Please apply d2155fe54ddb to 5.10 and 5.4

Please apply d2155fe54ddb to 5.10 and 5.4

[Qingfang Deng]

Hi Greg and Sasha,

Please consider applying d2155fe54ddb ("mm: compaction: remove
duplicate !list_empty(&sublist) check") to 5.10 and 5.4, as it
resolves a -Wdangling-pointer warning in recent GCC versions:

In function '__list_cut_position',
    inlined from 'list_cut_position' at ./include/linux/list.h:400:3,
    inlined from 'move_freelist_tail' at mm/compaction.c:1241:3:
./include/linux/list.h:370:21: warning: storing the address of local
variable 'sublist' in '*&freepage_6(D)->D.15621.D.15566.lru.next'
[-Wdangling-pointer=]

Regards,
Qingfang

Re: Please apply d2155fe54ddb to 5.10 and 5.4

[Greg Kroah-Hartman]

On Tue, Apr 22, 2025 at 02:04:45PM +0800, Qingfang Deng wrote:
> Hi Greg and Sasha,
> 
> Please consider applying d2155fe54ddb ("mm: compaction: remove
> duplicate !list_empty(&sublist) check") to 5.10 and 5.4, as it
> resolves a -Wdangling-pointer warning in recent GCC versions:
> 
> In function '__list_cut_position',
>     inlined from 'list_cut_position' at ./include/linux/list.h:400:3,
>     inlined from 'move_freelist_tail' at mm/compaction.c:1241:3:
> ./include/linux/list.h:370:21: warning: storing the address of local
> variable 'sublist' in '*&freepage_6(D)->D.15621.D.15566.lru.next'
> [-Wdangling-pointer=]

All mm patches MUST get approval from the mm maintainers/developers
before we can apply them to stable kernels.

Can you please do that here?

thanks,

greg k-h

Re: Please apply d2155fe54ddb to 5.10 and 5.4

[Qingfang Deng]

On Tue, Apr 22, 2025 at 2:06 PM Greg Kroah-Hartman
<gregkh@linuxfoundation.org> wrote:
> All mm patches MUST get approval from the mm maintainers/developers
> before we can apply them to stable kernels.
>
> Can you please do that here?

Sure. Added to Cc list.

>
> thanks,
>
> greg k-h

Re: Please apply d2155fe54ddb to 5.10 and 5.4

[Greg Kroah-Hartman]

On Tue, Apr 22, 2025 at 02:10:53PM +0800, Qingfang Deng wrote:
> On Tue, Apr 22, 2025 at 2:06 PM Greg Kroah-Hartman
> <gregkh@linuxfoundation.org> wrote:
> > All mm patches MUST get approval from the mm maintainers/developers
> > before we can apply them to stable kernels.
> >
> > Can you please do that here?
> 
> Sure. Added to Cc list.

They have no context here at all :(

Re: Please apply d2155fe54ddb to 5.10 and 5.4

[Qingfang Deng]

On Tue, Apr 22, 2025 at 2:27 PM Greg Kroah-Hartman
<gregkh@linuxfoundation.org> wrote:
> On Tue, Apr 22, 2025 at 02:10:53PM +0800, Qingfang Deng wrote:
> > On Tue, Apr 22, 2025 at 2:06 PM Greg Kroah-Hartman
> > <gregkh@linuxfoundation.org> wrote:
> > > All mm patches MUST get approval from the mm maintainers/developers
> > > before we can apply them to stable kernels.
> > >
> > > Can you please do that here?
> >
> > Sure. Added to Cc list.
>
> They have no context here at all :(

Let me post it again:

Please consider applying d2155fe54ddb ("mm: compaction: remove
duplicate !list_empty(&sublist) check") to 5.10 and 5.4, as it
resolves a -Wdangling-pointer warning in recent GCC versions:

In function '__list_cut_position',
    inlined from 'list_cut_position' at ./include/linux/list.h:400:3,
    inlined from 'move_freelist_tail' at mm/compaction.c:1241:3:
./include/linux/list.h:370:21: warning: storing the address of local
variable 'sublist' in '*&freepage_6(D)->D.15621.D.15566.lru.next'
[-Wdangling-pointer=]

Re: Please apply d2155fe54ddb to 5.10 and 5.4

[David Hildenbrand]

On 22.04.25 08:34, Qingfang Deng wrote:
> On Tue, Apr 22, 2025 at 2:27 PM Greg Kroah-Hartman
> <gregkh@linuxfoundation.org> wrote:
>> On Tue, Apr 22, 2025 at 02:10:53PM +0800, Qingfang Deng wrote:
>>> On Tue, Apr 22, 2025 at 2:06 PM Greg Kroah-Hartman
>>> <gregkh@linuxfoundation.org> wrote:
>>>> All mm patches MUST get approval from the mm maintainers/developers
>>>> before we can apply them to stable kernels.
>>>>
>>>> Can you please do that here?
>>>
>>> Sure. Added to Cc list.
>>
>> They have no context here at all :(
> 
> Let me post it again:
> 
> Please consider applying d2155fe54ddb ("mm: compaction: remove
> duplicate !list_empty(&sublist) check") to 5.10 and 5.4, as it
> resolves a -Wdangling-pointer warning in recent GCC versions:
> 
> In function '__list_cut_position',
>      inlined from 'list_cut_position' at ./include/linux/list.h:400:3,
>      inlined from 'move_freelist_tail' at mm/compaction.c:1241:3:
> ./include/linux/list.h:370:21: warning: storing the address of local
> variable 'sublist' in '*&freepage_6(D)->D.15621.D.15566.lru.next'
> [-Wdangling-pointer=]

The commit looks harmless. But I don't see how it could fix any warning?

