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bcachefs: Fix bch2_btree_node_iter_fix()

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bch2_btree_node_iter_prev_all() depends on an invariant that wasn't
being maintained for extent leaf nodes - specifically, the node iterator
may not have advanced past any keys that compare after the key the node
iterator points to.

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
This commit is contained in:
Kent Overstreet 2019-08-20 17:43:47 -04:00 committed by Kent Overstreet
parent e67ab0450c
commit 23bbd2bb8f
1 changed files with 45 additions and 45 deletions
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90
fs/bcachefs/btree_iter.c
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@ -496,6 +496,23 @@ static inline void __bch2_btree_iter_verify(struct btree_iter *iter,
#endif
static void btree_node_iter_set_set_pos(struct btree_node_iter *iter,
struct btree *b,
struct bset_tree *t,
struct bkey_packed *k)
{
struct btree_node_iter_set *set;
btree_node_iter_for_each(iter, set)
if (set->end == t->end_offset) {
set->k = __btree_node_key_to_offset(b, k);
bch2_btree_node_iter_sort(iter, b);
return;
}
bch2_btree_node_iter_push(iter, b, k, btree_bkey_last(b, t));
}
static void __bch2_btree_node_iter_fix(struct btree_iter *iter,
struct btree *b,
struct btree_node_iter *node_iter,
@ -527,7 +544,8 @@ static void __bch2_btree_node_iter_fix(struct btree_iter *iter,
bch2_btree_node_iter_peek_all(node_iter, b),
&iter->k);
}
return;
goto iter_current_key_not_modified;
found:
set->end = t->end_offset;
@ -569,60 +587,42 @@ static void __bch2_btree_node_iter_fix(struct btree_iter *iter,
bkey_disassemble(l->b, k, &iter->k);
}
iter_current_key_not_modified:
/*
* Interior nodes are special because iterators for interior nodes don't
* obey the usual invariants regarding the iterator position:
*
* We may have whiteouts that compare greater than the iterator
* position, and logically should be in the iterator, but that we
* skipped past to find the first live key greater than the iterator
* position. This becomes an issue when we insert a new key that is
* greater than the current iterator position, but smaller than the
* whiteouts we've already skipped past - this happens in the course of
* a btree split.
*
* We have to rewind the iterator past to before those whiteouts here,
* else bkey_node_iter_prev() is not going to work and who knows what
* else would happen. And we have to do it manually, because here we've
* already done the insert and the iterator is currently inconsistent:
*
* We've got multiple competing invariants, here - we have to be careful
* about rewinding iterators for interior nodes, because they should
* always point to the key for the child node the btree iterator points
* to.
* When a new key is added, and the node iterator now points to that
* key, the iterator might have skipped past deleted keys that should
* come after the key the iterator now points to. We have to rewind to
* before those deleted keys - otherwise bch2_btree_node_iter_prev_all()
* breaks:
*/
if (b->c.level && new_u64s &&
btree_iter_pos_cmp(iter, b, where) > 0) {
struct bset_tree *t, *where_set = bch2_bkey_to_bset_inlined(b, where);
struct bkey_packed *k;
if (!bch2_btree_node_iter_end(node_iter) &&
(b->c.level ||
(iter->flags & BTREE_ITER_IS_EXTENTS))) {
struct bset_tree *t;
struct bkey_packed *k, *k2, *p;
k = bch2_btree_node_iter_peek_all(node_iter, b);
for_each_bset(b, t) {
if (where_set == t)
bool set_pos = false;
if (node_iter->data[0].end == t->end_offset)
continue;
k = bch2_bkey_prev_all(b, t,
bch2_btree_node_iter_bset_pos(node_iter, b, t));
if (k &&
bkey_iter_cmp(b, k, where) > 0) {
struct btree_node_iter_set *set;
unsigned offset =
__btree_node_key_to_offset(b, bkey_next(k));
k2 = bch2_btree_node_iter_bset_pos(node_iter, b, t);
btree_node_iter_for_each(node_iter, set)
if (set->k == offset) {
set->k = __btree_node_key_to_offset(b, k);
bch2_btree_node_iter_sort(node_iter, b);
goto next_bset;
}
bch2_btree_node_iter_push(node_iter, b, k,
btree_bkey_last(b, t));
while ((p = bch2_bkey_prev_all(b, t, k2)) &&
bkey_iter_cmp(b, k, p) < 0) {
k2 = p;
set_pos = true;
}
next_bset:
t = t;
if (set_pos)
btree_node_iter_set_set_pos(node_iter,
b, t, k2);
}
}
bch2_btree_node_iter_verify(node_iter, b);
}
void bch2_btree_node_iter_fix(struct btree_iter *iter,