From 7780d04046a2288ab85d88bedacc60fa4fad9971 Mon Sep 17 00:00:00 2001
From: Hugh Dickins <hughd@google.com>
Date: Thu, 8 Jun 2023 18:17:26 -0700
Subject: mm/pagewalkers: ACTION_AGAIN if pte_offset_map_lock() fails
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Simple walk_page_range() users should set ACTION_AGAIN to retry when
pte_offset_map_lock() fails.

No need to check pmd_trans_unstable(): that was precisely to avoid the
possiblity of calling pte_offset_map() on a racily removed or inserted THP
entry, but such cases are now safely handled inside it.  Likewise there is
no need to check pmd_none() or pmd_bad() before calling it.

Link: https://lkml.kernel.org/r/c77d9d10-3aad-e3ce-4896-99e91c7947f3@google.com
Signed-off-by: Hugh Dickins <hughd@google.com>
Reviewed-by: SeongJae Park <sj@kernel.org> for mm/damon part
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: "Huang, Ying" <ying.huang@intel.com>
Cc: Ira Weiny <ira.weiny@intel.com>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Lorenzo Stoakes <lstoakes@gmail.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Mike Rapoport (IBM) <rppt@kernel.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Naoya Horiguchi <naoya.horiguchi@nec.com>
Cc: Pavel Tatashin <pasha.tatashin@soleen.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Qi Zheng <zhengqi.arch@bytedance.com>
Cc: Ralph Campbell <rcampbell@nvidia.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Song Liu <song@kernel.org>
Cc: Steven Price <steven.price@arm.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Cc: Will Deacon <will@kernel.org>
Cc: Yang Shi <shy828301@gmail.com>
Cc: Yu Zhao <yuzhao@google.com>
Cc: Zack Rusin <zackr@vmware.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---
 mm/damon/vaddr.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

(limited to 'mm/damon/vaddr.c')

diff --git a/mm/damon/vaddr.c b/mm/damon/vaddr.c
index 37994fb6120c..e814f66dfc2e 100644
--- a/mm/damon/vaddr.c
+++ b/mm/damon/vaddr.c
@@ -318,9 +318,11 @@ static int damon_mkold_pmd_entry(pmd_t *pmd, unsigned long addr,
 		spin_unlock(ptl);
 	}
 
-	if (pmd_none(*pmd) || unlikely(pmd_bad(*pmd)))
-		return 0;
 	pte = pte_offset_map_lock(walk->mm, pmd, addr, &ptl);
+	if (!pte) {
+		walk->action = ACTION_AGAIN;
+		return 0;
+	}
 	if (!pte_present(*pte))
 		goto out;
 	damon_ptep_mkold(pte, walk->vma, addr);
@@ -464,9 +466,11 @@ huge_out:
 regular_page:
 #endif	/* CONFIG_TRANSPARENT_HUGEPAGE */
 
-	if (pmd_none(*pmd) || unlikely(pmd_bad(*pmd)))
-		return -EINVAL;
 	pte = pte_offset_map_lock(walk->mm, pmd, addr, &ptl);
+	if (!pte) {
+		walk->action = ACTION_AGAIN;
+		return 0;
+	}
 	if (!pte_present(*pte))
 		goto out;
 	folio = damon_get_folio(pte_pfn(*pte));
-- 
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