Merge branch 'develop' into eoc_valgrind_bugfix

5 files changed, 131 insertions, 152 deletions

diff --git a/src/H5C.c b/src/H5C.c
index 147489b..e57dc81 100644
--- a/src/H5C.c
+++ b/src/H5C.c
@@ -216,9 +216,6 @@ H5FL_DEFINE_STATIC(H5C_t);
 /* Declare a free list to manage flush dependency arrays */
 H5FL_BLK_DEFINE_STATIC(parent);
 
-/* Declare extern free list to manage the H5C_collective_write_t struct */
-H5FL_EXTERN(H5C_collective_write_t);
-
 
 
 /*-------------------------------------------------------------------------
@@ -369,6 +366,7 @@ H5C_create(size_t		      max_cache_size,
     cache_ptr->coll_list_size			= (size_t)0;
     cache_ptr->coll_head_ptr			= NULL;
     cache_ptr->coll_tail_ptr			= NULL;
+    cache_ptr->coll_write_list			= NULL;
 #endif /* H5_HAVE_PARALLEL */
 
     cache_ptr->cLRU_list_len			= 0;
@@ -814,7 +812,7 @@ H5C_expunge_entry(H5F_t *f, hid_t dxpl_id, const H5C_class_t *type,
     /* Delete the entry from the skip list on destroy */
     flush_flags |= H5C__DEL_FROM_SLIST_ON_DESTROY_FLAG;
 
-    if(H5C__flush_single_entry(f, dxpl_id, entry_ptr, flush_flags, NULL) < 0)
+    if(H5C__flush_single_entry(f, dxpl_id, entry_ptr, flush_flags) < 0)
         HGOTO_ERROR(H5E_CACHE, H5E_CANTEXPUNGE, FAIL, "can't flush entry")
 
 done:
@@ -3114,7 +3112,7 @@ H5C_unprotect(H5F_t *		  f,
             /* Delete the entry from the skip list on destroy */
             flush_flags |= H5C__DEL_FROM_SLIST_ON_DESTROY_FLAG;
 
-            if(H5C__flush_single_entry(f, dxpl_id, entry_ptr, flush_flags, NULL) < 0)
+            if(H5C__flush_single_entry(f, dxpl_id, entry_ptr, flush_flags) < 0)
                 HGOTO_ERROR(H5E_CACHE, H5E_CANTUNPROTECT, FAIL, "Can't flush entry")
 
         }
@@ -3128,7 +3126,7 @@ H5C_unprotect(H5F_t *		  f,
             else if(test_entry_ptr != entry_ptr)
                 HGOTO_ERROR(H5E_CACHE, H5E_CANTUNPROTECT, FAIL, "hash table contains multiple entries for addr?!?.")
 
-            if(H5C__flush_single_entry(f, dxpl_id, entry_ptr, H5C__FLUSH_CLEAR_ONLY_FLAG | H5C__DEL_FROM_SLIST_ON_DESTROY_FLAG, NULL) < 0)
+            if(H5C__flush_single_entry(f, dxpl_id, entry_ptr, H5C__FLUSH_CLEAR_ONLY_FLAG | H5C__DEL_FROM_SLIST_ON_DESTROY_FLAG) < 0)
                 HGOTO_ERROR(H5E_CACHE, H5E_CANTUNPROTECT, FAIL, "Can't clear entry")
         }
 #endif /* H5_HAVE_PARALLEL */
@@ -4321,7 +4319,7 @@ H5C__autoadjust__ageout__evict_aged_out_entries(H5F_t * f,
                     cache_ptr->entries_removed_counter = 0;
                     cache_ptr->last_entry_removed_ptr  = NULL;
 
-                    if(H5C__flush_single_entry(f, dxpl_id, entry_ptr, H5C__NO_FLAGS_SET, NULL) < 0)
+                    if(H5C__flush_single_entry(f, dxpl_id, entry_ptr, H5C__NO_FLAGS_SET) < 0)
                         HGOTO_ERROR(H5E_CACHE, H5E_CANTFLUSH, FAIL, "unable to flush entry")
 
                     if(cache_ptr->entries_removed_counter > 1 || cache_ptr->last_entry_removed_ptr == prev_ptr)
@@ -4332,7 +4330,7 @@ H5C__autoadjust__ageout__evict_aged_out_entries(H5F_t * f,
 
                 bytes_evicted += entry_ptr->size;
 
-                if(H5C__flush_single_entry(f, dxpl_id, entry_ptr, H5C__FLUSH_INVALIDATE_FLAG | H5C__DEL_FROM_SLIST_ON_DESTROY_FLAG, NULL) < 0 )
+                if(H5C__flush_single_entry(f, dxpl_id, entry_ptr, H5C__FLUSH_INVALIDATE_FLAG | H5C__DEL_FROM_SLIST_ON_DESTROY_FLAG) < 0 )
                     HGOTO_ERROR(H5E_CACHE, H5E_CANTFLUSH, FAIL, "unable to flush entry")
             }
 
