/sbin/writeboost

#!/bin/sh
: <<=cut

=head1 NAME

writeboost - create dm-writeboost device-mapper mappings

=head1 SYNOPSYS

writeboost [ B<-u> ] [ B<device> ]

=head1 DESCRIPTION

writeboost is a utility to create dm-writeboost device-mapper
mappings as per definitions in the "/etc/writeboosttab" file.

=head1 OPTIONS

=over 4

=item B<device>

Act on given device from the first field of the I</etc/writeboosttab> file.
When not given writeboost acts on all devices listed in I</etc/writeboosttab>.

=item B<-h>, B<--help>

Show usage and options.

=item B<-u>

Un-map all mappings (or un-map only given B<device>).

=back

=head1 SEE ALSO

I<writeboosttab>(5)

=head1 DM-WRITEBOOST

dm-writeboost is a software using log-structured caching to accelerate
block IO. dm-writeboost is written by Akira Hayakawa <ruby.wktk@gmail.com>
and implemented as loadable module for Linux.

See more at https://github.com/akiradeveloper/dm-writeboost

=head1 AVAILABILITY

 https://gitlab.com/onlyjob/writeboost

=head1 VERSION

 1.20160718

=head1 DONATIONS

 Donations are much appreciated, please consider donating:

   Bitcoins : 15nCM6Rs4zoQKhBV55XxcPfwPKeAEHPbAn
  Litecoins : LZMLDNSfy3refx7bKQtEvPyYSbNHsfzLRZ
 AUD/PayPal : https://www.paypal.com/cgi-bin/webscr?cmd=_donations&business=onlyjob%40gmail%2ecom&lc=AU&currency_code=AUD

=head1 AUTHOR

 Dmitry Smirnov <onlyjob@member.fsf.org>

=head1 COPYRIGHT

 Copyright 2015-2016 Libre Solutions Pty Ltd (http://raid6.com.au)

=head1 LICENSE

 This program is free software: you can redistribute it and/or modify
 it under the terms of the GNU General Public License as published by
 the Free Software Foundation, either version 2 of the License, or
 (at your option) any later version.

 This package is distributed in the hope that it will be useful,
 but WITHOUT ANY WARRANTY; without even the implied warranty of
 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 GNU General Public License for more details.

 You should have received a copy of the GNU General Public License
 along with this program. If not, see <http://www.gnu.org/licenses/>.

=cut

U=""
DEV=""
while [ -n "$1" ]; do
    if [ "$1" = "-h" -o "$1" = "-?" -o "$1" = "--help" ]; then
        perldoc "$0" || grep --before-context=999 --regexp '^=cut$' "$0"
        exit 0
    elif [ "$1" = "-u" ]; then
        U=1
    elif [ "${1#-}" = "$1" ]; then
        DEV="${1##/dev/mapper/}"
    else
        echo -e "E: unknown option. Usage:" 1>&2
        echo "    $(basename $0) [ -t THRESHOLD ] [ -n ] [ -0 ] directory"
        exit 1
    fi
    shift
done

set -u

## writeboost
while read -r M H S O; do
    [ -z "${M%%#*}" ] && continue           ## skip comments.
    [ -z "${M%%/*}" ] && continue           ## skip invalid map names.

    ## skip empty lines / fields.
    [ -z "$M" ] && continue
    [ -z "$H" ] && continue
    [ -z "$S" ] && continue

    [ -n "${DEV}" -a ! "${DEV}" = "$M" ] && continue    ## act only on given device

#    echo ":: $M : $H : $S : $O"
    ## check block devices.
    if [ -b "/dev/mapper/$M" ]; then        ## already mapped.
        if [ -n "$U" ]; then
            logger --tag writeboost --stderr "un-mapping $M"
            (
            ## https://github.com/akiradeveloper/dm-writeboost/issues/57
            dmsetup suspend "$M"
            dmsetup message "$M" 0 drop_caches
            logger --tag writeboost --stderr "caches dropped; removing $M"
            E=$(dmsetup remove "$M" 2>&1 || dmsetup resume "$M")   ## unmap or resume suspended device.
            if [ -b "/dev/mapper/$M" ]; then
                logger --tag writeboost --stderr "error: unable to un-map $M ($E)"
            else
                dd if=/dev/zero of="$S" count=1 bs=4096 oflag=direct 2>>/dev/null
                logger --tag writeboost --stderr "$M un-mapped."
            fi
            ) &
        fi
        continue
    fi
    [ -n "$U" ] && continue                 ## not mapping because un-map is requested.
    [ -b "$H" ] || (logger --tag writeboost --stderr "error: $H is not a block device."; continue)
    [ -b "$S" ] || (logger --tag writeboost --stderr "error: $S is not a block device."; continue)

    B=$(blockdev --getsize $H)
    [ -z "$B" ] && continue                 ## unable to get size of cached device.
    logger --tag writeboost --stderr "mapping $M"
    dmsetup create "$M" --table "0 $B writeboost $H $S"
    if [ -b "/dev/mapper/$M" ]; then
        logger --tag writeboost --stderr "$M mapped."
        [ -z "$O" ] && continue
        IFS_BAK="${IFS}"
        IFS=','
        for I in $O; do
            dmsetup message "$M" 0 ${I%%=*} ${I##*=}
        done
        IFS="${IFS_BAK}"
    else
        logger --tag writeboost --stderr "error mapping $M"
    fi
done < "/etc/writeboosttab"

## wait for background jobs.
wait
writeboost 1.20160718-1 / sbin / writeboost
