[PATCH 2/3] mm/gup: small refactoring: simplify try_grab_page()

From: John Hubbard <jhubbard@nvidia.com>
To: Andrew Morton <akpm@linux-foundation.org>,
	Matthew Wilcox <willy@infradead.org>
Cc: LKML <linux-kernel@vger.kernel.org>, <linux-mm@kvack.org>,
	John Hubbard <jhubbard@nvidia.com>
Subject: [PATCH 2/3] mm/gup: small refactoring: simplify try_grab_page()
Date: Sun, 8 Aug 2021 16:50:17 -0700	[thread overview]
Message-ID: <20210808235018.1924918-3-jhubbard@nvidia.com> (raw)
In-Reply-To: <20210808235018.1924918-1-jhubbard@nvidia.com>

try_grab_page() does the same thing as try_grab_compound_head(...,
refs=1, ...), just with a different API. So there is a lot of code
duplication there.

Change try_grab_page() to call try_grab_compound_head(), while keeping
the API contract identical for callers.

Signed-off-by: John Hubbard <jhubbard@nvidia.com>
---
 mm/gup.c | 29 ++---------------------------
 1 file changed, 2 insertions(+), 27 deletions(-)

diff --git a/mm/gup.c b/mm/gup.c
index 5cb18b62921c..4be6f060fa0b 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -203,33 +203,8 @@ static void put_compound_head(struct page *page, int refs, unsigned int flags)
  */
 bool __must_check try_grab_page(struct page *page, unsigned int flags)
 {
-	WARN_ON_ONCE((flags & (FOLL_GET | FOLL_PIN)) == (FOLL_GET | FOLL_PIN));
-
-	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;
-
-		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);
-
-		mod_node_page_state(page_pgdat(page), NR_FOLL_PIN_ACQUIRED, 1);
-	}
+	if (flags & (FOLL_GET | FOLL_PIN))
+		return try_grab_compound_head(page, 1, flags) != NULL;
 
 	return true;
 }
-- 
2.32.0

