commit 6edf2576a6cc ("mm/slub: enable debugging memory wasting of
kmalloc") introduces 'SLAB_KMALLOC' bit specifying whether a
kmem_cache is a kmalloc cache for slab/slub (slob doesn't have
dedicated kmalloc caches).
Add a helper macro for other components like kasan to simplify code.
Signed-off-by: Feng Tang <[email protected]>
---
include/linux/slab.h | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/include/linux/slab.h b/include/linux/slab.h
index 1c670c16c737..ee6499088ad3 100644
--- a/include/linux/slab.h
+++ b/include/linux/slab.h
@@ -758,6 +758,12 @@ extern void kvfree_sensitive(const void *addr, size_t len);
unsigned int kmem_cache_size(struct kmem_cache *s);
+#ifndef CONFIG_SLOB
+#define is_kmalloc_cache(s) ((s)->flags & SLAB_KMALLOC)
+#else
+#define is_kmalloc_cache(s) (false)
+#endif
+
/**
* kmalloc_size_roundup - Report allocation bucket size for the given size
*
--
2.34.1
On Mon, 21 Nov 2022 21:50:23 +0800 Feng Tang <[email protected]> wrote:
> +#ifndef CONFIG_SLOB
> +#define is_kmalloc_cache(s) ((s)->flags & SLAB_KMALLOC)
> +#else
> +#define is_kmalloc_cache(s) (false)
> +#endif
Could be implemented as a static inline C function, yes?
If so, that's always best. For (silly) example, consider the behaviour
of
x = is_kmalloc_cache(s++);
with and without CONFIG_SLOB.
On Mon, Nov 21, 2022 at 12:19:38PM -0800, Andrew Morton wrote:
> On Mon, 21 Nov 2022 21:50:23 +0800 Feng Tang <[email protected]> wrote:
>
> > +#ifndef CONFIG_SLOB
> > +#define is_kmalloc_cache(s) ((s)->flags & SLAB_KMALLOC)
> > +#else
> > +#define is_kmalloc_cache(s) (false)
> > +#endif
>
> Could be implemented as a static inline C function, yes?
Right, I also did try inline function first, and met compilation error:
"
./include/linux/slab.h: In function ‘is_kmalloc_cache’:
./include/linux/slab.h:159:18: error: invalid use of undefined type ‘struct kmem_cache’
159 | return (s->flags & SLAB_KMALLOC);
| ^~
"
The reason is 'struct kmem_cache' definition for slab/slub/slob sit
separately in slab_def.h, slub_def.h and mm/slab.h, and they are not
included in this 'include/linux/slab.h'. So I chose the macro way.
Btw, I've worked on some patches related with sl[auo]b recently, and
really felt the pain when dealing with 3 allocators, on both reading
code and writing patches. And I really like the idea of fading away
SLOB as the first step :)
> If so, that's always best. For (silly) example, consider the behaviour
> of
>
> x = is_kmalloc_cache(s++);
>
> with and without CONFIG_SLOB.
Another solution I can think of is putting the implementation into
slab_common.c, like the below?
Thanks,
Feng
---
diff --git a/include/linux/slab.h b/include/linux/slab.h
index 067f0e80be9e..e4fcdbfb3477 100644
--- a/include/linux/slab.h
+++ b/include/linux/slab.h
@@ -149,6 +149,17 @@
struct list_lru;
struct mem_cgroup;
+
+#ifndef CONFIG_SLOB
+extern bool is_kmalloc_cache(struct kmem_cache *s);
+#else
+static inline bool is_kmalloc_cache(struct kmem_cache *s)
+{
+ return false;
+}
+#endif
+
/*
* struct kmem_cache related prototypes
*/
diff --git a/mm/slab_common.c b/mm/slab_common.c
index a5480d67f391..860e804b7c0a 100644
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@ -77,6 +77,13 @@ __setup_param("slub_merge", slub_merge, setup_slab_merge, 0);
__setup("slab_nomerge", setup_slab_nomerge);
__setup("slab_merge", setup_slab_merge);
+#ifndef CONFIG_SLOB
+bool is_kmalloc_cache(struct kmem_cache *s)
+{
+ return (s->flags & SLAB_KMALLOC);
+}
+#endif
+
/*
* Determine the size of a slab object
*/
On Tue, 22 Nov 2022 13:30:19 +0800 Feng Tang <[email protected]> wrote:
> > If so, that's always best. For (silly) example, consider the behaviour
> > of
> >
> > x = is_kmalloc_cache(s++);
> >
> > with and without CONFIG_SLOB.
>
> Another solution I can think of is putting the implementation into
> slab_common.c, like the below?
I'm not sure that's much of an improvement on the macro :(
How about we go with the macro and avoid the
expression-with-side-effects gotcha (and the potential CONFIG_SLOB=n
unused-variable gotcha)? That would involve evaluating the arg within
the CONFIG_SLOB=y version of the macro.
