Initial crack at page buffer tolerance

Accepts:
* Opening a non-pb file with fapl pb settings
* Opening a pb file with fapl page size < file pb size

Not working:
* Creating a pb file with a fapl page size < fcp pb size

Includes testing

src/H5Fint.c

@@ -2017,12 +2017,12 @@ H5F_open(const char *name, unsigned flags, hid_t fcpl_id, hid_t fapl_id)
         /* Temporary: fail file create when page buffering feature is enabled for parallel */
         HGOTO_ERROR(H5E_FILE, H5E_CANTOPENFILE, NULL, "page buffering is disabled for parallel");
 #endif /* H5_HAVE_PARALLEL */
-        /* Query for other page buffer cache properties */
-        if (H5P_get(a_plist, H5F_ACS_PAGE_BUFFER_MIN_META_PERC_NAME, &page_buf_min_meta_perc) < 0)
-            HGOTO_ERROR(H5E_FILE, H5E_CANTGET, NULL, "can't get minimum metadata fraction of page buffer");
-        if (H5P_get(a_plist, H5F_ACS_PAGE_BUFFER_MIN_RAW_PERC_NAME, &page_buf_min_raw_perc) < 0)
-            HGOTO_ERROR(H5E_FILE, H5E_CANTGET, NULL, "can't get minimum raw data fraction of page buffer");
-    } /* end if */
+    }
+    /* Query for other page buffer cache properties (might be needed later) */
+    if (H5P_get(a_plist, H5F_ACS_PAGE_BUFFER_MIN_META_PERC_NAME, &page_buf_min_meta_perc) < 0)
+        HGOTO_ERROR(H5E_FILE, H5E_CANTGET, NULL, "can't get minimum metadata fraction of page buffer");
+    if (H5P_get(a_plist, H5F_ACS_PAGE_BUFFER_MIN_RAW_PERC_NAME, &page_buf_min_raw_perc) < 0)
+        HGOTO_ERROR(H5E_FILE, H5E_CANTGET, NULL, "can't get minimum raw data fraction of page buffer");
 
     /* Get the evict on close setting */
     if (H5P_get(a_plist, H5F_ACS_EVICT_ON_CLOSE_FLAG_NAME, &evict_on_close) < 0)
@@ -2073,7 +2073,20 @@ H5F_open(const char *name, unsigned flags, hid_t fcpl_id, hid_t fapl_id)
         if (H5F__super_read(file, a_plist, true) < 0)
             HGOTO_ERROR(H5E_FILE, H5E_READERROR, NULL, "unable to read superblock");
 
-        /* Create the page buffer before initializing the superblock */
+        /* Tolerate opening files when H5Pset_page_buffer_size() was used to set
+         * fapl parameters but the file doesn't use page buffering.
+         */
+        if (shared->fs_strategy != H5F_FSPACE_STRATEGY_PAGE)
+            page_buf_size = 0;
+
+        /* Tolerate opening files when H5Pset_page_buffer_size() was used to set
+         * fapl parameters but the desired page buffer size is smaller than a
+         * single page.
+         */
+        if (shared->fs_page_size > page_buf_size)
+            page_buf_size = 0;
+
+        /* Create the page buffer *after* reading the superblock */
         if (page_buf_size)
             if (H5PB_create(shared, page_buf_size, page_buf_min_meta_perc, page_buf_min_raw_perc) < 0)
                 HGOTO_ERROR(H5E_FILE, H5E_CANTINIT, NULL, "unable to create page buffer");

src/H5Ppublic.h

@@ -5745,10 +5745,17 @@ H5_DLL herr_t H5Pset_mdc_image_config(hid_t plist_id, H5AC_cache_image_config_t
  *          file close, the page buffer is flushed writing all the pages to the
  *          file.
  *
- *          If a non-zero page buffer size is set, and the file space strategy
- *          is not set to paged or the page size for the file space strategy is
- *          larger than the page buffer size, the subsequent call to H5Fcreate()
- *          or H5Fopen() using the \p plist_id will fail.
+ * \note    Before HDF5 1.14.4, if a non-zero page buffer size were set, and
+ *          the file space strategy was not set to paged or the page size for
+ *          the file space strategy was larger than the page buffer size,
+ *          the subsequent call to H5Fcreate() or H5Fopen() using the
+ *          \p plist_id would fail. As of HDF5 1.14.4, this function is now
+ *          considered advisory, and unusable settings are ignored. This
+ *          allows setting a page buffer size without having to open a file
+ *          to get the page buffer characteristics.
+ *
+ * \note    The H5Fcreate() call will still fail when the fapl page size
+ *          is smaller than the fcpl page size.
  *
  *          The function also allows setting the minimum percentage of pages for
  *          metadata and raw data to prevent a certain type of data to evict hot

test/page_buffer.c

@@ -1650,6 +1650,94 @@ test_min_threshold(hid_t orig_fapl, const char *driver_name)
 