@@ -4415,7 +4413,7 @@ H5C__autoadjust__ageout__evict_aged_out_entries(H5F_t * f,
             prev_ptr = entry_ptr->prev;
 
             if ( ! (entry_ptr->is_dirty) ) {
-                if(H5C__flush_single_entry(f, dxpl_id, entry_ptr, H5C__FLUSH_INVALIDATE_FLAG | H5C__DEL_FROM_SLIST_ON_DESTROY_FLAG, NULL) < 0)
+                if(H5C__flush_single_entry(f, dxpl_id, entry_ptr, H5C__FLUSH_INVALIDATE_FLAG | H5C__DEL_FROM_SLIST_ON_DESTROY_FLAG) < 0)
                     HGOTO_ERROR(H5E_CACHE, H5E_CANTFLUSH, FAIL, "unable to flush clean entry")
             }
             /* just skip the entry if it is dirty, as we can't do
@@ -5212,7 +5210,7 @@ H5C_flush_invalidate_ring(const H5F_t * f, hid_t dxpl_id, H5C_ring_t ring,
                      */
                     protected_entries++;
                 } else if(entry_ptr->is_pinned) {
-                    if(H5C__flush_single_entry(f, dxpl_id, entry_ptr, H5C__DURING_FLUSH_FLAG, NULL) < 0)
+                    if(H5C__flush_single_entry(f, dxpl_id, entry_ptr, H5C__DURING_FLUSH_FLAG) < 0)
                         HGOTO_ERROR(H5E_CACHE, H5E_CANTFLUSH, FAIL, "dirty pinned entry flush failed.")
 
                     if(cache_ptr->slist_changed) {
@@ -5229,8 +5227,7 @@ H5C_flush_invalidate_ring(const H5F_t * f, hid_t dxpl_id, H5C_ring_t ring,
                     } /* end if */
                 } /* end if */
                 else {
-                    if(H5C__flush_single_entry(f, dxpl_id, entry_ptr, 
-                                (cooked_flags | H5C__DURING_FLUSH_FLAG | H5C__FLUSH_INVALIDATE_FLAG | H5C__DEL_FROM_SLIST_ON_DESTROY_FLAG), NULL) < 0)
+                    if(H5C__flush_single_entry(f, dxpl_id, entry_ptr, (cooked_flags | H5C__DURING_FLUSH_FLAG | H5C__FLUSH_INVALIDATE_FLAG | H5C__DEL_FROM_SLIST_ON_DESTROY_FLAG)) < 0)
                         HGOTO_ERROR(H5E_CACHE, H5E_CANTFLUSH, FAIL, "dirty entry flush destroy failed.")
 
                     if(cache_ptr->slist_changed) {
@@ -5327,8 +5324,7 @@ H5C_flush_invalidate_ring(const H5F_t * f, hid_t dxpl_id, H5C_ring_t ring,
                          * or three entries.
                          */
                         cache_ptr->entry_watched_for_removal = next_entry_ptr;
-                        if(H5C__flush_single_entry(f, dxpl_id, entry_ptr, 
-                                (cooked_flags | H5C__DURING_FLUSH_FLAG | H5C__FLUSH_INVALIDATE_FLAG | H5C__DEL_FROM_SLIST_ON_DESTROY_FLAG), NULL) < 0)
+                        if(H5C__flush_single_entry(f, dxpl_id, entry_ptr, (cooked_flags | H5C__DURING_FLUSH_FLAG | H5C__FLUSH_INVALIDATE_FLAG | H5C__DEL_FROM_SLIST_ON_DESTROY_FLAG)) < 0)
                             HGOTO_ERROR(H5E_CACHE, H5E_CANTFLUSH, FAIL, "Entry flush destroy failed.")
 
                         /* Check for the next entry getting removed */
@@ -5616,7 +5612,7 @@ H5C_flush_ring(H5F_t *f, hid_t dxpl_id, H5C_ring_t ring,  unsigned flags)
                     protected_entries++;
                 } /* end if */
                 else {
-                    if(H5C__flush_single_entry(f, dxpl_id, entry_ptr, (flags | H5C__DURING_FLUSH_FLAG), NULL) < 0)
+                    if(H5C__flush_single_entry(f, dxpl_id, entry_ptr, (flags | H5C__DURING_FLUSH_FLAG)) < 0)
                         HGOTO_ERROR(H5E_CACHE, H5E_CANTFLUSH, FAIL, "Can't flush entry.")
 
                     if(cache_ptr->slist_changed) {
@@ -5724,11 +5720,7 @@ done:
  */
 herr_t
 H5C__flush_single_entry(const H5F_t *f, hid_t dxpl_id, H5C_cache_entry_t *entry_ptr,
-    unsigned flags, H5SL_t
-#ifndef H5_HAVE_PARALLEL
-    H5_ATTR_UNUSED
-#endif /* NDEBUG */
-    *collective_write_list)
+    unsigned flags)
 {
     H5C_t *	     	cache_ptr;              /* Cache for file */
     hbool_t		destroy;		/* external flag */
@@ -5739,6 +5731,7 @@ H5C__flush_single_entry(const H5F_t *f, hid_t dxpl_id, H5C_cache_entry_t *entry_
     hbool_t		during_flush;		/* external flag */
     hbool_t		write_entry;		/* internal flag */
     hbool_t		destroy_entry;		/* internal flag */
+    hbool_t		generate_image;		/* internal flag */
     hbool_t		was_dirty;
     haddr_t             entry_addr = HADDR_UNDEF;
     herr_t		ret_value = SUCCEED;      /* Return value */
@@ -5759,6 +5752,7 @@ H5C__flush_single_entry(const H5F_t *f, hid_t dxpl_id, H5C_cache_entry_t *entry_
     take_ownership         = ((flags & H5C__TAKE_OWNERSHIP_FLAG) != 0);
     del_from_slist_on_destroy = ((flags & H5C__DEL_FROM_SLIST_ON_DESTROY_FLAG) != 0);
     during_flush           = ((flags & H5C__DURING_FLUSH_FLAG) != 0);
+    generate_image         = ((flags & H5C__GENERATE_IMAGE_FLAG) != 0);
 
