The is_ancestor bitmap is at optimization for bch2_snapshot_is_ancestor;
once we get sufficiently close to the ancestor ID we're searching for we
test a bitmap.
But initialization of the is_ancestor bitmap was broken; we do it by
using bch2_snapshot_parent(), but we call that on nodes that haven't
been initialized yet with bch2_mark_snapshot().
Fix this by adding a separate loop in bch2_snapshots_read() for
initializing the is_ancestor bitmap, and also add some new debug asserts
for checking this sort of breakage in the future.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
subvolume.c has gotten a bit large, this splits out a separate file just
for managing snapshot trees - BTREE_ID_snapshots.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
