Merge branch 'ps/reftable-concurrent-compaction'

The code path for compacting reftable files saw some bugfixes
against concurrent operation.

* ps/reftable-concurrent-compaction:
  reftable/stack: fix segfault when reload with reused readers fails
  reftable/stack: reorder swapping in the reloaded stack contents
  reftable/reader: keep readers alive during iteration
  reftable/reader: introduce refcounting
  reftable/stack: fix broken refnames in `write_n_ref_tables()`
  reftable/reader: inline `reader_close()`
  reftable/reader: inline `init_reader()`
  reftable/reader: rename `reftable_new_reader()`
  reftable/stack: inline `stack_compact_range_stats()`
  reftable/blocksource: drop malloc block source

1 files changed, 14 insertions, 5 deletions

diff --git a/reftable/reftable-reader.h b/reftable/reftable-reader.h
index 69621c5b0f..a600452b56 100644
--- a/reftable/reftable-reader.h
+++ b/reftable/reftable-reader.h
@@ -23,16 +23,28 @@
 /* The reader struct is a handle to an open reftable file. */
 struct reftable_reader;
 
-/* reftable_new_reader opens a reftable for reading. If successful,
+/* reftable_reader_new opens a reftable for reading. If successful,
  * returns 0 code and sets pp. The name is used for creating a
  * stack. Typically, it is the basename of the file. The block source
  * `src` is owned by the reader, and is closed on calling
  * reftable_reader_destroy(). On error, the block source `src` is
  * closed as well.
  */
-int reftable_new_reader(struct reftable_reader **pp,
+int reftable_reader_new(struct reftable_reader **pp,
 			struct reftable_block_source *src, const char *name);
 
+/*
+ * Manage the reference count of the reftable reader. A newly initialized
+ * reader starts with a refcount of 1 and will be deleted once the refcount has
+ * reached 0.
+ *
+ * This is required because readers may have longer lifetimes than the stack
+ * they belong to. The stack may for example be reloaded while the old tables
+ * are still being accessed by an iterator.
+ */
+void reftable_reader_incref(struct reftable_reader *reader);
+void reftable_reader_decref(struct reftable_reader *reader);
+
 /* Initialize a reftable iterator for reading refs. */
 void reftable_reader_init_ref_iterator(struct reftable_reader *r,
 				       struct reftable_iterator *it);
@@ -44,9 +56,6 @@ void reftable_reader_init_log_iterator(struct reftable_reader *r,
 /* returns the hash ID used in this table. */
 uint32_t reftable_reader_hash_id(struct reftable_reader *r);
 
-/* closes and deallocates a reader. */
-void reftable_reader_free(struct reftable_reader *);
-
 /* return an iterator for the refs pointing to `oid`. */
 int reftable_reader_refs_for(struct reftable_reader *r,
 			     struct reftable_iterator *it, uint8_t *oid);