[svn-r19617] Purpose:

    Merge accum_tests branch back to the trunk.
Description:
    Changes consist of addition of tests for H5Faccum.c source code,
    as well as some fixes that address some discovered bugs in the
    metadata accumulator on several corner cases.
Tested:
    h5committested

1 files changed, 426 insertions, 295 deletions

diff --git a/src/H5Faccum.c b/src/H5Faccum.c
index 600c3f3..6c9eb67 100644
--- a/src/H5Faccum.c
+++ b/src/H5Faccum.c
@@ -111,11 +111,11 @@ H5FL_BLK_DEFINE_STATIC(meta_accum);
  *
  *-------------------------------------------------------------------------
  */
-htri_t
+herr_t
 H5F_accum_read(const H5F_t *f, hid_t dxpl_id, H5FD_mem_t type, haddr_t addr,
     size_t size, void *buf/*out*/)
 {
-    htri_t      ret_value = FALSE;    /* Return value */
+    herr_t      ret_value = SUCCEED;    /* Return value */
 
     FUNC_ENTER_NOAPI(H5F_accum_read, FAIL)
 
@@ -124,90 +124,135 @@ H5F_accum_read(const H5F_t *f, hid_t dxpl_id, H5FD_mem_t type, haddr_t addr,
     HDassert(buf);
 
     /* Check if this information is in the metadata accumulator */
-    if((f->shared->feature_flags & H5FD_FEAT_ACCUMULATE_METADATA) && type != H5FD_MEM_DRAW
-            && size < H5F_ACCUM_MAX_SIZE) {
-        /* Sanity check */
-        HDassert(!f->shared->accum.buf || (f->shared->accum.alloc_size >= f->shared->accum.size));
-
-        /* Current read adjoins or overlaps with metadata accumulator */
-        if(H5F_addr_overlap(addr, size, f->shared->accum.loc, f->shared->accum.size)
-                || ((addr + size) == f->shared->accum.loc)
-                || (f->shared->accum.loc + f->shared->accum.size) == addr) {
-            size_t amount_before;       /* Amount to read before current accumulator */
-            haddr_t new_addr;           /* New address of the accumulator buffer */
-            size_t new_size;            /* New size of the accumulator buffer */
-
-            /* Compute new values for accumulator */
-            new_addr = MIN(addr, f->shared->accum.loc);
-            new_size = (size_t)(MAX((addr + size), (f->shared->accum.loc + f->shared->accum.size))
-                    - new_addr);
-
-            /* Check if we need more buffer space */
-            if(new_size > f->shared->accum.alloc_size) {
-                size_t new_alloc_size;        /* New size of accumulator */
-
-                /* Adjust the buffer size to be a power of 2 that is large enough to hold data */
-                new_alloc_size = (size_t)1 << (1 + H5V_log2_gen((uint64_t)(new_size - 1)));
-
-                /* Reallocate the metadata accumulator buffer */
-                if(NULL == (f->shared->accum.buf = H5FL_BLK_REALLOC(meta_accum, f->shared->accum.buf, new_alloc_size)))
-                    HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, FAIL, "unable to allocate metadata accumulator buffer")
-
-                /* Note the new buffer size */
-                f->shared->accum.alloc_size = new_alloc_size;
+    if((f->shared->feature_flags & H5FD_FEAT_ACCUMULATE_METADATA) && type != H5FD_MEM_DRAW) {
+        if(size < H5F_ACCUM_MAX_SIZE) {
+            /* Sanity check */
+            HDassert(!f->shared->accum.buf || (f->shared->accum.alloc_size >= f->shared->accum.size));
+
+            /* Current read adjoins or overlaps with metadata accumulator */
+            if(H5F_addr_overlap(addr, size, f->shared->accum.loc, f->shared->accum.size)
+                    || ((addr + size) == f->shared->accum.loc)
+                    || (f->shared->accum.loc + f->shared->accum.size) == addr) {
+                size_t amount_before;       /* Amount to read before current accumulator */
+                haddr_t new_addr;           /* New address of the accumulator buffer */
+                size_t new_size;            /* New size of the accumulator buffer */
+
+                /* Compute new values for accumulator */
+                new_addr = MIN(addr, f->shared->accum.loc);
+                new_size = (size_t)(MAX((addr + size), (f->shared->accum.loc + f->shared->accum.size))
+                        - new_addr);
+
+                /* Check if we need more buffer space */
+                if(new_size > f->shared->accum.alloc_size) {
+                    size_t new_alloc_size;        /* New size of accumulator */
+
+                    /* Adjust the buffer size to be a power of 2 that is large enough to hold data */
+                    new_alloc_size = (size_t)1 << (1 + H5V_log2_gen((uint64_t)(new_size - 1)));
+
+                    /* Reallocate the metadata accumulator buffer */
+                    if(NULL == (f->shared->accum.buf = H5FL_BLK_REALLOC(meta_accum, f->shared->accum.buf, new_alloc_size)))
+                        HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, FAIL, "unable to allocate metadata accumulator buffer")
+
+                    /* Note the new buffer size */
+                    f->shared->accum.alloc_size = new_alloc_size;
 #ifdef H5_CLEAR_MEMORY
-HDmemset(f->shared->accum.buf + f->shared->accum.size, 0, (f->shared->accum.alloc_size - f->shared->accum.size));
+    HDmemset(f->shared->accum.buf + f->shared->accum.size, 0, (f->shared->accum.alloc_size - f->shared->accum.size));
 #endif /* H5_CLEAR_MEMORY */
-            } /* end if */
+                } /* end if */
 
-            /* Read the part before the metadata accumulator */
-            if(addr < f->shared->accum.loc) {
-                /* Set the amount to read */
-                H5_ASSIGN_OVERFLOW(amount_before, (f->shared->accum.loc - addr), hsize_t, size_t);
+                /* Read the part before the metadata accumulator */
+                if(addr < f->shared->accum.loc) {
+                    /* Set the amount to read */
+                    H5_ASSIGN_OVERFLOW(amount_before, (f->shared->accum.loc - addr), hsize_t, size_t);
 
-                /* Make room for the metadata to read in */
-                HDmemmove(f->shared->accum.buf + amount_before, f->shared->accum.buf, f->shared->accum.size);
+                    /* Make room for the metadata to read in */
+                    HDmemmove(f->shared->accum.buf + amount_before, f->shared->accum.buf, f->shared->accum.size);
 
