From: "Fabio M. De Francesco" <fabio.maria.de.francesco@xxxxxxxxxxxxxxx>
kmap_atomic() has been deprecated in favor of kmap_local_{folio,page}.
Therefore, replace kmap_atomic() with kmap_local_page in
__wp_page_copy_user().
kmap_atomic() disables preemption in !PREEMPT_RT kernels and
unconditionally disables also page-faults. My limited knowledge of the
implementation of __wp_page_copy_user() makes me think that the latter
side effect is still needed here, but kmap_local_page() is implemented
not to disable page-faults.
So, in addition to the conversion to local mapping, add explicit
pagefault_disable() / pagefault_enable() between mapping and un-mapping.
Cc: Ira Weiny <ira.weiny@xxxxxxxxx>
Signed-off-by: Fabio M. De Francesco <fabio.maria.de.francesco@xxxxxxxxxxxxxxx>
---
mm/memory.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/mm/memory.c b/mm/memory.c
index 1f18ed4a5497..0ba63007c580 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -2835,7 +2835,8 @@ static inline int __wp_page_copy_user(struct page *dst, struct page *src,
* just copying from the original user address. If that
* fails, we just zero-fill it. Live with it.
*/
- kaddr = kmap_atomic(dst);
+ kaddr = kmap_local_page(dst);
+ pagefault_disable();
uaddr = (void __user *)(addr & PAGE_MASK);
/*
@@ -2903,7 +2904,8 @@ static inline int __wp_page_copy_user(struct page *dst, struct page *src,
pte_unlock:
if (vmf->pte)
pte_unmap_unlock(vmf->pte, vmf->ptl);
- kunmap_atomic(kaddr);
+ pagefault_enable();
+ kunmap_local(kaddr);
flush_dcache_page(dst);
return ret;
--
2.42.0
