1 files changed, 230 insertions, 0 deletions
diff --git a/src/backend/storage/aio/aio_funcs.c b/src/backend/storage/aio/aio_funcs.c
new file mode 100644
index 00000000000..584e683371a
--- /dev/null
+++ b/src/backend/storage/aio/aio_funcs.c
@@ -0,0 +1,230 @@
+/*-------------------------------------------------------------------------
+ *
+ * aio_funcs.c
+ *    AIO - SQL interface for AIO
+ *
+ *
+ * Portions Copyright (c) 1996-2025, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * IDENTIFICATION
+ *    src/backend/storage/aio/aio_funcs.c
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#include "fmgr.h"
+#include "funcapi.h"
+#include "nodes/execnodes.h"
+#include "port/atomics.h"
+#include "storage/aio_internal.h"
+#include "storage/lock.h"
+#include "storage/proc.h"
+#include "storage/procnumber.h"
+#include "utils/builtins.h"
+#include "utils/fmgrprotos.h"
+#include "utils/tuplestore.h"
+
+
+/*
+ * Byte length of an iovec.
+ */
+static size_t
+iov_byte_length(const struct iovec *iov, int cnt)
+{
+	size_t		len = 0;
+
+	for (int i = 0; i < cnt; i++)
+	{
+		len += iov[i].iov_len;
+	}
+
+	return len;
+}
+
+Datum
+pg_get_aios(PG_FUNCTION_ARGS)
+{
+	ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
+
+	InitMaterializedSRF(fcinfo, 0);
+
+#define PG_GET_AIOS_COLS	15
+
+	for (uint64 i = 0; i < pgaio_ctl->io_handle_count; i++)
+	{
+		PgAioHandle *live_ioh = &pgaio_ctl->io_handles[i];
+		uint32		ioh_id = pgaio_io_get_id(live_ioh);
+		Datum		values[PG_GET_AIOS_COLS] = {0};
+		bool		nulls[PG_GET_AIOS_COLS] = {0};
+		ProcNumber	owner;
+		PGPROC	   *owner_proc;
+		int32		owner_pid;
+		PgAioHandleState start_state;
+		uint64		start_generation;
+		PgAioHandle ioh_copy;
+		struct iovec iov_copy[PG_IOV_MAX];
+
+
+		/*
+		 * There is no lock that could prevent the state of the IO to advance
+		 * concurrently - and we don't want to introduce one, as that would
+		 * introduce atomics into a very common path. Instead we
+		 *
+		 * 1) Determine the state + generation of the IO.
+		 *
+		 * 2) Copy the IO to local memory.
+		 *
+		 * 3) Check if state or generation of the IO changed. If the state
+		 * changed, retry, if the generation changed don't display the IO.
+		 */
+
+		/* 1) from above */
+		start_generation = live_ioh->generation;
+
+		/*
+		 * Retry at this point, so we can accept changing states, but not
+		 * changing generations.
+		 */
+retry:
+		pg_read_barrier();
+		start_state = live_ioh->state;
+
+		if (start_state == PGAIO_HS_IDLE)
+			continue;
+
+		/* 2) from above */
+		memcpy(&ioh_copy, live_ioh, sizeof(PgAioHandle));
+
+		/*
+		 * Safe to copy even if no iovec is used - we always reserve the
+		 * required space.
+		 */
+		memcpy(&iov_copy, &pgaio_ctl->iovecs[ioh_copy.iovec_off],
+			   PG_IOV_MAX * sizeof(struct iovec));
+
+		/*
+		 * Copy information about owner before 3) below, if the process exited
+		 * it'd have to wait for the IO to finish first, which we would detect
+		 * in 3).
+		 */
+		owner = ioh_copy.owner_procno;
+		owner_proc = GetPGProcByNumber(owner);
+		owner_pid = owner_proc->pid;
+
+		/* 3) from above */
+		pg_read_barrier();
+
+		/*
+		 * The IO completed and a new one was started with the same ID. Don't
+		 * display it - it really started after this function was called.
+		 * There be a risk of a livelock if we just retried endlessly, if IOs
+		 * complete very quickly.