-                /* Adjust dirty region tracking info, if present */
-                if(f->shared->accum.dirty)
-                    f->shared->accum.dirty_off += amount_before;
+                    /* Adjust dirty region tracking info, if present */
+                    if(f->shared->accum.dirty)
+                        f->shared->accum.dirty_off += amount_before;
 
-                /* Dispatch to driver */
-                if(H5FD_read(f->shared->lf, dxpl_id, type, addr, amount_before, f->shared->accum.buf) < 0)
-                    HGOTO_ERROR(H5E_IO, H5E_READERROR, FAIL, "driver read request failed")
-            } /* end if */
-            else
-                amount_before = 0;
+                    /* Dispatch to driver */
+                    if(H5FD_read(f->shared->lf, dxpl_id, type, addr, amount_before, f->shared->accum.buf) < 0)
+                        HGOTO_ERROR(H5E_IO, H5E_READERROR, FAIL, "driver read request failed")
+                } /* end if */
+                else
+                    amount_before = 0;
 
-            /* Read the part after the metadata accumulator */
-            if((addr + size) > (f->shared->accum.loc + f->shared->accum.size)) {
-                size_t amount_after;         /* Amount to read at a time */
+                /* Read the part after the metadata accumulator */
+                if((addr + size) > (f->shared->accum.loc + f->shared->accum.size)) {
+                    size_t amount_after;         /* Amount to read at a time */
 
-                /* Set the amount to read */
-                H5_ASSIGN_OVERFLOW(amount_after, ((addr + size) - (f->shared->accum.loc + f->shared->accum.size)), hsize_t, size_t);
+                    /* Set the amount to read */
+                    H5_ASSIGN_OVERFLOW(amount_after, ((addr + size) - (f->shared->accum.loc + f->shared->accum.size)), hsize_t, size_t);
 
-                /* Dispatch to driver */
-                if(H5FD_read(f->shared->lf, dxpl_id, type, (f->shared->accum.loc + f->shared->accum.size), amount_after, (f->shared->accum.buf + f->shared->accum.size + amount_before)) < 0)
-                    HGOTO_ERROR(H5E_IO, H5E_READERROR, FAIL, "driver read request failed")
-            } /* end if */
+                    /* Dispatch to driver */
+                    if(H5FD_read(f->shared->lf, dxpl_id, type, (f->shared->accum.loc + f->shared->accum.size), amount_after, (f->shared->accum.buf + f->shared->accum.size + amount_before)) < 0)
+                        HGOTO_ERROR(H5E_IO, H5E_READERROR, FAIL, "driver read request failed")
+                } /* end if */
 
-            /* Copy the data out of the buffer */
-            HDmemcpy(buf, f->shared->accum.buf + (addr - new_addr), size);
+                /* Copy the data out of the buffer */
+                HDmemcpy(buf, f->shared->accum.buf + (addr - new_addr), size);
 
-            /* Adjust the accumulator address & size */
-            f->shared->accum.loc = new_addr;
-            f->shared->accum.size = new_size;
+                /* Adjust the accumulator address & size */
+                f->shared->accum.loc = new_addr;
+                f->shared->accum.size = new_size;
+            } /* end if */
+            /* Current read doesn't overlap with metadata accumulator, read it from file */
+            else {
+                /* Dispatch to driver */
+                if(H5FD_read(f->shared->lf, dxpl_id, type, addr, size, buf) < 0)
+                    HGOTO_ERROR(H5E_IO, H5E_READERROR, FAIL, "driver read request failed")
+            } /* end else */
         } /* end if */
-        /* Current read doesn't overlap with metadata accumulator, read it from file */
         else {
-            /* Dispatch to driver */
+            /* Read the data */
             if(H5FD_read(f->shared->lf, dxpl_id, type, addr, size, buf) < 0)
                 HGOTO_ERROR(H5E_IO, H5E_READERROR, FAIL, "driver read request failed")
-        } /* end else */
 
-        /* Indicate success */
-        HGOTO_DONE(TRUE);
+            /* Check for overlap w/dirty accumulator */
+            /* (Note that this could be improved by updating the non-dirty
+             *  information in the accumulator with [some of] the information
+             *  just read in. -QAK)
+             */
+            if(f->shared->accum.dirty &&
+                    H5F_addr_overlap(addr, size, f->shared->accum.loc + f->shared->accum.dirty_off, f->shared->accum.dirty_len)) {
+                haddr_t dirty_loc = f->shared->accum.loc + f->shared->accum.dirty_off;  /* File offset of dirty information */
+                size_t buf_off;         /* Offset of dirty region in buffer */
+                size_t dirty_off;       /* Offset within dirty region */
+                size_t overlap_size;    /* Size of overlap with dirty region */
+
+                /* Check for read starting before beginning dirty region */
+                if(H5F_addr_le(addr, dirty_loc)) {
+                    /* Compute offset of dirty region within buffer */
+                    buf_off = (size_t)(dirty_loc - addr);
+
+                    /* Compute offset within dirty region */
+                    dirty_off = 0;
+
+                    /* Check for read ending within dirty region */
+                    if(H5F_addr_le(addr + size, dirty_loc + f->shared->accum.dirty_len))
+                        overlap_size = (size_t)((addr + size) - buf_off);
+                    else        /* Access covers whole dirty region */
+                        overlap_size = f->shared->accum.dirty_len;
+                } /* end if */
+                else { /* Read starts after beginning of dirty region */
+                    /* Compute dirty offset within buffer and overlap size */
+                    buf_off = 0;
+                    dirty_off = (size_t)(addr - dirty_loc);
+                    overlap_size = (size_t)((dirty_loc + f->shared->accum.dirty_len) - addr);
+                } /* end else */
+
+                /* Copy the dirty region to buffer */
+                HDmemcpy((unsigned char *)buf + buf_off, (unsigned char *)f->shared->accum.buf + f->shared->accum.dirty_off + dirty_off, overlap_size);
+            } /* end if */
+        } /* end else */
     } /* end if */
+    else {
+        /* Read the data */
+        if(H5FD_read(f->shared->lf, dxpl_id, type, addr, size, buf) < 0)
+            HGOTO_ERROR(H5E_IO, H5E_READERROR, FAIL, "driver read request failed")
+    } /* end else */
 
 done:
     FUNC_LEAVE_NOAPI(ret_value)
@@ -355,8 +400,8 @@ done:
 /*-------------------------------------------------------------------------
  * Function:	H5F_accum_write
  *
- * Purpose:	Attempts to read some data from the metadata accumulator for
- *              a file into a buffer.
+ * Purpose:	Attempts to write some data to the metadata accumulator for
+ *              a file from a buffer.
  *
  * Return:	Non-negative on success/Negative on failure
  *
@@ -366,11 +411,11 @@ done:
  *
  *-------------------------------------------------------------------------
  */
-htri_t
+herr_t
 H5F_accum_write(const H5F_t *f, hid_t dxpl_id, H5FD_mem_t type, haddr_t addr,
     size_t size, const void *buf)
 {
-    htri_t      ret_value = FALSE;    /* Return value */
+    herr_t      ret_value = SUCCEED;    /* Return value */
 
