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bcachefs: backpointer_get_key() doesn't pull in btree node

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We may not need to pull in a btree node when walking backpointers -
don't do so unnecessarily when using backpointer_get_key().

It'll still fall back to backpointer_get_node() in a few situations,
including btree roots (where an iterator can't point at just the key),
and races due to the interior update path not having deleted a
backpointer to an old node yet.

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
This commit is contained in:
Kent Overstreet
2024-12-28 16:20:38 -05:00
parent dff6de9518
commit ca16fa6b86
1 changed files with 20 additions and 16 deletions
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36
fs/bcachefs/backpointers.c
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@@ -244,27 +244,31 @@ struct bkey_s_c bch2_backpointer_get_key(struct btree_trans *trans,
if (unlikely(bp.v->btree_id >= btree_id_nr_alive(c)))
return bkey_s_c_null;
if (likely(!bp.v->level)) {
bch2_trans_node_iter_init(trans, iter,
bp.v->btree_id,
bp.v->pos,
0, 0,
iter_flags);
struct bkey_s_c k = bch2_btree_iter_peek_slot(iter);
if (bkey_err(k)) {
bch2_trans_iter_exit(trans, iter);
return k;
}
if (k.k &&
extent_matches_bp(c, bp.v->btree_id, bp.v->level, k, bp))
return k;
bch2_trans_node_iter_init(trans, iter,
bp.v->btree_id,
bp.v->pos,
0,
bp.v->level,
iter_flags);
struct bkey_s_c k = bch2_btree_iter_peek_slot(iter);
if (bkey_err(k)) {
bch2_trans_iter_exit(trans, iter);
return k;
}
if (k.k &&
extent_matches_bp(c, bp.v->btree_id, bp.v->level, k, bp))
return k;
bch2_trans_iter_exit(trans, iter);
if (!bp.v->level) {
int ret = backpointer_target_not_found(trans, bp, k, last_flushed);
return ret ? bkey_s_c_err(ret) : bkey_s_c_null;
} else {
struct btree *b = bch2_backpointer_get_node(trans, bp, iter, last_flushed);
if (b == ERR_PTR(-BCH_ERR_backpointer_to_overwritten_btree_node))
return bkey_s_c_null;
if (IS_ERR_OR_NULL(b))
return ((struct bkey_s_c) { .k = ERR_CAST(b) });