fs/ext2/genext2fs.sh
#!/bin/sh
# genext2fs wrapper calculating needed blocks/inodes values if not specified
set -e

export LC_ALL=C

CALC_BLOCKS=1
CALC_INODES=1
EXT_OPTS=
EXT_OPTS_O=

while getopts x:d:D:b:i:N:m:g:e:zfqUPhVv f
do
    case $f in
	b) CALC_BLOCKS=0 ;;
	N) CALC_INODES=0; INODES=$OPTARG ;;
	d) TARGET_DIR=$OPTARG ;;
    esac
done
eval IMG="\"\${${OPTIND}}\""

# calculate needed inodes
if [ $CALC_INODES -eq 1 ];
then
    INODES=$(find $TARGET_DIR | wc -l)
    INODES=$(expr $INODES + 400)
    set -- $@ -N $INODES
fi

# calculate needed blocks
if [ $CALC_BLOCKS -eq 1 ];
then
    # size ~= superblock, block+inode bitmaps, inodes (8 per block), blocks
    # we scale inodes / blocks with 10% to compensate for bitmaps size + slack
    BLOCKS=$(du -s -c -k $TARGET_DIR | grep total | sed -e "s/total//")
    BLOCKS=$(expr 500 + \( $BLOCKS + $INODES / 8 \) \* 11 / 10)
    # we add 1300 blocks (a bit more than 1 MiB, assuming 1KiB blocks) for
    # the journal if ext3/4
    # Note: I came to 1300 blocks after trial-and-error checks. YMMV.
    if [ ${GEN} -ge 3 ]; then
        BLOCKS=$(expr 1300 + $BLOCKS )
    fi
    set -- $@ -b $BLOCKS
fi

e2tunefsck() {
    # genext2fs does not generate a UUID, but fsck will whine if one is
    # is missing, so we need to add a UUID.
    # Of course, this has to happend _before_ we run fsck.
    # Also, some ext4 metadata are based on the UUID, so we must
    # set it before we can convert the filesystem to ext4.
    # Although a random UUID may seem bad for reproducibility, there
    # already are so many things that are not reproducible in a
    # filesystem: file dates, file ordering, content of the files...
    tune2fs -U random "${IMG}"

    # Upgrade the filesystem
    if [ $# -ne 0 ]; then
        tune2fs "$@" "${IMG}"
    fi

    # After changing filesystem options, running fsck is required
    # (see: man tune2fs). Running e2fsck in other cases will ensure
    # coherency of the filesystem, although it is not required.
    # 'e2fsck -pDf' means:
    #  - automatically repair
    #  - optimise and check for duplicate entries
    #  - force checking
    # Sending output to oblivion, as e2fsck can be *very* verbose,
    # especially with filesystems generated by genext2fs.
    # Exit codes 1 & 2 are OK, it means fs errors were successfully
    # corrected, hence our little trick with $ret.
    ret=0
    e2fsck -pDf "${IMG}" >/dev/null || ret=$?
    case ${ret} in
       0|1|2) ;;
       *)   exit ${ret};;
    esac
    printf "\ne2fsck was successfully run on '%s' (ext%d)\n\n"  \
           "${IMG##*/}" "${GEN}"

    # Remove count- and time-based checks, they are not welcome
    # on embedded devices, where they can cause serious boot-time
    # issues by tremendously slowing down the boot.
    tune2fs -c 0 -i 0 "${IMG}"
}

# Check we know what generation to generate
case "${GEN}:${REV}" in
    2:0|2:1|3:1|4:1)
	;;
    *)
	printf "%s: unknown ext generation '%s' and/or revision '%s'\n" \
	       "${0##*/}" "${GEN}" "${REV}" >&2
	exit 1
	;;
esac

# Upgrade to rev1 if needed
if [ ${REV} -ge 1 ]; then
    EXT_OPTS_O="${EXT_OPTS_O},filetype"
fi

# Add a journal for ext3 and above
if [ ${GEN} -ge 3 ]; then
    EXT_OPTS="${EXT_OPTS} -j -J size=1"
fi

# Add ext4 specific features
if [ ${GEN} -ge 4 ]; then
    EXT_OPTS_O="${EXT_OPTS_O},extents,uninit_bg,dir_index"
fi

# Add our -O options (there will be at most one leading comma, remove it)
if [ -n "${EXT_OPTS_O}" ]; then
    EXT_OPTS="${EXT_OPTS} -O ${EXT_OPTS_O#,}"
fi

# Generate and upgrade the filesystem
genext2fs "$@"
e2tunefsck ${EXT_OPTS}
