NFS: Convert kmap_atomic() to kmap_local_folio()

kmap_atomic() is deprecated in favor of kmap_local_{folio,page}().

Therefore, replace kmap_atomic() with kmap_local_folio() in
nfs_readdir_folio_array_append().

kmap_atomic() disables page-faults and preemption (the latter only for
!PREEMPT_RT kernels), However, the code within the mapping/un-mapping in
nfs_readdir_folio_array_append() does not depend on the above-mentioned
side effects.

Therefore, a mere replacement of the old API with the new one is all that
is required (i.e., there is no need to explicitly add any calls to
pagefault_disable() and/or preempt_disable()).

Tested with (x)fstests in a QEMU/KVM x86_32 VM, 6GB RAM, booting a kernel
with HIGHMEM64GB enabled.

Cc: Ira Weiny <ira.weiny@intel.com>
Signed-off-by: Fabio M. De Francesco <fmdefrancesco@gmail.com>
Fixes: ec108d3c ("NFS: Convert readdir page array functions to use a folio")
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

fs/nfs/dir.c

@@ -317,7 +317,7 @@ static int nfs_readdir_folio_array_append(struct folio *folio,
 
 	name = nfs_readdir_copy_name(entry->name, entry->len);
 
-	array = kmap_atomic(folio_page(folio, 0));
+	array = kmap_local_folio(folio, 0);
 	if (!name)
 		goto out;
 	ret = nfs_readdir_array_can_expand(array);
@@ -340,7 +340,7 @@ static int nfs_readdir_folio_array_append(struct folio *folio,
 		nfs_readdir_array_set_eof(array);
 out:
 	*cookie = array->last_cookie;
-	kunmap_atomic(array);
+	kunmap_local(array);
 	return ret;
 }