MDEV-24442 Assertion space->referenced() failed in fil_crypt_space_needs_rotation

A race condition between deleting an .ibd file and fil_crypt_thread
marking pages dirty was introduced in
commit 118e258a (part of MDEV-23855).

fil_space_t::acquire_if_not_stopped(): Correctly return false
if the STOPPING flag is set, indicating that any further activity
on the tablespace must be avoided. Also, remove the constant parameter
have_mutex=true and move the function declaration to the same
compilation unit with the only callers.

fil_crypt_flush_space(): Remove an unused variable.

storage/innobase/fil/fil0crypt.cc

@@ -1430,6 +1430,19 @@ static void fil_crypt_return_iops(rotate_thread_t *state, bool wake= true)
 	fil_crypt_update_total_stat(state);
 }
 
+/** Acquire a tablespace reference.
+@return whether a tablespace reference was successfully acquired */
+inline bool fil_space_t::acquire_if_not_stopped()
+{
+  ut_ad(mutex_own(&fil_system.mutex));
+  const uint32_t n= acquire_low();
+  if (UNIV_LIKELY(!(n & (STOPPING | CLOSING))))
+    return true;
+  if (UNIV_UNLIKELY(n & STOPPING))
+    return false;
+  return UNIV_LIKELY(!(n & CLOSING)) || prepare(true);
+}
+
 /** Return the next tablespace from rotation_list.
 @param space   previous tablespace (NULL to start from the start)
 @param recheck whether the removal condition needs to be rechecked after
@@ -1478,7 +1491,7 @@ inline fil_space_t *fil_system_t::keyrotate_next(fil_space_t *space,
   do
   {
     space= &*it;
-    if (space->acquire_if_not_stopped(true))
+    if (space->acquire_if_not_stopped())
       return space;
     if (++it == end)
       return nullptr;
@@ -2007,12 +2020,10 @@ fil_crypt_flush_space(
 	mtr_t mtr;
 	mtr.start();
 
-	dberr_t err;
-
 	if (buf_block_t* block = buf_page_get_gen(
 		    page_id_t(space->id, 0), space->zip_size(),
 		    RW_X_LATCH, NULL, BUF_GET_POSSIBLY_FREED,
-		    __FILE__, __LINE__, &mtr, &err)) {
+		    __FILE__, __LINE__, &mtr)) {
 		mtr.set_named_space(space);
 		crypt_data->write_page0(block, &mtr);
 	}
@@ -2250,7 +2261,7 @@ static void fil_crypt_rotation_list_fill()
 		if (space->purpose != FIL_TYPE_TABLESPACE
 		    || space->is_in_rotation_list
 		    || UT_LIST_GET_LEN(space->chain) == 0
-		    || !space->acquire_if_not_stopped(true)) {
+		    || !space->acquire_if_not_stopped()) {
 			continue;
 		}
 

storage/innobase/include/fil0fil.h

@@ -520,8 +520,9 @@ struct fil_space_t final
   }
 public:
   MY_ATTRIBUTE((warn_unused_result))
-  /** @return whether a tablespace reference was successfully acquired */
-  inline bool acquire_if_not_stopped(bool have_mutex= false);
+  /** Acquire a tablespace reference.
+  @return whether a tablespace reference was successfully acquired */
+  inline bool acquire_if_not_stopped();
 
   MY_ATTRIBUTE((warn_unused_result))
   /** Acquire a tablespace reference for I/O.
@@ -1434,15 +1435,6 @@ inline void fil_space_t::reacquire()
   ut_ad(UT_LIST_GET_FIRST(chain)->is_open());
 }
 
-inline bool fil_space_t::acquire_if_not_stopped(bool have_mutex)
-{
-  ut_ad(mutex_own(&fil_system.mutex) == have_mutex);
-  const uint32_t n= acquire_low();
-  if (UNIV_LIKELY(!(n & (STOPPING | CLOSING))))
-    return true;
-  return UNIV_LIKELY(!(n & CLOSING)) || prepare(have_mutex);
-}
-
 /** Note that operations on the tablespace must stop or can resume */
 inline void fil_space_t::set_stopping(bool stopping)
 {