     FUNC_ENTER_NOAPI(H5F_accum_write, FAIL)
 
@@ -380,248 +425,284 @@ H5F_accum_write(const H5F_t *f, hid_t dxpl_id, H5FD_mem_t type, haddr_t addr,
     HDassert(buf);
 
     /* Check for accumulating metadata */
-    if((f->shared->feature_flags & H5FD_FEAT_ACCUMULATE_METADATA) && type != H5FD_MEM_DRAW
-            && size < H5F_ACCUM_MAX_SIZE) {
-        /* Sanity check */
-        HDassert(!f->shared->accum.buf || (f->shared->accum.alloc_size >= f->shared->accum.size));
-
-        /* Check if there is already metadata in the accumulator */
-        if(f->shared->accum.size > 0) {
-            /* Check if the new metadata adjoins the beginning of the current accumulator */
-            if((addr + size) == f->shared->accum.loc) {
-                /* Check if we need to adjust accumulator size */
-                if(H5F_accum_adjust(&f->shared->accum, f->shared->lf, dxpl_id, H5F_ACCUM_PREPEND, size) < 0)
-                    HGOTO_ERROR(H5E_IO, H5E_CANTRESIZE, FAIL, "can't adjust metadata accumulator")
-
-                /* Move the existing metadata to the proper location */
-                HDmemmove(f->shared->accum.buf + size, f->shared->accum.buf, f->shared->accum.size);
-
-                /* Copy the new metadata at the front */
-                HDmemcpy(f->shared->accum.buf, buf, size);
-
-                /* Set the new size & location of the metadata accumulator */
-                f->shared->accum.loc = addr;
-                f->shared->accum.size += size;
-
-                /* Adjust the dirty region and mark accumulator dirty */
-                if(f->shared->accum.dirty)
-                    f->shared->accum.dirty_len = size + f->shared->accum.dirty_off
-                            + f->shared->accum.dirty_len;
-                else {
-                    f->shared->accum.dirty_len = size;
-                    f->shared->accum.dirty = TRUE;
-                } /* end else */
-                f->shared->accum.dirty_off = 0;
-            } /* end if */
-            /* Check if the new metadata adjoins the end of the current accumulator */
-            else if(addr == (f->shared->accum.loc + f->shared->accum.size)) {
-                /* Check if we need to adjust accumulator size */
-                if(H5F_accum_adjust(&f->shared->accum, f->shared->lf, dxpl_id, H5F_ACCUM_APPEND, size) < 0)
-                    HGOTO_ERROR(H5E_IO, H5E_CANTRESIZE, FAIL, "can't adjust metadata accumulator")
+    if((f->shared->feature_flags & H5FD_FEAT_ACCUMULATE_METADATA) && type != H5FD_MEM_DRAW) {
+        if(size < H5F_ACCUM_MAX_SIZE) {
+            /* Sanity check */
+            HDassert(!f->shared->accum.buf || (f->shared->accum.alloc_size >= f->shared->accum.size));
+
+            /* Check if there is already metadata in the accumulator */
+            if(f->shared->accum.size > 0) {
+                /* Check if the new metadata adjoins the beginning of the current accumulator */
+                if((addr + size) == f->shared->accum.loc) {
+                    /* Check if we need to adjust accumulator size */
+                    if(H5F_accum_adjust(&f->shared->accum, f->shared->lf, dxpl_id, H5F_ACCUM_PREPEND, size) < 0)
+                        HGOTO_ERROR(H5E_IO, H5E_CANTRESIZE, FAIL, "can't adjust metadata accumulator")
 
-                /* Copy the new metadata to the end */
-                HDmemcpy(f->shared->accum.buf + f->shared->accum.size, buf, size);
+                    /* Move the existing metadata to the proper location */
+                    HDmemmove(f->shared->accum.buf + size, f->shared->accum.buf, f->shared->accum.size);
 
-                /* Adjust the dirty region and mark accumulator dirty */
-                if(f->shared->accum.dirty)
-                    f->shared->accum.dirty_len = size + (f->shared->accum.size - 
-                            f->shared->accum.dirty_off);
-                else {
-                    f->shared->accum.dirty_off = f->shared->accum.size;
-                    f->shared->accum.dirty_len = size;
-                    f->shared->accum.dirty = TRUE;
-                } /* end else */
+                    /* Copy the new metadata at the front */
+                    HDmemcpy(f->shared->accum.buf, buf, size);
 
-                /* Set the new size of the metadata accumulator */
-                f->shared->accum.size += size;
-            } /* end if */
-            /* Check if the piece of metadata being written overlaps the metadata accumulator */
-            else if(H5F_addr_overlap(addr, size, f->shared->accum.loc, f->shared->accum.size)) {
-                size_t add_size;    /* New size of the accumulator buffer */
+                    /* Set the new size & location of the metadata accumulator */
+                    f->shared->accum.loc = addr;
+                    f->shared->accum.size += size;
 
-                /* Check if the new metadata is entirely within the current accumulator */
-                if(addr >= f->shared->accum.loc && (addr + size) <= (f->shared->accum.loc + f->shared->accum.size)) {
-                    size_t dirty_off = (size_t)(addr - f->shared->accum.loc);
+                    /* Adjust the dirty region and mark accumulator dirty */
+                    if(f->shared->accum.dirty)
+                        f->shared->accum.dirty_len = size + f->shared->accum.dirty_off
+                                + f->shared->accum.dirty_len;
+                    else {
+                        f->shared->accum.dirty_len = size;
+                        f->shared->accum.dirty = TRUE;
+                    } /* end else */
+                    f->shared->accum.dirty_off = 0;
+                } /* end if */
+                /* Check if the new metadata adjoins the end of the current accumulator */
+                else if(addr == (f->shared->accum.loc + f->shared->accum.size)) {
+                    /* Check if we need to adjust accumulator size */
+                    if(H5F_accum_adjust(&f->shared->accum, f->shared->lf, dxpl_id, H5F_ACCUM_APPEND, size) < 0)
+                        HGOTO_ERROR(H5E_IO, H5E_CANTRESIZE, FAIL, "can't adjust metadata accumulator")
 
