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cache_streamed_mutation: Call fast_forward_to() outside allocating section

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On bad_alloc the section is retried. If the exception happened inside
fast_forward_to() on the underlying reader, that call will be
retried. However, the reader should not be used after exception is
thrown, since it is in unspecified state. Also, calling
fast_forward_to() with cache region locked increases the chances of it
failing to allocate.

We shouldn't call fast_forward_to() with the cache region locked.

Fixes #2791.
This commit is contained in:
Tomasz Grabiec
2017-09-15 15:09:10 +02:00
parent 3b790a1e80
commit 22019577cc
1 changed files with 16 additions and 4 deletions
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20
cache_streamed_mutation.hh
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@@ -78,6 +78,12 @@ class cache_streamed_mutation final : public streamed_mutation::impl {
// - _next_row_in_range = _next.position() < _upper_bound
reading_from_cache,
// Starts reading from underlying reader.
// The range to read is position_range(_lower_bound, min(_next_row.position(), _upper_bound)).
// Invariants:
// - _next_row_in_range = _next.position() < _upper_bound
move_to_underlying,
// Invariants:
// - Upper bound of the read is min(_next_row.position(), _upper_bound)
// - _next_row_in_range = _next.position() < _upper_bound
@@ -218,6 +224,14 @@ future<> cache_streamed_mutation::fill_buffer() {
inline
future<> cache_streamed_mutation::do_fill_buffer() {
if (_state == state::move_to_underlying) {
_state = state::reading_from_underlying;
auto end = _next_row_in_range ? position_in_partition(_next_row.position())
: position_in_partition(_upper_bound);
return _read_context->fast_forward_to(position_range{_lower_bound, std::move(end)}).then([this] {
return read_from_underlying();
});
}
if (_state == state::reading_from_underlying) {
return read_from_underlying();
}
@@ -364,10 +378,8 @@ bool cache_streamed_mutation::after_current_range(position_in_partition_view p)
inline
future<> cache_streamed_mutation::start_reading_from_underlying() {
_state = state::reading_from_underlying;
auto end = _next_row_in_range ? position_in_partition(_next_row.position())
: position_in_partition(_upper_bound);
return _read_context->fast_forward_to(position_range{_lower_bound, std::move(end)});
_state = state::move_to_underlying;
return make_ready_future<>();
}
inline