[PATCH v2] io_uring: fix sparce warnings about __kernel_rwf_t casts

[PATCH v2] io_uring: fix sparce warnings about __kernel_rwf_t casts

[Vasily Averin]

sparse generates follwong warnings:
fs/io_uring.c: note: in included file (through include/trace/perf.h,
include/trace/define_trace.h, include/trace/events/io_uring.h):
./include/trace/events/io_uring.h:488:1: sparse:
 warning: incorrect type in assignment (different base types)
    expected unsigned int [usertype] op_flags
    got restricted __kernel_rwf_t const [usertype] rw_flags
fs/io_uring.c:3164:23: sparse:
 warning: incorrect type in assignment (different base types)
    expected unsigned int [usertype] flags
    got restricted __kernel_rwf_t
fs/io_uring.c:3769:48: sparse:
 warning: incorrect type in argument 2 (different base types)
    expected restricted __kernel_rwf_t [usertype] flags
    got unsigned int [usertype] flags

__kernel_rwf_t type is bitwise and requires __force attribute for casts.

To fix the warnings, the patch changes the type of fields in the
corresponding structures: poll32_events and rw_flags are neighbours
in the same union.

Signed-off-by: Vasily Averin <vvs@openvz.org>
---
v2: updated according to comments by Christoph Hellwig
---
 fs/io_uring.c                   | 2 +-
 include/trace/events/io_uring.h | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 91de361ea9ab..e2a40c58654c 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -585,7 +585,7 @@ struct io_rw {
 	struct kiocb			kiocb;
 	u64				addr;
 	u32				len;
-	u32				flags;
+	rwf_t				flags;
 };
 
 struct io_connect {
diff --git a/include/trace/events/io_uring.h b/include/trace/events/io_uring.h
index cddf5b6fbeb4..34839f30caee 100644
--- a/include/trace/events/io_uring.h
+++ b/include/trace/events/io_uring.h
@@ -520,7 +520,7 @@ TRACE_EVENT(io_uring_req_failed,
 		__entry->off		= sqe->off;
 		__entry->addr		= sqe->addr;
 		__entry->len		= sqe->len;
-		__entry->op_flags	= sqe->rw_flags;
+		__entry->op_flags	= sqe->poll32_events;
 		__entry->buf_index	= sqe->buf_index;
 		__entry->personality	= sqe->personality;
 		__entry->file_index	= sqe->file_index;
-- 
2.31.1

Re: [PATCH v2] io_uring: fix sparce warnings about __kernel_rwf_t casts

[Christoph Hellwig]

On Wed, May 18, 2022 at 12:20:46PM +0300, Vasily Averin wrote:
> __kernel_rwf_t type is bitwise and requires __force attribute for casts.
> 
> To fix the warnings, the patch changes the type of fields in the
> corresponding structures: poll32_events and rw_flags are neighbours
> in the same union.

Jens actually picked up a series from me that picked up most of this,
except for this hunk:

> index cddf5b6fbeb4..34839f30caee 100644
> --- a/include/trace/events/io_uring.h
> +++ b/include/trace/events/io_uring.h
> @@ -520,7 +520,7 @@ TRACE_EVENT(io_uring_req_failed,
>  		__entry->off		= sqe->off;
>  		__entry->addr		= sqe->addr;
>  		__entry->len		= sqe->len;
> -		__entry->op_flags	= sqe->rw_flags;
> +		__entry->op_flags	= sqe->poll32_events;
>  		__entry->buf_index	= sqe->buf_index;
>  		__entry->personality	= sqe->personality;
>  		__entry->file_index	= sqe->file_index;

For which I did not see a warning even if it looks real to me.
But this union with basically a lot of __u32s here looks pretty
strange to start with to me.