-                    /* Copy the new metadata to the proper location within the accumulator */
-                    HDmemcpy(f->shared->accum.buf + dirty_off, buf, size);
+                    /* Copy the new metadata to the end */
+                    HDmemcpy(f->shared->accum.buf + f->shared->accum.size, buf, size);
 
                     /* Adjust the dirty region and mark accumulator dirty */
-                    if(f->shared->accum.dirty) {
-                        /* Check for new metadata starting before current dirty region */
-                        if(dirty_off <= f->shared->accum.dirty_off) {
-                            if((dirty_off + size) <= (f->shared->accum.dirty_off + f->shared->accum.dirty_len))
-                                f->shared->accum.dirty_len = (f->shared->accum.dirty_off + f->shared->accum.dirty_len) - dirty_off;
-                            else
-                                f->shared->accum.dirty_len = size;
-                            f->shared->accum.dirty_off = dirty_off;
-                        } /* end if */
-                        else {
-                            if((dirty_off + size) <= (f->shared->accum.dirty_off + f->shared->accum.dirty_len))
-                                ; /* f->shared->accum.dirty_len doesn't change */
-                            else
-                                f->shared->accum.dirty_len = (dirty_off + size) - f->shared->accum.dirty_off;
-                        } /* end else */
-                    } /* end if */
+                    if(f->shared->accum.dirty)
+                        f->shared->accum.dirty_len = size + (f->shared->accum.size - 
+                                f->shared->accum.dirty_off);
                     else {
-                        f->shared->accum.dirty_off = dirty_off;
+                        f->shared->accum.dirty_off = f->shared->accum.size;
                         f->shared->accum.dirty_len = size;
                         f->shared->accum.dirty = TRUE;
                     } /* end else */
+
+                    /* Set the new size of the metadata accumulator */
+                    f->shared->accum.size += size;
                 } /* end if */
-                /* Check if the new metadata overlaps the beginning of the current accumulator */
-                else if(addr < f->shared->accum.loc && (addr + size) <= (f->shared->accum.loc + f->shared->accum.size)) {
-                    size_t old_offset;  /* Offset of old data within the accumulator buffer */
+                /* Check if the piece of metadata being written overlaps the metadata accumulator */
+                else if(H5F_addr_overlap(addr, size, f->shared->accum.loc, f->shared->accum.size)) {
+                    size_t add_size;    /* New size of the accumulator buffer */
+
+                    /* Check if the new metadata is entirely within the current accumulator */
+                    if(addr >= f->shared->accum.loc && (addr + size) <= (f->shared->accum.loc + f->shared->accum.size)) {
+                        size_t dirty_off = (size_t)(addr - f->shared->accum.loc);
+
+                        /* Copy the new metadata to the proper location within the accumulator */
+                        HDmemcpy(f->shared->accum.buf + dirty_off, buf, size);
+
+                        /* Adjust the dirty region and mark accumulator dirty */
+                        if(f->shared->accum.dirty) {
+                            /* Check for new metadata starting before current dirty region */
+                            if(dirty_off <= f->shared->accum.dirty_off) {
+                                if((dirty_off + size) <= (f->shared->accum.dirty_off + f->shared->accum.dirty_len))
+                                    f->shared->accum.dirty_len = (f->shared->accum.dirty_off + f->shared->accum.dirty_len) - dirty_off;
+                                else
+                                    f->shared->accum.dirty_len = size;
+                                f->shared->accum.dirty_off = dirty_off;
+                            } /* end if */
+                            else {
+                                if((dirty_off + size) <= (f->shared->accum.dirty_off + f->shared->accum.dirty_len))
+                                    ; /* f->shared->accum.dirty_len doesn't change */
+                                else
+                                    f->shared->accum.dirty_len = (dirty_off + size) - f->shared->accum.dirty_off;
+                            } /* end else */
+                        } /* end if */
+                        else {
+                            f->shared->accum.dirty_off = dirty_off;
+                            f->shared->accum.dirty_len = size;
+                            f->shared->accum.dirty = TRUE;
+                        } /* end else */
+                    } /* end if */
+                    /* Check if the new metadata overlaps the beginning of the current accumulator */
+                    else if(addr < f->shared->accum.loc && (addr + size) <= (f->shared->accum.loc + f->shared->accum.size)) {
+                        size_t old_offset;  /* Offset of old data within the accumulator buffer */
 
-                    /* Calculate the amount we will need to add to the accumulator size, based on the amount of overlap */
-                    H5_ASSIGN_OVERFLOW(add_size, (f->shared->accum.loc - addr), hsize_t, size_t);
+                        /* Calculate the amount we will need to add to the accumulator size, based on the amount of overlap */
+                        H5_ASSIGN_OVERFLOW(add_size, (f->shared->accum.loc - addr), hsize_t, size_t);
 
-                    /* Check if we need to adjust accumulator size */
-                    if(H5F_accum_adjust(&f->shared->accum, f->shared->lf, dxpl_id, H5F_ACCUM_PREPEND, add_size) < 0)
-                        HGOTO_ERROR(H5E_IO, H5E_CANTRESIZE, FAIL, "can't adjust metadata accumulator")
+                        /* Check if we need to adjust accumulator size */
+                        if(H5F_accum_adjust(&f->shared->accum, f->shared->lf, dxpl_id, H5F_ACCUM_PREPEND, add_size) < 0)
+                            HGOTO_ERROR(H5E_IO, H5E_CANTRESIZE, FAIL, "can't adjust metadata accumulator")
 
-                    /* Calculate the proper offset of the existing metadata */
-                    H5_ASSIGN_OVERFLOW(old_offset, (addr + size) - f->shared->accum.loc, hsize_t, size_t);
+                        /* Calculate the proper offset of the existing metadata */
+                        H5_ASSIGN_OVERFLOW(old_offset, (addr + size) - f->shared->accum.loc, hsize_t, size_t);
 
-                    /* Move the existing metadata to the proper location */
-                    HDmemmove(f->shared->accum.buf + size, f->shared->accum.buf + old_offset, (f->shared->accum.size - old_offset));
+                        /* Move the existing metadata to the proper location */
+                        HDmemmove(f->shared->accum.buf + size, f->shared->accum.buf + old_offset, (f->shared->accum.size - old_offset));
 
-                    /* Copy the new metadata at the front */
-                    HDmemcpy(f->shared->accum.buf, buf, size);
+                        /* Copy the new metadata at the front */
+                        HDmemcpy(f->shared->accum.buf, buf, size);
 
