[PATCH 01/75] mm/gup: Increment the page refcount before the pincount
From: Matthew Wilcox (Oracle)
Date: Fri Feb 04 2022 - 15:01:09 EST
We should always increase the refcount before doing anything else to
the page so that other page users see the elevated refcount first.
Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
---
mm/gup.c | 12 ++++++------
1 file changed, 6 insertions(+), 6 deletions(-)
diff --git a/mm/gup.c b/mm/gup.c
index a9d4d724aef7..08020987dfc0 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -220,18 +220,18 @@ bool __must_check try_grab_page(struct page *page, unsigned int flags)
if (WARN_ON_ONCE(page_ref_count(page) <= 0))
return false;
- if (hpage_pincount_available(page))
- hpage_pincount_add(page, 1);
- else
- refs = GUP_PIN_COUNTING_BIAS;
-
/*
* Similar to try_grab_compound_head(): even if using the
* hpage_pincount_add/_sub() routines, be sure to
* *also* increment the normal page refcount field at least
* once, so that the page really is pinned.
*/
- page_ref_add(page, refs);
+ if (hpage_pincount_available(page)) {
+ page_ref_add(page, 1);
+ hpage_pincount_add(page, 1);
+ } else {
+ page_ref_add(page, GUP_PIN_COUNTING_BIAS);
+ }
mod_node_page_state(page_pgdat(page), NR_FOLL_PIN_ACQUIRED, 1);
}
--
2.34.1