Make a VFD SWMR writer use the SWMR VFD, to facilitate avoiding conflicting

multiple opens of the same file with VFD SWMR---i.e., twice for writing, or for
reading and for writing.  In the long run, this will help me encapsulate more
of the SWMR functionality in the VFD, too.

2 files changed, 25 insertions, 35 deletions

diff --git a/src/H5FDvfd_swmr.c b/src/H5FDvfd_swmr.c
index ab80a82..2acdca4 100644
--- a/src/H5FDvfd_swmr.c
+++ b/src/H5FDvfd_swmr.c
@@ -58,6 +58,7 @@ typedef struct H5FD_vfd_swmr_t {
                                                 /* when the page buffer is    */
                                                 /* and to FALSE otherwise.    */
                                                 /* Used for sanity checking.  */
+    bool writer;                            /* True iff configured to write. */
 } H5FD_vfd_swmr_t;
 
 #define MAXADDR (((haddr_t)1<<(8*sizeof(HDoff_t)-1))-1)
@@ -293,9 +294,6 @@ H5FD_vfd_swmr_open(const char *name, unsigned flags, hid_t fapl_id,
                     "can't get VFD SWMR config info");
     }
 
-    /* Ensure that this is the reader */
-    HDassert(!vfd_swmr_config->writer);
-
     /* Create the new driver struct */
     if(NULL == (file = H5FL_CALLOC(H5FD_vfd_swmr_t))) {
         HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, NULL,
@@ -314,6 +312,12 @@ H5FD_vfd_swmr_open(const char *name, unsigned flags, hid_t fapl_id,
               sizeof(file->md_file_path));
     file->md_file_path[sizeof(file->md_file_path) - 1] = '\0';
 
+    file->writer = vfd_swmr_config->writer;
+
+    /* Ensure that this is the reader */
+    if (vfd_swmr_config->writer)
+        goto finish;
+
     file->api_elapsed_nslots = vfd_swmr_config->max_lag + 1;
 
     file->api_elapsed_ticks =
@@ -346,6 +350,8 @@ H5FD_vfd_swmr_open(const char *name, unsigned flags, hid_t fapl_id,
         HGOTO_ERROR(H5E_VFL, H5E_CANTGET, NULL,
                     "unable to load/decode the md file header/index");
 
+finish:
+
     /* Hard-wired to open the underlying HDF5 file with SEC2 */
     if((file->hdf5_file_lf = H5FD_open(name, flags, H5P_FILE_ACCESS_DEFAULT, 
                                        maxaddr)) == NULL)
@@ -419,6 +425,9 @@ H5FD_vfd_swmr_close(H5FD_t *_file)
                         "unable to close the HDF5 file")
     }
 
+    if (!file->writer)
+        goto finish;
+
     vfd_swmr_reader_did_increase_tick_to(0);
 
     if (file->api_elapsed_ticks != NULL) {
@@ -442,6 +451,8 @@ H5FD_vfd_swmr_close(H5FD_t *_file)
         file->md_index.entries = H5FL_SEQ_FREE(H5FD_vfd_swmr_idx_entry_t, 
                                                file->md_index.entries);
 
+finish:
+
     /* Release the driver info */
     file = H5FL_FREE(H5FD_vfd_swmr_t, file);
 
@@ -702,6 +713,9 @@ H5FD_vfd_swmr_read(H5FD_t *_file, H5FD_mem_t type,
     herr_t ret_value = SUCCEED;
     char *p = buf;
 
+    if (file->writer)
+        return H5FD_read(file->hdf5_file_lf, type, addr, size, buf);
+
     FUNC_ENTER_NOAPI_NOINIT
 
     HDassert(file && file->pub.cls);
@@ -823,23 +837,11 @@ H5FD_vfd_swmr_write(H5FD_t *_file, H5FD_mem_t type,
     hid_t H5_ATTR_UNUSED dxpl_id, haddr_t addr, size_t size, const void *buf)
 {
     H5FD_vfd_swmr_t     *file       = (H5FD_vfd_swmr_t *)_file;
-    herr_t              ret_value   = SUCCEED;
-
-    FUNC_ENTER_NOAPI_NOINIT
-
-    HDassert(file && file->pub.cls);
-    HDassert(buf);
 
-    /* This function should always fail.  For now assert FALSE */
-    HDassert(FALSE);
+    HDassert(file->writer);
     
-    /* SHOULDN'T come here ?? */
-    if(H5FD_write(file->hdf5_file_lf, type, addr, size, buf) < 0)
-        HGOTO_ERROR(H5E_VFL, H5E_WRITEERROR, FAIL, "file write request failed")
-
-done:
-    FUNC_LEAVE_NOAPI(ret_value)
-} /* end H5FD_vfd_swmr_write() */
+    return H5FD_write(file->hdf5_file_lf, type, addr, size, buf);
+}
 
 
 /*-------------------------------------------------------------------------
@@ -857,9 +859,6 @@ H5FD_vfd_swmr_truncate(H5FD_t *_file, hid_t H5_ATTR_UNUSED dxpl_id,
    hbool_t closing)
 {
     H5FD_vfd_swmr_t *file = (H5FD_vfd_swmr_t *)_file; /* VFD SWMR file struct */
-    herr_t ret_value = SUCCEED;                       /* Return value */
-
-    FUNC_ENTER_NOAPI_NOINIT
 
     /* The VFD SWMR vfd should only be used by the VFD SWMR reader, 
      * and thus this file should only be opened R/O.
@@ -868,16 +867,10 @@ H5FD_vfd_swmr_truncate(H5FD_t *_file, hid_t H5_ATTR_UNUSED dxpl_id,
      *
      * For now, just assert FALSE.
      */
-    HDassert(FALSE);
+    HDassert(file->writer);
 
-    HDassert(file);
-
-    if(H5FD_truncate(file->hdf5_file_lf, closing) < 0)
-        HGOTO_ERROR(H5E_IO, H5E_BADVALUE, FAIL, "unable to truncate the HDF5 file")
-
-done:
-    FUNC_LEAVE_NOAPI(ret_value)
-} /* end H5FD_vfd_swmr_truncate() */
+    return H5FD_truncate(file->hdf5_file_lf, closing);
+}
 
 
 /*-------------------------------------------------------------------------
diff --git a/src/H5Pfapl.c b/src/H5Pfapl.c
index a3dc2a7..f616c70 100644
--- a/src/H5Pfapl.c
+++ b/src/H5Pfapl.c
@@ -5591,11 +5591,8 @@ H5Pset_vfd_swmr_config(hid_t plist_id, H5F_vfd_swmr_config_t *config_ptr)
     if(H5P_set(plist, H5F_ACS_VFD_SWMR_CONFIG_NAME, config_ptr) < 0)
         HGOTO_ERROR(H5E_PLIST, H5E_CANTSET, FAIL, "can't set metadata cache initial config")
 
-    /* Hard-wired to use SWMR VFD */
-    if(!config_ptr->writer) {
-        if(H5P_set_driver(plist, H5FD_VFD_SWMR, NULL) < 0)
-            HGOTO_ERROR(H5E_PLIST, H5E_CANTSET, FAIL, "can't set VFD SWMR driver info")
-    }
+    if(H5P_set_driver(plist, H5FD_VFD_SWMR, NULL) < 0)
+        HGOTO_ERROR(H5E_PLIST, H5E_CANTSET, FAIL, "can't set VFD SWMR driver info");
 
 done:
     FUNC_LEAVE_API(ret_value)