-                    /* Set the new size & location of the metadata accumulator */
-                    f->shared->accum.loc = addr;
-                    f->shared->accum.size += add_size;
+                        /* Set the new size & location of the metadata accumulator */
+                        f->shared->accum.loc = addr;
+                        f->shared->accum.size += add_size;
 
-                    /* Adjust the dirty region and mark accumulator dirty */
-                    if(f->shared->accum.dirty) {
-                        size_t curr_dirty_end = add_size + f->shared->accum.dirty_off + f->shared->accum.dirty_len;
+                        /* Adjust the dirty region and mark accumulator dirty */
+                        if(f->shared->accum.dirty) {
+                            size_t curr_dirty_end = add_size + f->shared->accum.dirty_off + f->shared->accum.dirty_len;
 
-                        f->shared->accum.dirty_off = 0;
-                        if(size <= curr_dirty_end)
-                            f->shared->accum.dirty_len = curr_dirty_end;
-                        else
+                            f->shared->accum.dirty_off = 0;
+                            if(size <= curr_dirty_end)
+                                f->shared->accum.dirty_len = curr_dirty_end;
+                            else
+                                f->shared->accum.dirty_len = size;
+                        } /* end if */
+                        else {
+                            f->shared->accum.dirty_off = 0;
                             f->shared->accum.dirty_len = size;
+                            f->shared->accum.dirty = TRUE;
+                        } /* end else */
                     } /* end if */
-                    else {
-                        f->shared->accum.dirty_off = 0;
-                        f->shared->accum.dirty_len = size;
-                        f->shared->accum.dirty = TRUE;
-                    } /* end else */
-                } /* end if */
-                /* Check if the new metadata overlaps the end of the current accumulator */
-                else if(addr >= f->shared->accum.loc && (addr + size) > (f->shared->accum.loc + f->shared->accum.size)) {
-                    size_t dirty_off = (size_t)(addr - f->shared->accum.loc);
+                    /* Check if the new metadata overlaps the end of the current accumulator */
+                    else if(addr >= f->shared->accum.loc && (addr + size) > (f->shared->accum.loc + f->shared->accum.size)) {
+                        size_t dirty_off;           /* Offset of dirty region */
 
-                    /* Calculate the amount we will need to add to the accumulator size, based on the amount of overlap */
-                    H5_ASSIGN_OVERFLOW(add_size, (addr + size) - (f->shared->accum.loc + f->shared->accum.size), hsize_t, size_t);
+                        /* Calculate the amount we will need to add to the accumulator size, based on the amount of overlap */
+                        H5_ASSIGN_OVERFLOW(add_size, (addr + size) - (f->shared->accum.loc + f->shared->accum.size), hsize_t, size_t);
 
-                    /* Check if we need to adjust accumulator size */
-                    if(H5F_accum_adjust(&f->shared->accum, f->shared->lf, dxpl_id, H5F_ACCUM_APPEND, add_size) < 0)
-                        HGOTO_ERROR(H5E_IO, H5E_CANTRESIZE, FAIL, "can't adjust metadata accumulator")
+                        /* Check if we need to adjust accumulator size */
+                        if(H5F_accum_adjust(&f->shared->accum, f->shared->lf, dxpl_id, H5F_ACCUM_APPEND, add_size) < 0)
+                            HGOTO_ERROR(H5E_IO, H5E_CANTRESIZE, FAIL, "can't adjust metadata accumulator")
 
-                    /* Copy the new metadata to the end */
-                    HDmemcpy(f->shared->accum.buf + dirty_off, buf, size);
+                        /* Compute offset of dirty region (after adjusting accumulator) */
+                        dirty_off = (size_t)(addr - f->shared->accum.loc);
 
-                    /* Set the new size of the metadata accumulator */
-                    f->shared->accum.size += add_size;
+                        /* Copy the new metadata to the end */
+                        HDmemcpy(f->shared->accum.buf + dirty_off, buf, size);
 
-                    /* Adjust the dirty region and mark accumulator dirty */
-                    if(f->shared->accum.dirty) {
-                        /* Check for new metadata starting before current dirty region */
-                        if(dirty_off <= f->shared->accum.dirty_off) {
-                            f->shared->accum.dirty_off = dirty_off;
-                            f->shared->accum.dirty_len = size;
+                        /* Set the new size of the metadata accumulator */
+                        f->shared->accum.size += add_size;
+
+                        /* Adjust the dirty region and mark accumulator dirty */
+                        if(f->shared->accum.dirty) {
+                            /* Check for new metadata starting before current dirty region */
+                            if(dirty_off <= f->shared->accum.dirty_off) {
+                                f->shared->accum.dirty_off = dirty_off;
+                                f->shared->accum.dirty_len = size;
+                            } /* end if */
+                            else {
+                                f->shared->accum.dirty_len = (dirty_off + size) - f->shared->accum.dirty_off;
+                            } /* end else */
                         } /* end if */
                         else {
-                            f->shared->accum.dirty_len = (dirty_off + size) - f->shared->accum.dirty_off;
+                            f->shared->accum.dirty_off = dirty_off;
+                            f->shared->accum.dirty_len = size;
+                            f->shared->accum.dirty = TRUE;
                         } /* end else */
                     } /* end if */
+                    /* New metadata overlaps both ends of the current accumulator */
                     else {
-                        f->shared->accum.dirty_off = dirty_off;
+                        /* Check if we need more buffer space */
+                        if(size > f->shared->accum.alloc_size) {
+                            size_t new_alloc_size;        /* New size of accumulator */
+
+                            /* Adjust the buffer size to be a power of 2 that is large enough to hold data */
+                            new_alloc_size = (size_t)1 << (1 + H5V_log2_gen((uint64_t)(size - 1)));
+
+                            /* Reallocate the metadata accumulator buffer */
+                            if(NULL == (f->shared->accum.buf = H5FL_BLK_REALLOC(meta_accum, f->shared->accum.buf, new_alloc_size)))
+                                HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, FAIL, "unable to allocate metadata accumulator buffer")
+
+                            /* Note the new buffer size */
+                            f->shared->accum.alloc_size = new_alloc_size;
+#ifdef H5_CLEAR_MEMORY
+HDmemset(f->shared->accum.buf + size, 0, (f->shared->accum.alloc_size - size));
+#endif /* H5_CLEAR_MEMORY */
+                        } /* end if */
+
+                        /* Copy the new metadata to the buffer */
+                        HDmemcpy(f->shared->accum.buf, buf, size);
+
+                        /* Set the new size & location of the metadata accumulator */
+                        f->shared->accum.loc = addr;
+                        f->shared->accum.size = size;
+
+                        /* Adjust the dirty region and mark accumulator dirty */
+                        f->shared->accum.dirty_off = 0;
                         f->shared->accum.dirty_len = size;
                         f->shared->accum.dirty = TRUE;
                     } /* end else */
                 } /* end if */
-                /* New metadata overlaps both ends of the current accumulator */
+                /* New piece of metadata doesn't adjoin or overlap the existing accumulator */
                 else {
-                    /* Check if we need more buffer space */
+                    /* Write out the existing metadata accumulator, with dispatch to driver */
+                    if(f->shared->accum.dirty) {
+                        if(H5FD_write(f->shared->lf, dxpl_id, H5FD_MEM_DEFAULT, f->shared->accum.loc + f->shared->accum.dirty_off, f->shared->accum.dirty_len, f->shared->accum.buf + f->shared->accum.dirty_off) < 0)
+                            HGOTO_ERROR(H5E_IO, H5E_WRITEERROR, FAIL, "file write failed")
+
+                        /* Reset accumulator dirty flag */
+                        f->shared->accum.dirty = FALSE;
+                    } /* end if */
+
+                    /* Cache the new piece of metadata */
+                    /* Check if we need to resize the buffer */
                     if(size > f->shared->accum.alloc_size) {
-                        size_t new_alloc_size;        /* New size of accumulator */
+                        size_t new_size;        /* New size of accumulator */
 
