2020-02-06 04:58:18

by Randy Dunlap

Subject: [PATCH] io_uring: fix 1-bit bitfields to be unsigned

From: Randy Dunlap <[email protected]>

Make bitfields of size 1 bit be unsigned (since there is no room
for the sign bit).
This clears up the sparse warnings:

CHECK ../fs/io_uring.c
../fs/io_uring.c:207:50: error: dubious one-bit signed bitfield
../fs/io_uring.c:208:55: error: dubious one-bit signed bitfield
../fs/io_uring.c:209:63: error: dubious one-bit signed bitfield
../fs/io_uring.c:210:54: error: dubious one-bit signed bitfield
../fs/io_uring.c:211:57: error: dubious one-bit signed bitfield

Found by sight and then verified with sparse.

Fixes: 69b3e546139a ("io_uring: change io_ring_ctx bool fields into bit fields")
Signed-off-by: Randy Dunlap <[email protected]>
Cc: Jens Axboe <[email protected]>
Cc: [email protected]
---
fs/io_uring.c | 10 +++++-----
1 file changed, 5 insertions(+), 5 deletions(-)

--- linux-next-20200205.orig/fs/io_uring.c
+++ linux-next-20200205/fs/io_uring.c
@@ -204,11 +204,11 @@ struct io_ring_ctx {

struct {
unsigned int flags;
- int compat: 1;
- int account_mem: 1;
- int cq_overflow_flushed: 1;
- int drain_next: 1;
- int eventfd_async: 1;
+ unsigned int compat: 1;
+ unsigned int account_mem: 1;
+ unsigned int cq_overflow_flushed: 1;
+ unsigned int drain_next: 1;
+ unsigned int eventfd_async: 1;

/*
* Ring buffer of indices into array of io_uring_sqe, which is

2020-02-06 20:43:28

by Jens Axboe

Subject: Re: [PATCH] io_uring: fix 1-bit bitfields to be unsigned

On 2/5/20 9:57 PM, Randy Dunlap wrote:
> From: Randy Dunlap <[email protected]>
>
> Make bitfields of size 1 bit be unsigned (since there is no room
> for the sign bit).
> This clears up the sparse warnings:
>
> CHECK ../fs/io_uring.c
> ../fs/io_uring.c:207:50: error: dubious one-bit signed bitfield
> ../fs/io_uring.c:208:55: error: dubious one-bit signed bitfield
> ../fs/io_uring.c:209:63: error: dubious one-bit signed bitfield
> ../fs/io_uring.c:210:54: error: dubious one-bit signed bitfield
> ../fs/io_uring.c:211:57: error: dubious one-bit signed bitfield
>
> Found by sight and then verified with sparse.

Always thought those were pretty silly, it's not like this change is
suddenly going to make:

if (ctx->compat < 0)

be anymore valid (or invalid) than they already are. We also have
cases of:

bool foo:1;

does sparse warn about those?

--
Jens Axboe