linux-kernel - [PATCH v2] mm/memory: Don't require head page for do_set

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Message-Id: <20240611153216.2794513-1-abrestic@rivosinc.com>
Date: Tue, 11 Jun 2024 08:32:16 -0700
From: Andrew Bresticker <abrestic@...osinc.com>
To: Andrew Morton <akpm@...ux-foundation.org>,
	David Hildenbrand <david@...hat.com>
Cc: linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	Andrew Bresticker <abrestic@...osinc.com>
Subject: [PATCH v2] mm/memory: Don't require head page for do_set_pmd()

The requirement that the head page be passed to do_set_pmd() was added
in commit ef37b2ea08ac ("mm/memory: page_add_file_rmap() ->
folio_add_file_rmap_[pte|pmd]()") and prevents pmd-mapping in the
finish_fault() and filemap_map_pages() paths if the page to be inserted
is anything but the head page for an otherwise suitable vma and pmd-sized
page.

Fixes: ef37b2ea08ac ("mm/memory: page_add_file_rmap() -> folio_add_file_rmap_[pte|pmd]()")
Signed-off-by: Andrew Bresticker <abrestic@...osinc.com>
---
 mm/memory.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/mm/memory.c b/mm/memory.c
index 0f47a533014e..a1fce5ddacb3 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -4614,8 +4614,9 @@ vm_fault_t do_set_pmd(struct vm_fault *vmf, struct page *page)
 	if (!thp_vma_suitable_order(vma, haddr, PMD_ORDER))
 		return ret;
 
-	if (page != &folio->page || folio_order(folio) != HPAGE_PMD_ORDER)
+	if (folio_order(folio) != HPAGE_PMD_ORDER)
 		return ret;
+	page = &folio->page;
 
 	/*
 	 * Just backoff if any subpage of a THP is corrupted otherwise
-- 
2.34.1