diff mbox series

[-next,1/1] percpu: cleanup invalid assignment to err in pcpu_alloc

Message ID 20221204031430.662169-1-mawupeng1@huawei.com (mailing list archive)
State New
Headers show
Series [-next,1/1] percpu: cleanup invalid assignment to err in pcpu_alloc | expand

Commit Message

mawupeng Dec. 4, 2022, 3:14 a.m. UTC
From: Ma Wupeng <mawupeng1@huawei.com>

Assignment to err if is_atomic is true will never be used since warn
message can only be shown if is_atomic is false after label fail. So drop
it.

Signed-off-by: Ma Wupeng <mawupeng1@huawei.com>
---
 mm/percpu.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

Comments

Baoquan He Dec. 4, 2022, 12:11 p.m. UTC | #1
On 12/04/22 at 11:14am, Wupeng Ma wrote:
> From: Ma Wupeng <mawupeng1@huawei.com>
> 
> Assignment to err if is_atomic is true will never be used since warn
> message can only be shown if is_atomic is false after label fail. So drop
> it.
> 
> Signed-off-by: Ma Wupeng <mawupeng1@huawei.com>
> ---
>  mm/percpu.c | 4 +---
>  1 file changed, 1 insertion(+), 3 deletions(-)
> 
> diff --git a/mm/percpu.c b/mm/percpu.c
> index acd78da0493b..df86d79325b2 100644
> --- a/mm/percpu.c
> +++ b/mm/percpu.c
> @@ -1817,10 +1817,8 @@ static void __percpu *pcpu_alloc(size_t size, size_t align, bool reserved,
>  
>  	spin_unlock_irqrestore(&pcpu_lock, flags);
>  
> -	if (is_atomic) {
> -		err = "atomic alloc failed, no space left";
> +	if (is_atomic)
>  		goto fail;
> -	}

This is good catch. But I think Dennis may not like this way because he
added the message intentionally in commit 11df02bf9bc1 ("percpu: resolve
err may not be initialized in pcpu_alloc").

Can we change the conditional checking in fail part as below?

diff --git a/mm/percpu.c b/mm/percpu.c
index 27697b2429c2..0ac55500fad9 100644
--- a/mm/percpu.c
+++ b/mm/percpu.c
@@ -1897,7 +1897,7 @@ static void __percpu *pcpu_alloc(size_t size, size_t align, bool reserved,
 fail:
 	trace_percpu_alloc_percpu_fail(reserved, is_atomic, size, align);
 
-	if (!is_atomic && do_warn && warn_limit) {
+	if (do_warn && warn_limit) {
 		pr_warn("allocation failed, size=%zu align=%zu atomic=%d, %s\n",
 			size, align, is_atomic, err);
 		dump_stack();
Christoph Lameter Dec. 4, 2022, 4:21 p.m. UTC | #2
On Sun, 4 Dec 2022, Baoquan He wrote:

> Can we change the conditional checking in fail part as below?

Yes please. This is potentially a rare condition that should get some
visibility.
Dennis Zhou Dec. 5, 2022, 12:30 a.m. UTC | #3
Hi Baoquan and Wupeng,

On Sun, Dec 04, 2022 at 08:11:23PM +0800, Baoquan He wrote:
> On 12/04/22 at 11:14am, Wupeng Ma wrote:
> > From: Ma Wupeng <mawupeng1@huawei.com>
> > 
> > Assignment to err if is_atomic is true will never be used since warn
> > message can only be shown if is_atomic is false after label fail. So drop
> > it.
> > 
> > Signed-off-by: Ma Wupeng <mawupeng1@huawei.com>
> > ---
> >  mm/percpu.c | 4 +---
> >  1 file changed, 1 insertion(+), 3 deletions(-)
> > 
> > diff --git a/mm/percpu.c b/mm/percpu.c
> > index acd78da0493b..df86d79325b2 100644
> > --- a/mm/percpu.c
> > +++ b/mm/percpu.c
> > @@ -1817,10 +1817,8 @@ static void __percpu *pcpu_alloc(size_t size, size_t align, bool reserved,
> >  
> >  	spin_unlock_irqrestore(&pcpu_lock, flags);
> >  
> > -	if (is_atomic) {
> > -		err = "atomic alloc failed, no space left";
> > +	if (is_atomic)
> >  		goto fail;
> > -	}
> 
> This is good catch. But I think Dennis may not like this way because he
> added the message intentionally in commit 11df02bf9bc1 ("percpu: resolve
> err may not be initialized in pcpu_alloc").
> 

You're right Baoquan haha. I agree with Christoph as well we should
surface atomic.

