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bcachefs: Fix bch2_btree_node_iter_prev_filter()

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bch2_btree_node_iter_prev_filter() tried to be smart about iterating
backwards when skipping over whiteouts/discards - but unfortunately,
doing so can leave the node iterator in an inconsistent state; the sane
solution is to just always iterate backwards one key at a time.

But we compact btree nodes when more than a quarter of the keys are
whiteouts/discards, so the optimization wasn't buying us that much
anyways.

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
This commit is contained in:
Kent Overstreet 2019-08-19 13:43:01 -04:00 committed by Kent Overstreet
parent 9df279407a
commit e67ab0450c
2 changed files with 19 additions and 24 deletions
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35
fs/bcachefs/bset.c
View File

@ -1682,12 +1682,10 @@ void bch2_btree_node_iter_advance(struct btree_node_iter *iter,
/*
* Expensive:
*/
struct bkey_packed *bch2_btree_node_iter_prev_filter(struct btree_node_iter *iter,
struct btree *b,
unsigned min_key_type)
struct bkey_packed *bch2_btree_node_iter_prev_all(struct btree_node_iter *iter,
struct btree *b)
{
struct bkey_packed *k, *prev = NULL;
struct bkey_packed *orig_pos = bch2_btree_node_iter_peek_all(iter, b);
struct btree_node_iter_set *set;
struct bset_tree *t;
unsigned end = 0;
@ -1695,9 +1693,8 @@ struct bkey_packed *bch2_btree_node_iter_prev_filter(struct btree_node_iter *ite
bch2_btree_node_iter_verify(iter, b);
for_each_bset(b, t) {
k = bch2_bkey_prev_filter(b, t,
bch2_btree_node_iter_bset_pos(iter, b, t),
min_key_type);
k = bch2_bkey_prev_all(b, t,
bch2_btree_node_iter_bset_pos(iter, b, t));
if (k &&
(!prev || bkey_iter_cmp(b, k, prev) > 0)) {
prev = k;
@ -1706,7 +1703,7 @@ struct bkey_packed *bch2_btree_node_iter_prev_filter(struct btree_node_iter *ite
}
if (!prev)
goto out;
return NULL;
/*
* We're manually memmoving instead of just calling sort() to ensure the
@ -1727,18 +1724,20 @@ found:
iter->data[0].k = __btree_node_key_to_offset(b, prev);
iter->data[0].end = end;
out:
if (btree_keys_expensive_checks(b)) {
struct btree_node_iter iter2 = *iter;
if (prev)
__bch2_btree_node_iter_advance(&iter2, b);
bch2_btree_node_iter_verify(iter, b);
return prev;
}
while ((k = bch2_btree_node_iter_peek_all(&iter2, b)) != orig_pos) {
BUG_ON(k->type >= min_key_type);
__bch2_btree_node_iter_advance(&iter2, b);
}
}
struct bkey_packed *bch2_btree_node_iter_prev_filter(struct btree_node_iter *iter,
struct btree *b,
unsigned min_key_type)
{
struct bkey_packed *prev;
do {
prev = bch2_btree_node_iter_prev_all(iter, b);
} while (prev && prev->type < min_key_type);
return prev;
}

8
fs/bcachefs/bset.h
View File

@ -543,15 +543,11 @@ bch2_btree_node_iter_next_all(struct btree_node_iter *iter, struct btree *b)
return ret;
}
struct bkey_packed *bch2_btree_node_iter_prev_all(struct btree_node_iter *,
struct btree *);
struct bkey_packed *bch2_btree_node_iter_prev_filter(struct btree_node_iter *,
struct btree *, unsigned);
static inline struct bkey_packed *
bch2_btree_node_iter_prev_all(struct btree_node_iter *iter, struct btree *b)
{
return bch2_btree_node_iter_prev_filter(iter, b, 0);
}
static inline struct bkey_packed *
bch2_btree_node_iter_prev(struct btree_node_iter *iter, struct btree *b)
{