Import wiredtiger: 280c572c8097a322e429a349f73135266f3faacf from branch mongodb-4.2

ref: 1a1197ef3c..280c572c80
for: 4.2.1

WT-4344       Add more test cases for metadata salvage
WT-4460       Optimize for in-order, non-overlapping modifications
WT-4858       Add compatibility support for gcc-9 and clang-8
WT-4909       Fix potential code caching/re-ordering issue in __search_insert_append
WT-4917       Fix test/format where truncate operations not correctly compared with previous updates
WT-4946       Tighten up failure checks for cursor join
WT-4956       Handle the case where 4 billion updates are made to a page without eviction
WT-4957       Revert part of a change about when pages are queued for urgent eviction
WT-4963       Add debugging for rare test hang
WT-4965       Disable problematic eviction during checkpoints
WT-5036       Fix test/format where tracking buffer wrap causes repeatable operation failure
WT-5038       Prevent eviction of prepared updates during commit
WT-5040       Add dumping of cursor's page on a mismatch
WT-5050       Assertion failure during urgent eviction of metadata page
WT-5054       Fix test/format bug where truncation operations could fail repeatable read testing

1 files changed, 14 insertions, 3 deletions

diff --git a/src/third_party/wiredtiger/src/include/btmem.h b/src/third_party/wiredtiger/src/include/btmem.h
index a7c289a7b7f..03643f473e1 100644
--- a/src/third_party/wiredtiger/src/include/btmem.h
+++ b/src/third_party/wiredtiger/src/include/btmem.h
@@ -489,10 +489,21 @@ struct __wt_page_modify {
 	WT_SPINLOCK page_lock;		/* Page's spinlock */
 
 	/*
-	 * The write generation is incremented when a page is modified, a page
-	 * is clean if the write generation is 0.
+	 * The page state is incremented when a page is modified.
+	 *
+	 * WT_PAGE_CLEAN --
+	 *	The page is clean.
+	 * WT_PAGE_DIRTY_FIRST --
+	 *	The page is in this state after the first operation that marks a
+	 *	page dirty, or when reconciliation is checking to see if it has
+	 *	done enough work to be able to mark the page clean.
+	 * WT_PAGE_DIRTY --
+	 *	Two or more updates have been added to the page.
 	 */
-	uint32_t write_gen;
+#define	WT_PAGE_CLEAN		0
+#define	WT_PAGE_DIRTY_FIRST	1
+#define	WT_PAGE_DIRTY		2
+	uint32_t page_state;
 
 #define	WT_PM_REC_EMPTY		1	/* Reconciliation: no replacement */
 #define	WT_PM_REC_MULTIBLOCK	2	/* Reconciliation: multiple blocks */