+		 */
+		if (live_ioh->generation != start_generation)
+			continue;
+
+		/*
+		 * The IO's state changed while we were "rendering" it. Just start
+		 * from scratch. There's no risk of a livelock here, as an IO has a
+		 * limited sets of states it can be in, and state changes go only in a
+		 * single direction.
+		 */
+		if (live_ioh->state != start_state)
+			goto retry;
+
+		/*
+		 * Now that we have copied the IO into local memory and checked that
+		 * it's still in the same state, we are not allowed to access "live"
+		 * memory anymore. To make it slightly easier to catch such cases, set
+		 * the "live" pointers to NULL.
+		 */
+		live_ioh = NULL;
+		owner_proc = NULL;
+
+
+		/* column: owning pid */
+		if (owner_pid != 0)
+			values[0] = Int32GetDatum(owner_pid);
+		else
+			nulls[0] = false;
+
+		/* column: IO's id */
+		values[1] = ioh_id;
+
+		/* column: IO's generation */
+		values[2] = Int64GetDatum(start_generation);
+
+		/* column: IO's state */
+		values[3] = CStringGetTextDatum(pgaio_io_get_state_name(&ioh_copy));
+
+		/*
+		 * If the IO is in PGAIO_HS_HANDED_OUT state, none of the following
+		 * fields are valid yet (or are in the process of being set).
+		 * Therefore we don't want to display any other columns.
+		 */
+		if (start_state == PGAIO_HS_HANDED_OUT)
+		{
+			memset(nulls + 4, 1, (lengthof(nulls) - 4) * sizeof(bool));
+			goto display;
+		}
+
+		/* column: IO's operation */
+		values[4] = CStringGetTextDatum(pgaio_io_get_op_name(&ioh_copy));
+
+		/* columns: details about the IO's operation (offset, length) */
+		switch (ioh_copy.op)
+		{
+			case PGAIO_OP_INVALID:
+				nulls[5] = true;
+				nulls[6] = true;
+				break;
+			case PGAIO_OP_READV:
+				values[5] = Int64GetDatum(ioh_copy.op_data.read.offset);
+				values[6] =
+					Int64GetDatum(iov_byte_length(iov_copy, ioh_copy.op_data.read.iov_length));
+				break;
+			case PGAIO_OP_WRITEV:
+				values[5] = Int64GetDatum(ioh_copy.op_data.write.offset);
+				values[6] =
+					Int64GetDatum(iov_byte_length(iov_copy, ioh_copy.op_data.write.iov_length));
+				break;
+		}
+
+		/* column: IO's target */
+		values[7] = CStringGetTextDatum(pgaio_io_get_target_name(&ioh_copy));
+
+		/* column: length of IO's data array */
+		values[8] = Int16GetDatum(ioh_copy.handle_data_len);
+
+		/* column: raw result (i.e. some form of syscall return value) */
+		if (start_state == PGAIO_HS_COMPLETED_IO
+			|| start_state == PGAIO_HS_COMPLETED_SHARED
+			|| start_state == PGAIO_HS_COMPLETED_LOCAL)
+			values[9] = Int32GetDatum(ioh_copy.result);
+		else
+			nulls[9] = true;
+
+		/*
+		 * column: result in the higher level representation (unknown if not
+		 * finished)
+		 */
+		values[10] =
+			CStringGetTextDatum(pgaio_result_status_string(ioh_copy.distilled_result.status));
+
+		/* column: target description */
+		values[11] = CStringGetTextDatum(pgaio_io_get_target_description(&ioh_copy));
+
+		/* columns: one for each flag */
+		values[12] = BoolGetDatum(ioh_copy.flags & PGAIO_HF_SYNCHRONOUS);
+		values[13] = BoolGetDatum(ioh_copy.flags & PGAIO_HF_REFERENCES_LOCAL);
+		values[14] = BoolGetDatum(ioh_copy.flags & PGAIO_HF_BUFFERED);
+
+display:
+		tuplestore_putvalues(rsinfo->setResult, rsinfo->setDesc, values, nulls);
+	}
+
+	return (Datum) 0;
+}