[PATCH makedumpfile 7/9] Add PG_INCLUDE_HEAD extension return status

[Stephen Brennan]

This allows an extension to request that only the head page of a
compound page be included in the dump.

Signed-off-by: Stephen Brennan <stephen.s.brennan at oracle.com>
---
 extension.c    | 2 +-
 extension.h    | 7 ++++---
 makedumpfile.c | 9 +++++++++
 3 files changed, 14 insertions(+), 4 deletions(-)

diff --git a/extension.c b/extension.c
index 9b29f0c..a7360d0 100644
--- a/extension.c
+++ b/extension.c
@@ -314,7 +314,7 @@ int run_extension_callback(unsigned long pfn, const void *pcache, const struct p
 	for (int i = 0; i < handle_cbs_len; i++) {
 		if (handle_cbs[i]->cb) {
 			result = handle_cbs[i]->cb(pfn, pcache, inf);
-			if (result == PG_INCLUDE) {
+			if (result == PG_INCLUDE || result == PG_INCLUDE_HEAD) {
 				ret = result;
 				goto out;
 			} else if (result == PG_EXCLUDE) {
diff --git a/extension.h b/extension.h
index 22af9a6..3edfbeb 100644
--- a/extension.h
+++ b/extension.h
@@ -4,9 +4,10 @@
 
 struct pginfo;
 enum {
-	PG_INCLUDE,	// Exntesion will keep the page
-	PG_EXCLUDE,	// Exntesion will discard the page
-	PG_UNDECID,	// Exntesion makes no decision
+	PG_INCLUDE,		// Extension will keep the full page
+	PG_INCLUDE_HEAD,	// Extension will keep just the head page
+	PG_EXCLUDE,		// Extension will discard the full page
+	PG_UNDECID,		// Extension makes no decision
 };
 int run_extension_callback(unsigned long pfn, const void *pcache, const struct pginfo *i);
 void init_extensions(void);
diff --git a/makedumpfile.c b/makedumpfile.c
index f277360..69abb17 100644
--- a/makedumpfile.c
+++ b/makedumpfile.c
@@ -6667,6 +6667,15 @@ check_order:
 			 * retained by an extension. */
 			num_extension_retained += nr_pages;
 			continue;
+		} else if (filter_pg == PG_INCLUDE_HEAD) {
+			num_extension_retained += 1;
+			if (nr_pages == 1)
+				continue;
+
+			/* FALL THROUGH and exclude tail pages */
+			pfn++;
+			mem_map += SIZE(page);
+			nr_pages--;
 		}
 
 		/*
-- 
2.47.3