From: Xiongwei Song <[email protected]>
There is no need to do anything if sysfs_slab_alias() return nonzero
value after getting a mergeable cache.
Signed-off-by: Xiongwei Song <[email protected]>
Reviewed-by: Muchun Song <[email protected]>
---
v2: Collect Reviewed-by tag from Muchun.
---
mm/slub.c | 8 +++-----
1 file changed, 3 insertions(+), 5 deletions(-)
diff --git a/mm/slub.c b/mm/slub.c
index d8d5abf49f5f..9444277d669a 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -4861,6 +4861,9 @@ __kmem_cache_alias(const char *name, unsigned int size, unsigned int align,
s = find_mergeable(size, align, flags, name, ctor);
if (s) {
+ if (sysfs_slab_alias(s, name))
+ return NULL;
+
s->refcount++;
/*
@@ -4869,11 +4872,6 @@ __kmem_cache_alias(const char *name, unsigned int size, unsigned int align,
*/
s->object_size = max(s->object_size, size);
s->inuse = max(s->inuse, ALIGN(size, sizeof(void *)));
-
- if (sysfs_slab_alias(s, name)) {
- s->refcount--;
- s = NULL;
- }
}
return s;
--
2.30.2
On Sat, Jun 4, 2022 at 5:43 PM Hyeonggon Yoo <[email protected]> wrote:
>
> On Fri, Jun 03, 2022 at 10:35:55PM +0800, [email protected] wrote:
> > From: Xiongwei Song <[email protected]>
> >
> > There is no need to do anything if sysfs_slab_alias() return nonzero
> > value after getting a mergeable cache.
> >
> > Signed-off-by: Xiongwei Song <[email protected]>
> > Reviewed-by: Muchun Song <[email protected]>
> > ---
> > v2: Collect Reviewed-by tag from Muchun.
> > ---
> > mm/slub.c | 8 +++-----
> > 1 file changed, 3 insertions(+), 5 deletions(-)
> >
> > diff --git a/mm/slub.c b/mm/slub.c
> > index d8d5abf49f5f..9444277d669a 100644
> > --- a/mm/slub.c
> > +++ b/mm/slub.c
> > @@ -4861,6 +4861,9 @@ __kmem_cache_alias(const char *name, unsigned int size, unsigned int align,
> >
> > s = find_mergeable(size, align, flags, name, ctor);
> > if (s) {
> > + if (sysfs_slab_alias(s, name))
> > + return NULL;
> > +
> > s->refcount++;
> >
>
> I think we should not expose sysfs attributes before initializing
> what can be read via sysfs attribute (object_size).
>
> > /*
> > @@ -4869,11 +4872,6 @@ __kmem_cache_alias(const char *name, unsigned int size, unsigned int align,
> > */
> > s->object_size = max(s->object_size, size);
>
> this calculation should be done before sysfs_slab_alias().
Yeah, understood. Should we restore s->object_size and s->inuse if
sysfs_slab_alias() returns non zero value?
Regards,
Xiongwwei
>
> Thanks,
> Hyeonggon
>
> > s->inuse = max(s->inuse, ALIGN(size, sizeof(void *)));
> > -
> > - if (sysfs_slab_alias(s, name)) {
> > - s->refcount--;
> > - s = NULL;
> > - }
> > }
> >
> > return s;
> > --
> > 2.30.2
> >
>
On Fri, Jun 03, 2022 at 10:35:55PM +0800, [email protected] wrote:
> From: Xiongwei Song <[email protected]>
>
> There is no need to do anything if sysfs_slab_alias() return nonzero
> value after getting a mergeable cache.
>
> Signed-off-by: Xiongwei Song <[email protected]>
> Reviewed-by: Muchun Song <[email protected]>
> ---
> v2: Collect Reviewed-by tag from Muchun.
> ---
> mm/slub.c | 8 +++-----
> 1 file changed, 3 insertions(+), 5 deletions(-)
>
> diff --git a/mm/slub.c b/mm/slub.c
> index d8d5abf49f5f..9444277d669a 100644
> --- a/mm/slub.c
> +++ b/mm/slub.c
> @@ -4861,6 +4861,9 @@ __kmem_cache_alias(const char *name, unsigned int size, unsigned int align,
>
> s = find_mergeable(size, align, flags, name, ctor);
> if (s) {
> + if (sysfs_slab_alias(s, name))
> + return NULL;
> +
> s->refcount++;
>
I think we should not expose sysfs attributes before initializing
what can be read via sysfs attribute (object_size).
