The patch adds description for page flags policies.
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
---
include/linux/page-flags.h | 18 +++++++++++++++++-
1 file changed, 17 insertions(+), 1 deletion(-)
diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
index 465ca42af633..19e4129f00e5 100644
--- a/include/linux/page-flags.h
+++ b/include/linux/page-flags.h
@@ -133,7 +133,23 @@ enum pageflags {
#ifndef __GENERATING_BOUNDS_H
-/* Page flags policies wrt compound pages */
+/*
+ * Page flags policies wrt compound pages
+ *
+ * PF_ANY:
+ * the page flag is relevant for small, head and tail pages.
+ *
+ * PF_HEAD:
+ * for compound page all operations related to the page flag applied to
+ * head page.
+ *
+ * PF_NO_TAIL:
+ * modifications of the page flag must be done on small or head pages,
+ * checks can be done on tail pages too.
+ *
+ * PF_NO_COMPOUND:
+ * the page flag is not relevant for compound pages.
+ */
#define PF_ANY(page, enforce) page
#define PF_HEAD(page, enforce) compound_head(page)
#define PF_NO_TAIL(page, enforce) ({ \
--
2.5.1
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