librbd/cache/pwl: remove RBD_FEATURE_DIRTY_CACHE check in DiscardRequest

"m_image_ctx.features &&RBD_FEATURE_DIRTY_CACHE" is obviously wrong
because it would pretty much always be true.  However, even if bitwise
AND was used, this check would still be dead because DiscardRequest is
only invoked if RBD_FEATURE_DIRTY_CACHE is enabled:

  int invalidate_cache(ImageCtx *ictx) {
  {
    ...
    // Delete writeback cache if it is not initialized
    if ((!ictx->exclusive_lock ||
         !ictx->exclusive_lock->is_lock_owner()) &&
	ictx->test_features(RBD_FEATURE_DIRTY_CACHE)) {
      C_SaferCond ctx3;
      ictx->plugin_registry->discard(&ctx3);
      r = ctx3.wait();
    }

Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
(cherry picked from commit aee78bbb9d7edd606a8a235c57b2b704d7b94e4c)

diff --git a/src/librbd/cache/pwl/DiscardRequest.cc b/src/librbd/cache/pwl/DiscardRequest.cc
index 69f48d243e801a99e427a50e6758ed4c11365d2b..eaf24137d05c03ea7223fbb38f177452d3939d32 100644 (file)
--- a/src/librbd/cache/pwl/DiscardRequest.cc
+++ b/src/librbd/cache/pwl/DiscardRequest.cc
@@ -117,10 +117,6 @@ void DiscardRequest<I>::remove_feature_bit() {
   CephContext *cct = m_image_ctx.cct;
   ldout(cct, 10) << dendl;
 
-  if (!(m_image_ctx.features &&RBD_FEATURE_DIRTY_CACHE)) {
-    finish();
-    return;
-  }
   uint64_t new_features = m_image_ctx.features & ~RBD_FEATURE_DIRTY_CACHE;
   uint64_t features_mask = RBD_FEATURE_DIRTY_CACHE;
   ldout(cct, 10) << "old_features=" << m_image_ctx.features