     /* Set the flag for destroying the entry, based on the 'take ownership'
      * and 'destroy' flags
@@ -5818,29 +5812,13 @@ H5C__flush_single_entry(const H5F_t *f, hid_t dxpl_id, H5C_cache_entry_t *entry_
     entry_ptr->flush_in_progress = TRUE;
     entry_ptr->flush_marker = FALSE;
 
-    /* serialize the entry if necessary, and then write it to disk. */
-    if(write_entry) {
-
-	/* The entry is dirty, and we are doing either a flush,
-	 * or a flush destroy.  In either case, serialize the
-	 * entry and write it to disk.
-         *
-         * Note that this may cause the entry to be re-sized and/or
-         * moved in the cache.  
-	 *
-         * As we will not update the metadata cache's data structures 
-         * until we we finish the write, we must touch up these 
-         * data structures for size and location changes even if we 
-         * are about to delete the entry from the cache (i.e. on a 
-         * flush destroy).
-         */
+    /* The entry is dirty, and we are doing a flush, a flush destroy or have
+     * been requested to generate an image.  In those cases, serialize the
+     * entry.
+     */
+    if(write_entry || generate_image) {
         HDassert(entry_ptr->is_dirty);
 
-#if H5C_DO_SANITY_CHECKS
-        if(cache_ptr->check_write_permitted && !(cache_ptr->write_permitted))
-            HGOTO_ERROR(H5E_CACHE, H5E_SYSTEM, FAIL, "Write when writes are always forbidden!?!?!")
-#endif /* H5C_DO_SANITY_CHECKS */
-
         if(NULL == entry_ptr->image_ptr) {
             if(NULL == (entry_ptr->image_ptr = H5MM_malloc(entry_ptr->size + H5C_IMAGE_EXTRA_SPACE)))
                 HGOTO_ERROR(H5E_CACHE, H5E_CANTALLOC, FAIL, "memory allocation failed for on disk image buffer")
@@ -5854,30 +5832,27 @@ H5C__flush_single_entry(const H5F_t *f, hid_t dxpl_id, H5C_cache_entry_t *entry_
             if(H5C__generate_image(f, cache_ptr, entry_ptr, dxpl_id) < 0)
                 HGOTO_ERROR(H5E_CACHE, H5E_CANTGET, FAIL, "can't generate entry's image")
         } /* end if ( ! (entry_ptr->image_up_to_date) ) */
+    } /* end if */
 
-        /* Finally, write the image to disk.  
-         * 
-         * Note that if the H5AC__CLASS_SKIP_WRITES flag is set in the 
-         * in the entry's type, we silently skip the write.  This
-         * flag should only be used in test code. 
-         */
-        if(((entry_ptr->type->flags) & H5C__CLASS_SKIP_WRITES) == 0) {
-#ifdef H5_HAVE_PARALLEL
-            if(collective_write_list) {
-                H5C_collective_write_t *item;
-
-                if(NULL == (item = (H5C_collective_write_t *)H5FL_MALLOC(H5C_collective_write_t)))
-                    HGOTO_ERROR(H5E_CACHE, H5E_CANTALLOC, FAIL, "unable to allocate skip list item")
+    /* Finally, write the image to disk.  
+     * 
+     * Note that if the H5AC__CLASS_SKIP_WRITES flag is set in the 
+     * in the entry's type, we silently skip the write.  This
+     * flag should only be used in test code. 
+     */
+    if(write_entry) {
+        HDassert(entry_ptr->is_dirty);
 
-                item->length = entry_ptr->size;
-                item->free_buf = FALSE;
-                item->buf = entry_ptr->image_ptr;
-                item->offset = entry_ptr->addr;
+#if H5C_DO_SANITY_CHECKS
+        if(cache_ptr->check_write_permitted && !(cache_ptr->write_permitted))
+            HGOTO_ERROR(H5E_CACHE, H5E_SYSTEM, FAIL, "Write when writes are always forbidden!?!?!")
+#endif /* H5C_DO_SANITY_CHECKS */
 
-                if(H5SL_insert(collective_write_list, item, &item->offset) < 0) {
-                    H5MM_free(item);
+        if(((entry_ptr->type->flags) & H5C__CLASS_SKIP_WRITES) == 0) {
+#ifdef H5_HAVE_PARALLEL
+            if(cache_ptr->coll_write_list) {
+                if(H5SL_insert(cache_ptr->coll_write_list, entry_ptr, &entry_ptr->addr) < 0)
                     HGOTO_ERROR(H5E_CACHE, H5E_CANTINSERT, FAIL, "unable to insert skip list item")
-                } /* end if */
             } /* end if */
             else
 #endif /* H5_HAVE_PARALLEL */
@@ -6699,7 +6674,7 @@ H5C_make_space_in_cache(H5F_t *	f,
                     } /* end if */
 #endif
 
-                    if(H5C__flush_single_entry(f, dxpl_id, entry_ptr, H5C__NO_FLAGS_SET, NULL) < 0)
+                    if(H5C__flush_single_entry(f, dxpl_id, entry_ptr, H5C__NO_FLAGS_SET) < 0)
                         HGOTO_ERROR(H5E_CACHE, H5E_CANTFLUSH, FAIL, "unable to flush entry")
 
 		    if ( ( cache_ptr->entries_removed_counter > 1 ) ||
@@ -6716,7 +6691,7 @@ H5C_make_space_in_cache(H5F_t *	f,
                     cache_ptr->entries_scanned_to_make_space++;
 #endif /* H5C_COLLECT_CACHE_STATS */
 