Though I don't think below is quite right either. We should likely have
a separate warn_limit for atomic and I need to think about dump_stack()
if there are any requirements there.

Thanks,
Dennis

> Can we change the conditional checking in fail part as below?
> 
> diff --git a/mm/percpu.c b/mm/percpu.c
> index 27697b2429c2..0ac55500fad9 100644
> --- a/mm/percpu.c
> +++ b/mm/percpu.c
> @@ -1897,7 +1897,7 @@ static void __percpu *pcpu_alloc(size_t size, size_t align, bool reserved,
>  fail:
>  	trace_percpu_alloc_percpu_fail(reserved, is_atomic, size, align);
>  
> -	if (!is_atomic && do_warn && warn_limit) {
> +	if (do_warn && warn_limit) {
>  		pr_warn("allocation failed, size=%zu align=%zu atomic=%d, %s\n",
>  			size, align, is_atomic, err);
>  		dump_stack();
>
Baoquan He Dec. 5, 2022, 2:24 a.m. UTC | #4
On 12/04/22 at 04:30pm, Dennis Zhou wrote:
> Hi Baoquan and Wupeng,
> 
> On Sun, Dec 04, 2022 at 08:11:23PM +0800, Baoquan He wrote:
> > On 12/04/22 at 11:14am, Wupeng Ma wrote:
> > > From: Ma Wupeng <mawupeng1@huawei.com>
> > > 
> > > Assignment to err if is_atomic is true will never be used since warn
> > > message can only be shown if is_atomic is false after label fail. So drop
> > > it.
> > > 
> > > Signed-off-by: Ma Wupeng <mawupeng1@huawei.com>
> > > ---
> > >  mm/percpu.c | 4 +---
> > >  1 file changed, 1 insertion(+), 3 deletions(-)
> > > 
> > > diff --git a/mm/percpu.c b/mm/percpu.c
> > > index acd78da0493b..df86d79325b2 100644
> > > --- a/mm/percpu.c
> > > +++ b/mm/percpu.c
> > > @@ -1817,10 +1817,8 @@ static void __percpu *pcpu_alloc(size_t size, size_t align, bool reserved,
> > >  
> > >  	spin_unlock_irqrestore(&pcpu_lock, flags);
> > >  
> > > -	if (is_atomic) {
> > > -		err = "atomic alloc failed, no space left";
> > > +	if (is_atomic)
> > >  		goto fail;
> > > -	}
> > 
> > This is good catch. But I think Dennis may not like this way because he
> > added the message intentionally in commit 11df02bf9bc1 ("percpu: resolve
> > err may not be initialized in pcpu_alloc").
> > 
> 
> You're right Baoquan haha. I agree with Christoph as well we should
> surface atomic.
> 
> Though I don't think below is quite right either. We should likely have
> a separate warn_limit for atomic and I need to think about dump_stack()
> if there are any requirements there.

Yeah, sounds reasonable. I didn't think it over. 

> 
> 
> > Can we change the conditional checking in fail part as below?
> > 
> > diff --git a/mm/percpu.c b/mm/percpu.c
> > index 27697b2429c2..0ac55500fad9 100644
> > --- a/mm/percpu.c
> > +++ b/mm/percpu.c
> > @@ -1897,7 +1897,7 @@ static void __percpu *pcpu_alloc(size_t size, size_t align, bool reserved,
> >  fail:
> >  	trace_percpu_alloc_percpu_fail(reserved, is_atomic, size, align);
> >  
> > -	if (!is_atomic && do_warn && warn_limit) {
> > +	if (do_warn && warn_limit) {
> >  		pr_warn("allocation failed, size=%zu align=%zu atomic=%d, %s\n",
> >  			size, align, is_atomic, err);
> >  		dump_stack();
> > 
>
diff mbox series

Patch

diff --git a/mm/percpu.c b/mm/percpu.c
index acd78da0493b..df86d79325b2 100644
--- a/mm/percpu.c
+++ b/mm/percpu.c
@@ -1817,10 +1817,8 @@  static void __percpu *pcpu_alloc(size_t size, size_t align, bool reserved,
 
 	spin_unlock_irqrestore(&pcpu_lock, flags);
 
-	if (is_atomic) {
-		err = "atomic alloc failed, no space left";
+	if (is_atomic)
 		goto fail;
-	}
 
 	/* No space left.  Create a new chunk. */
 	if (list_empty(&pcpu_chunk_lists[pcpu_free_slot])) {