Re: [PATCH v2] io_uring: fix sparce warnings about __kernel_rwf_t casts

[Jens Axboe]

On 5/19/22 1:03 AM, Christoph Hellwig wrote:
>> index cddf5b6fbeb4..34839f30caee 100644
>> --- a/include/trace/events/io_uring.h
>> +++ b/include/trace/events/io_uring.h
>> @@ -520,7 +520,7 @@ TRACE_EVENT(io_uring_req_failed,
>>  		__entry->off		= sqe->off;
>>  		__entry->addr		= sqe->addr;
>>  		__entry->len		= sqe->len;
>> -		__entry->op_flags	= sqe->rw_flags;
>> +		__entry->op_flags	= sqe->poll32_events;
>>  		__entry->buf_index	= sqe->buf_index;
>>  		__entry->personality	= sqe->personality;
>>  		__entry->file_index	= sqe->file_index;
> 
> For which I did not see a warning even if it looks real to me.
> But this union with basically a lot of __u32s here looks pretty
> strange to start with to me.

Vasily, if this is still causing unnecessary sparse spews, please send a
revised one against the current branch.

The union is the per-op flags. The requests that use them have a member
in there, either one can be used for printing it obviously.

-- 
Jens Axboe

[PATCH v3] io_uring: fix incorrect __kernel_rwf_t cast

[Vasily Averin]

Currently 'make C=1 fs/io_uring.o' generates sparse warning:

  CHECK   fs/io_uring.c
fs/io_uring.c: note: in included file (through
include/trace/trace_events.h, include/trace/define_trace.h, i
nclude/trace/events/io_uring.h):
./include/trace/events/io_uring.h:488:1:
 warning: incorrect type in assignment (different base types)
    expected unsigned int [usertype] op_flags
    got restricted __kernel_rwf_t const [usertype] rw_flags

This happen on cast of sqe->rw_flags which is defined as __kernel_rwf_t,
this type is bitwise and requires __force attribute for any casts.
However rw_flags is a member of the union, and its access can be safely
replaced by using of its neighbours, so let's use poll32_events to fix
the sparse warning.

Signed-off-by: Vasily Averin <vvs@openvz.org>
---
v3:
  1) fix only hunk in TRACE_EVENT(io_uring_req_failed),
     rest ones was fixed by Christoph Hellwig already.
  2) updated patch description

v2: updated according to comments by Christoph Hellwig

---
 include/trace/events/io_uring.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/trace/events/io_uring.h b/include/trace/events/io_uring.h
index 80d2588a090c..6ba87a290a24 100644
--- a/include/trace/events/io_uring.h
+++ b/include/trace/events/io_uring.h
@@ -520,7 +520,7 @@ TRACE_EVENT(io_uring_req_failed,
 		__entry->off		= sqe->off;
 		__entry->addr		= sqe->addr;
 		__entry->len		= sqe->len;
-		__entry->op_flags	= sqe->rw_flags;
+		__entry->op_flags	= sqe->poll32_events;
 		__entry->buf_index	= sqe->buf_index;
 		__entry->personality	= sqe->personality;
 		__entry->file_index	= sqe->file_index;
-- 
2.31.1

Re: [PATCH v3] io_uring: fix incorrect __kernel_rwf_t cast

[Jens Axboe]

On Thu, 19 May 2022 17:30:49 +0300, Vasily Averin wrote:
> Currently 'make C=1 fs/io_uring.o' generates sparse warning:
> 
>   CHECK   fs/io_uring.c
> fs/io_uring.c: note: in included file (through
> include/trace/trace_events.h, include/trace/define_trace.h, i
> nclude/trace/events/io_uring.h):
> ./include/trace/events/io_uring.h:488:1:
>  warning: incorrect type in assignment (different base types)
>     expected unsigned int [usertype] op_flags
>     got restricted __kernel_rwf_t const [usertype] rw_flags
> 
> [...]

Applied, thanks!

[1/1] io_uring: fix incorrect __kernel_rwf_t cast
      commit: 0e7579ca732a39cc377e17509dda9bfc4f6ba78e

Best regards,
-- 
Jens Axboe