linux-kernel - [PATCH v4 1/2] mm/gup: fixup for 9947ea2c1e608e32 "mm/gup: track FOLL

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Date:   Fri,  6 Mar 2020 14:25:36 +0100
From:   Claudio Imbrenda <imbrenda@...ux.ibm.com>
To:     linux-next@...r.kernel.org, akpm@...ux-foundation.org,
        jack@...e.cz, kirill@...temov.name
Cc:     borntraeger@...ibm.com, david@...hat.com, aarcange@...hat.com,
        linux-mm@...ck.org, frankja@...ux.ibm.com, sfr@...b.auug.org.au,
        jhubbard@...dia.com, linux-kernel@...r.kernel.org,
        linux-s390@...r.kernel.org
Subject: [PATCH v4 1/2] mm/gup: fixup for 9947ea2c1e608e32 "mm/gup: track FOLL_PIN pages"

In case pin fails, we need to unpin, a simple put_page will not be enough

fixup for commit 9947ea2c1e608e32 ("mm/gup: track FOLL_PIN pages")

it can be simply squashed in

Signed-off-by: Claudio Imbrenda <imbrenda@...ux.ibm.com>
Reviewed-by: John Hubbard <jhubbard@...dia.com>
---
 mm/gup.c | 46 +++++++++++++++++++++++-----------------------
 1 file changed, 23 insertions(+), 23 deletions(-)

diff --git a/mm/gup.c b/mm/gup.c
index f589299b0d4a..81a95fbe9901 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -116,6 +116,28 @@ static __maybe_unused struct page *try_grab_compound_head(struct page *page,
 	return NULL;
 }
 
+static void put_compound_head(struct page *page, int refs, unsigned int flags)
+{
+	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);
+		else
+			refs *= GUP_PIN_COUNTING_BIAS;
+	}
+
+	VM_BUG_ON_PAGE(page_ref_count(page) < refs, page);
+	/*
+	 * Calling put_page() for each ref is unnecessarily slow. Only the last
+	 * ref needs a put_page().
+	 */
+	if (refs > 1)
+		page_ref_sub(page, refs - 1);
+	put_page(page);
+}
+
 /**
  * try_grab_page() - elevate a page's refcount by a flag-dependent amount
  *
@@ -2134,7 +2156,7 @@ static int gup_pte_range(pmd_t pmd, unsigned long addr, unsigned long end,
 			goto pte_unmap;
 
 		if (unlikely(pte_val(pte) != pte_val(*ptep))) {
-			put_page(head);
+			put_compound_head(head, 1, flags);
 			goto pte_unmap;
 		}
 
@@ -2267,28 +2289,6 @@ static int record_subpages(struct page *page, unsigned long addr,
 	return nr;
 }
 
-static void put_compound_head(struct page *page, int refs, unsigned int flags)
-{
-	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);
-		else
-			refs *= GUP_PIN_COUNTING_BIAS;
-	}
-
-	VM_BUG_ON_PAGE(page_ref_count(page) < refs, page);
-	/*
-	 * Calling put_page() for each ref is unnecessarily slow. Only the last
-	 * ref needs a put_page().
-	 */
-	if (refs > 1)
-		page_ref_sub(page, refs - 1);
-	put_page(page);
-}
-
 #ifdef CONFIG_ARCH_HAS_HUGEPD
 static unsigned long hugepte_addr_end(unsigned long addr, unsigned long end,
 				      unsigned long sz)
-- 
2.24.1