* [PATCH 4/4] mm,hugetlb: compute page_size_log properly
[not found] <1486673582-6979-1-git-send-email-dave@stgolabs.net>
@ 2017-02-09 20:53 ` Davidlohr Bueso
2017-02-10 10:20 ` Michal Hocko
0 siblings, 1 reply; 6+ messages in thread
From: Davidlohr Bueso @ 2017-02-09 20:53 UTC (permalink / raw)
To: akpm; +Cc: manfred, dave, linux-kernel, linux-mm, Davidlohr Bueso
The SHM_HUGE_* stuff was introduced in:
42d7395feb5 (mm: support more pagesizes for MAP_HUGETLB/SHM_HUGETLB)
It unnecessarily adds another layer, specific to sysv shm, without
anything special about it: the macros are identical to the MAP_HUGE_*
stuff, which in turn does correctly describe the hugepage subsystem.
One example of the problems with extra layers what this patch fixes:
mmap_pgoff() should never be using SHM_HUGE_* logic. It is obviously
harmless but it would still be grand to get rid of it -- although
now in the manpages I don't see that happening.
Cc: linux-mm@kvack.org
Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
---
mm/mmap.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/mm/mmap.c b/mm/mmap.c
index 499b988b1639..40b29aca18c1 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -1479,7 +1479,7 @@ SYSCALL_DEFINE6(mmap_pgoff, unsigned long, addr, unsigned long, len,
struct user_struct *user = NULL;
struct hstate *hs;
- hs = hstate_sizelog((flags >> MAP_HUGE_SHIFT) & SHM_HUGE_MASK);
+ hs = hstate_sizelog((flags >> MAP_HUGE_SHIFT) & MAP_HUGE_MASK);
if (!hs)
return -EINVAL;
--
2.6.6
--
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^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [PATCH 4/4] mm,hugetlb: compute page_size_log properly
2017-02-09 20:53 ` [PATCH 4/4] mm,hugetlb: compute page_size_log properly Davidlohr Bueso
@ 2017-02-10 10:20 ` Michal Hocko
2017-02-10 16:51 ` Davidlohr Bueso
0 siblings, 1 reply; 6+ messages in thread
From: Michal Hocko @ 2017-02-10 10:20 UTC (permalink / raw)
To: Davidlohr Bueso; +Cc: akpm, manfred, linux-kernel, linux-mm, Davidlohr Bueso
On Thu 09-02-17 12:53:02, Davidlohr Bueso wrote:
> The SHM_HUGE_* stuff was introduced in:
>
> 42d7395feb5 (mm: support more pagesizes for MAP_HUGETLB/SHM_HUGETLB)
>
> It unnecessarily adds another layer, specific to sysv shm, without
> anything special about it: the macros are identical to the MAP_HUGE_*
> stuff, which in turn does correctly describe the hugepage subsystem.
>
> One example of the problems with extra layers what this patch fixes:
> mmap_pgoff() should never be using SHM_HUGE_* logic. It is obviously
> harmless but it would still be grand to get rid of it -- although
> now in the manpages I don't see that happening.
Can we just drop SHM_HUGE_MASK altogether? It is not exported in uapi
headers AFAICS.
>
> Cc: linux-mm@kvack.org
> Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
> ---
> mm/mmap.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/mm/mmap.c b/mm/mmap.c
> index 499b988b1639..40b29aca18c1 100644
> --- a/mm/mmap.c
> +++ b/mm/mmap.c
> @@ -1479,7 +1479,7 @@ SYSCALL_DEFINE6(mmap_pgoff, unsigned long, addr, unsigned long, len,
> struct user_struct *user = NULL;
> struct hstate *hs;
>
> - hs = hstate_sizelog((flags >> MAP_HUGE_SHIFT) & SHM_HUGE_MASK);
> + hs = hstate_sizelog((flags >> MAP_HUGE_SHIFT) & MAP_HUGE_MASK);
> if (!hs)
> return -EINVAL;
>
> --
> 2.6.6
>
> --
> To unsubscribe, send a message with 'unsubscribe linux-mm' in
> the body to majordomo@kvack.org. For more info on Linux MM,
> see: http://www.linux-mm.org/ .
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--
Michal Hocko
SUSE Labs
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^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH 4/4] mm,hugetlb: compute page_size_log properly
2017-02-10 10:20 ` Michal Hocko
@ 2017-02-10 16:51 ` Davidlohr Bueso
2017-02-20 16:11 ` Michal Hocko
0 siblings, 1 reply; 6+ messages in thread
From: Davidlohr Bueso @ 2017-02-10 16:51 UTC (permalink / raw)
To: Michal Hocko; +Cc: akpm, manfred, linux-kernel, linux-mm, Davidlohr Bueso
On Fri, 10 Feb 2017, Michal Hocko wrote:
>On Thu 09-02-17 12:53:02, Davidlohr Bueso wrote:
>> The SHM_HUGE_* stuff was introduced in:
>>
>> 42d7395feb5 (mm: support more pagesizes for MAP_HUGETLB/SHM_HUGETLB)
>>
>> It unnecessarily adds another layer, specific to sysv shm, without
>> anything special about it: the macros are identical to the MAP_HUGE_*
>> stuff, which in turn does correctly describe the hugepage subsystem.
>>
>> One example of the problems with extra layers what this patch fixes:
>> mmap_pgoff() should never be using SHM_HUGE_* logic. It is obviously
>> harmless but it would still be grand to get rid of it -- although
>> now in the manpages I don't see that happening.
