io_uring: add REQ_F_APOLL_MULTISHOT for requests

Add a flag to indicate multishot mode for fast poll. currently only
accept use it, but there may be more operations leveraging it in the
future. Also add a mask IO_APOLL_MULTI_POLLED which stands for
REQ_F_APOLL_MULTI | REQ_F_POLLED, to make the code short and cleaner.

Signed-off-by: Hao Xu <howeyxu@tencent.com>
Link: https://lore.kernel.org/r/20220514142046.58072-3-haoxu.linux@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Author: Hao Xu

fs/io_uring.c

@@ -116,6 +116,8 @@
 #define IO_REQ_CLEAN_SLOW_FLAGS (REQ_F_REFCOUNT | REQ_F_LINK | REQ_F_HARDLINK |\
 				 IO_REQ_CLEAN_FLAGS)
 
+#define IO_APOLL_MULTI_POLLED (REQ_F_APOLL_MULTISHOT | REQ_F_POLLED)
+
 #define IO_TCTX_REFS_CACHE_NR	(1U << 10)
 
 struct io_uring {
@@ -812,6 +814,7 @@ enum {
 	REQ_F_SINGLE_POLL_BIT,
 	REQ_F_DOUBLE_POLL_BIT,
 	REQ_F_PARTIAL_IO_BIT,
+	REQ_F_APOLL_MULTISHOT_BIT,
 	/* keep async read/write and isreg together and in order */
 	REQ_F_SUPPORT_NOWAIT_BIT,
 	REQ_F_ISREG_BIT,
@@ -876,6 +879,8 @@ enum {
 	REQ_F_DOUBLE_POLL	= BIT(REQ_F_DOUBLE_POLL_BIT),
 	/* request has already done partial IO */
 	REQ_F_PARTIAL_IO	= BIT(REQ_F_PARTIAL_IO_BIT),
+	/* fast poll multishot mode */
+	REQ_F_APOLL_MULTISHOT	= BIT(REQ_F_APOLL_MULTISHOT_BIT),
 };
 
 struct async_poll {