cpukit/jffs2: Handle used empty file system

On JFFS2 file systems on NOR flash or dataflash that does not have spare
area for metadata and thus does not invoke delayed writes, it is
possible to put the file system into a state where all blocks have been
written to and all files have been deleted from the filesystem. There is
a bug in the JFFS2 file system scan routine that detects this situation
as a corrupted file system since the scan routine relies on "used" space
to discriminate a valid file system when there are blocks that need to
be erased. The correct fix would require a partial rewrite of the scan
routine, so instead this patch tracks the space marked as obsolete along
with space at the end of each block that is otherwise too small to
contain a JFFS2 node so that it can me compared with the dirty space.
Corrupted data (or otherwise non-JFFS2 blocks) will still cause this
check to fail as corrupted data isn't recognized as obsoleted (deleted)
nodes.

cpukit/libfs/src/jffs2/src/jffs2_fs_sb.h

@@ -75,6 +75,9 @@ struct jffs2_sb_info {
 	uint32_t bad_size;
 	uint32_t sector_size;
 	uint32_t unchecked_size;
+#ifdef __rtems__
+	uint32_t obsolete_size;
+#endif
 
 	uint32_t nr_free_blocks;
 	uint32_t nr_erasing_blocks;

cpukit/libfs/src/jffs2/src/scan.c

@@ -264,14 +264,32 @@ int jffs2_scan_medium(struct jffs2_sb_info *c)
 	}
 #endif
 	if (c->nr_erasing_blocks) {
+#ifdef __rtems__
+		if (c->obsolete_size != c->dirty_size) {
+#endif
 		if (!c->used_size && !c->unchecked_size &&
 			((c->nr_free_blocks+empty_blocks+bad_blocks) != c->nr_blocks || bad_blocks == c->nr_blocks)) {
 			pr_notice("Cowardly refusing to erase blocks on filesystem with no valid JFFS2 nodes\n");
 			pr_notice("empty_blocks %d, bad_blocks %d, c->nr_blocks %d\n",
 				  empty_blocks, bad_blocks, c->nr_blocks);
+#ifdef __rtems__
+			pr_notice("nr_erasing_blocks %d, used 0x%x, dirty 0x%x, wasted 0x%x, free 0x%x, erasing 0x%x, bad 0x%x, obsolete 0x%x, unchecked 0x%x\n",
+				  c->nr_erasing_blocks,
+				  c->used_size,
+				  c->dirty_size,
+				  c->wasted_size,
+				  c->free_size,
+				  c->erasing_size,
+				  c->bad_size,
+				  c->obsolete_size,
+				  c->unchecked_size);
+#endif
 			ret = -EIO;
 			goto out;
 		}
+#ifdef __rtems__
+		}
+#endif
 		spin_lock(&c->erase_completion_lock);
 		jffs2_garbage_collect_trigger(c);
 		spin_unlock(&c->erase_completion_lock);
@@ -646,6 +664,9 @@ scan_more:
 				  sizeof(struct jffs2_unknown_node),
 				  jeb->offset, c->sector_size, ofs,
 				  sizeof(*node));
+#ifdef __rtems__
+			c->obsolete_size += (jeb->offset + c->sector_size - ofs);
+#endif
 			if ((err = jffs2_scan_dirty_space(c, jeb, (jeb->offset + c->sector_size)-ofs)))
 				return err;
 			break;
@@ -796,6 +817,9 @@ scan_more:
 			if ((err = jffs2_scan_dirty_space(c, jeb, PAD(je32_to_cpu(node->totlen)))))
 				return err;
 			ofs += PAD(je32_to_cpu(node->totlen));
+#ifdef __rtems__
+			c->obsolete_size += PAD(je32_to_cpu(node->totlen));
+#endif
 			continue;
 		}