> /*
> @@ -4869,11 +4872,6 @@ __kmem_cache_alias(const char *name, unsigned int size, unsigned int align,
> */
> s->object_size = max(s->object_size, size);
this calculation should be done before sysfs_slab_alias().
Thanks,
Hyeonggon
> s->inuse = max(s->inuse, ALIGN(size, sizeof(void *)));
> -
> - if (sysfs_slab_alias(s, name)) {
> - s->refcount--;
> - s = NULL;
> - }
> }
>
> return s;
> --
> 2.30.2
>
On Sun, Jun 05, 2022 at 03:04:44PM +0800, Xiongwei Song wrote:
> On Sat, Jun 4, 2022 at 5:43 PM Hyeonggon Yoo <[email protected]> wrote:
> >
> > On Fri, Jun 03, 2022 at 10:35:55PM +0800, [email protected] wrote:
> > > From: Xiongwei Song <[email protected]>
> > >
> > > There is no need to do anything if sysfs_slab_alias() return nonzero
> > > value after getting a mergeable cache.
> > >
> > > Signed-off-by: Xiongwei Song <[email protected]>
> > > Reviewed-by: Muchun Song <[email protected]>
> > > ---
> > > v2: Collect Reviewed-by tag from Muchun.
> > > ---
> > > mm/slub.c | 8 +++-----
> > > 1 file changed, 3 insertions(+), 5 deletions(-)
> > >
> > > diff --git a/mm/slub.c b/mm/slub.c
> > > index d8d5abf49f5f..9444277d669a 100644
> > > --- a/mm/slub.c
> > > +++ b/mm/slub.c
> > > @@ -4861,6 +4861,9 @@ __kmem_cache_alias(const char *name, unsigned int size, unsigned int align,
> > >
> > > s = find_mergeable(size, align, flags, name, ctor);
> > > if (s) {
> > > + if (sysfs_slab_alias(s, name))
> > > + return NULL;
> > > +
> > > s->refcount++;
> > >
> >
> > I think we should not expose sysfs attributes before initializing
> > what can be read via sysfs attribute (object_size).
> >
> > > /*
> > > @@ -4869,11 +4872,6 @@ __kmem_cache_alias(const char *name, unsigned int size, unsigned int align,
> > > */
> > > s->object_size = max(s->object_size, size);
> >
> > this calculation should be done before sysfs_slab_alias().
>
Sorry for the late reply.
> Yeah, understood. Should we restore s->object_size and s->inuse if
> sysfs_slab_alias() returns non zero value?
In my opinion, yes.
Thanks,
Hyeonggon
> Regards,
> Xiongwwei
>
> >
> > Thanks,
> > Hyeonggon
> >
> > > s->inuse = max(s->inuse, ALIGN(size, sizeof(void *)));
> > > -
> > > - if (sysfs_slab_alias(s, name)) {
> > > - s->refcount--;
> > > - s = NULL;
> > > - }
> > > }
> > >
> > > return s;
> > > --
> > > 2.30.2
> > >
> >
--
Thanks,
Hyeonggon
On 6/5/22 09:04, Xiongwei Song wrote:
> On Sat, Jun 4, 2022 at 5:43 PM Hyeonggon Yoo <[email protected]> wrote:
>>
>> On Fri, Jun 03, 2022 at 10:35:55PM +0800, [email protected] wrote:
>> > From: Xiongwei Song <[email protected]>
>> >
>> > There is no need to do anything if sysfs_slab_alias() return nonzero
>> > value after getting a mergeable cache.
>> >
>> > Signed-off-by: Xiongwei Song <[email protected]>
>> > Reviewed-by: Muchun Song <[email protected]>
>> > ---
>> > v2: Collect Reviewed-by tag from Muchun.
Hmm I added v1 (with the Reviewed tag) before getting to the v2 thread. But
I think it's fine, see below.
>> > ---
>> > mm/slub.c | 8 +++-----
>> > 1 file changed, 3 insertions(+), 5 deletions(-)
>> >
>> > diff --git a/mm/slub.c b/mm/slub.c
>> > index d8d5abf49f5f..9444277d669a 100644
>> > --- a/mm/slub.c
>> > +++ b/mm/slub.c
>> > @@ -4861,6 +4861,9 @@ __kmem_cache_alias(const char *name, unsigned int size, unsigned int align,
>> >
>> > s = find_mergeable(size, align, flags, name, ctor);
>> > if (s) {
>> > + if (sysfs_slab_alias(s, name))
>> > + return NULL;
>> > +
>> > s->refcount++;
>> >
>>
>> I think we should not expose sysfs attributes before initializing
>> what can be read via sysfs attribute (object_size).
