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btrfs-tree: harden rlower_bound against exceptional objects

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Rearrange the logic in `rlower_bound` so it can cope with a tree
that contains mostly block-aligned objects, with a few exceptions
filtered out by `hdr_stop`.

Signed-off-by: Zygo Blaxell <bees@furryterror.org>
This commit is contained in:
Zygo Blaxell 2025-01-27 20:04:13 -05:00
parent dd08f6379f
commit d32f31f411
1 changed files with 25 additions and 23 deletions
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48
lib/btrfs-tree.cc
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@ -413,8 +413,8 @@ namespace crucible {
uint64_t closest_logical = 0;
BtrfsIoctlSearchKey &sk = m_sk;
size_t loops = 0;
BTFRLB_DEBUG("rlower_bound: " << to_hex(logical) << endl);
seek_backward(scale_logical(logical), [&](uint64_t lower_bound, uint64_t upper_bound) {
BTFRLB_DEBUG("rlower_bound: " << to_hex(logical) << " in tree " << tree() << endl);
seek_backward(scale_logical(logical), [&](uint64_t const lower_bound, uint64_t const upper_bound) {
++loops;
fill_sk(sk, unscale_logical(min(scaled_max_logical(), lower_bound)));
set<uint64_t> rv;
@ -424,29 +424,31 @@ namespace crucible {
BTFRLB_DEBUG("fetch: loop " << loops << " lower_bound..upper_bound " << to_hex(lower_bound) << ".." << to_hex(upper_bound));
for (auto &i : sk.m_result) {
next_sk(sk, i);
const auto this_logical = hdr_logical(i);
const auto scaled_hdr_logical = scale_logical(this_logical);
BTFRLB_DEBUG(" " << to_hex(scaled_hdr_logical));
if (hdr_match(i)) {
if (this_logical <= logical && this_logical > closest_logical) {
closest_logical = this_logical;
closest_item = i;
}
BTFRLB_DEBUG("(match)");
rv.insert(scaled_hdr_logical);
}
if (scaled_hdr_logical > upper_bound || hdr_stop(i)) {
if (scaled_hdr_logical >= upper_bound) {
BTFRLB_DEBUG("(" << to_hex(scaled_hdr_logical) << " >= " << to_hex(upper_bound) << ")");
}
if (hdr_stop(i)) {
rv.insert(numeric_limits<uint64_t>::max());
BTFRLB_DEBUG("(stop)");
}
// If hdr_stop or !hdr_match, don't inspect the item
if (hdr_stop(i)) {
rv.insert(numeric_limits<uint64_t>::max());
BTFRLB_DEBUG("(stop)");
break;
} else {
BTFRLB_DEBUG("(cont'd)");
}
if (!hdr_match(i)) {
BTFRLB_DEBUG("(no match)");
continue;
}
const auto this_logical = hdr_logical(i);
BTFRLB_DEBUG(" " << to_hex(this_logical) << " " << i);
const auto scaled_hdr_logical = scale_logical(this_logical);
BTFRLB_DEBUG(" " << "(match)");
if (this_logical <= logical && this_logical > closest_logical) {
closest_logical = this_logical;
closest_item = i;
BTFRLB_DEBUG("(closest)");
}
rv.insert(scaled_hdr_logical);
if (scaled_hdr_logical > upper_bound) {
BTFRLB_DEBUG("(" << to_hex(scaled_hdr_logical) << " >= " << to_hex(upper_bound) << ")");
break;
}
BTFRLB_DEBUG("(cont'd)");
}
BTFRLB_DEBUG(endl);
// We might get a search result that contains only non-matching items.