io_uring: add feature flag for rsrc tags

Add IORING_FEAT_RSRC_TAGS indicating that io_uring supports a bunch of
new IORING_REGISTER operations, in particular
IORING_REGISTER_[FILES[,UPDATE]2,BUFFERS[2,UPDATE]] that support rsrc
tagging, and also indicating implemented dynamic fixed buffer updates.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/9b995d4045b6c6b4ab7510ca124fd25ac2203af7.1623339162.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

fs/io_uring.c

@@ -9676,7 +9676,8 @@ static int io_uring_create(unsigned entries, struct io_uring_params *p,
 			IORING_FEAT_SUBMIT_STABLE | IORING_FEAT_RW_CUR_POS |
 			IORING_FEAT_CUR_PERSONALITY | IORING_FEAT_FAST_POLL |
 			IORING_FEAT_POLL_32BITS | IORING_FEAT_SQPOLL_NONFIXED |
-			IORING_FEAT_EXT_ARG | IORING_FEAT_NATIVE_WORKERS;
+			IORING_FEAT_EXT_ARG | IORING_FEAT_NATIVE_WORKERS |
+			IORING_FEAT_RSRC_TAGS;
 
 	if (copy_to_user(params, p, sizeof(*p))) {
 		ret = -EFAULT;

include/uapi/linux/io_uring.h

@@ -280,6 +280,7 @@ struct io_uring_params {
 #define IORING_FEAT_SQPOLL_NONFIXED	(1U << 7)
 #define IORING_FEAT_EXT_ARG		(1U << 8)
 #define IORING_FEAT_NATIVE_WORKERS	(1U << 9)
+#define IORING_FEAT_RSRC_TAGS		(1U << 10)
 
 /*
  * io_uring_register(2) opcodes and arguments