On 2/4/22 11:57, Matthew Wilcox (Oracle) wrote:
It's clearer to call atomic_add() in the callers; the assertions clearly
can't fire there because they're part of the condition for calling
atomic_add().
Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
---
mm/gup.c | 33 +++++++++++----------------------
1 file changed, 11 insertions(+), 22 deletions(-)
Looks nice.
Reviewed-by: John Hubbard <jhubbard@xxxxxxxxxx>
thanks,
--
John Hubbard
NVIDIA
diff --git a/mm/gup.c b/mm/gup.c
index 923a0d44203c..60168a09d52a 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -29,14 +29,6 @@ struct follow_page_context {
unsigned int page_mask;
};
-static void hpage_pincount_add(struct page *page, int refs)
-{
- VM_BUG_ON_PAGE(!hpage_pincount_available(page), page);
- VM_BUG_ON_PAGE(page != compound_head(page), page);
-
- atomic_add(refs, compound_pincount_ptr(page));
-}
-
static void hpage_pincount_sub(struct page *page, int refs)
{
VM_BUG_ON_PAGE(!hpage_pincount_available(page), page);
@@ -151,17 +143,17 @@ __maybe_unused struct page *try_grab_compound_head(struct page *page,
return NULL;
/*
- * When pinning a compound page of order > 1 (which is what
- * hpage_pincount_available() checks for), use an exact count to
- * track it, via hpage_pincount_add/_sub().
+ * When pinning a compound page of order > 1 (which is
+ * what hpage_pincount_available() checks for), use an
+ * exact count to track it.
*
- * However, be sure to *also* increment the normal page refcount
- * field at least once, so that the page really is pinned.
- * That's why the refcount from the earlier
+ * However, be sure to *also* increment the normal page
+ * refcount field at least once, so that the page really
+ * is pinned. That's why the refcount from the earlier
* try_get_compound_head() is left intact.
*/
if (hpage_pincount_available(page))
- hpage_pincount_add(page, refs);
+ atomic_add(refs, compound_pincount_ptr(page));
else
page_ref_add(page, refs * (GUP_PIN_COUNTING_BIAS - 1));
@@ -216,22 +208,19 @@ bool __must_check try_grab_page(struct page *page, unsigned int flags)
if (flags & FOLL_GET)
return try_get_page(page);
else if (flags & FOLL_PIN) {
- int refs = 1;
-
page = compound_head(page);
if (WARN_ON_ONCE(page_ref_count(page) <= 0))
return false;
/*
- * 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.
+ * Similar to try_grab_compound_head(): be sure to *also*
+ * increment the normal page refcount field at least once,
+ * so that the page really is pinned.
*/
if (hpage_pincount_available(page)) {
page_ref_add(page, 1);
- hpage_pincount_add(page, 1);
+ atomic_add(1, compound_pincount_ptr(page));
} else {
page_ref_add(page, GUP_PIN_COUNTING_BIAS);
}