-                    if(H5C__flush_single_entry(f, dxpl_id, entry_ptr, H5C__FLUSH_INVALIDATE_FLAG | H5C__DEL_FROM_SLIST_ON_DESTROY_FLAG, NULL) < 0)
+                    if(H5C__flush_single_entry(f, dxpl_id, entry_ptr, H5C__FLUSH_INVALIDATE_FLAG | H5C__DEL_FROM_SLIST_ON_DESTROY_FLAG) < 0)
                         HGOTO_ERROR(H5E_CACHE, H5E_CANTFLUSH, FAIL, "unable to flush entry")
                 } else {
                     /* We have enough space so don't flush clean entry. */
@@ -6857,7 +6832,7 @@ H5C_make_space_in_cache(H5F_t *	f,
 #ifdef H5_HAVE_PARALLEL
             if(!(entry_ptr->coll_access)) {
 #endif /* H5_HAVE_PARALLEL */
-                if(H5C__flush_single_entry(f, dxpl_id, entry_ptr, H5C__FLUSH_INVALIDATE_FLAG | H5C__DEL_FROM_SLIST_ON_DESTROY_FLAG, NULL) < 0)
+                if(H5C__flush_single_entry(f, dxpl_id, entry_ptr, H5C__FLUSH_INVALIDATE_FLAG | H5C__DEL_FROM_SLIST_ON_DESTROY_FLAG) < 0)
                     HGOTO_ERROR(H5E_CACHE, H5E_CANTFLUSH, FAIL, "unable to flush entry")
 #ifdef H5_HAVE_PARALLEL
             } /* end if */
@@ -7600,6 +7575,15 @@ H5C__assert_flush_dep_nocycle(const H5C_cache_entry_t * entry,
  *
  * Purpose:     Serialize an entry and generate its image.
  *
+ * Note:	This may cause the entry to be re-sized and/or moved in
+ *              the cache.  
+ *
+ *              As we will not update the metadata cache's data structures 
+ *              until we we finish the write, we must touch up these 
+ *              data structures for size and location changes even if we 
+ *              are about to delete the entry from the cache (i.e. on a 
+ *              flush destroy).
+ *
  * Return:      Non-negative on success/Negative on failure
  *
  * Programmer:  Mohamad Chaarawi
diff --git a/src/H5Cmpio.c b/src/H5Cmpio.c
index 8a28f88..ab94879 100644
--- a/src/H5Cmpio.c
+++ b/src/H5Cmpio.c
@@ -64,9 +64,7 @@
 /********************/
 /* Local Prototypes */
 /********************/
-static herr_t H5C__collective_write(H5F_t *f, hid_t dxpl_id,
-    H5SL_t *collective_write_list);
-static herr_t H5C__collective_write_free(void *_item, void *key, void *op_data);
+static herr_t H5C__collective_write(H5F_t *f, hid_t dxpl_id);
 
 
 /*********************/
@@ -83,9 +81,6 @@ static herr_t H5C__collective_write_free(void *_item, void *key, void *op_data);
 /* Local Variables */
 /*******************/
 
-/* Declare a free list to manage the H5C_collective_write_t struct */
-H5FL_DEFINE(H5C_collective_write_t);
-
 
 
 /*-------------------------------------------------------------------------
@@ -230,7 +225,6 @@ H5C_apply_candidate_list(H5F_t * f,
     H5C_cache_entry_t *	entry_ptr = NULL;
     H5C_cache_entry_t *	flush_ptr = NULL;
     H5C_cache_entry_t * delayed_ptr = NULL;
-    H5SL_t            * collective_write_list = NULL;
 #if H5C_DO_SANITY_CHECKS
     haddr_t		last_addr;
 #endif /* H5C_DO_SANITY_CHECKS */
@@ -264,8 +258,11 @@ H5C_apply_candidate_list(H5F_t * f,
 #endif /* H5C_APPLY_CANDIDATE_LIST__DEBUG */
 
     if(f->coll_md_write) {
+        /* Sanity check */
+        HDassert(NULL == cache_ptr->coll_write_list);
+
         /* Create skip list of entries for collective write */
-        if(NULL == (collective_write_list = H5SL_create(H5SL_TYPE_HADDR, NULL)))
+        if(NULL == (cache_ptr->coll_write_list = H5SL_create(H5SL_TYPE_HADDR, NULL)))
             HGOTO_ERROR(H5E_DATASET, H5E_CANTCREATE, FAIL, "can't create skip list for entries")
     } /* end if */
 
@@ -454,13 +451,37 @@ H5C_apply_candidate_list(H5F_t * f,
               (long long)clear_ptr->addr);
 #endif /* H5C_APPLY_CANDIDATE_LIST__DEBUG */
 
