mm/memory: use kmap_local_page() in __wp_page_copy_user()

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.

Link: https://lkml.kernel.org/r/20231120142418.6977-1-fmdefrancesco@gmail.com
Signed-off-by: Fabio M. De Francesco <fabio.maria.de.francesco@linux.intel.com>
Cc: Ira Weiny <ira.weiny@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/memory.c b/mm/memory.c
index e27e2e5beb3f5175abe4ff47e34ceec9db6ebab0..a8ff3489211bcf66323268cc33762fa07fd60c7e 100644 (file)
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -2841,7 +2841,8 @@ 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);
 
        /*
@@ -2909,7 +2910,8 @@ warn:
 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;