io_uring: re-arrange struct io_ring_ctx to reduce padding

Nothing major here, just moving a few things around to reduce the
padding. This reduces the size on a non-debug kernel from 1536 to
1472 bytes, saving a full cacheline.

Signed-off-by: Jens Axboe <axboe@kernel.dk>

include/linux/io_uring_types.h

@@ -240,6 +240,7 @@ struct io_ring_ctx {
 		unsigned int		poll_activated: 1;
 		unsigned int		drain_disabled: 1;
 		unsigned int		compat: 1;
+		unsigned int		iowq_limits_set : 1;
 
 		struct task_struct	*submitter_task;
 		struct io_rings		*rings;
@@ -274,10 +275,20 @@ struct io_ring_ctx {
 		 */
 		struct io_rsrc_node	*rsrc_node;
 		atomic_t		cancel_seq;
+
+		/*
+		 * ->iopoll_list is protected by the ctx->uring_lock for
+		 * io_uring instances that don't use IORING_SETUP_SQPOLL.
+		 * For SQPOLL, only the single threaded io_sq_thread() will
+		 * manipulate the list, hence no extra locking is needed there.
+		 */
+		bool			poll_multi_queue;
+		struct io_wq_work_list	iopoll_list;
+
 		struct io_file_table	file_table;
+		struct io_mapped_ubuf	**user_bufs;
 		unsigned		nr_user_files;
 		unsigned		nr_user_bufs;
-		struct io_mapped_ubuf	**user_bufs;
 
 		struct io_submit_state	submit_state;
 
@@ -288,15 +299,6 @@ struct io_ring_ctx {
 		struct io_alloc_cache	apoll_cache;
 		struct io_alloc_cache	netmsg_cache;
 
-		/*
-		 * ->iopoll_list is protected by the ctx->uring_lock for
-		 * io_uring instances that don't use IORING_SETUP_SQPOLL.
-		 * For SQPOLL, only the single threaded io_sq_thread() will
-		 * manipulate the list, hence no extra locking is needed there.
-		 */
-		struct io_wq_work_list	iopoll_list;
-		bool			poll_multi_queue;
-
 		/*
 		 * Any cancelable uring_cmd is added to this list in
 		 * ->uring_cmd() by io_uring_cmd_insert_cancelable()
@@ -343,8 +345,8 @@ struct io_ring_ctx {
 	spinlock_t		completion_lock;
 
 	/* IRQ completion list, under ->completion_lock */
-	struct io_wq_work_list	locked_free_list;
 	unsigned int		locked_free_nr;
+	struct io_wq_work_list	locked_free_list;
 
 	struct list_head	io_buffers_comp;
 	struct list_head	cq_overflow_list;
@@ -366,9 +368,6 @@ struct io_ring_ctx {
 	unsigned int		file_alloc_start;
 	unsigned int		file_alloc_end;
 
-	struct xarray		personalities;
-	u32			pers_next;
-
 	struct list_head	io_buffers_cache;
 
 	/* deferred free list, protected by ->uring_lock */
@@ -389,6 +388,9 @@ struct io_ring_ctx {
 	struct wait_queue_head		rsrc_quiesce_wq;
 	unsigned			rsrc_quiesce;
 
+	u32			pers_next;
+	struct xarray		personalities;
+
 	/* hashed buffered write serialization */
 	struct io_wq_hash		*hash_map;
 
@@ -405,7 +407,6 @@ struct io_ring_ctx {
 
 	/* io-wq management, e.g. thread count */
 	u32				iowq_limits[2];
-	bool				iowq_limits_set;
 
 	struct callback_head		poll_wq_task_work;
 	struct list_head		defer_list;