mm: Export 'pageflag_names' array

mm: Export 'pageflag_names' array

[Anatol Pomozov]

Hi Wu

I have a request wrt your old commit 718a38211.

I think it makes sense to export array pageflag_names so kernel dump
debug tools (like 'crash') can use it as well. Currently the tool
hard-codes flag names but it is suboptimal as flags are different for
different configs.

What do you think? (I can send a patch if you are ok).

Re: mm: Export 'pageflag_names' array

[Fengguang Wu]

Hi Anatol,

On Mon, Oct 07, 2013 at 10:53:32AM -0700, Anatol Pomozov wrote:
> Hi Wu
> 
> I have a request wrt your old commit 718a38211.
> 
> I think it makes sense to export array pageflag_names so kernel dump
> debug tools (like 'crash') can use it as well. Currently the tool
> hard-codes flag names but it is suboptimal as flags are different for
> different configs.
> 
> What do you think? (I can send a patch if you are ok).

I wonder if the KPF_* defined in

        include/uapi/linux/kernel-page-flags.h

fit your needs. These are kernel page flags exported to the user space
and will be maintained stable and immune to kconfig changes. You can
find use examples of them in

        fs/proc/page.c
        tools/vm/page-types.c

Thanks,
Fengguang

Re: mm: Export 'pageflag_names' array

[Dave Anderson]

----- Original Message -----
> Hi Anatol,
> 
> On Mon, Oct 07, 2013 at 10:53:32AM -0700, Anatol Pomozov wrote:
> > Hi Wu
> > 
> > I have a request wrt your old commit 718a38211.
> > 
> > I think it makes sense to export array pageflag_names so kernel dump
> > debug tools (like 'crash') can use it as well. Currently the tool
> > hard-codes flag names but it is suboptimal as flags are different for
> > different configs.
> > 
> > What do you think? (I can send a patch if you are ok).
> 
> I wonder if the KPF_* defined in
> 
>         include/uapi/linux/kernel-page-flags.h
> 
> fit your needs. These are kernel page flags exported to the user space
> and will be maintained stable and immune to kconfig changes. You can
> find use examples of them in
> 
>         fs/proc/page.c
>         tools/vm/page-types.c
> 
> Thanks,
> Fengguang
> 

Nothing is required for the crash utility.  The pageflag_names array (as well
as the pageflags enumerator) are readily available in the kernel debuginfo
data.

Dave
  

Re: mm: Export 'pageflag_names' array

[Anatol Pomozov]

Hi

On Tue, Oct 8, 2013 at 5:40 AM, Dave Anderson <anderson@redhat.com> wrote:
>
>
> ----- Original Message -----
>> Hi Anatol,
>>
>> On Mon, Oct 07, 2013 at 10:53:32AM -0700, Anatol Pomozov wrote:
>> > Hi Wu
>> >
>> > I have a request wrt your old commit 718a38211.
>> >
>> > I think it makes sense to export array pageflag_names so kernel dump
>> > debug tools (like 'crash') can use it as well. Currently the tool
>> > hard-codes flag names but it is suboptimal as flags are different for
>> > different configs.
>> >
>> > What do you think? (I can send a patch if you are ok).
>>
>> I wonder if the KPF_* defined in
>>
>>         include/uapi/linux/kernel-page-flags.h
>>
>> fit your needs. These are kernel page flags exported to the user space
>> and will be maintained stable and immune to kconfig changes. You can
>> find use examples of them in
>>
>>         fs/proc/page.c
>>         tools/vm/page-types.c
>>
>> Thanks,
>> Fengguang
>>
>
> Nothing is required for the crash utility.  The pageflag_names array (as well
> as the pageflags enumerator) are readily available in the kernel debuginfo
> data.

D'oh. You are right Dave. Everyone, please ignore my original question
I mislooked this variable in symbols map (or maybe looked at an old
kernel map).

Dave, do you think 'crash' should use pageflag_names to output flag names?

Re: mm: Export 'pageflag_names' array

[Dave Anderson]

----- Original Message -----
> Hi
> 
> On Tue, Oct 8, 2013 at 5:40 AM, Dave Anderson <anderson@redhat.com> wrote:
> >
> >
> > ----- Original Message -----
> >> Hi Anatol,
> >>
> >> On Mon, Oct 07, 2013 at 10:53:32AM -0700, Anatol Pomozov wrote:
> >> > Hi Wu
> >> >
> >> > I have a request wrt your old commit 718a38211.
> >> >
> >> > I think it makes sense to export array pageflag_names so kernel dump
> >> > debug tools (like 'crash') can use it as well. Currently the tool
> >> > hard-codes flag names but it is suboptimal as flags are different for
> >> > different configs.
> >> >
> >> > What do you think? (I can send a patch if you are ok).
> >>
> >> I wonder if the KPF_* defined in
> >>
> >>         include/uapi/linux/kernel-page-flags.h
> >>
> >> fit your needs. These are kernel page flags exported to the user space
> >> and will be maintained stable and immune to kconfig changes. You can
> >> find use examples of them in
> >>
> >>         fs/proc/page.c
> >>         tools/vm/page-types.c
> >>
> >> Thanks,
> >> Fengguang
> >>
> >
> > Nothing is required for the crash utility.  The pageflag_names array (as well
> > as the pageflags enumerator) are readily available in the kernel debuginfo data.
> 
> D'oh. You are right Dave. Everyone, please ignore my original question
> I mislooked this variable in symbols map (or maybe looked at an old
> kernel map).
> 
> Dave, do you think 'crash' should use pageflag_names to output flag names?

It's a good addition -- I'm working on a patch as we speak...

Thanks,
  Dave