-	    /* No need to check for the next entry in the scan being 
-             * removed from the cache, as this call to H5C__flush_single_entry()
-             * will not call either the pre_serialize or serialize callbacks.
+            /* reset entries_removed_counter and
+             * last_entry_removed_ptr prior to the call to
+             * H5C__flush_single_entry() so that we can spot
+             * unexpected removals of entries from the cache,
+             * and set the restart_scan flag if proceeding
+             * would be likely to cause us to scan an entry
+             * that is no longer in the cache.
+             *
+             * Note that as of this writing (April 2015) this 
+             * case cannot occur in the parallel case.  However 
+             * Quincey is making noises about changing this, hence 
+             * the insertion of this test.
+             *
+             * Note also that there is no test code to verify 
+             * that this code actually works (although similar code
+             * in the serial version exists and is tested).  
+             * 
+             * Implementing a test will likely require implementing
+             * flush op like facilities in the parallel tests.  At
+             * a guess this will not be terribly painful, but it 
+             * will take a bit of time.
              */
+            cache_ptr->entries_removed_counter = 0;
+            cache_ptr->last_entry_removed_ptr  = NULL;
 
-            if(H5C__flush_single_entry(f, dxpl_id, clear_ptr, H5C__FLUSH_CLEAR_ONLY_FLAG | H5C__DEL_FROM_SLIST_ON_DESTROY_FLAG, NULL) < 0)
+            if(H5C__flush_single_entry(f, dxpl_id, clear_ptr, H5C__FLUSH_CLEAR_ONLY_FLAG | H5C__GENERATE_IMAGE_FLAG | H5C__DEL_FROM_SLIST_ON_DESTROY_FLAG) < 0)
                 HGOTO_ERROR(H5E_CACHE, H5E_CANTFLUSH, FAIL, "Can't clear entry.")
+
+            if((cache_ptr->entries_removed_counter > 1) ||
+                    (cache_ptr->last_entry_removed_ptr == entry_ptr))
+                restart_scan = TRUE;
         } /* end if */
 
         /* Else, if this process needs to flush this entry. */
@@ -505,14 +526,12 @@ H5C_apply_candidate_list(H5F_t * f,
             cache_ptr->last_entry_removed_ptr  = NULL;
 
             /* Add this entry to the list of entries to collectively write */
-            if(H5C__flush_single_entry(f, dxpl_id, flush_ptr, H5C__DEL_FROM_SLIST_ON_DESTROY_FLAG, collective_write_list) < 0)
+            if(H5C__flush_single_entry(f, dxpl_id, flush_ptr, H5C__DEL_FROM_SLIST_ON_DESTROY_FLAG) < 0)
                 HGOTO_ERROR(H5E_CACHE, H5E_CANTFLUSH, FAIL, "Can't flush entry.")
 
-            if ( ( cache_ptr->entries_removed_counter > 1 ) ||
-                 ( cache_ptr->last_entry_removed_ptr == entry_ptr ) )
-
+            if((cache_ptr->entries_removed_counter > 1) ||
+                    (cache_ptr->last_entry_removed_ptr == entry_ptr))
                 restart_scan = TRUE;
-
         } /* end else-if */
 
         /* Otherwise, no action to be taken on this entry. Grab the next. */
@@ -663,7 +682,7 @@ H5C_apply_candidate_list(H5F_t * f,
                           (long long)clear_ptr->addr);
 #endif /* H5C_APPLY_CANDIDATE_LIST__DEBUG */
 
-                if(H5C__flush_single_entry(f, dxpl_id, clear_ptr, H5C__FLUSH_CLEAR_ONLY_FLAG | H5C__DEL_FROM_SLIST_ON_DESTROY_FLAG, NULL) < 0)
+                if(H5C__flush_single_entry(f, dxpl_id, clear_ptr, H5C__FLUSH_CLEAR_ONLY_FLAG | H5C__GENERATE_IMAGE_FLAG | H5C__DEL_FROM_SLIST_ON_DESTROY_FLAG) < 0)
                     HGOTO_ERROR(H5E_CACHE, H5E_CANTFLUSH, FAIL, "Can't clear entry.")
             } /* end else-if */
 
@@ -680,7 +699,7 @@ H5C_apply_candidate_list(H5F_t * f,
 #endif /* H5C_APPLY_CANDIDATE_LIST__DEBUG */
 
                 /* Add this entry to the list of entries to collectively write */
-                if(H5C__flush_single_entry(f, dxpl_id, flush_ptr, H5C__DEL_FROM_SLIST_ON_DESTROY_FLAG, collective_write_list) < 0)
+                if(H5C__flush_single_entry(f, dxpl_id, flush_ptr, H5C__DEL_FROM_SLIST_ON_DESTROY_FLAG) < 0)
                     HGOTO_ERROR(H5E_CACHE, H5E_CANTFLUSH, FAIL, "Can't clear entry.")
             } /* end else-if */
         } /* end if */
@@ -714,14 +733,14 @@ H5C_apply_candidate_list(H5F_t * f,
     if (delayed_ptr) {
 
         if (delayed_ptr->clear_on_unprotect) {
-            if(H5C__flush_single_entry(f, dxpl_id, delayed_ptr, H5C__FLUSH_CLEAR_ONLY_FLAG, NULL) < 0)
+            if(H5C__flush_single_entry(f, dxpl_id, delayed_ptr, H5C__FLUSH_CLEAR_ONLY_FLAG | H5C__GENERATE_IMAGE_FLAG) < 0)
                 HGOTO_ERROR(H5E_CACHE, H5E_CANTFLUSH, FAIL, "Can't flush entry.")
 
