2021-10-25 18:21:13

by Qian Cai

Subject: [PATCH] io_uring: fix a GCC warning in wq_list_for_each()

fs/io_uring.c: In function '__io_submit_flush_completions':
fs/io_uring.c:2367:33: warning: variable 'prev' set but not used
[-Wunused-but-set-variable]
2367 | struct io_wq_work_node *node, *prev;
| ^~~~

Fixed it by open-coded the wq_list_for_each() without an unused previous
node pointer.

Fixes: 6f33b0bc4ea4 ("io_uring: use slist for completion batching")
Signed-off-by: Qian Cai <[email protected]>
---
fs/io_uring.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 23641d9e0871..b8968bd43e3f 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -2361,11 +2361,11 @@ static void io_free_batch_list(struct io_ring_ctx *ctx,
static void __io_submit_flush_completions(struct io_ring_ctx *ctx)
__must_hold(&ctx->uring_lock)
{
- struct io_wq_work_node *node, *prev;
+ struct io_wq_work_node *node;
struct io_submit_state *state = &ctx->submit_state;

spin_lock(&ctx->completion_lock);
- wq_list_for_each(node, prev, &state->compl_reqs) {
+ for (node = state->compl_reqs.first; node; node = node->next) {
struct io_kiocb *req = container_of(node, struct io_kiocb,
comp_list);

--
2.30.2

2021-10-27 21:23:00

by Pavel Begunkov

Subject: Re: [PATCH] io_uring: fix a GCC warning in wq_list_for_each()

On 10/25/21 15:59, Qian Cai wrote:
> fs/io_uring.c: In function '__io_submit_flush_completions':
> fs/io_uring.c:2367:33: warning: variable 'prev' set but not used
> [-Wunused-but-set-variable]
> 2367 | struct io_wq_work_node *node, *prev;
> | ^~~~
>
> Fixed it by open-coded the wq_list_for_each() without an unused previous
> node pointer.

That's intentional, the var is optimised out and it's better to
not hand code it (if possible).


> Fixes: 6f33b0bc4ea4 ("io_uring: use slist for completion batching")
> Signed-off-by: Qian Cai <[email protected]>
> ---
> fs/io_uring.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/fs/io_uring.c b/fs/io_uring.c
> index 23641d9e0871..b8968bd43e3f 100644
> --- a/fs/io_uring.c
> +++ b/fs/io_uring.c
> @@ -2361,11 +2361,11 @@ static void io_free_batch_list(struct io_ring_ctx *ctx,
> static void __io_submit_flush_completions(struct io_ring_ctx *ctx)
> __must_hold(&ctx->uring_lock)
> {
> - struct io_wq_work_node *node, *prev;
> + struct io_wq_work_node *node;
> struct io_submit_state *state = &ctx->submit_state;
>
> spin_lock(&ctx->completion_lock);
> - wq_list_for_each(node, prev, &state->compl_reqs) {
> + for (node = state->compl_reqs.first; node; node = node->next) {
> struct io_kiocb *req = container_of(node, struct io_kiocb,
> comp_list);
>
>

--
Pavel Begunkov

2021-10-27 21:30:57

by Qian Cai

Subject: Re: [PATCH] io_uring: fix a GCC warning in wq_list_for_each()

On 10/27/21 5:56 AM, Pavel Begunkov wrote:
> On 10/25/21 15:59, Qian Cai wrote:
>> fs/io_uring.c: In function '__io_submit_flush_completions':
>> fs/io_uring.c:2367:33: warning: variable 'prev' set but not used
>> [-Wunused-but-set-variable]
>>   2367 |  struct io_wq_work_node *node, *prev;
>>        |                                 ^~~~
>>
>> Fixed it by open-coded the wq_list_for_each() without an unused previous
>> node pointer.
>
> That's intentional, the var is optimised out and it's better to
> not hand code it (if possible).

Yes, this is pretty minor. Not going to insist if people don't like for
some reasons.