Address issue #1 and issue #3 of the group test failures.

See Kent's documentation "Designed to Fail Tests and Issues".
(A) Fix for issue #1: HDassert the < and = cases between old and new
entry length.  John will take care of the > case.
(B) Fix for issue #3:  set the cache copy of page_size again if different
    from f->shared->fs_page_size.

src/H5AC.c

@@ -2777,3 +2777,34 @@ H5AC_get_mdc_image_info(const H5AC_t *cache_ptr, haddr_t *image_addr, hsize_t *i
 done:
     FUNC_LEAVE_NOAPI(ret_value)
 } /* H5AC_get_mdc_image_info() */
+
+/*-------------------------------------------------------------------------
+ * Function:    H5AC_set_vfd_swmr_reader
+ *
+ * Purpose:     Wrapper function for H5C_set_vfd_swmr_reader().
+ *
+ * Return:      SUCCEED on success, and FAIL on failure.
+ *
+ * Programmer:  Vailin Choi; Dec 2021
+ *
+ *-------------------------------------------------------------------------
+ */
+herr_t
+H5AC_set_vfd_swmr_reader(H5AC_t *cache_ptr, hbool_t vfd_swmr_reader, hsize_t page_size)
+{
+    herr_t ret_value = SUCCEED; /* Return value */
+
+    FUNC_ENTER_NOAPI(FAIL)
+
+    /* Sanity checks */
+    HDassert(cache_ptr);
+
+    if(cache_ptr->page_size != page_size) {
+
+        if (H5C_set_vfd_swmr_reader((H5C_t *)cache_ptr, vfd_swmr_reader, page_size) < 0)
+            HGOTO_ERROR(H5E_CACHE, H5E_CANTSET, FAIL, "can't set page_size for VFD SWMR reader")
+    }
+
+done:
+    FUNC_LEAVE_NOAPI(ret_value)
+} /* H5AC_set_vfd_swmr_reader() */

src/H5ACprivate.h

@@ -433,6 +433,7 @@ H5_DLL herr_t H5AC_unsettle_ring(H5F_t *f, H5AC_ring_t ring);
 H5_DLL herr_t H5AC_expunge_tag_type_metadata(H5F_t *f, haddr_t tag, int type_id, unsigned flags,
                                              hbool_t type_match);
 H5_DLL herr_t H5AC_get_tag(const void *thing, /*OUT*/ haddr_t *tag);
+H5_DLL herr_t H5AC_set_vfd_swmr_reader(H5AC_t *cache_ptr, hbool_t vfd_swmr_reader, hsize_t page_size);
 
 /* Virtual entry routines */
 H5_DLL H5AC_proxy_entry_t *H5AC_proxy_entry_create(void);

src/H5Fvfd_swmr.c

@@ -169,7 +169,7 @@ H5FL_DEFINE(eot_queue_entry_t);
  * Return:      Success:        SUCCEED
  *              Failure:        FAIL
  *
- * Programmer:  Vailin Choi -- 11/??/18
+ * Programmer:  Vailin Choi -- 10/??/18
  *
  * Changes:     None.
  *
@@ -252,6 +252,21 @@ H5F_vfd_swmr_init(H5F_t *f, hbool_t file_create)
 
         HDassert(!shared->vfd_swmr_config.writer);
 
+        HDassert(shared->fs_page_size > 0);
+        /* This is a bug uncovered by issue #3 of the group test failures.
+         *  See Kent's documentation "Designed to Fail Tests and Issues".
+         *  The file opening process in H5F__new() initializes the cache copy of 
+         *  page_size via H5AC_create().  However, later on H5F__super_read() 
+         *  may change page size due to non-default setting of 
+         *  'free-space manager info' in superblock extension.
+         *  Fix: set the cache copy of page_size again if different from 
+         *  f->shared->fs_page_size.
+         */
+        if(shared->cache) {
+            if (H5AC_set_vfd_swmr_reader(shared->cache, TRUE, shared->fs_page_size) < 0)
+                HGOTO_ERROR(H5E_CACHE, H5E_CANTSET, FAIL, "can't set page size in cache for VFD SWMR reader");
+        }
+
         shared->vfd_swmr_writer = FALSE;
         shared->max_jump_ticks  = 0;
 
@@ -1258,6 +1273,14 @@ H5F_vfd_swmr_reader_end_of_tick(H5F_t *f, hbool_t entering_api)
 #if 0 /*Kent*/
                     HDassert(oent->length == nent->length);
 #endif
+                    /* This is a bug uncovered by issue #1 of the 
+                     * group test failures.  See Kent's documentation
+                     * "Designed to Fail Tests and Issues".
+                     * nent->length can be <, =, > to oent->length.
+                     * Fix: HDassert the 1st two cases: < and =.
+                     * John will address the > case.
+                     */
+                    HDassert(nent->length <= oent->length);
 
                     /* the page has been altered -- evict it and
                      * any contained metadata cache entries.

test/testvfdswmr.sh.in

@@ -1,4 +1,4 @@
-#!/usr/bin/env bash
+#!/us/bin/env bash
 #
 # Copyright by The HDF Group.
 # Copyright by the Board of Trustees of the University of Illinois.
@@ -74,6 +74,13 @@ DSETOPS_FIFO_READER_TO_WRITER=fifo_dsetops_reader_to_writer
 DSETCHKS_FIFO_WRITER_TO_READER=fifo_dsetchks_writer_to_reader
 DSETCHKS_FIFO_READER_TO_WRITER=fifo_dsetchks_reader_to_writer
 