>
>Can we just drop SHM_HUGE_MASK altogether? It is not exported in uapi
>headers AFAICS.
Yeah that was my original idea, however I noticed that shmget.2 mentions
kernel internals as part of SHM_HUGE_{2MB,1GB}, ie: SHM_HUGE_SHIFT. So
dropping _MASK doesn't make sense if we are going to keep _SHIFT.
Thanks,
Davidlohr
--
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^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH 4/4] mm,hugetlb: compute page_size_log properly
2017-02-10 16:51 ` Davidlohr Bueso
@ 2017-02-20 16:11 ` Michal Hocko
2017-02-22 16:03 ` Davidlohr Bueso
0 siblings, 1 reply; 6+ messages in thread
From: Michal Hocko @ 2017-02-20 16:11 UTC (permalink / raw)
To: Davidlohr Bueso; +Cc: akpm, manfred, linux-kernel, linux-mm, Davidlohr Bueso
Sorry for a late reply, I wasn't online last week
On Fri 10-02-17 08:51:11, Davidlohr Bueso wrote:
> On Fri, 10 Feb 2017, Michal Hocko wrote:
>
> > On Thu 09-02-17 12:53:02, Davidlohr Bueso wrote:
> > > The SHM_HUGE_* stuff was introduced in:
> > >
> > > 42d7395feb5 (mm: support more pagesizes for MAP_HUGETLB/SHM_HUGETLB)
> > >
> > > It unnecessarily adds another layer, specific to sysv shm, without
> > > anything special about it: the macros are identical to the MAP_HUGE_*
> > > stuff, which in turn does correctly describe the hugepage subsystem.
> > >
> > > One example of the problems with extra layers what this patch fixes:
> > > mmap_pgoff() should never be using SHM_HUGE_* logic. It is obviously
> > > harmless but it would still be grand to get rid of it -- although
> > > now in the manpages I don't see that happening.
> >
> > Can we just drop SHM_HUGE_MASK altogether? It is not exported in uapi
> > headers AFAICS.
>
> Yeah that was my original idea, however I noticed that shmget.2 mentions
> kernel internals as part of SHM_HUGE_{2MB,1GB}, ie: SHM_HUGE_SHIFT. So
> dropping _MASK doesn't make sense if we are going to keep _SHIFT.
I am not sure I understand.
$ git grep SHM_HUGE_ include/uapi/
$
So there doesn't seem to be any user visible constant. The man page
mentiones is but I do not really see how is the userspace supposed to
use it.
--
Michal Hocko
SUSE Labs
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^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH 4/4] mm,hugetlb: compute page_size_log properly
2017-02-20 16:11 ` Michal Hocko
@ 2017-02-22 16:03 ` Davidlohr Bueso
2017-02-22 16:11 ` Michal Hocko
0 siblings, 1 reply; 6+ messages in thread
From: Davidlohr Bueso @ 2017-02-22 16:03 UTC (permalink / raw)
To: Michal Hocko; +Cc: akpm, manfred, linux-kernel, linux-mm, Davidlohr Bueso
On Mon, 20 Feb 2017, Michal Hocko wrote:
>I am not sure I understand.
>$ git grep SHM_HUGE_ include/uapi/
>$
>
>So there doesn't seem to be any user visible constant. The man page
>mentiones is but I do not really see how is the userspace supposed to
>use it.
Yeah, userspace is not supposed to use it, it's just there because
the manpage describes kernel internals. I'm not really a big fan
of touching manpages (and ipc is already full of corner cases),
but I guess nobody can really complain if we rip out all the
SHM_HUGE_ stuff.
Thanks,
Davidlohr
--
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^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH 4/4] mm,hugetlb: compute page_size_log properly
2017-02-22 16:03 ` Davidlohr Bueso
@ 2017-02-22 16:11 ` Michal Hocko
0 siblings, 0 replies; 6+ messages in thread
From: Michal Hocko @ 2017-02-22 16:11 UTC (permalink / raw)
To: Davidlohr Bueso; +Cc: akpm, manfred, linux-kernel, linux-mm, Davidlohr Bueso
On Wed 22-02-17 08:03:19, Davidlohr Bueso wrote:
> On Mon, 20 Feb 2017, Michal Hocko wrote:
>
> > I am not sure I understand.
> > $ git grep SHM_HUGE_ include/uapi/
> > $
> >
> > So there doesn't seem to be any user visible constant. The man page
> > mentiones is but I do not really see how is the userspace supposed to
> > use it.
>
> Yeah, userspace is not supposed to use it, it's just there because
> the manpage describes kernel internals.
Which is wrong!
> I'm not really a big fan
> of touching manpages (and ipc is already full of corner cases),
> but I guess nobody can really complain if we rip out all the
> SHM_HUGE_ stuff.
yeah, let's just get rid of it.
--
Michal Hocko
SUSE Labs
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^ permalink raw reply [flat|nested] 6+ messages in thread
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2017-02-09 20:53 ` [PATCH 4/4] mm,hugetlb: compute page_size_log properly Davidlohr Bueso
2017-02-10 10:20 ` Michal Hocko
2017-02-10 16:51 ` Davidlohr Bueso
2017-02-20 16:11 ` Michal Hocko
2017-02-22 16:03 ` Davidlohr Bueso
2017-02-22 16:11 ` Michal Hocko
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