                         /* Adjust the buffer size to be a power of 2 that is large enough to hold data */
-                        new_alloc_size = (size_t)1 << (1 + H5V_log2_gen((uint64_t)(size - 1)));
+                        new_size = (size_t)1 << (1 + H5V_log2_gen((uint64_t)(size - 1)));
 
-                        /* Reallocate the metadata accumulator buffer */
-                        if(NULL == (f->shared->accum.buf = H5FL_BLK_REALLOC(meta_accum, f->shared->accum.buf, new_alloc_size)))
+                        /* Grow the metadata accumulator buffer */
+                        if(NULL == (f->shared->accum.buf = H5FL_BLK_REALLOC(meta_accum, f->shared->accum.buf, new_size)))
                             HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, FAIL, "unable to allocate metadata accumulator buffer")
 
                         /* Note the new buffer size */
-                        f->shared->accum.alloc_size = new_alloc_size;
+                        f->shared->accum.alloc_size = new_size;
 #ifdef H5_CLEAR_MEMORY
-HDmemset(f->shared->accum.buf + size, 0, (f->shared->accum.alloc_size - size));
+{
+size_t clear_size = MAX(f->shared->accum.size, size);
+HDmemset(f->shared->accum.buf + clear_size, 0, (f->shared->accum.alloc_size - clear_size));
+}
 #endif /* H5_CLEAR_MEMORY */
                     } /* end if */
+                    else {
+                        /* Check if we should shrink the accumulator buffer */
+                        if(size < (f->shared->accum.alloc_size / H5F_ACCUM_THROTTLE) &&
+                                f->shared->accum.alloc_size > H5F_ACCUM_THRESHOLD) {
+                            size_t tmp_size = (f->shared->accum.alloc_size / H5F_ACCUM_THROTTLE); /* New size of accumulator buffer */
 
-                    /* Copy the new metadata to the buffer */
-                    HDmemcpy(f->shared->accum.buf, buf, size);
+                            /* Shrink the accumulator buffer */
+                            if(NULL == (f->shared->accum.buf = H5FL_BLK_REALLOC(meta_accum, f->shared->accum.buf, tmp_size)))
+                                HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, FAIL, "unable to allocate metadata accumulator buffer")
 
-                    /* Set the new size & location of the metadata accumulator */
+                            /* Note the new buffer size */
+                            f->shared->accum.alloc_size = tmp_size;
+                        } /* end if */
+                    } /* end else */
+
+                    /* Update the metadata accumulator information */
                     f->shared->accum.loc = addr;
                     f->shared->accum.size = size;
 
+                    /* Store the piece of metadata in the accumulator */
+                    HDmemcpy(f->shared->accum.buf, buf, size);
+
                     /* Adjust the dirty region and mark accumulator dirty */
                     f->shared->accum.dirty_off = 0;
                     f->shared->accum.dirty_len = size;
                     f->shared->accum.dirty = TRUE;
                 } /* end else */
             } /* end if */
-            /* New piece of metadata doesn't adjoin or overlap the existing accumulator */
+            /* No metadata in the accumulator, grab this piece and keep it */
             else {
-                /* Write out the existing metadata accumulator, with dispatch to driver */
-                if(f->shared->accum.dirty) {
-                    if(H5FD_write(f->shared->lf, dxpl_id, H5FD_MEM_DEFAULT, f->shared->accum.loc + f->shared->accum.dirty_off, f->shared->accum.dirty_len, f->shared->accum.buf + f->shared->accum.dirty_off) < 0)
-                        HGOTO_ERROR(H5E_IO, H5E_WRITEERROR, FAIL, "file write failed")
-
-                    /* Reset accumulator dirty flag */
-                    f->shared->accum.dirty = FALSE;
-                } /* end if */
-
-                /* Cache the new piece of metadata */
-                /* Check if we need to resize the buffer */
+                /* Check if we need to reallocate the buffer */
                 if(size > f->shared->accum.alloc_size) {
                     size_t new_size;        /* New size of accumulator */
 
                     /* Adjust the buffer size to be a power of 2 that is large enough to hold data */
                     new_size = (size_t)1 << (1 + H5V_log2_gen((uint64_t)(size - 1)));
 
-                    /* Grow the metadata accumulator buffer */
+                    /* Reallocate the metadata accumulator buffer */
                     if(NULL == (f->shared->accum.buf = H5FL_BLK_REALLOC(meta_accum, f->shared->accum.buf, new_size)))
                         HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, FAIL, "unable to allocate metadata accumulator buffer")
 
