linux-kernel - [PATCH 11/75] mm/gup: Remove hpage_pincount

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Date:   Fri,  4 Feb 2022 19:57:48 +0000
From:   "Matthew Wilcox (Oracle)" <willy@...radead.org>
To:     linux-mm@...ck.org
Cc:     "Matthew Wilcox (Oracle)" <willy@...radead.org>,
        linux-kernel@...r.kernel.org, Christoph Hellwig <hch@....de>,
        John Hubbard <jhubbard@...dia.com>,
        Jason Gunthorpe <jgg@...dia.com>,
        William Kucharski <william.kucharski@...cle.com>
Subject: [PATCH 11/75] mm/gup: Remove hpage_pincount_sub()

Move the assertion (and correct it to be a cheaper variant),
and inline the atomic_sub() operation.

Signed-off-by: Matthew Wilcox (Oracle) <willy@...radead.org>
Reviewed-by: Christoph Hellwig <hch@....de>
Reviewed-by: John Hubbard <jhubbard@...dia.com>
Reviewed-by: Jason Gunthorpe <jgg@...dia.com>
Reviewed-by: William Kucharski <william.kucharski@...cle.com>
---
 mm/gup.c | 13 +++----------
 1 file changed, 3 insertions(+), 10 deletions(-)

diff --git a/mm/gup.c b/mm/gup.c
index 60168a09d52a..af623a139995 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_sub(struct page *page, int refs)
-{
-	VM_BUG_ON_PAGE(!hpage_pincount_available(page), page);
-	VM_BUG_ON_PAGE(page != compound_head(page), page);
-
-	atomic_sub(refs, compound_pincount_ptr(page));
-}
-
 /* Equivalent to calling put_page() @refs times. */
 static void put_page_refs(struct page *page, int refs)
 {
@@ -169,12 +161,13 @@ __maybe_unused struct page *try_grab_compound_head(struct page *page,
 
 static void put_compound_head(struct page *page, int refs, unsigned int flags)
 {
+	VM_BUG_ON_PAGE(PageTail(page), page);
+
 	if (flags & FOLL_PIN) {
 		mod_node_page_state(page_pgdat(page), NR_FOLL_PIN_RELEASED,
 				    refs);
-
 		if (hpage_pincount_available(page))
-			hpage_pincount_sub(page, refs);
+			atomic_sub(refs, compound_pincount_ptr(page));
 		else
 			refs *= GUP_PIN_COUNTING_BIAS;
 	}
-- 
2.34.1