delete all llogs:
#    # bash remove_updatelog <ldiskfs_mount>
#
# For better llogs compression xz can be used as well, pass it to the script
# via GZIP env variable:
#    # GZIP=xz bash remove_updatelog -n -z /tmp/llogs_saved <ldiskfs_mount>
# Archive name will ends with .xz in that case instead of .gz

ECHO=echo
PROG=$(basename $0)
LLOG_READER=${LLOG_READER:-llog_reader}
GZIP=${GZIP:-gzip}

usage() {
    cat -- <<USAGE 1>&2
usage: remove_updatelog [--dry-run|-n] [--help|-h] [--quiet|-q] <localmount>
	--help|-h	   show this usage message
	--dry-run|-n	   only print the names of files to be removed
	--quiet|-q	   run quietly (don't print filenames or status)
	--zip|-z <name_prefix>
			save all llogs into compressed tar archive with given
			name prefix using gzip by default. Other compression
			tools can be used via GZIP env variable.

The 'localmount' argument should be an ldiskfs mounted MDT device mountpoint.

Examples:
      remove_updatelog /mnt/mdt0
      remove_updatelog --dry-run /mnt/mdt0
      remove_changelog -z /tmp/llogs /mnt/mdt0
USAGE
    exit 1
}

OPT_DRYRUN=false
OPT_ARCH=""
OPT_MOUNT=""
OPT_MDTS=()

# Examine any long options and arguments
while [ -n "$*" ]; do
	arg="$1"
	case "$arg" in
	-h|--help) usage;;
	-n|--dry-run) OPT_DRYRUN=true;;
	-q|--quiet) ECHO=:;;
	-z|--zip) OPT_ARCH="$2.tar"; shift;;
	*)
	   [ -e "$arg" ] && OPT_MOUNT="$arg" && break
	esac
	shift
done

remove_updatelog() {
	local mntpoint=$OPT_MOUNT
	local catlist=${mntpoint}/update_log
	local dir=${mntpoint}/update_log_dir
	local arch=$OPT_ARCH
	local length=0

	if [[ -z $(df -t ldiskfs $mntpoint 2>/dev/null) ]] ; then
		echo "$PROG: '$mntpoint' is not ldiskfs mount."
		exit 1
	fi

	if $OPT_DRYRUN; then
		$ECHO "Dry run was requested, no changes will be applied"
	fi

	$ECHO "Scan update_log at '$mntpoint':"
	if [[ ! -f $catlist ]] ; then
		echo "$PROG: $catlist doesn't exist already."
	else
		read -r -d '' -a OPT_MDTS < <(hexdump -v -e '2/8 " %16x" 2/8 "\n"' $catlist |
					      awk '{print "[0x"$2":0x"$1":0x0]"}')

		if [[ ! $(which $LLOG_READER 2>/dev/null) ]] ; then
			echo "$PROG: $LLOG_READER is missing."
			exit 1
		fi
		[[ -z $arch ]] || tar -cf $arch $catlist 2>/dev/null
		length=${#OPT_MDTS[@]}
		for (( i = 0; i < ${length}; i++ )); do
			local catalog=$dir/${OPT_MDTS[$i]}

			$ECHO "Processing MDT$i llogs ..."
			if [[ ! -f $catalog ]] ; then
				echo "$PROG: $catalog doesn't exist already."
				continue
			fi
			[[ -z $arch ]] || tar -rf $arch $catalog 2>/dev/null
			if (( $(stat -c %s $catalog) >= 8192 )) ; then
				while read -r plain ; do
					local path

					# compatibility checks:
					# old llog reader reports path in /O
					# but correct path in update_log_dir
					if [ ${plain:0:1} == 'O' ] ; then
						local fid=${plain#"O/"*}

						# old format: O/8589935617/d3/3
						# get sequence and oid in hex:
						fid=$(printf "[0x%x:0x%x:0x0]" ${fid%%/*} ${fid##*/})
						path="$dir/$fid"
					else
						path=$mntpoint/$plain
					fi
					[[ -z $arch ]] ||
						tar -rf $arch $path 2>/dev/null
					$ECHO "rm -f $path"
					$OPT_DRYRUN || rm -f $path
				done < <(llog_reader $catalog |
					 awk -F "path=" '/path=/ { print $2 }')
			else
				echo "$PROG: $catalog is too small."
			fi
			$ECHO "> $catalog"
			$OPT_DRYRUN || > $catalog
		done
	fi
	if [[ "$arch" ]] ; then
		$GZIP -3 $arch
		$ECHO "llog archive was created by $GZIP"
	fi
}

if [ -z $OPT_MOUNT ] ; then
	echo "Mount is not specified, exiting"
	exit 1
fi
remove_updatelog