WT-2725 Prevent eviction of read-only pages with recent updates. (#2919)

Reverts some of 0136888b3b677d67ff929c6f5b1f8d6aa6793b13.

2 files changed, 17 insertions, 14 deletions

diff --git a/src/evict/evict_lru.c b/src/evict/evict_lru.c
index 42966d636f6..1314f715907 100644
--- a/src/evict/evict_lru.c
+++ b/src/evict/evict_lru.c
@@ -1265,16 +1265,23 @@ fast:		/* If the page can't be evicted, give up. */
 			continue;
 
 		/*
-		 * If the page is clean but has modifications that appear too
-		 * new to evict, skip it.
+		 * If the oldest transaction hasn't changed since the last time
+		 * this page was written, it's unlikely that we can make
+		 * progress.  Similarly, if the most recent update on the page
+		 * is not yet globally visible, eviction will fail.  These
+		 * heuristics attempt to avoid repeated attempts to evict the
+		 * same page.
 		 *
-		 * Note: take care with ordering: if we detected that the page
-		 * is modified above, we expect mod != NULL.
+		 * That said, if eviction is stuck, or we are helping with
+		 * forced eviction, try anyway: maybe a transaction that was
+		 * running last time we wrote the page has since rolled back,
+		 * or we can help get the checkpoint completed sooner.
 		 */
 		mod = page->modify;
-		if (!modified && mod != NULL && !LF_ISSET(
+		if (modified && !LF_ISSET(
 		    WT_EVICT_PASS_AGGRESSIVE | WT_EVICT_PASS_WOULD_BLOCK) &&
-		    !__wt_txn_visible_all(session, mod->rec_max_txn))
+		    (mod->disk_snap_min == S2C(session)->txn_global.oldest_id ||
+		    !__wt_txn_visible_all(session, mod->update_txn)))
 			continue;
 
 		WT_ASSERT(session, evict->ref == NULL);
diff --git a/src/include/btree.i b/src/include/btree.i
index 8086df92087..c58abd356cf 100644
--- a/src/include/btree.i
+++ b/src/include/btree.i
@@ -1136,15 +1136,11 @@ __wt_page_can_evict(WT_SESSION_IMPL *session,
 	}
 
 	/*
-	 * If the oldest transaction hasn't changed since the last time this
-	 * page was written, it's unlikely that we can make progress.
-	 * Similarly, if the most recent update on the page is not yet globally
-	 * visible, eviction must fail.  These checks also aim to avoid
-	 * repeated attempts to evict the same page.
+	 * If the page is clean, check if it has an update that is too new to
+	 * evict.
 	 */
-	if (modified &&
-	    (mod->disk_snap_min == __wt_txn_oldest_id(session) ||
-	    !__wt_txn_visible_all(session, mod->update_txn)))
+	if (!modified && mod != NULL &&
+	    !__wt_txn_visible_all(session, mod->rec_max_txn))
 		return (false);
 
 	return (true);