             entry_ptr->clear_on_unprotect = FALSE;
             entries_cleared++;
         } else if (delayed_ptr->flush_immediately) {
             /* Add this entry to the list of entries to collectively write */
-            if(H5C__flush_single_entry(f, dxpl_id, delayed_ptr, H5C__DEL_FROM_SLIST_ON_DESTROY_FLAG, collective_write_list) < 0)
+            if(H5C__flush_single_entry(f, dxpl_id, delayed_ptr, H5C__DEL_FROM_SLIST_ON_DESTROY_FLAG) < 0)
                 HGOTO_ERROR(H5E_CACHE, H5E_CANTFLUSH, FAIL, "Can't flush entry collectively.")
 
             entry_ptr->flush_immediately = FALSE;
@@ -734,10 +753,11 @@ H5C_apply_candidate_list(H5F_t * f,
 
     /* If we've deferred writing to do it collectively, take care of that now */
     if(f->coll_md_write) {
-        HDassert(collective_write_list);
+        /* Sanity check */
+        HDassert(cache_ptr->coll_write_list);
 
         /* Write collective list */
-        if(H5C__collective_write(f, dxpl_id, collective_write_list) < 0)
+        if(H5C__collective_write(f, dxpl_id) < 0)
             HGOTO_ERROR(H5E_CACHE, H5E_WRITEERROR, FAIL, "Can't write metadata collectively")
     } /* end if */
 
@@ -760,9 +780,11 @@ done:
     if(candidate_assignment_table != NULL)
         candidate_assignment_table = (int *)H5MM_xfree((void *)candidate_assignment_table);
 
-    if(collective_write_list)
-        if(H5SL_destroy(collective_write_list, H5C__collective_write_free, NULL) < 0)
+    if(cache_ptr->coll_write_list) {
+        if(H5SL_close(cache_ptr->coll_write_list) < 0)
             HDONE_ERROR(H5E_CACHE, H5E_CANTFREE, FAIL, "failed to destroy skip list")
+        cache_ptr->coll_write_list = NULL;
+    } /* end if */
 
     FUNC_LEAVE_NOAPI(ret_value)
 } /* H5C_apply_candidate_list() */
@@ -1001,7 +1023,7 @@ done:
  *
  *		Note that unlike H5C_apply_candidate_list(), 
  *		H5C_mark_entries_as_clean() makes all its calls to 
- *		H6C_flush_single_entry() with the 
+ *		H5C__flush_single_entry() with the 
  *		H5C__FLUSH_CLEAR_ONLY_FLAG set.  As a result, 
  *		the pre_serialize() and serialize calls are not made.
  *
@@ -1160,7 +1182,7 @@ H5C_mark_entries_as_clean(H5F_t *  f,
      *
      * Note that unlike H5C_apply_candidate_list(), 
      * H5C_mark_entries_as_clean() makes all its calls to 
-     * H6C_flush_single_entry() with the H5C__FLUSH_CLEAR_ONLY_FLAG 
+     * H5C__flush_single_entry() with the H5C__FLUSH_CLEAR_ONLY_FLAG 
      * set.  As a result, the pre_serialize() and serialize calls are 
      * not made.
      *
@@ -1195,7 +1217,7 @@ H5C_mark_entries_as_clean(H5F_t *  f,
             entry_ptr = entry_ptr->prev;
             entries_cleared++;
 
-            if(H5C__flush_single_entry(f, dxpl_id, clear_ptr, H5C__FLUSH_CLEAR_ONLY_FLAG | H5C__DEL_FROM_SLIST_ON_DESTROY_FLAG, NULL) < 0)
+            if(H5C__flush_single_entry(f, dxpl_id, clear_ptr, H5C__FLUSH_CLEAR_ONLY_FLAG | H5C__DEL_FROM_SLIST_ON_DESTROY_FLAG) < 0)
                 HGOTO_ERROR(H5E_CACHE, H5E_CANTFLUSH, FAIL, "Can't clear entry.")
         } else {
 
@@ -1223,7 +1245,7 @@ H5C_mark_entries_as_clean(H5F_t *  f,
             entry_ptr = entry_ptr->next;
             entries_cleared++;
 
-            if(H5C__flush_single_entry(f, dxpl_id, clear_ptr, H5C__FLUSH_CLEAR_ONLY_FLAG | H5C__DEL_FROM_SLIST_ON_DESTROY_FLAG, NULL) < 0 )
+            if(H5C__flush_single_entry(f, dxpl_id, clear_ptr, H5C__FLUSH_CLEAR_ONLY_FLAG | H5C__DEL_FROM_SLIST_ON_DESTROY_FLAG) < 0 )
                 HGOTO_ERROR(H5E_CACHE, H5E_CANTFLUSH, FAIL, "Can't clear entry.")
         } else {
 
@@ -1331,8 +1353,9 @@ done:
  *-------------------------------------------------------------------------
  */
 static herr_t
-H5C__collective_write(H5F_t *f, hid_t dxpl_id, H5SL_t *collective_write_list)
+H5C__collective_write(H5F_t *f, hid_t dxpl_id)
 {
+    H5AC_t              *cache_ptr;
     H5P_genplist_t      *plist = NULL;
     H5FD_mpio_xfer_t    orig_xfer_mode = H5FD_MPIO_COLLECTIVE;
     int                 count;
@@ -1348,6 +1371,12 @@ H5C__collective_write(H5F_t *f, hid_t dxpl_id, H5SL_t *collective_write_list)
 
