Fix memory leaks when freeing WAL readers Commit 3f1ce97346 introduced a circular buffer for decoded WAL records, with separate allocations for records that do not fit in the buffer. However, XLogReaderFree() did not release separately allocated records remaining in the decode queue. In particular, the last record returned by XLogReadRecord() remains queued until released, so freeing the reader could leak that record.
For many callers, the leaked memory is reclaimed when the containing memory context is reset or deleted. However, it can accumulate in long-lived contexts. For example, when checkpointing prepared transactions, XlogReadTwoPhaseData() creates a WAL reader, reads the PREPARE record, and frees the reader. Large PREPARE records can therefore leave allocations in checkpointer_context, which is not reset during normal operation. These allocations accumulate until an error resets the context or the checkpointer exits. Fix this by calling ResetDecoder() in XLogReaderFree() to release all separately allocated records in the queue. Do this before freeing the decode buffer, since the queue can also contain records stored in that buffer. Backpatch to v15, where the circular WAL decoding buffer was introduced. Author: Tomás Senart <[email protected]> Reviewed-by: Fujii Masao <[email protected]> Discussion: https://postgr.es/m/caeeba3uai8tgpd6p5sx_fzbu3khmwsvu9wuqa8jpspq1rjr...@mail.gmail.com Backpatch-through: 15 Branch ------ REL_16_STABLE Details ------- https://git.postgresql.org/pg/commitdiff/4c271dc216065c8e6c99ba3097e831e6ef6cd9e1 Modified Files -------------- src/backend/access/transam/xlogreader.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-)