+###############################################################################
+## For gfail{1,2,3,4} test: definitions for fifo files to coordinate test runs
+###############################################################################
+#
+GFAIL_FIFO_WRITER_TO_READER=fifo_group_writer_to_reader
+GFAIL_FIFO_READER_TO_WRITER=fifo_group_reader_to_writer
+
 ###############################################################################
 ## short hands and function definitions
 ###############################################################################
@@ -147,6 +154,7 @@ all_tests="${all_tests} groups groups_attrs groups_ops few_big many_small attrds
 # For exhaustive run, add: os_groups_attrs, os_groups_ops, os_groups_seg, dsetops, dsetchks,independ_wr
 if [[ "$HDF5TestExpress" -eq 0 ]] ; then         # exhaustive run
     all_tests="${all_tests} os_groups_attrs os_groups_ops os_groups_seg dsetops dsetchks independ_wr"
+    all_tests="${all_tests} gfail_entry_length gfail_page_size"
 fi
 
 tests=${all_tests}
@@ -1387,6 +1395,118 @@ if [ ${do_independ_wr:-no} = yes ]; then
 fi
 
 
+###############################################################################
+#
+# "gfail_entry_length" test
+#
+# Only for exhaustive run
+#
+# Verify that the assertion failure for old and new entry length is fixed.
+# (See issue #1 in Kent's documentation "Designed to Fail Tests and Issues".
+#
+###############################################################################
+#
+#
+if [ ${do_gfail_entry_length:-no} = yes ]; then
+    #
+    # Clean up any existing fifo files from previous runs
+    if [ -e ./$GFAIL_FIFO_WRITER_TO_READER ]; then     # If writer fifo file is found
+        rm -f ./$GFAIL_FIFO_WRITER_TO_READER
+    fi
+    if [ -e ./$GFAIL_FIFO_READER_TO_WRITER ]; then      # If reader fifo file is found
+        rm -f ./$GFAIL_FIFO_READER_TO_WRITER
+    fi
+    #
+	echo launch vfd_swmr_gfail_writer -q -m 10 -n 340000
+	catch_out_err_and_rc vfd_swmr_gfail_entry_length_writer \
+	    ../vfd_swmr_gfail_writer -q -m 10 -n 340000 &
+	pid_writer=$!
+
+	echo launch vfd_swmr_gfail_reader -m 10 -n 340000
+	catch_out_err_and_rc vfd_swmr_gfail_entry_length_reader \
+	    ../vfd_swmr_gfail_reader -m 10 -n 340000 &
+	pid_reader=$!
+
+	# Wait for the reader to finish before signaling the
+	# writer to quit: the writer holds the file open so that the
+	# reader will find the shadow file when it opens
+	# the .h5 file.
+	wait $pid_reader
+	wait $pid_writer
+
+	# Collect exit code of the reader
+    if [ $(cat vfd_swmr_gfail_entry_length_reader.rc) -ne 0 ]; then
+	    echo reader had error
+	    nerrors=$((nerrors + 1))
+    fi
+
+	# Collect exit code of the writer
+	if [ $(cat vfd_swmr_gfail_entry_length_writer.rc) -ne 0 ]; then
+	    echo writer had error
+	    nerrors=$((nerrors + 1))
+	fi
+
+	# Clean up output files
+	rm -f vfd_swmr_gfail_entry_length_writer.{out,rc}
+	rm -f vfd_swmr_gfail_entry_length_reader.*.{out,rc}
+fi
+
+###############################################################################
+#
+# "gfail_page_size" test
+#
+# Only for exhaustive run
+#
+# Verify that the assertion failure is fixed when non-default page size is set.
+# (See issue #3 in Kent's documentation "Designed to Fail Tests and Issues".
+#
+###############################################################################
+#
+#
+if [ ${do_gfail_page_size:-no} = yes ]; then
+    #
+    # Clean up any existing fifo files from previous runs
+    if [ -e ./$GFAIL_FIFO_WRITER_TO_READER ]; then     # If writer fifo file is found
+        rm -f ./$GFAIL_FIFO_WRITER_TO_READER
+    fi
+    if [ -e ./$GFAIL_FIFO_READER_TO_WRITER ]; then      # If reader fifo file is found
+        rm -f ./$GFAIL_FIFO_READER_TO_WRITER
+    fi
+    #
+	echo launch vfd_swmr_gfail_writer -q -m 10 -B 8192 -s 8192 -n 320000
+	catch_out_err_and_rc vfd_swmr_gfail_page_size_writer \
+	    ../vfd_swmr_gfail_writer -q -m 10 -B 8192 -s 8192 -n 320000 &
+	pid_writer=$!
+
+	echo launch vfd_swmr_gfail_reader -m 10 -B 8192 -s 8192 -n 320000
+	catch_out_err_and_rc vfd_swmr_gfail_page_size_reader  \
+	    ../vfd_swmr_gfail_reader -m 10 -B 8192 -s 8192 -n 320000 &
+	pid_reader=$!
+
+	# Wait for the reader to finish before signaling the
+	# writer to quit: the writer holds the file open so that the
+	# reader will find the shadow file when it opens
+	# the .h5 file.
+	wait $pid_reader
+	wait $pid_writer
+
+	# Collect exit code of the reader
+	if [ $(cat vfd_swmr_gfail_page_size_reader.rc) -ne 0 ]; then
+	    echo reader had error
+	    nerrors=$((nerrors + 1))
+	fi
+
+	# Collect exit code of the writer
+	if [ $(cat vfd_swmr_gfail_page_size_writer.rc) -ne 0 ]; then
+	    echo writer had error
+	    nerrors=$((nerrors + 1))
+	fi
+
+	# Clean up output files
+	rm -f vfd_swmr_gfail_page_size_writer.{out,rc}
+	rm -f vfd_swmr_gfail_page_size_reader.*.{out,rc}
+fi
+
 ###############################################################################
 ## Report and exit
 ###############################################################################