libblock: PR2040: Add starvation threshold

Do not use the unavailable block count as the erased blocks starvation
threshold.  Use instead the block count of the largest segment.  This
improves the starvation resolution gain of available blocks.

cpukit/libblock/src/flashdisk.c

@@ -177,6 +177,7 @@ typedef struct rtems_flashdisk
                                                 mappings. */
   uint32_t block_count;                    /**< The number of avail. blocks. */
   uint32_t unavail_blocks;                 /**< The number of unavail blocks. */
+  uint32_t starvation_threshold;           /**< Erased blocks starvation threshold. */
   uint32_t erased_blocks;                  /**< The number of erased blocks. */
 
   rtems_fdisk_device_ctl* devices;         /**< The flash devices for this
@@ -280,7 +281,7 @@ rtems_fdisk_printf (const rtems_flashdisk* fd, const char *format, ...)
 static bool
 rtems_fdisk_is_erased_blocks_starvation (rtems_flashdisk* fd)
 {
-  bool starvation = fd->erased_blocks < fd->unavail_blocks;
+  bool starvation = fd->erased_blocks < fd->starvation_threshold;
 
   if (starvation)
     fd->starvations++;
@@ -1405,6 +1406,10 @@ rtems_fdisk_compact (rtems_flashdisk* fd)
 
   if (rtems_fdisk_is_erased_blocks_starvation (fd))
   {
+#if RTEMS_FDISK_TRACE
+    rtems_fdisk_printf (fd, " resolve starvation");
+#endif
+
     ssc = rtems_fdisk_segment_queue_pop_head (&fd->used);
     if (!ssc)
       ssc = rtems_fdisk_segment_queue_pop_head (&fd->available);
@@ -1482,7 +1487,12 @@ rtems_fdisk_compact (rtems_flashdisk* fd)
      */
 
     if (!ssc || (pages == 0) || ((compacted_segs + segments) == 1))
+    {
+#if RTEMS_FDISK_TRACE
+      rtems_fdisk_printf (fd, " nothing to compact");
+#endif
       break;
+    }
 
 #if RTEMS_FDISK_TRACE
     rtems_fdisk_printf (fd, " ssc scan: %d-%d: p=%ld, seg=%ld",
@@ -1539,6 +1549,7 @@ rtems_fdisk_recover_block_mappings (rtems_flashdisk* fd)
    * Scan each segment or each device recovering the valid pages.
    */
   fd->erased_blocks = 0;
+  fd->starvation_threshold = 0;
   for (device = 0; device < fd->device_count; device++)
   {
     uint32_t segment;
@@ -1557,6 +1568,8 @@ rtems_fdisk_recover_block_mappings (rtems_flashdisk* fd)
       sc->pages_desc = rtems_fdisk_page_desc_pages (sd, fd->block_size);
       sc->pages =
         rtems_fdisk_pages_in_segment (sd, fd->block_size) - sc->pages_desc;
+      if (sc->pages > fd->starvation_threshold)
+        fd->starvation_threshold = sc->pages;
 
       sc->pages_active = 0;
       sc->pages_used   = 0;
@@ -2225,6 +2238,7 @@ rtems_fdisk_print_status (rtems_flashdisk* fd)
 
   rtems_fdisk_printf (fd, "Block count\t%d", fd->block_count);
   rtems_fdisk_printf (fd, "Unavail blocks\t%d", fd->unavail_blocks);
+  rtems_fdisk_printf (fd, "Starvation threshold\t%d", fd->starvation_threshold);
   rtems_fdisk_printf (fd, "Starvations\t%d", fd->starvations);
   count = rtems_fdisk_segment_count_queue (&fd->available);
   total = count;