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makechrootpkg: sync_chroot: Make more general. 

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.
This commit is contained in:
Luke Shumaker 2017-05-05 18:41:00 -04:00 committed by Jan Alexander Steffens (heftig)
parent 928744cbc4
commit 6d1992909c
No known key found for this signature in database
GPG Key ID: A5E9288C4FA415FA
2 changed files with 26 additions and 12 deletions
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8
lib/archroot.sh
View File

@ -33,6 +33,14 @@ is_subvolume() {
[[ -e "$1" && "$(stat -f -c %T "$1")" == btrfs && "$(stat -c %i "$1")" == 256 ]]
}
##
# 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 )
#

30
makechrootpkg.in
View File

@ -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"
slock 8 "$rootdir.lock" \
"Locking clean chroot [%s]" "$rootdir"
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 ||
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" \