This is inspired by the thought that went in to the delete_chroot is_subvolume commit. sync_chroot($chrootdir, $copydir) copies `$chrootdir/root` to `$copydir`. That seems a little silly; why do we care about "$chrootdir"? Have it just be sync_chroot(source, destination) like every other sync/copy command. Where this becomes tricky is check to decide if we are going to use btrfs subvolumes or not. We don't care if "$source/.." is on btrfs; the root could be a directly-mounted subvolume, but and the destination could be another subvolume of the same btrfs mounted somewhere else. The things we do care about are: - The source is a btrfs subvolume (so that we can snapshot it) - The source is on the same filesystem as the directory that the copy will be created in. - If the destination exists: * that it is not a mountpoint (so that we can delete and recreate it) * that it is a btrfs subvolume (so that we can quickly delete it) On the last point, it isn't necessary for creating the new snapshot, just for quick deletion. That can be a separate check, where we use regular `rm` for deleting the existing copy, but use subvolume snapshots for creating the new one. --- lib/archroot.sh | 8 ++++++++ makechrootpkg.in | 32 +++++++++++++++++++------------- 2 files changed, 27 insertions(+), 13 deletions(-) diff --git a/lib/archroot.sh b/lib/archroot.sh index 87c28a2..6b1b52e 100644 --- a/lib/archroot.sh +++ b/lib/archroot.sh @@ -34,6 +34,14 @@ is_subvolume() { } ## +# usage : is_same_fs( $path_a, $path_b ) +# return : whether $path_a and $path_b are on the same filesystem +## +is_same_fs() { + [[ "$(stat -c %d "$1")" == "$(stat -c %d "$1")" ]] +} + +## # usage : subvolume_delete_recursive( $path ) # # Find all btrfs subvolumes under and including $path and delete them. diff --git a/makechrootpkg.in b/makechrootpkg.in index d92d6ab..cc3c738 100644 --- a/makechrootpkg.in +++ b/makechrootpkg.in @@ -98,31 +98,37 @@ load_vars() { return 0 } -# Usage: sync_chroot $chrootdir $copydir [$copy] +# Usage: sync_chroot $rootdir $copydir [$copy] sync_chroot() { - local chrootdir=$1 + local rootdir=$1 local copydir=$2 local copy=${3:-$2} - if [[ "$chrootdir/root" -ef "$copydir" ]]; then + if [[ "$rootdir" -ef "$copydir" ]]; then error 'Cannot sync copy with itself: %s' "$copydir" return 1 fi # Get a read lock on the root chroot to make # sure we don't clone a half-updated chroot - slock 8 "$chrootdir/root.lock" \ - "Locking clean chroot [%s]" "$chrootdir/root" - - stat_busy "Synchronizing chroot copy [%s] -> [%s]" "$chrootdir/root" "$copy" - if is_btrfs "$chrootdir" && ! mountpoint -q "$copydir"; then - subvolume_delete_recursive "$copydir" || - die "Unable to delete subvolume %s" "$copydir" - btrfs subvolume snapshot "$chrootdir/root" "$copydir" >/dev/null || + slock 8 "$rootdir.lock" \ + "Locking clean chroot [%s]" "$rootdir" + + stat_busy "Synchronizing chroot copy [%s] -> [%s]" "$rootdir" "$copy" + if is_subvolume "$rootdir" && is_same_fs "$rootdir" "$(dirname -- "$copydir")" && ! mountpoint -q "$copydir"; then + if is_subvolume "$copydir"; then + subvolume_delete_recursive "$copydir" || + die "Unable to delete subvolume %s" "$copydir" + else + # avoid change of filesystem in case of an umount failure + rm --recursive --force --one-file-system "$copydir" || + die "Unable to delete %s" "$copydir" + fi + btrfs subvolume snapshot "$rootdir" "$copydir" >/dev/null || die "Unable to create subvolume %s" "$copydir" else mkdir -p "$copydir" - rsync -a --delete -q -W -x "$chrootdir/root/" "$copydir" + rsync -a --delete -q -W -x "$rootdir/" "$copydir" fi stat_done @@ -374,7 +380,7 @@ main() { lock 9 "$copydir.lock" "Locking chroot copy [%s]" "$copy" if [[ ! -d $copydir ]] || $clean_first; then - sync_chroot "$chrootdir" "$copydir" "$copy" + sync_chroot "$chrootdir/root" "$copydir" "$copy" fi $update_first && arch-nspawn "$copydir" \ -- 2.12.2