     FUNC_ENTER_STATIC
 
+    /* Sanity checks */
+    HDassert(f != NULL);
+    cache_ptr = f->shared->cache;
+    HDassert(cache_ptr != NULL);
+    HDassert(cache_ptr->coll_write_list != NULL);
+
     /* Get original transfer mode */
     if(NULL == (plist = (H5P_genplist_t *)H5I_object(dxpl_id)))
         HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "not a data transfer property list")
@@ -1355,12 +1384,12 @@ H5C__collective_write(H5F_t *f, hid_t dxpl_id, H5SL_t *collective_write_list)
         HGOTO_ERROR(H5E_PLIST, H5E_CANTSET, FAIL, "can't set MPI-I/O property")
 
     /* Get number of entries in collective write list */
-    count = (int)H5SL_count(collective_write_list);
+    count = (int)H5SL_count(cache_ptr->coll_write_list);
 
     if(count > 0) {
         H5FD_mpio_xfer_t    xfer_mode = H5FD_MPIO_COLLECTIVE;
         H5SL_node_t         *node;
-        H5C_collective_write_t *item;
+        H5C_cache_entry_t   *entry_ptr;
         void                *base_buf;
         int                 i;
 
@@ -1376,27 +1405,27 @@ H5C__collective_write(H5F_t *f, hid_t dxpl_id, H5SL_t *collective_write_list)
             HGOTO_ERROR(H5E_RESOURCE, H5E_CANTALLOC, FAIL, "memory allocation failed for collective offset table length array")
 
         /* Fill arrays */
-        node = H5SL_first(collective_write_list);
+        node = H5SL_first(cache_ptr->coll_write_list);
         HDassert(node);
-        if(NULL == (item = (H5C_collective_write_t *)H5SL_item(node)))
+        if(NULL == (entry_ptr = (H5C_cache_entry_t *)H5SL_item(node)))
             HGOTO_ERROR(H5E_CACHE, H5E_NOTFOUND, FAIL, "can't retrieve skip list item")
 
         /* Set up initial array position & buffer base address */
-        length_array[0] = (int)item->length;
-        base_buf = item->buf;
+        length_array[0] = (int)entry_ptr->size;
+        base_buf = entry_ptr->image_ptr;
         buf_array[0] = (MPI_Aint)0;
-        offset_array[0] = (MPI_Aint)item->offset;
+        offset_array[0] = (MPI_Aint)entry_ptr->addr;
 
         node = H5SL_next(node);
         i = 1;
         while(node) {
-            if(NULL == (item = (H5C_collective_write_t *)H5SL_item(node)))
+            if(NULL == (entry_ptr = (H5C_cache_entry_t *)H5SL_item(node)))
                 HGOTO_ERROR(H5E_CACHE, H5E_NOTFOUND, FAIL, "can't retrieve skip list item")
 
             /* Set up array position */
-            length_array[i] = (int)item->length;
-            buf_array[i] = (MPI_Aint)item->buf - (MPI_Aint)base_buf;
-            offset_array[i] = (MPI_Aint)item->offset;
+            length_array[i] = (int)entry_ptr->size;
+            buf_array[i] = (MPI_Aint)entry_ptr->image_ptr - (MPI_Aint)base_buf;
+            offset_array[i] = (MPI_Aint)entry_ptr->addr;
 
             /* Advance to next node & array location */
             node = H5SL_next(node);
@@ -1469,36 +1498,5 @@ done:
 
     FUNC_LEAVE_NOAPI(ret_value);
 } /* end H5C__collective_write() */
-
-
-/*-------------------------------------------------------------------------
- *
- * Function:    H5C__collective_write_free
- *
- * Purpose:     Release node on collective write skiplist
- *
- * Return:      FAIL if error is detected, SUCCEED otherwise.
- *
- * Programmer:  Mohamad Chaarawi
- *              February, 2016
- *
- *-------------------------------------------------------------------------
- */
-static herr_t
-H5C__collective_write_free(void *_item, void H5_ATTR_UNUSED *key, void H5_ATTR_UNUSED *op_data)
-{
-    H5C_collective_write_t *item = (H5C_collective_write_t *)_item;
-
-    FUNC_ENTER_STATIC_NOERR
-
-    /* Sanity check */
-    HDassert(item);
-
-    if(item->free_buf)
-        item->buf = H5MM_xfree(item->buf);
-    H5FL_FREE(H5C_collective_write_t, item);
-
-    FUNC_LEAVE_NOAPI(SUCCEED)
-} /* end H5C__collective_write_free() */
 #endif /* H5_HAVE_PARALLEL */
 
diff --git a/src/H5Cpkg.h b/src/H5Cpkg.h
index 78ae930..16efb5c 100644
--- a/src/H5Cpkg.h
+++ b/src/H5Cpkg.h
@@ -3430,7 +3430,7 @@ typedef struct H5C_tag_info_t {
  *		entry is removed from the cache by any means (eviction, 
  *		expungement, or take ownership at this point in time).
  *		Functions that perform scans on lists may set this field
- *		to zero prior to calling H5C_flush_single_entry().  
+ *		to zero prior to calling H5C__flush_single_entry().  
  *		Unexpected changes to the counter indicate that an entry 
  *		was removed from the cache as a side effect of the flush.
  *
@@ -3438,7 +3438,7 @@ typedef struct H5C_tag_info_t {
  *		which contained the last entry to be removed from the cache,
  *		or NULL if there either is no such entry, or if a function
  *		performing a scan of a list has set this field to NULL prior
- *		to calling H5C_flush_single_entry().
+ *		to calling H5C__flush_single_entry().
  *
  *		WARNING!!! This field must NEVER be dereferenced.  It is 
  *		maintained to allow functions that perform scans of lists
@@ -4069,17 +4069,17 @@ typedef struct H5C_tag_info_t {
  * obtain estimates of how frequently these restarts occur.
  *
  * slist_scan_restarts: Number of times a scan of the slist (that contains
- *		calls to H5C_flush_single_entry()) has been restarted to 
+ *		calls to H5C__flush_single_entry()) has been restarted to 
  *		avoid potential issues with change of status of the next 
  *		entry in the scan.
  *
  * LRU_scan_restarts: Number of times a scan of the LRU list (that contains
- *              calls to H5C_flush_single_entry()) has been restarted to 
+ *              calls to H5C__flush_single_entry()) has been restarted to 
  *              avoid potential issues with change of status of the next 
  *              entry in the scan.
  *
  * hash_bucket_scan_restarts: Number of times a scan of a hash bucket list
- *		(that contains calls to H5C_flush_single_entry()) has been 
+ *		(that contains calls to H5C__flush_single_entry()) has been 
  *		restarted to avoid potential issues with change of status 
  *		of the next entry in the scan.
  *
@@ -4205,10 +4205,14 @@ struct H5C_t {
     H5C_cache_entry_t *	        dLRU_tail_ptr;
 
