The patch titled
Subject: userfaultfd: use kmap_local_page() in copy_huge_page_from_user()
has been added to the -mm mm-unstable branch. Its filename is
userfaultfd-use-kmap_local_page-in-copy_huge_page_from_user.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/userfaultfd-use-kmap_local_page-in-copy_huge_page_from_user.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: ZhangPeng <zhangpeng362@xxxxxxxxxx>
Subject: userfaultfd: use kmap_local_page() in copy_huge_page_from_user()
Date: Mon, 10 Apr 2023 21:39:28 +0800
kmap() and kmap_atomic() are being deprecated in favor of
kmap_local_page() which is appropriate for any thread local context.[1]
Let's replace the kmap() and kmap_atomic() with kmap_local_page() in
copy_huge_page_from_user(). When allow_pagefault is false, disable page
faults to prevent potential deadlock.[2]
[1] https://lore.kernel.org/all/20220813220034.806698-1-ira.weiny@xxxxxxxxx/
[2] https://lkml.kernel.org/r/20221025220136.2366143-1-ira.weiny@xxxxxxxxx
Link: https://lkml.kernel.org/r/20230410133932.32288-3-zhangpeng362@xxxxxxxxxx
Signed-off-by: ZhangPeng <zhangpeng362@xxxxxxxxxx>
Reviewed-by: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
Cc: Kefeng Wang <wangkefeng.wang@xxxxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Cc: Muchun Song <muchun.song@xxxxxxxxx>
Cc: Nanyong Sun <sunnanyong@xxxxxxxxxx>
Cc: Sidhartha Kumar <sidhartha.kumar@xxxxxxxxxx>
Cc: Vishal Moola (Oracle) <vishal.moola@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/memory.c | 14 ++++++--------
1 file changed, 6 insertions(+), 8 deletions(-)
--- a/mm/memory.c~userfaultfd-use-kmap_local_page-in-copy_huge_page_from_user
+++ a/mm/memory.c
@@ -5866,16 +5866,14 @@ long copy_huge_page_from_user(struct pag
for (i = 0; i < pages_per_huge_page; i++) {
subpage = nth_page(dst_page, i);
- if (allow_pagefault)
- page_kaddr = kmap(subpage);
- else
- page_kaddr = kmap_atomic(subpage);
+ page_kaddr = kmap_local_page(subpage);
+ if (!allow_pagefault)
+ pagefault_disable();
rc = copy_from_user(page_kaddr,
usr_src + i * PAGE_SIZE, PAGE_SIZE);
- if (allow_pagefault)
- kunmap(subpage);
- else
- kunmap_atomic(page_kaddr);
+ if (!allow_pagefault)
+ pagefault_enable();
+ kunmap_local(page_kaddr);
ret_val -= (PAGE_SIZE - rc);
if (rc)
_
Patches currently in -mm which might be from zhangpeng362@xxxxxxxxxx are
mm-madvise-use-vma_lookup-instead-of-find_vma.patch
userfaultfd-convert-mfill_atomic_pte_copy-to-use-a-folio.patch
userfaultfd-use-kmap_local_page-in-copy_huge_page_from_user.patch
userfaultfd-convert-copy_huge_page_from_user-to-copy_folio_from_user.patch
userfaultfd-convert-mfill_atomic_hugetlb-to-use-a-folio.patch
mm-convert-copy_user_huge_page-to-copy_user_large_folio.patch
userfaultfd-convert-mfill_atomic-to-use-a-folio.patch
