WT-2904 Fix a bug where the reported checkpoint size could be many times data size (#3102)

Correct the rolling checkpoint size for the current checkpoint's root
page size, it shouldn't be included because it's an allocation that's
not part of the next checkpoint.

2 files changed, 34 insertions, 5 deletions

diff --git a/src/block/block_ckpt.c b/src/block/block_ckpt.c
index b7ac953cdb1..a9bd706acbe 100644
--- a/src/block/block_ckpt.c
+++ b/src/block/block_ckpt.c
@@ -615,8 +615,6 @@ live_update:
 	WT_CKPT_FOREACH(ckptbase, ckpt)
 		if (F_ISSET(ckpt, WT_CKPT_ADD)) {
 			/*
-			 * Set the checkpoint size for the live system.
-			 *
 			 * !!!
 			 * Our caller wants the final checkpoint size.  Setting
 			 * the size here violates layering, but the alternative
@@ -624,7 +622,29 @@ live_update:
 			 * cookie into its components, and that's a fair amount
 			 * of work.
 			 */
-			ckpt->ckpt_size = ci->ckpt_size = ckpt_size;
+			ckpt->ckpt_size = ckpt_size;
+
+			/*
+			 * Set the rolling checkpoint size for the live system.
+			 * The current size includes the current checkpoint's
+			 * root page size (root pages are on the checkpoint's
+			 * block allocation list as root pages are allocated
+			 * with the usual block allocation functions). That's
+			 * correct, but we don't want to include it in the size
+			 * for the next checkpoint.
+			 */
+			ckpt_size -= ci->root_size;
+
+			/*
+			 * Additionally, we had a bug for awhile where the live
+			 * checkpoint size grew without bound. We can't sanity
+			 * check the value, that would require walking the tree
+			 * as part of the checkpoint. Bound any bug at the size
+			 * of the file.
+			 */
+			WT_ASSERT(session, ckpt_size <= (uint64_t)block->size);
+			ci->ckpt_size =
+			    WT_MIN(ckpt_size, (uint64_t)block->size);
 
 			WT_ERR(__ckpt_update(session, block, ckpt, ci, true));
 		}
diff --git a/test/format/config.c b/test/format/config.c
index 95b05c3c833..839ff5058de 100644
--- a/test/format/config.c
+++ b/test/format/config.c
@@ -187,8 +187,17 @@ config_setup(void)
 	/* Give in-memory configuration a final review. */
 	config_in_memory_check();
 
-	/* Make the default maximum-run length 20 minutes. */
-	if (!config_is_perm("timer"))
+	/*
+	 * Run-length configured by a number of operations and a timer. If the
+	 * operation count and the timer are both set by a configuration, there
+	 * isn't anything to do. If only the operation count was configured,
+	 * set a default maximum-run of 20 minutes. If only the timer is set,
+	 * clear the operations count (which was set randomly).
+	 */
+	if (config_is_perm("timer")) {
+		if (!config_is_perm("ops"))
+			config_single("ops=0", 0);
+	} else
 		config_single("timer=20", 0);
 
 	/*