io_uring: conditional ->async_data allocation

There are opcodes that need ->async_data only in some cases and
allocation it unconditionally may hurt performance. Add an option to
opdef to make move the allocation part from the core io_uring to opcode
specific code.
Note, we can't just set opdef->async_size to zero because there are
other helpers that rely on it, e.g. io_alloc_async_data().

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/9dc62be9e88dd0ed63c48365340e8922d2498293.1661342812.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c
index ebfdb22..7761627 100644 (file)
--- a/io_uring/io_uring.c
+++ b/io_uring/io_uring.c
@@ -1450,9 +1450,10 @@ int io_req_prep_async(struct io_kiocb *req)
                return 0;
        if (WARN_ON_ONCE(req_has_async_data(req)))
                return -EFAULT;
-       if (io_alloc_async_data(req))
-               return -EAGAIN;
-
+       if (!io_op_defs[req->opcode].manual_alloc) {
+               if (io_alloc_async_data(req))
+                       return -EAGAIN;
+       }
        return def->prep_async(req);
 }
 

diff --git a/io_uring/opdef.h b/io_uring/opdef.h
index ece8ed4..763c6e5 100644 (file)
--- a/io_uring/opdef.h
+++ b/io_uring/opdef.h
@@ -25,6 +25,8 @@ struct io_op_def {
        unsigned                ioprio : 1;
        /* supports iopoll */
        unsigned                iopoll : 1;
+       /* opcode specific path will handle ->async_data allocation if needed */
+       unsigned                manual_alloc : 1;
        /* size of async data needed, if any */
        unsigned short          async_size;