[patch -mm] mm, compaction: persistently skip hugetlbfs pageblocks fix

[David Rientjes <rientjes@xxxxxxxxxx>]

Fix build:

mm/compaction.c: In function ‘isolate_freepages_block’:
mm/compaction.c:469:4: error: implicit declaration of function ‘pageblock_skip_persistent’ [-Werror=implicit-function-declaration]
    if (pageblock_skip_persistent(page, order)) {
    ^
mm/compaction.c:470:5: error: implicit declaration of function ‘set_pageblock_skip’ [-Werror=implicit-function-declaration]
     set_pageblock_skip(page);
     ^

CMA doesn't guarantee pageblock skip will get reset when migration and 
freeing scanners meet, and pageblock skip is a CONFIG_COMPACTION only 
feature, so disable it when CONFIG_COMPACTION=n.

Signed-off-by: David Rientjes <rientjes@xxxxxxxxxx>
---
 include/linux/pageblock-flags.h | 11 +++++++++++
 mm/compaction.c                 |  8 +++++++-
 2 files changed, 18 insertions(+), 1 deletion(-)

diff --git a/include/linux/pageblock-flags.h b/include/linux/pageblock-flags.h
--- a/include/linux/pageblock-flags.h
+++ b/include/linux/pageblock-flags.h
@@ -96,6 +96,17 @@ void set_pfnblock_flags_mask(struct page *page,
 #define set_pageblock_skip(page) \
 			set_pageblock_flags_group(page, 1, PB_migrate_skip,  \
 							PB_migrate_skip)
+#else
+static inline bool get_pageblock_skip(struct page *page)
+{
+	return false;
+}
+static inline void clear_pageblock_skip(struct page *page)
+{
+}
+static inline void set_pageblock_skip(struct page *page)
+{
+}
 #endif /* CONFIG_COMPACTION */
 
 #endif	/* PAGEBLOCK_FLAGS_H */
diff --git a/mm/compaction.c b/mm/compaction.c
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -322,7 +322,13 @@ static inline bool isolation_suitable(struct compact_control *cc,
 	return true;
 }
 
-static void update_pageblock_skip(struct compact_control *cc,
+static inline bool pageblock_skip_persistent(struct page *page,
+					     unsigned int order)
+{
+	return false;
+}
+
+static inline void update_pageblock_skip(struct compact_control *cc,
 			struct page *page, unsigned long nr_isolated,
 			bool migrate_scanner)
 {