[PATCH 1/1] io_uring: compile out compat param passing

[PATCH 1/1] io_uring: compile out compat param passing

[Pavel Begunkov]

Even when COMPAT is compiled out, we still have to pass
ctx->compat to __import_iovec(). Replace the read with an indirection
with a constant when the kernel doesn't support compat.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
---
 io_uring/io_uring.h | 5 +++++
 io_uring/rw.c       | 4 ++--
 2 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/io_uring/io_uring.h b/io_uring/io_uring.h
index 650f81dac5d0..da71067a10bc 100644
--- a/io_uring/io_uring.h
+++ b/io_uring/io_uring.h
@@ -147,6 +147,11 @@ static inline void io_lockdep_assert_cq_locked(struct io_ring_ctx *ctx)
 #endif
 }
 
+static inline bool io_is_compat(struct io_ring_ctx *ctx)
+{
+	return IS_ENABLED(CONFIG_COMPAT) && ctx->compat;
+}
+
 static inline void io_req_task_work_add(struct io_kiocb *req)
 {
 	__io_req_task_work_add(req, 0);
diff --git a/io_uring/rw.c b/io_uring/rw.c
index 16f12f94943f..c3849a370a2e 100644
--- a/io_uring/rw.c
+++ b/io_uring/rw.c
@@ -75,7 +75,7 @@ static int io_iov_buffer_select_prep(struct io_kiocb *req)
 		return -EINVAL;
 
 #ifdef CONFIG_COMPAT
-	if (req->ctx->compat)
+	if (io_is_compat(req->ctx))
 		return io_iov_compat_buffer_select_prep(rw);
 #endif
 
@@ -120,7 +120,7 @@ static int __io_import_iovec(int ddir, struct io_kiocb *req,
 		nr_segs = 1;
 	}
 	ret = __import_iovec(ddir, buf, sqe_len, nr_segs, &iov, &io->iter,
-				req->ctx->compat);
+				io_is_compat(req->ctx));
 	if (unlikely(ret < 0))
 		return ret;
 	if (iov) {
-- 
2.48.1

Re: [PATCH 1/1] io_uring: compile out compat param passing

[Anuj gupta]

>  #ifdef CONFIG_COMPAT
> -       if (req->ctx->compat)
> +       if (io_is_compat(req->ctx))
>                 return io_iov_compat_buffer_select_prep(rw);
>  #endif

Should the #ifdef CONFIG_COMPAT be removed here since io_is_compat() already
accounts for it?

> @@ -120,7 +120,7 @@ static int __io_import_iovec(int ddir, struct io_kiocb *req,
>                 nr_segs = 1;
>         }
>         ret = __import_iovec(ddir, buf, sqe_len, nr_segs, &iov, &io->iter,
> -                               req->ctx->compat);
> +                               io_is_compat(req->ctx));

Should we also update other places that use ctx->compat (e.g., rsrc.c, net.c,
uring_cmd.c) to use the new io_is_compat() helper for consistency?

Re: [PATCH 1/1] io_uring: compile out compat param passing

[Pavel Begunkov]

On 2/24/25 02:56, Anuj gupta wrote:
>>   #ifdef CONFIG_COMPAT
>> -       if (req->ctx->compat)
>> +       if (io_is_compat(req->ctx))
>>                  return io_iov_compat_buffer_select_prep(rw);
>>   #endif
> 
> Should the #ifdef CONFIG_COMPAT be removed here since io_is_compat() already
> accounts for it?

We can if same is done for io_iov_compat_buffer_select_prep() and
we can prove it doesn't use anything compiled out for !COMPAT (which
seems so).

  
>> @@ -120,7 +120,7 @@ static int __io_import_iovec(int ddir, struct io_kiocb *req,
>>                  nr_segs = 1;
>>          }
>>          ret = __import_iovec(ddir, buf, sqe_len, nr_segs, &iov, &io->iter,
>> -                               req->ctx->compat);
>> +                               io_is_compat(req->ctx));
> 
> Should we also update other places that use ctx->compat (e.g., rsrc.c, net.c,
> uring_cmd.c) to use the new io_is_compat() helper for consistency?

That would be a wider messier change split in multiple patches, which
I was thinking to avoid. This patch is a good first step, and once
merged future changes can be made independently.

Let me see what I can do, but I don't want touching rsrc.c for now
to avoid unnecessary changes. And then more can be done to get more
code out of ifdef and let the compiler optimise it out.

-- 
Pavel Begunkov