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Date:   Sun, 21 May 2023 21:54:25 -0700 (PDT)
From:   Hugh Dickins <hughd@google.com>
To:     Andrew Morton <akpm@linux-foundation.org>
cc:     Mike Kravetz <mike.kravetz@oracle.com>,
        Mike Rapoport <rppt@kernel.org>,
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        linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: [PATCH 05/31] mm/filemap: allow pte_offset_map_lock() to fail
In-Reply-To: <68a97fbe-5c1e-7ac6-72c-7b9c6290b370@google.com>
Message-ID: <3e6d4f8-9f4d-fa7e-304e-1494dddd45b@google.com>
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filemap_map_pages() allow pte_offset_map_lock() to fail; and remove the
pmd_devmap_trans_unstable() check from filemap_map_pmd(), which can safely
return to filemap_map_pages() and let pte_offset_map_lock() discover that.

Signed-off-by: Hugh Dickins <hughd@google.com>
---
 mm/filemap.c | 12 +++++-------
 1 file changed, 5 insertions(+), 7 deletions(-)

diff --git a/mm/filemap.c b/mm/filemap.c
index 28b42ee848a4..9e129ad43e0d 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -3408,13 +3408,6 @@ static bool filemap_map_pmd(struct vm_fault *vmf, struct folio *folio,
 	if (pmd_none(*vmf->pmd))
 		pmd_install(mm, vmf->pmd, &vmf->prealloc_pte);
 
-	/* See comment in handle_pte_fault() */
-	if (pmd_devmap_trans_unstable(vmf->pmd)) {
-		folio_unlock(folio);
-		folio_put(folio);
-		return true;
-	}
-
 	return false;
 }
 
@@ -3501,6 +3494,11 @@ vm_fault_t filemap_map_pages(struct vm_fault *vmf,
 
 	addr = vma->vm_start + ((start_pgoff - vma->vm_pgoff) << PAGE_SHIFT);
 	vmf->pte = pte_offset_map_lock(vma->vm_mm, vmf->pmd, addr, &vmf->ptl);
+	if (!vmf->pte) {
+		folio_unlock(folio);
+		folio_put(folio);
+		goto out;
+	}
 	do {
 again:
 		page = folio_file_page(folio, xas.xa_index);
-- 
2.35.3