linux-kernel - [PATCH v1 3/4] smaps: use vm_normal_page_pmd() instead of follow_trans_huge

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Date:   Thu, 27 Jul 2023 23:28:44 +0200
From:   David Hildenbrand <david@...hat.com>
To:     linux-kernel@...r.kernel.org
Cc:     linux-mm@...ck.org, linux-fsdevel@...r.kernel.org,
        David Hildenbrand <david@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        liubo <liubo254@...wei.com>, Peter Xu <peterx@...hat.com>,
        Matthew Wilcox <willy@...radead.org>,
        Hugh Dickins <hughd@...gle.com>,
        Jason Gunthorpe <jgg@...pe.ca>,
        John Hubbard <jhubbard@...dia.com>
Subject: [PATCH v1 3/4] smaps: use vm_normal_page_pmd() instead of follow_trans_huge_pmd()

We really shouldn't be using a GUP-internal helper if it can be avoided,
and avoiding the FOLL_FORCE here is certainly desirable.

Similar to smaps_pte_entry() that uses vm_normal_page(), let's use
vm_normal_page_pmd() -- that didn't exist back when we introduced that
code -- that similarly refuses to return the huge zeropage.

Signed-off-by: David Hildenbrand <david@...hat.com>
---
 fs/proc/task_mmu.c | 7 +------
 1 file changed, 1 insertion(+), 6 deletions(-)

diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 7075ce11dc7d..b8ea270bf68b 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -571,12 +571,7 @@ static void smaps_pmd_entry(pmd_t *pmd, unsigned long addr,
 	bool migration = false;
 
 	if (pmd_present(*pmd)) {
-		/*
-		 * FOLL_DUMP will return -EFAULT on huge zero page
-		 * FOLL_FORCE follow a PROT_NONE mapped page
-		 */
-		page = follow_trans_huge_pmd(vma, addr, pmd,
-					     FOLL_DUMP | FOLL_FORCE);
+		page = vm_normal_page_pmd(vma, addr, *pmd);
 	} else if (unlikely(thp_migration_supported() && is_swap_pmd(*pmd))) {
 		swp_entry_t entry = pmd_to_swp_entry(*pmd);
 
-- 
2.41.0