Bump flash-attn to v2.0.4 (#816)

* Bump flash-attn to v2.0.4

* flash-attn v2.0.3 fixed this issue

* prompt user to update submodules again if they forgot to use --recursive

* fix for latest flash-attn function signatures

setup.py

@@ -143,13 +143,13 @@ def get_flash_attention_extensions(cuda_version: int, extra_compile_args):
         nvcc_windows_flags = ["-Xcompiler", "/permissive-"]
 
     flash_root = os.path.join(this_dir, "third_party", "flash-attention")
-    if not os.path.exists(flash_root):
+    cutlass_inc = os.path.join(flash_root, "csrc", "cutlass", "include")
+    if not os.path.exists(flash_root) or not os.path.exists(cutlass_inc):
         raise RuntimeError(
             "flashattention submodule not found. Did you forget "
             "to run `git submodule update --init --recursive` ?"
         )
 
-    flash_root = os.path.join(this_dir, "third_party", "flash-attention")
     sources = ["csrc/flash_attn/flash_api.cpp"]
     for f in glob.glob(os.path.join(flash_root, "csrc", "flash_attn", "src", "*.cu")):
         sources.append(str(Path(f).relative_to(flash_root)))

xformers/ops/fmha/flash.py

@@ -67,6 +67,7 @@ def _flash_fwd(
             out_padded,
             softmax_lse,
             p,
+            rng_state,
         ) = _C_flashattention.varlen_fwd(
             query,
             key,
@@ -83,7 +84,7 @@ def _flash_fwd(
             return_softmax,
             None,
         )
-        return out, softmax_lse, None
+        return out, softmax_lse, rng_state
 
     def _flash_bwd(
         grad,
@@ -123,6 +124,7 @@ def _flash_bwd(
             False,  # zero_tensors
             causal,
             None,
+            rng_state,
         )
         return dq
 
@@ -302,18 +304,6 @@ class BwOp(AttentionBwOpBase):
 
     MAX_HEADDIM_SM8x = 192
 
-    @classmethod
-    def shape_not_supported_reasons(
-        cls, Mq: int, Mkv: int, K: int, Kv: int
-    ) -> List[str]:
-        reasons = super().shape_not_supported_reasons(Mq, Mkv, K, Kv)
-        if (Mq % 128) or (Mkv % 128):
-            reasons.append(
-                "flashv2 beta: BW is incorrect when seqlen is not aligned on 128 "
-                "(https://github.com/Dao-AILab/flash-attention/issues/334)"
-            )
-        return reasons
-
     @classmethod
     def not_supported_reasons(cls, d: Inputs) -> List[str]:
         reasons = super(BwOp, cls).not_supported_reasons(d)