From: Fabio De Francesco <[email protected]>
kmap_atomic() has been deprecated in favor of kmap_local_page().
Therefore, replace kmap_atomic() with kmap_local_page() in
memcmp_pages().
kmap_atomic() is implemented like a kmap_local_page() which also
disables page-faults and preemption (the latter only in !PREEMPT_RT
kernels). The kernel virtual addresses returned by these two API are
only valid in the context of the callers (i.e., they cannot be handed to
other threads).
With kmap_local_page() the mappings are per thread and CPU local like
in kmap_atomic(); however, they can handle page-faults and can be called
from any context (including interrupts). The tasks that call
kmap_local_page() can be preempted and, when they are scheduled to run
again, the kernel virtual addresses are restored and are still valid.
In memcmp_pages(), the block of code between the mapping and un-mapping
does not depend on the above-mentioned side effects of kmap_aatomic(), so
that mere replacements of the old API with the new one is all that is
required (i.e., there is no need to explicitly call pagefault_disable()
and/or preempt_disable()).
Cc: Ira Weiny <[email protected]>
Signed-off-by: Fabio M. De Francesco <[email protected]>
---
mm/util.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/mm/util.c b/mm/util.c
index 744b4d7e3fae..5a6a9802583b 100644
--- a/mm/util.c
+++ b/mm/util.c
@@ -1047,11 +1047,11 @@ int __weak memcmp_pages(struct page *page1, struct page *page2)
char *addr1, *addr2;
int ret;
- addr1 = kmap_atomic(page1);
- addr2 = kmap_atomic(page2);
+ addr1 = kmap_local_page(page1);
+ addr2 = kmap_local_page(page2);
ret = memcmp(addr1, addr2, PAGE_SIZE);
- kunmap_atomic(addr2);
- kunmap_atomic(addr1);
+ kunmap_local(addr2);
+ kunmap_local(addr1);
return ret;
}
--
2.42.0