I mean, we replace two !list_empty() checks by a single one ... and the 
warning is about list_cut_position() ?

-- 
Cheers,

David / dhildenb

Re: Please apply d2155fe54ddb to 5.10 and 5.4

[Qingfang Deng]

Hi David,


On Tue, Apr 22, 2025 at 3:04 PM David Hildenbrand <david@redhat.com> wrote:
> > Let me post it again:
> >
> > Please consider applying d2155fe54ddb ("mm: compaction: remove
> > duplicate !list_empty(&sublist) check") to 5.10 and 5.4, as it
> > resolves a -Wdangling-pointer warning in recent GCC versions:
> >
> > In function '__list_cut_position',
> >      inlined from 'list_cut_position' at ./include/linux/list.h:400:3,
> >      inlined from 'move_freelist_tail' at mm/compaction.c:1241:3:
> > ./include/linux/list.h:370:21: warning: storing the address of local
> > variable 'sublist' in '*&freepage_6(D)->D.15621.D.15566.lru.next'
> > [-Wdangling-pointer=]
>
> The commit looks harmless. But I don't see how it could fix any warning?
>
> I mean, we replace two !list_empty() checks by a single one ... and the
> warning is about list_cut_position() ?

I have no idea, actually. Maybe the double !list_empty() confuses the
compiler, making it think `sublist` can be referenced out of the
scope?

>
> --
> Cheers,
>
> David / dhildenb
>

Re: Please apply d2155fe54ddb to 5.10 and 5.4

[Greg Kroah-Hartman]

On Tue, Apr 22, 2025 at 05:58:26PM +0800, Qingfang Deng wrote:
> Hi David,
> 
> 
> On Tue, Apr 22, 2025 at 3:04 PM David Hildenbrand <david@redhat.com> wrote:
> > > Let me post it again:
> > >
> > > Please consider applying d2155fe54ddb ("mm: compaction: remove
> > > duplicate !list_empty(&sublist) check") to 5.10 and 5.4, as it
> > > resolves a -Wdangling-pointer warning in recent GCC versions:
> > >
> > > In function '__list_cut_position',
> > >      inlined from 'list_cut_position' at ./include/linux/list.h:400:3,
> > >      inlined from 'move_freelist_tail' at mm/compaction.c:1241:3:
> > > ./include/linux/list.h:370:21: warning: storing the address of local
> > > variable 'sublist' in '*&freepage_6(D)->D.15621.D.15566.lru.next'
> > > [-Wdangling-pointer=]
> >
> > The commit looks harmless. But I don't see how it could fix any warning?
> >
> > I mean, we replace two !list_empty() checks by a single one ... and the
> > warning is about list_cut_position() ?
> 
> I have no idea, actually. Maybe the double !list_empty() confuses the
> compiler, making it think `sublist` can be referenced out of the
> scope?

That is odd, are you sure this isn't a compiler bug?

Re: Please apply d2155fe54ddb to 5.10 and 5.4

[Qingfang Deng]

On Tue, Apr 22, 2025 at 8:41 PM Greg Kroah-Hartman
<gregkh@linuxfoundation.org> wrote:
> > >
> > > The commit looks harmless. But I don't see how it could fix any warning?
> > >
> > > I mean, we replace two !list_empty() checks by a single one ... and the
> > > warning is about list_cut_position() ?
> >
> > I have no idea, actually. Maybe the double !list_empty() confuses the
> > compiler, making it think `sublist` can be referenced out of the
> > scope?
>
> That is odd, are you sure this isn't a compiler bug?

I think it is a compiler bug. If so, what should we do to fix the warning?

Re: Please apply d2155fe54ddb to 5.10 and 5.4

[Greg Kroah-Hartman]

On Wed, Apr 23, 2025 at 03:37:39PM +0800, Qingfang Deng wrote:
> On Tue, Apr 22, 2025 at 8:41 PM Greg Kroah-Hartman
> <gregkh@linuxfoundation.org> wrote:
> > > >
> > > > The commit looks harmless. But I don't see how it could fix any warning?
> > > >
> > > > I mean, we replace two !list_empty() checks by a single one ... and the
> > > > warning is about list_cut_position() ?
> > >
> > > I have no idea, actually. Maybe the double !list_empty() confuses the
> > > compiler, making it think `sublist` can be referenced out of the
> > > scope?
> >
> > That is odd, are you sure this isn't a compiler bug?
> 
> I think it is a compiler bug. If so, what should we do to fix the warning?

Fix the compiler :)