 } /* test_min_threshold */
 
+/*-------------------------------------------------------------------------
+ * Function:    test_pb_fapl_tolerance_at_open()
+ *
+ * Purpose:     Tests if the library tolerates setting fapl page buffer
+ *              values via H5Pset_page_buffer_size() when opening a file
+ *              that does not use page buffering.
+ *
+ * Return:      0 if test is successful
+ *              1 if test fails
+ *
+ *-------------------------------------------------------------------------
+ */
+static unsigned
+test_pb_fapl_tolerance_at_open(void)
+{
+    const char   *filename = "pb_fapl_tolerance.h5";
+    hid_t   fapl    = H5I_INVALID_HID;
+    hid_t   fcpl    = H5I_INVALID_HID;
+    hid_t   fid     = H5I_INVALID_HID;
+
+    TESTING("if opening non-page-buffered files works w/ H5Pset_page_buffer_size()");
+
+    /* Create a file WITHOUT page buffering */
+    if ((fid = H5Fcreate(filename, H5F_ACC_TRUNC, H5P_DEFAULT, H5P_DEFAULT)) < 0)
+        TEST_ERROR;
+    if (H5Fclose(fid) < 0)
+        TEST_ERROR;
+
+    /* Set up page buffering values on a fapl */
+    if ((fapl = H5Pcreate(H5P_FILE_ACCESS)) < 0)
+        TEST_ERROR;
+    if (H5Pset_page_buffer_size(fapl, 512, 0, 0) < 0)
+        TEST_ERROR;
+
+    /* Attempt to open non-page-buf file w/ page buf fapl */
+    if ((fid = H5Fopen(filename, H5F_ACC_RDWR, fapl)) < 0)
+        TEST_ERROR;
+    if (H5Fclose(fid) < 0)
+        TEST_ERROR;
+
+    /* Set up a fcpl with a page size that is larger than the fapl size */
+    if ((fcpl = H5Pcreate(H5P_FILE_CREATE)) < 0)
+        TEST_ERROR;
+    if (H5Pset_file_space_strategy(fcpl, H5F_FSPACE_STRATEGY_PAGE, false, 1) < 0)
+        TEST_ERROR;
+    if (H5Pset_file_space_page_size(fcpl, 4096) < 0)
+        TEST_ERROR;
+
+    /* Create a file that uses page buffering while using a fapl with
+     * a page buf size that is too small
+     */
+    if ((fid = H5Fcreate(filename, H5F_ACC_TRUNC, fcpl, H5P_DEFAULT)) < 0)
+        TEST_ERROR;
+    if (H5Fclose(fid) < 0)
+        TEST_ERROR;
+
+    /* Attempt to open page-buf file w/ fapl page buf size that is too small */
+    if ((fid = H5Fopen(filename, H5F_ACC_RDWR, fapl)) < 0)
+        TEST_ERROR;
+    if (H5Fclose(fid) < 0)
+        TEST_ERROR;
+
+    /* Shut down */
+    if (H5Pclose(fcpl) < 0)
+        TEST_ERROR;
+    if (H5Pclose(fapl) < 0)
+        TEST_ERROR;
+
+    HDremove(filename);
+
+    PASSED();
+
+    return 0;
+
+error:
+
+    H5E_BEGIN_TRY
+    {
+        H5Pclose(fapl);
+        H5Pclose(fcpl);
+        H5Fclose(fid);
+    }
+    H5E_END_TRY
+
+    return 1;
+
+} /* test_pb_fapl_tolerance_at_open */
+
 /*-------------------------------------------------------------------------
  * Function:    test_stats_collection()
  *
@@ -2083,12 +2171,12 @@ main(void)
         SKIPPED();
         puts("Skip page buffering test because paged aggregation is disabled for multi/split drivers");
         exit(EXIT_SUCCESS);
-    } /* end if */
+    }
 
     if ((fapl = h5_fileaccess()) < 0) {
         nerrors++;
         PUTS_ERROR("Can't get VFD-dependent fapl");
-    } /* end if */
+    }
 
     /* Push API context */
     if (H5CX_push() < 0)
@@ -2107,6 +2195,7 @@ main(void)
     nerrors += test_lru_processing(fapl, driver_name);
     nerrors += test_min_threshold(fapl, driver_name);
     nerrors += test_stats_collection(fapl, driver_name);
+    nerrors += test_pb_fapl_tolerance_at_open();
 
 #endif /* H5_HAVE_PARALLEL */