More comments on the patch:

  - typo (double “get”) in the updated buf_LRU_free_page() comments:
   “function returns false, the buf_page_get_get_mutex() might be temporarily”

  - what’s the reason for changing buf_page_t::in_LRU_list to be present
    in release builds? Unless I’m missing something in the current code,
    it is only assigned, but never read in release builds?

  - spurious blank line changes in buf_buddy_relocate(),
    buf_buddy_free_low(), buf_pool_watch_set(), buf_page_get_gen(),
    buf_page_init_for_read(), buf_pool_validate_instance(),
    buf_flush_check_neighbor(), buf_flush_LRU_list_batch(), buf_LRU_drop_page_hash_for_tablespace()
    and innodb_buffer_pool_evict_uncompressed().

  - the following change in buf_block_try_discard_uncompressed() does
    not release block_mutex if buf_LRU_free_page() returns false.

 	bpage = buf_page_hash_get(buf_pool, space, offset);
 
 	if (bpage) {
-		buf_LRU_free_page(bpage, false);
+
+		ib_mutex_t* block_mutex = buf_page_get_mutex(bpage);
+
+		mutex_enter(block_mutex);
+
+		if (buf_LRU_free_page(bpage, false)) {
+
+			mutex_exit(block_mutex);
+			return;
+		}
 	}
 
  - do you really need this change?

@@ -2114,8 +2098,8 @@ buf_page_get_zip(
 		break;
 	case BUF_BLOCK_ZIP_PAGE:
 	case BUF_BLOCK_ZIP_DIRTY:
+		buf_enter_zip_mutex_for_page(bpage);
 		block_mutex = &buf_pool->zip_mutex;
-		mutex_enter(block_mutex);
 		bpage->buf_fix_count++;
 		goto got_block;
 	case BUF_BLOCK_FILE_PAGE:

  - in the following change:

@@ -2721,13 +2707,14 @@ buf_page_get_gen(
 		}
 
 		bpage = &block->page;
+		ut_ad(buf_own_zip_mutex_for_page(bpage));
 
 		if (bpage->buf_fix_count
 		    || buf_page_get_io_fix(bpage) != BUF_IO_NONE) {
 			/* This condition often occurs when the buffer
 			is not buffer-fixed, but I/O-fixed by
 			buf_page_init_for_read(). */
-			mutex_exit(block_mutex);
+			mutex_exit(&buf_pool->zip_mutex);
 wait_until_unfixed:
 			/* The block is buffer-fixed or I/O-fixed.
 			Try again later. */

     is there a reason for replacing block_mutex with zip_mutex? you
     could just assert that block_mutex is zip_mutex next to, or even
     instead of the buf_own_zip_mutex_for_page() call.

  - same comments for this change:

@@ -2737,11 +2724,11 @@ buf_page_get_gen(
 		}
 
 		/* Allocate an uncompressed page. */
-		mutex_exit(block_mutex);
+		mutex_exit(&buf_pool->zip_mutex);
 		block = buf_LRU_get_free_block(buf_pool);
 		ut_a(block);
 
-		buf_pool_mutex_enter(buf_pool);
+		mutex_enter(&buf_pool->LRU_list_mutex);
 
 		/* As we have released the page_hash lock and the
 		block_mutex to allocate an uncompressed page it is

  - in buf_mark_space_corrupt() I see LRU_list_mutex, hash_lock and
    buf_page_get_mutex() being acquired, but only LRU_list_mutex and
    buf_page_get_mutex() being released, i.e. it returns with hash_lock
    acquired?

  - it looks like with the changes in buf_page_io_complete() for io_type
    == BUF_IO_WRITE we don’t set io_fix to BUF_IO_NONE, though we did
    before the changes?

  - more spurious changes:

@@ -475,8 +473,8 @@ buf_flush_insert_sorted_into_flush_list(
 	if (prev_b == NULL) {
 		UT_LIST_ADD_FIRST(list, buf_pool->flush_list, &block->page);
 	} else {
-		UT_LIST_INSERT_AFTER(list, buf_pool->flush_list,
-				     prev_b, &block->page);
+		UT_LIST_INSERT_AFTER(list, buf_pool->flush_list, prev_b,
+				     &block->page);
 	}
 
 	incr_flush_list_size_in_bytes(block, buf_pool);

@@ -573,7 +567,7 @@ buf_flush_ready_for_flush(
 }

and
 
 /********************************************************************//**
-Remove a block from the flush list of modified blocks. */
+Remove a block from the flush list of modified blocks.  */
 UNIV_INTERN
 void
 buf_flush_remove(

and

@@ -1693,7 +1729,7 @@ buf_flush_batch(
 					(if their number does not exceed
 					min_n), otherwise ignored */
 {
-	ulint		count	= 0;
+	ulint	count	= 0;
 
 	ut_ad(flush_type == BUF_FLUSH_LRU || flush_type == BUF_FLUSH_LIST);
 #ifdef UNIV_SYNC_DEBUG

and

@@ -1836,7 +1870,7 @@ buf_flush_wait_batch_end(
 		}
 	} else {
 		thd_wait_begin(NULL, THD_WAIT_DISKIO);
-	os_event_wait(buf_pool->no_flush[type]);
+		os_event_wait(buf_pool->no_flush[type]);
 		thd_wait_end(NULL);
 	}
 }

and

 		if (buf_pool->n_flush[BUF_FLUSH_LRU] > 0
-		   || buf_pool->init_flush[BUF_FLUSH_LRU]) {
+		    || buf_pool->init_flush[BUF_FLUSH_LRU]) {
 
and

@@ -958,10 +1018,10 @@ buf_LRU_free_from_unzip_LRU_list(
 					srv_LRU_scan_depth / 2 blocks. */
 {
 	buf_block_t*	block;
-	ibool 		freed;
+	ibool		freed;
 	ulint		scanned;



  - in the following hunk there’s no really need for the “else” block,
    and a call to mutex_exit() can be moved out of the “if” statement:

@@ -1316,14 +1317,14 @@ buf_flush_try_neighbors(
 
 				buf_flush_page(buf_pool, bpage, flush_type, false);
 				ut_ad(!mutex_own(block_mutex));
-				ut_ad(!buf_pool_mutex_own(buf_pool));
 				count++;
 				continue;
-			} else {
-				mutex_exit(block_mutex);
 			}
+			mutex_exit(block_mutex);
+		} else {
+
+			mutex_exit(block_mutex);
 		}
-		buf_pool_mutex_exit(buf_pool);
 	}
 
 	if (count > 0) {

  - typo in the comments:

+	/* The following call will release the buf_pgae_get_mutex() mutex. */
...
+	As we are not holding LRU list or buf_pgae_get_mutex() mutex therefore