userfaultfd: use kmap_local_page() in copy_huge_page_from_user()

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/[email protected]/
[2] https://lkml.kernel.org/r/[email protected]

Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: ZhangPeng <[email protected]>
Reviewed-by: Mike Kravetz <[email protected]>
Cc: Kefeng Wang <[email protected]>
Cc: Matthew Wilcox <[email protected]>
Cc: Muchun Song <[email protected]>
Cc: Nanyong Sun <[email protected]>
Cc: Sidhartha Kumar <[email protected]>
Cc: Vishal Moola (Oracle) <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

1 files changed, 6 insertions, 8 deletions

diff --git a/mm/memory.c b/mm/memory.c
index 387226d6094d..808f354bce65 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -5880,16 +5880,14 @@ long copy_huge_page_from_user(struct page *dst_page,
 
 	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)