VFD ctl feature (#981)

* Added "ctl" callback to the VFD interface, and the associated
H5FDctl() and H5FD_ctl() calls.

Modified the MPIO VFD accordingly -- specifically:

Added ctl() call with op-code support to expose rank, size,
and communicator.

Modified H5FD_mpi_get_rank(), H5FD_mpi_get_size(),
and H5FD_mpi_get_comm() to use the new ctl() callback.  In passing
removed the const qualifier from the file parameter of these
functions, as the file parameter of the ctl callback is not
const.

Deleted the old  H5FD__mpio_mpi_rank(), H5FD__mpio_mpi_size(), and
H5FD__mpio_communicator() calls from the MPIO VFD.

Deleted H5FD_class_mpi_t from H5FDprivate.h, and modified the
MPIO VFD accordingly.  Note that all VFDs now use H5FD_class_t,
with no special class for VFDs that that support MPI.

Some minor touch ups to the Neil's selection I/O mods in passing.

Tested serial and parallel, debug and production on charis and
jelly.

* Reserve a range of VFD "ctl" opcodes for library and experimental usage

* Add "ctl" callbacks to passthrough VFDs

* Add RELEASE.txt entry for "ctl" callback

* Use H5FDopen with H5F_ACC_RDWR flag instead of H5F_ACC_TRUNC in vfd test

* Remove handling of passthrough "ctl" flag from multi VFD

* Move logic for testing H5FD_CTL__TEST_OPCODE into a testing VFD

Revise description of "ctl" callback in RELEASE.txt

Remove unused H5FD_CTL__NUM_OPCODES definition

Fix some warnings in multi VFD

Co-authored-by: mainzer <mainzer#hdfgroup.org>

1 files changed, 51 insertions, 0 deletions

diff --git a/src/H5FDmulti.c b/src/H5FDmulti.c
index cae4174..0d1967d 100644
--- a/src/H5FDmulti.c
+++ b/src/H5FDmulti.c
@@ -166,6 +166,8 @@ static herr_t  H5FD_multi_truncate(H5FD_t *_file, hid_t dxpl_id, hbool_t closing
 static herr_t  H5FD_multi_lock(H5FD_t *_file, hbool_t rw);
 static herr_t  H5FD_multi_unlock(H5FD_t *_file);
 static herr_t  H5FD_multi_delete(const char *filename, hid_t fapl_id);
+static herr_t  H5FD_multi_ctl(H5FD_t *_file, uint64_t op_code, uint64_t flags, const void *input,
+                              void **output);
 
 /* The class struct */
 static const H5FD_class_t H5FD_multi_g = {
@@ -201,6 +203,7 @@ static const H5FD_class_t H5FD_multi_g = {
     H5FD_multi_lock,           /* lock              */
     H5FD_multi_unlock,         /* unlock            */
     H5FD_multi_delete,         /* del               */
+    H5FD_multi_ctl,            /* ctl               */
     H5FD_FLMAP_DEFAULT         /* fl_map            */
 };
 
@@ -2070,6 +2073,54 @@ H5FD_multi_delete(const char *filename, hid_t fapl_id)
 } /* end H5FD_multi_delete() */
 H5_MULTI_GCC_DIAG_ON("format-nonliteral")
 
+/*-------------------------------------------------------------------------
+ * Function:    H5FD_multi_ctl
+ *
+ * Purpose:     Multi VFD version of the ctl callback.
+ *
+ *              The desired operation is specified by the op_code
+ *              parameter.
+ *
+ *              The flags parameter controls management of op_codes that
+ *              are unknown to the callback
+ *
+ *              The input and output parameters allow op_code specific
+ *              input and output
+ *
+ *              At present, this VFD supports no op codes of its own.
+ *
+ * Return:      Non-negative on success/Negative on failure
+ *
+ *-------------------------------------------------------------------------
+ */
+static herr_t
+H5FD_multi_ctl(H5FD_t *_file, uint64_t op_code, uint64_t flags, const void *input, void **output)
+{
+    H5FD_multi_t *     file      = (H5FD_multi_t *)_file;
+    static const char *func      = "H5FD_multi_ctl"; /* Function Name for error reporting */
+    herr_t             ret_value = 0;
+
+    /* Silence compiler */
+    (void)file;
+    (void)input;
+    (void)output;
+
+    /* Clear the error stack */
+    H5Eclear2(H5E_DEFAULT);
+
+    switch (op_code) {
+        /* Unknown op code */
+        default:
+            if (flags & H5FD_CTL__FAIL_IF_UNKNOWN_FLAG)
+                H5Epush_ret(func, H5E_ERR_CLS, H5E_VFL, H5E_FCNTL,
+                            "VFD ctl request failed (unknown op code and fail if unknown flag is set)", -1);
+
+            break;
+    }
+
+    return ret_value;
+} /* end H5FD_multi_ctl() */
+
 #ifdef H5private_H
 /*
  * This is not related to the functionality of the driver code.