[PATCH 4/5] mm: gup: fix potential pgmap refcnt leak in __gup_device_huge()

[Miaohe Lin <linmiaohe@huawei.com>]

When failed to try_grab_page, put_dev_pagemap() is missed. So pgmap
refcnt will leak in this case. Also we remove the check for pgmap
against NULL as it's also checked inside the put_dev_pagemap().

Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Fixes: 3faa52c03f44 ("mm/gup: track FOLL_PIN pages")
---
 mm/gup.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/mm/gup.c b/mm/gup.c
index d7e4507de6b1..8c89e614d4aa 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -2253,14 +2253,14 @@ static int __gup_device_huge(unsigned long pfn, unsigned long addr,
 		pages[*nr] = page;
 		if (unlikely(!try_grab_page(page, flags))) {
 			undo_dev_pagemap(nr, nr_start, flags, pages);
+			put_dev_pagemap(pgmap);
 			return 0;
 		}
 		(*nr)++;
 		pfn++;
 	} while (addr += PAGE_SIZE, addr != end);
 
-	if (pgmap)
-		put_dev_pagemap(pgmap);
+	put_dev_pagemap(pgmap);
 	return 1;
 }
 
-- 
2.23.0