Hmm I don't think they are unitialized. They have an old value from the
cache we are merging with, which is updated if the new aliased cache has a
larger one.
So yeah we might briefly during creation expose an alias that will have an
incorrect value, but I doubt anything will break. The values are not stable
anyway as new aliases are added, as we are bumping them for the 'root' cache
and all aliases that share it already.
>> > /*
>> > @@ -4869,11 +4872,6 @@ __kmem_cache_alias(const char *name, unsigned int size, unsigned int align,
>> > */
>> > s->object_size = max(s->object_size, size);
>>
>> this calculation should be done before sysfs_slab_alias().
>
> Yeah, understood. Should we restore s->object_size and s->inuse if
> sysfs_slab_alias() returns non zero value?
And by bailing out early this patch effectively achieves that, so I'd say
it's a better state than before the patch so I'll keep it unless proven
otherwise. Thanks!
> Regards,
> Xiongwwei
>
>>
>> Thanks,
>> Hyeonggon
>>
>> > s->inuse = max(s->inuse, ALIGN(size, sizeof(void *)));
>> > -
>> > - if (sysfs_slab_alias(s, name)) {
>> > - s->refcount--;
>> > - s = NULL;
>> > - }
>> > }
>> >
>> > return s;
>> > --
>> > 2.30.2
>> >
>>
On Wed, Jun 15, 2022 at 4:37 PM Vlastimil Babka <[email protected]> wrote:
>
> On 6/5/22 09:04, Xiongwei Song wrote:
> > On Sat, Jun 4, 2022 at 5:43 PM Hyeonggon Yoo <[email protected]> wrote:
> >>
> >> On Fri, Jun 03, 2022 at 10:35:55PM +0800, [email protected] wrote:
> >> > From: Xiongwei Song <[email protected]>
> >> >
> >> > There is no need to do anything if sysfs_slab_alias() return nonzero
> >> > value after getting a mergeable cache.
> >> >
> >> > Signed-off-by: Xiongwei Song <[email protected]>
> >> > Reviewed-by: Muchun Song <[email protected]>
> >> > ---
> >> > v2: Collect Reviewed-by tag from Muchun.
>
> Hmm I added v1 (with the Reviewed tag) before getting to the v2 thread. But
> I think it's fine, see below.
>
> >> > ---
> >> > mm/slub.c | 8 +++-----
> >> > 1 file changed, 3 insertions(+), 5 deletions(-)
> >> >
> >> > diff --git a/mm/slub.c b/mm/slub.c
> >> > index d8d5abf49f5f..9444277d669a 100644
> >> > --- a/mm/slub.c
> >> > +++ b/mm/slub.c
> >> > @@ -4861,6 +4861,9 @@ __kmem_cache_alias(const char *name, unsigned int size, unsigned int align,
> >> >
> >> > s = find_mergeable(size, align, flags, name, ctor);
> >> > if (s) {
> >> > + if (sysfs_slab_alias(s, name))
> >> > + return NULL;
> >> > +
> >> > s->refcount++;
> >> >
> >>
> >> I think we should not expose sysfs attributes before initializing
> >> what can be read via sysfs attribute (object_size).
>
> Hmm I don't think they are unitialized. They have an old value from the
> cache we are merging with, which is updated if the new aliased cache has a
> larger one.
> So yeah we might briefly during creation expose an alias that will have an
> incorrect value, but I doubt anything will break. The values are not stable
> anyway as new aliases are added, as we are bumping them for the 'root' cache
> and all aliases that share it already.
>
> >> > /*
> >> > @@ -4869,11 +4872,6 @@ __kmem_cache_alias(const char *name, unsigned int size, unsigned int align,
> >> > */
> >> > s->object_size = max(s->object_size, size);
> >>
> >> this calculation should be done before sysfs_slab_alias().
> >
> > Yeah, understood. Should we restore s->object_size and s->inuse if
> > sysfs_slab_alias() returns non zero value?
>
> And by bailing out early this patch effectively achieves that, so I'd say
> it's a better state than before the patch so I'll keep it unless proven
> otherwise. Thanks!
Thank you for your comments Vlastimil and Hyeonggon.
Regards,
Xiongwei
>
> > Regards,
> > Xiongwwei
> >
> >>
> >> Thanks,
> >> Hyeonggon
> >>
> >> > s->inuse = max(s->inuse, ALIGN(size, sizeof(void *)));
> >> > -
> >> > - if (sysfs_slab_alias(s, name)) {
> >> > - s->refcount--;
> >> > - s = NULL;
> >> > - }
> >> > }
> >> >
> >> > return s;
> >> > --
> >> > 2.30.2
> >> >
> >>
>