                     /* Note the new buffer size */
                     f->shared->accum.alloc_size = new_size;
 #ifdef H5_CLEAR_MEMORY
-{
-size_t clear_size = MAX(f->shared->accum.size, size);
-HDmemset(f->shared->accum.buf + clear_size, 0, (f->shared->accum.alloc_size - clear_size));
-}
+HDmemset(f->shared->accum.buf + size, 0, (f->shared->accum.alloc_size - size));
 #endif /* H5_CLEAR_MEMORY */
                 } /* end if */
-                else {
-                    /* Check if we should shrink the accumulator buffer */
-                    if(size < (f->shared->accum.alloc_size / H5F_ACCUM_THROTTLE) &&
-                            f->shared->accum.alloc_size > H5F_ACCUM_THRESHOLD) {
-                        size_t tmp_size = (f->shared->accum.alloc_size / H5F_ACCUM_THROTTLE); /* New size of accumulator buffer */
-
-                        /* Shrink the accumulator buffer */
-                        if(NULL == (f->shared->accum.buf = H5FL_BLK_REALLOC(meta_accum, f->shared->accum.buf, tmp_size)))
-                            HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, FAIL, "unable to allocate metadata accumulator buffer")
-
-                        /* Note the new buffer size */
-                        f->shared->accum.alloc_size = tmp_size;
-                    } /* end if */
-                } /* end else */
 
                 /* Update the metadata accumulator information */
                 f->shared->accum.loc = addr;
@@ -636,42 +717,96 @@ HDmemset(f->shared->accum.buf + clear_size, 0, (f->shared->accum.alloc_size - cl
                 f->shared->accum.dirty = TRUE;
             } /* end else */
         } /* end if */
-        /* No metadata in the accumulator, grab this piece and keep it */
         else {
-            /* Check if we need to reallocate the buffer */
-            if(size > f->shared->accum.alloc_size) {
-                size_t new_size;        /* New size of accumulator */
+            /* Write the data */
+            if(H5FD_write(f->shared->lf, dxpl_id, type, addr, size, buf) < 0)
+                HGOTO_ERROR(H5E_IO, H5E_WRITEERROR, FAIL, "file write failed")
+
+            /* Check for overlap w/accumulator */
+            /* (Note that this could be improved by updating the accumulator
+             *  with [some of] the information just read in. -QAK)
+             */
+            if(H5F_addr_overlap(addr, size, f->shared->accum.loc, f->shared->accum.size)) {
+                /* Check for write starting before beginning of accumulator */
+                if(H5F_addr_le(addr, f->shared->accum.loc)) {
+                    /* Check for write ending within accumulator */
+                    if(H5F_addr_le(addr + size, f->shared->accum.loc + f->shared->accum.size)) {
+                        size_t overlap_size;    /* Size of overlapping region */
+
+                        /* Compute overlap size */
+                        overlap_size = (size_t)((addr + size) - f->shared->accum.loc);
+
+                        /* Check for dirty region */
+                        if(f->shared->accum.dirty) {
+                            haddr_t dirty_start = f->shared->accum.loc + f->shared->accum.dirty_off;    /* File address of start of dirty region */
+                            haddr_t dirty_end = dirty_start + f->shared->accum.dirty_len;               /* File address of end of dirty region */
+
+                            /* Check if entire dirty region is overwritten */
+                            if(H5F_addr_le(dirty_end, addr + size)) {
+                                f->shared->accum.dirty = FALSE;
+                                f->shared->accum.dirty_len = 0;
+                            } /* end if */
+                            else {
+                                /* Check for dirty region falling after write */
+                                if(H5F_addr_le(addr + size, dirty_start))
+                                    f->shared->accum.dirty_off = overlap_size;
+                                else {    /* Dirty region overlaps w/written region */
+                                    f->shared->accum.dirty_off = 0;
+                                    f->shared->accum.dirty_len -= (size_t)((addr + size) - dirty_start);
+                                } /* end else */
+                            } /* end if */
+                        } /* end if */
 
-                /* Adjust the buffer size to be a power of 2 that is large enough to hold data */
-                new_size = (size_t)1 << (1 + H5V_log2_gen((uint64_t)(size - 1)));
+                        /* Trim bottom of accumulator off */
+                        f->shared->accum.loc += overlap_size;
+                        f->shared->accum.size -= overlap_size;
+                        HDmemmove(f->shared->accum.buf, f->shared->accum.buf + overlap_size, f->shared->accum.size);
+                    } /* end if */
+                    else {        /* Access covers whole accumulator */
+                        /* Reset accumulator, but don't flush */
+                        if(H5F_accum_reset(f, dxpl_id, FALSE) < 0)
+                            HGOTO_ERROR(H5E_IO, H5E_CANTRESET, FAIL, "can't reset accumulator")
+                    } /* end else */
+                } /* end if */
+                else {  /* Write starts after beginning of accumulator */
+                    size_t overlap_size;    /* Size of overlapping region */
 
-                /* Reallocate the metadata accumulator buffer */
-                if(NULL == (f->shared->accum.buf = H5FL_BLK_REALLOC(meta_accum, f->shared->accum.buf, new_size)))
-                    HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, FAIL, "unable to allocate metadata accumulator buffer")
+                    /* Sanity check */
+                    HDassert(H5F_addr_gt(addr + size, f->shared->accum.loc + f->shared->accum.size));
 
-                /* Note the new buffer size */
-                f->shared->accum.alloc_size = new_size;
-#ifdef H5_CLEAR_MEMORY
-HDmemset(f->shared->accum.buf + size, 0, (f->shared->accum.alloc_size - size));
-#endif /* H5_CLEAR_MEMORY */
-            } /* end if */
+                    /* Compute overlap size */
+                    overlap_size = (size_t)((f->shared->accum.loc + f->shared->accum.size) - addr);
 
-            /* Update the metadata accumulator information */
-            f->shared->accum.loc = addr;
-            f->shared->accum.size = size;
+                    /* Check for dirty region */
+                    if(f->shared->accum.dirty) {
+                        haddr_t dirty_start = f->shared->accum.loc + f->shared->accum.dirty_off;    /* File address of start of dirty region */
+                        haddr_t dirty_end = dirty_start + f->shared->accum.dirty_len;               /* File address of end of dirty region */
 
-            /* Store the piece of metadata in the accumulator */
-            HDmemcpy(f->shared->accum.buf, buf, size);
+                        /* Check if entire dirty region is overwritten */
+                        if(H5F_addr_ge(dirty_start, addr)) {
+                            f->shared->accum.dirty = FALSE;
+                            f->shared->accum.dirty_len = 0;
+                        } /* end if */
+                        else {
+                            /* Check for dirty region falling before write */
+                            if(H5F_addr_le(dirty_end, addr))
+                                ; /* noop */
+                            else    /* Dirty region overlaps w/written region */
+                                f->shared->accum.dirty_len = (size_t)(addr - dirty_start);
+                        } /* end if */
+                    } /* end if */
 
