aio: Basic subsystem initialization

This commit just does the minimal wiring up of the AIO subsystem, added in the
next commit, to the rest of the system. The next commit contains more details
about motivation and architecture.

This commit is kept separate to make it easier to review, separating the
changes across the tree, from the implementation of the new subsystem.

We discussed squashing this commit with the main commit before merging AIO,
but there has been a mild preference for keeping it separate.

Reviewed-by: Heikki Linnakangas <[email protected]>
Reviewed-by: Noah Misch <[email protected]>
Discussion: https://postgr.es/m/uvrtrknj4kdytuboidbhwclo4gxhswwcpgadptsjvjqcluzmah%40brqs62irg4dt

5 files changed, 79 insertions, 0 deletions

diff --git a/src/include/storage/aio.h b/src/include/storage/aio.h
new file mode 100644
index 00000000000..e79d5343038
--- /dev/null
+++ b/src/include/storage/aio.h
@@ -0,0 +1,38 @@
+/*-------------------------------------------------------------------------
+ *
+ * aio.h
+ *    Main AIO interface
+ *
+ *
+ * Portions Copyright (c) 1996-2025, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * src/include/storage/aio.h
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef AIO_H
+#define AIO_H
+
+
+
+/* Enum for io_method GUC. */
+typedef enum IoMethod
+{
+	IOMETHOD_SYNC = 0,
+} IoMethod;
+
+/* We'll default to synchronous execution. */
+#define DEFAULT_IO_METHOD IOMETHOD_SYNC
+
+
+struct dlist_node;
+extern void pgaio_io_release_resowner(struct dlist_node *ioh_node, bool on_error);
+
+
+/* GUCs */
+extern PGDLLIMPORT int io_method;
+extern PGDLLIMPORT int io_max_concurrency;
+
+
+#endif							/* AIO_H */
diff --git a/src/include/storage/aio_subsys.h b/src/include/storage/aio_subsys.h
new file mode 100644
index 00000000000..2a6ca1c27a9
--- /dev/null
+++ b/src/include/storage/aio_subsys.h
@@ -0,0 +1,33 @@
+/*-------------------------------------------------------------------------
+ *
+ * aio_subsys.h
+ *    Interaction with AIO as a subsystem, rather than actually issuing AIO
+ *
+ * This header is for AIO related functionality that's being called by files
+ * that don't perform AIO, but interact with the AIO subsystem in some
+ * form. E.g. postmaster.c and shared memory initialization need to initialize
+ * AIO but don't perform AIO.
+ *
+ * Portions Copyright (c) 1996-2025, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * src/include/storage/aio_subsys.h
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef AIO_SUBSYS_H
+#define AIO_SUBSYS_H
+
+
+/* aio_init.c */
+extern Size AioShmemSize(void);
+extern void AioShmemInit(void);
+
+extern void pgaio_init_backend(void);
+
+
+/* aio.c */
+extern void pgaio_error_cleanup(void);
+extern void AtEOXact_Aio(bool is_commit);
+
+#endif							/* AIO_SUBSYS_H */
diff --git a/src/include/utils/guc.h b/src/include/utils/guc.h
index 24444cbc365..f619100467d 100644
--- a/src/include/utils/guc.h
+++ b/src/include/utils/guc.h
@@ -318,6 +318,7 @@ extern PGDLLIMPORT bool optimize_bounded_sort;
  */
 extern PGDLLIMPORT const struct config_enum_entry archive_mode_options[];
 extern PGDLLIMPORT const struct config_enum_entry dynamic_shared_memory_options[];
+extern PGDLLIMPORT const struct config_enum_entry io_method_options[];
 extern PGDLLIMPORT const struct config_enum_entry recovery_target_action_options[];
 extern PGDLLIMPORT const struct config_enum_entry wal_level_options[];
 extern PGDLLIMPORT const struct config_enum_entry wal_sync_method_options[];
diff --git a/src/include/utils/guc_hooks.h b/src/include/utils/guc_hooks.h
index 9a0d8ec85c7..a3eba8fbe21 100644
--- a/src/include/utils/guc_hooks.h
+++ b/src/include/utils/guc_hooks.h
@@ -64,6 +64,8 @@ extern bool check_default_with_oids(bool *newval, void **extra,
 extern bool check_effective_io_concurrency(int *newval, void **extra,
 										   GucSource source);
 extern bool check_huge_page_size(int *newval, void **extra, GucSource source);
+extern void assign_io_method(int newval, void *extra);
+extern bool check_io_max_concurrency(int *newval, void **extra, GucSource source);
 extern const char *show_in_hot_standby(void);
 extern bool check_locale_messages(char **newval, void **extra, GucSource source);
 extern void assign_locale_messages(const char *newval, void *extra);
diff --git a/src/include/utils/resowner.h b/src/include/utils/resowner.h
index e8d452ca7ee..aede4bfc820 100644
--- a/src/include/utils/resowner.h
+++ b/src/include/utils/resowner.h
@@ -164,4 +164,9 @@ struct LOCALLOCK;
 extern void ResourceOwnerRememberLock(ResourceOwner owner, struct LOCALLOCK *locallock);
 extern void ResourceOwnerForgetLock(ResourceOwner owner, struct LOCALLOCK *locallock);
 
+/* special support for AIO */
+struct dlist_node;
+extern void ResourceOwnerRememberAioHandle(ResourceOwner owner, struct dlist_node *ioh_node);
+extern void ResourceOwnerForgetAioHandle(ResourceOwner owner, struct dlist_node *ioh_node);
+
 #endif							/* RESOWNER_H */