[PATCH 03/12] mm: add PG_uncached page flag

Jens Axboe
2024-12-03T15:32:50Z

Add a page flag that file IO can use to indicate that the IO being done
is uncached, as in it should not persist in the page cache after the IO
has been completed.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
---
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 2220bfec278e..14346fa2470f 100644
--- a/include/linux/page-flags.h
+++ b/include/linux/page-flags.h
@@ -110,6 +110,7 @@ enum pageflags {
PG_reclaim, /* To be reclaimed asap */
PG_swapbacked, /* Page is backed by RAM/swap */
PG_unevictable, /* Page is "unevictable" */
+ PG_uncached, /* uncached read/write IO */
#ifdef CONFIG_MMU
PG_mlocked, /* Page is vma mlocked */
#endif
@@ -562,6 +563,10 @@ PAGEFLAG(Reclaim, reclaim, PF_NO_TAIL)
FOLIO_FLAG(readahead, FOLIO_HEAD_PAGE)
FOLIO_TEST_CLEAR_FLAG(readahead, FOLIO_HEAD_PAGE)

+FOLIO_FLAG(uncached, FOLIO_HEAD_PAGE)
+ FOLIO_TEST_CLEAR_FLAG(uncached, FOLIO_HEAD_PAGE)
+ __FOLIO_SET_FLAG(uncached, FOLIO_HEAD_PAGE)
+
#ifdef CONFIG_HIGHMEM
/*
* Must use a macro here due to header dependency issues. page_zone() is not
diff --git a/include/trace/events/mmflags.h b/include/trace/events/mmflags.h
index bb8a59c6caa2..b60057284102 100644
--- a/include/trace/events/mmflags.h
+++ b/include/trace/events/mmflags.h
@@ -116,7 +116,8 @@
DEF_PAGEFLAG_NAME(head), \
DEF_PAGEFLAG_NAME(reclaim), \
DEF_PAGEFLAG_NAME(swapbacked), \
- DEF_PAGEFLAG_NAME(unevictable) \
+ DEF_PAGEFLAG_NAME(unevictable), \
+ DEF_PAGEFLAG_NAME(uncached) \
IF_HAVE_PG_MLOCK(mlocked) \
IF_HAVE_PG_HWPOISON(hwpoison) \
IF_HAVE_PG_IDLE(idle) \
--
2.45.2