[RFC PATCH 2/8] mm: Add PG_atomic

[Ojaswin Mujoo]

From: John Garry <john.g.garry@xxxxxxxxxx>

Add page flag PG_atomic, meaning that a folio needs to be written back
atomically. This will be used by for handling RWF_ATOMIC buffered IO
in upcoming patches.

Co-developed-by: Ojaswin Mujoo <ojaswin@xxxxxxxxxxxxx>
Signed-off-by: Ojaswin Mujoo <ojaswin@xxxxxxxxxxxxx>
Signed-off-by: John Garry <john.g.garry@xxxxxxxxxx>
---
 include/linux/page-flags.h     | 5 +++++
 include/trace/events/mmflags.h | 3 ++-
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
index 0091ad1986bf..bdce0f58a77a 100644
--- a/include/linux/page-flags.h
+++ b/include/linux/page-flags.h
@@ -111,6 +111,7 @@ enum pageflags {
 	PG_swapbacked,		/* Page is backed by RAM/swap */
 	PG_unevictable,		/* Page is "unevictable"  */
 	PG_dropbehind,		/* drop pages on IO completion */
+	PG_atomic,		/* Page is marked atomic for buffered atomic writes */
 #ifdef CONFIG_MMU
 	PG_mlocked,		/* Page is vma mlocked */
 #endif
@@ -644,6 +645,10 @@ FOLIO_FLAG(unevictable, FOLIO_HEAD_PAGE)
 	__FOLIO_CLEAR_FLAG(unevictable, FOLIO_HEAD_PAGE)
 	FOLIO_TEST_CLEAR_FLAG(unevictable, FOLIO_HEAD_PAGE)
 
+FOLIO_FLAG(atomic, FOLIO_HEAD_PAGE)
+	__FOLIO_CLEAR_FLAG(atomic, FOLIO_HEAD_PAGE)
+	FOLIO_TEST_CLEAR_FLAG(atomic, FOLIO_HEAD_PAGE)
+
 #ifdef CONFIG_MMU
 FOLIO_FLAG(mlocked, FOLIO_HEAD_PAGE)
 	__FOLIO_CLEAR_FLAG(mlocked, FOLIO_HEAD_PAGE)
diff --git a/include/trace/events/mmflags.h b/include/trace/events/mmflags.h
index aa441f593e9a..a8294f6146a5 100644
--- a/include/trace/events/mmflags.h
+++ b/include/trace/events/mmflags.h
@@ -159,7 +159,8 @@ TRACE_DEFINE_ENUM(___GFP_LAST_BIT);
 	DEF_PAGEFLAG_NAME(reclaim),					\
 	DEF_PAGEFLAG_NAME(swapbacked),					\
 	DEF_PAGEFLAG_NAME(unevictable),					\
-	DEF_PAGEFLAG_NAME(dropbehind)					\
+	DEF_PAGEFLAG_NAME(dropbehind),					\
+	DEF_PAGEFLAG_NAME(atomic)					\
 IF_HAVE_PG_MLOCK(mlocked)						\
 IF_HAVE_PG_HWPOISON(hwpoison)						\
 IF_HAVE_PG_IDLE(idle)							\
-- 
2.51.0