 #ifdef H5_HAVE_PARALLEL
+    /* Fields for collective metadata reads */
     int32_t                     coll_list_len;
     size_t                      coll_list_size;
     H5C_cache_entry_t *		coll_head_ptr;
     H5C_cache_entry_t *		coll_tail_ptr;
+
+    /* Fields for collective metadata writes */
+    H5SL_t *                    coll_write_list;
 #endif /* H5_HAVE_PARALLEL */
 
     /* Fields for automatic cache size adjustment */
@@ -4310,15 +4314,6 @@ struct H5C_t {
     char			prefix[H5C__PREFIX_LEN];
 };
 
-#ifdef H5_HAVE_PARALLEL
-typedef struct H5C_collective_write_t {
-    size_t length;
-    hbool_t free_buf;
-    void *buf;
-    haddr_t offset;
-} H5C_collective_write_t;
-#endif /* H5_HAVE_PARALLEL */
-
 /* Define typedef for tagged cache entry iteration callbacks */
 typedef int (*H5C_tag_iter_cb_t)(H5C_cache_entry_t *entry, void *ctx);
 
@@ -4337,7 +4332,7 @@ H5_DLLVAR const H5C_class_t H5C__epoch_marker_class;
 
 /* General routines */
 H5_DLL herr_t H5C__flush_single_entry(const H5F_t *f, hid_t dxpl_id,
-    H5C_cache_entry_t *entry_ptr, unsigned flags, H5SL_t *collective_write_list);
+    H5C_cache_entry_t *entry_ptr, unsigned flags);
 H5_DLL herr_t H5C__flush_marked_entries(H5F_t * f, hid_t dxpl_id);
 H5_DLL herr_t H5C__iter_tagged_entries(H5C_t *cache, haddr_t tag, hbool_t match_global,
     H5C_tag_iter_cb_t cb, void *cb_ctx);
diff --git a/src/H5Cprivate.h b/src/H5Cprivate.h
index c03e2e7..923083f 100644
--- a/src/H5Cprivate.h
+++ b/src/H5Cprivate.h
@@ -183,6 +183,7 @@
  * 	H5C__FLUSH_MARKED_ENTRIES_FLAG
  *      H5C__TAKE_OWNERSHIP_FLAG
  *      H5C__DEL_FROM_SLIST_ON_DESTROY_FLAG
+ *      H5C__GENERATE_IMAGE_FLAG
  */
 #define H5C__NO_FLAGS_SET			0x00000
 #define H5C__SET_FLUSH_MARKER_FLAG		0x00001
@@ -202,6 +203,7 @@
 #define H5C__EVICT_ALLOW_LAST_PINS_FLAG         0x04000
 #define H5C__DEL_FROM_SLIST_ON_DESTROY_FLAG     0x08000
 #define H5C__DURING_FLUSH_FLAG                  0x10000 /* Set when the entire cache is being flushed */
+#define H5C__GENERATE_IMAGE_FLAG                0x20000 /* Set during parallel I/O */
 
 /* Debugging/sanity checking/statistics settings */
 #ifndef NDEBUG
diff --git a/src/H5Ctag.c b/src/H5Ctag.c
index 33f7c22..6d5b454 100644
--- a/src/H5Ctag.c
+++ b/src/H5Ctag.c
@@ -467,7 +467,7 @@ H5C__evict_tagged_entries_cb(H5C_cache_entry_t *entry, void *_ctx)
         ctx->pinned_entries_need_evicted = TRUE;
     else {
         /* Evict the Entry */
-        if(H5C__flush_single_entry(ctx->f, ctx->dxpl_id, entry, H5C__FLUSH_INVALIDATE_FLAG | H5C__FLUSH_CLEAR_ONLY_FLAG | H5C__DEL_FROM_SLIST_ON_DESTROY_FLAG, NULL) < 0)
+        if(H5C__flush_single_entry(ctx->f, ctx->dxpl_id, entry, H5C__FLUSH_INVALIDATE_FLAG | H5C__FLUSH_CLEAR_ONLY_FLAG | H5C__DEL_FROM_SLIST_ON_DESTROY_FLAG) < 0)
             HGOTO_ERROR(H5E_CACHE, H5E_CANTFLUSH, H5_ITER_ERROR, "Entry eviction failed.")
         ctx->evicted_entries_last_pass = TRUE;
     } /* end else */