From: Zi Yan <ziy@nvidia.com>
Date: Tue, 22 Oct 2024 14:33:40 +0000 (-0400)
Subject: mm-avoid-zeroing-user-movable-page-twice-with-init_on_alloc=1-fix
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=e52b7c34cb8effc8337b415c0d2431b312ea8f1d;p=users%2Fjedix%2Flinux-maple.git

mm-avoid-zeroing-user-movable-page-twice-with-init_on_alloc=1-fix

comment fixes, per David

Link: https://lkml.kernel.org/r/97DB52E1-C594-49B5-9736-89AC302FAB01@nvidia.com
Signed-off-by: Zi Yan <ziy@nvidia.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: "Huang, Ying" <ying.huang@intel.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 8d4ab7cf8039..0f8ea7d98be2 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1165,6 +1165,11 @@ static struct folio *vma_alloc_anon_folio_pmd(struct vm_area_struct *vma,
 	}
 	folio_throttle_swaprate(folio, gfp);
 
+       /*
+	* When a folio is not zeroed during allocation (__GFP_ZERO not used),
+	* folio_zero_user() is used to make sure that the page corresponding
+	* to the faulting address will be hot in the cache after zeroing.
+	*/
 	if (!alloc_zeroed())
 		folio_zero_user(folio, addr);
 	/*
diff --git a/mm/memory.c b/mm/memory.c
index 5c503a4a95a9..68e57b33363b 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -4719,6 +4719,13 @@ static struct folio *alloc_anon_folio(struct vm_fault *vmf)
 				goto next;
 			}
 			folio_throttle_swaprate(folio, gfp);
+			/*
+			 * When a folio is not zeroed during allocation
+			 * (__GFP_ZERO not used), folio_zero_user() is used
+			 * to make sure that the page corresponding to the
+			 * faulting address will be hot in the cache after
+			 * zeroing.
+			 */
 			if (!alloc_zeroed())
 				folio_zero_user(folio, vmf->address);
 			return folio;