-            /* Adjust the dirty region and mark accumulator dirty */
-            f->shared->accum.dirty_off = 0;
-            f->shared->accum.dirty_len = size;
-            f->shared->accum.dirty = TRUE;
+                    /* Trim top of accumulator off */
+                    f->shared->accum.size -= overlap_size;
+                } /* end else */
+            } /* end if */
         } /* end else */
-
-        /* Indicate success */
-        HGOTO_DONE(TRUE);
     } /* end if */
+    else {
+        /* Write the data */
+        if(H5FD_write(f->shared->lf, dxpl_id, type, addr, size, buf) < 0)
+            HGOTO_ERROR(H5E_IO, H5E_WRITEERROR, FAIL, "file write failed")
+    } /* end else */
 
 done:
     FUNC_LEAVE_NOAPI(ret_value)
@@ -778,22 +913,20 @@ H5F_accum_free(H5F_t *f, hid_t dxpl_id, H5FD_mem_t UNUSED type, haddr_t addr,
                             HGOTO_ERROR(H5E_IO, H5E_WRITEERROR, FAIL, "file write failed")
                     } /* end if */
                     /* Block to free overlaps with some/all of dirty region */
-                    else {
+                    /* Check for unfreed dirty region to write */
+                    else if(H5F_addr_lt(tail_addr, dirty_end)) {
                         size_t write_size;
+                        size_t dirty_delta;
 
                         write_size = (size_t)(dirty_end - tail_addr);
+                        dirty_delta = f->shared->accum.dirty_len - write_size;
 
-                        /* Check for unfreed dirty region to write */
-                        if(write_size > 0) {
-                            size_t dirty_delta;
-
-                            dirty_delta = f->shared->accum.dirty_len - write_size;
+                        HDassert(write_size > 0);
 
-                            /* Write out the unfreed dirty region of the accumulator */
-                            if(H5FD_write(f->shared->lf, dxpl_id, H5FD_MEM_DEFAULT, dirty_start + dirty_delta, write_size, f->shared->accum.buf + f->shared->accum.dirty_off + dirty_delta) < 0)
-                                HGOTO_ERROR(H5E_IO, H5E_WRITEERROR, FAIL, "file write failed")
-                        } /* end if */
-                    } /* end else */
+                        /* Write out the unfreed dirty region of the accumulator */
+                        if(H5FD_write(f->shared->lf, dxpl_id, H5FD_MEM_DEFAULT, dirty_start + dirty_delta, write_size, f->shared->accum.buf + f->shared->accum.dirty_off + dirty_delta) < 0)
+                            HGOTO_ERROR(H5E_IO, H5E_WRITEERROR, FAIL, "file write failed")
+                    } /* end if */
 
                     /* Reset dirty flag */
                     f->shared->accum.dirty = FALSE;
@@ -803,19 +936,16 @@ H5F_accum_free(H5F_t *f, hid_t dxpl_id, H5FD_mem_t UNUSED type, haddr_t addr,
                     /* Check if block to free ends before end of dirty region */
                     if(H5F_addr_lt(tail_addr, dirty_end)) {
                         size_t write_size;
+                        size_t dirty_delta;
 
                         write_size = (size_t)(dirty_end - tail_addr);
+                        dirty_delta = f->shared->accum.dirty_len - write_size;
 
-                        /* Check for unfreed dirty region to write */
-                        if(write_size > 0) {
-                            size_t dirty_delta;
+                        HDassert(write_size > 0);
 
-                            dirty_delta = f->shared->accum.dirty_len - write_size;
-
-                            /* Write out the unfreed end of the dirty region of the accumulator */
-                            if(H5FD_write(f->shared->lf, dxpl_id, H5FD_MEM_DEFAULT, dirty_start + dirty_delta, write_size, f->shared->accum.buf + f->shared->accum.dirty_off + dirty_delta) < 0)
-                                HGOTO_ERROR(H5E_IO, H5E_WRITEERROR, FAIL, "file write failed")
-                        } /* end if */
+                        /* Write out the unfreed end of the dirty region of the accumulator */
+                        if(H5FD_write(f->shared->lf, dxpl_id, H5FD_MEM_DEFAULT, dirty_start + dirty_delta, write_size, f->shared->accum.buf + f->shared->accum.dirty_off + dirty_delta) < 0)
+                            HGOTO_ERROR(H5E_IO, H5E_WRITEERROR, FAIL, "file write failed")
                     } /* end if */
 
                     /* Check for block to free beginning at same location as dirty region */
@@ -825,7 +955,7 @@ H5F_accum_free(H5F_t *f, hid_t dxpl_id, H5FD_mem_t UNUSED type, haddr_t addr,
                     } /* end if */
                     /* Block to free eliminates end of dirty region */
                     else {
-                        f->shared->accum.dirty_len = (addr - dirty_start);
+                        f->shared->accum.dirty_len = (size_t)(addr - dirty_start);
                     } /* end else */
                 } /* end else */
 
@@ -855,7 +985,7 @@ done:
  *-------------------------------------------------------------------------
  */
 herr_t
-H5F_accum_flush(H5F_t *f, hid_t dxpl_id)
+H5F_accum_flush(const H5F_t *f, hid_t dxpl_id)
 {
     herr_t      ret_value = SUCCEED;    /* Return value */
 
@@ -893,7 +1023,7 @@ done:
  *-------------------------------------------------------------------------
  */
 herr_t
-H5F_accum_reset(H5F_t *f, hid_t dxpl_id)
+H5F_accum_reset(const H5F_t *f, hid_t dxpl_id, hbool_t flush)
 {
     herr_t      ret_value = SUCCEED;    /* Return value */
 
@@ -902,9 +1032,10 @@ H5F_accum_reset(H5F_t *f, hid_t dxpl_id)
     HDassert(f);
     HDassert(f->shared);
 
-    /* Flush any dirty data in accumulator */
-    if(H5F_accum_flush(f, dxpl_id) < 0)
-        HGOTO_ERROR(H5E_FILE, H5E_CANTFLUSH, FAIL, "can't flush metadata accumulator")
+    /* Flush any dirty data in accumulator, if requested */
+    if(flush)
+        if(H5F_accum_flush(f, dxpl_id) < 0)
+            HGOTO_ERROR(H5E_FILE, H5E_CANTFLUSH, FAIL, "can't flush metadata accumulator")
 
     /* Check if we need to reset the metadata accumulator information */
     if(f->shared->feature_flags & H5FD_FEAT_ACCUMULATE_METADATA) {