remove backfill_inplace and call to _fillna_prep

Author: simonjayhawkins

pandas/_libs_numba/algos.py

@@ -734,13 +734,6 @@ def _pad_inplace_with_limit(values: np.ndarray, mask: np.ndarray, limit: int) ->
 #     return indexer
 
 
-def backfill_inplace(
-    values: np.ndarray, mask: np.ndarray, limit: int | None = None
-) -> None:
-    _validate_limit(limit)
-    _pad_inplace(values[::-1], mask[::-1], limit)
-
-
 # @cython.boundscheck(False)
 # @cython.wraparound(False)
 # def backfill_2d_inplace(algos_t[:, :] values,

pandas/core/missing.py

@@ -694,15 +694,16 @@ def _fillna_prep(values, mask=None):
 
 
 def _pad_1d(values, limit=None, mask=None):
-    values, mask = _fillna_prep(values, mask)
+    if mask is None:
+        mask = isna(values)
     algos_numba.pad_inplace(values, mask, limit=limit)
     return values
 
 
 def _backfill_1d(values, limit=None, mask=None):
-    values, mask = _fillna_prep(values, mask)
-    algos_numba.backfill_inplace(values, mask, limit=limit)
-    return values
+    if mask is not None:
+        mask = mask[::-1]
+    return _pad_1d(values[::-1], limit, mask)[::-1]
 
 
 def _pad_2d(values, limit=None, mask=None):