On 11/22/22 06:30, Feng Tang wrote:
> On Mon, Nov 21, 2022 at 12:19:38PM -0800, Andrew Morton wrote:
>> On Mon, 21 Nov 2022 21:50:23 +0800 Feng Tang <[email protected]> wrote:
>>
>> > +#ifndef CONFIG_SLOB
>> > +#define is_kmalloc_cache(s) ((s)->flags & SLAB_KMALLOC)
>> > +#else
>> > +#define is_kmalloc_cache(s) (false)
>> > +#endif
>>
>> Could be implemented as a static inline C function, yes?
>
> Right, I also did try inline function first, and met compilation error:
>
> "
> ./include/linux/slab.h: In function ‘is_kmalloc_cache’:
> ./include/linux/slab.h:159:18: error: invalid use of undefined type ‘struct kmem_cache’
> 159 | return (s->flags & SLAB_KMALLOC);
> | ^~
> "
>
> The reason is 'struct kmem_cache' definition for slab/slub/slob sit
> separately in slab_def.h, slub_def.h and mm/slab.h, and they are not
> included in this 'include/linux/slab.h'. So I chose the macro way.
You could try mm/slab.h instead, below the slub_def.h includes there.
is_kmalloc_cache(s) shouldn't have random consumers in the kernel anyway.
It's fine if kasan includes it, as it's intertwined with slab a lot anyway.
> Btw, I've worked on some patches related with sl[auo]b recently, and
> really felt the pain when dealing with 3 allocators, on both reading
> code and writing patches. And I really like the idea of fading away
> SLOB as the first step :)
Can't agree more :)
>> If so, that's always best. For (silly) example, consider the behaviour
>> of
>>
>> x = is_kmalloc_cache(s++);
>>
>> with and without CONFIG_SLOB.
>
> Another solution I can think of is putting the implementation into
> slab_common.c, like the below?
The overhead of function call between compilation units (sans LTO) is not
worth it.
> Thanks,
> Feng
>
> ---
> diff --git a/include/linux/slab.h b/include/linux/slab.h
> index 067f0e80be9e..e4fcdbfb3477 100644
> --- a/include/linux/slab.h
> +++ b/include/linux/slab.h
> @@ -149,6 +149,17 @@
>
> struct list_lru;
> struct mem_cgroup;
> +
> +#ifndef CONFIG_SLOB
> +extern bool is_kmalloc_cache(struct kmem_cache *s);
> +#else
> +static inline bool is_kmalloc_cache(struct kmem_cache *s)
> +{
> + return false;
> +}
> +#endif
> +
> /*
> * struct kmem_cache related prototypes
> */
> diff --git a/mm/slab_common.c b/mm/slab_common.c
> index a5480d67f391..860e804b7c0a 100644
> --- a/mm/slab_common.c
> +++ b/mm/slab_common.c
> @@ -77,6 +77,13 @@ __setup_param("slub_merge", slub_merge, setup_slab_merge, 0);
> __setup("slab_nomerge", setup_slab_nomerge);
> __setup("slab_merge", setup_slab_merge);
>
> +#ifndef CONFIG_SLOB
> +bool is_kmalloc_cache(struct kmem_cache *s)
> +{
> + return (s->flags & SLAB_KMALLOC);
> +}
> +#endif
> +
> /*
> * Determine the size of a slab object
> */
On Wed, Nov 23, 2022 at 10:21:03AM +0100, Vlastimil Babka wrote:
> On 11/22/22 06:30, Feng Tang wrote:
> > On Mon, Nov 21, 2022 at 12:19:38PM -0800, Andrew Morton wrote:
> >> On Mon, 21 Nov 2022 21:50:23 +0800 Feng Tang <[email protected]> wrote:
> >>
> >> > +#ifndef CONFIG_SLOB
> >> > +#define is_kmalloc_cache(s) ((s)->flags & SLAB_KMALLOC)
> >> > +#else
> >> > +#define is_kmalloc_cache(s) (false)
> >> > +#endif
> >>
> >> Could be implemented as a static inline C function, yes?
> >
> > Right, I also did try inline function first, and met compilation error:
> >
> > "
> > ./include/linux/slab.h: In function ‘is_kmalloc_cache’:
> > ./include/linux/slab.h:159:18: error: invalid use of undefined type ‘struct kmem_cache’
> > 159 | return (s->flags & SLAB_KMALLOC);
> > | ^~
> > "
> >
> > The reason is 'struct kmem_cache' definition for slab/slub/slob sit
> > separately in slab_def.h, slub_def.h and mm/slab.h, and they are not
> > included in this 'include/linux/slab.h'. So I chose the macro way.
>
> You could try mm/slab.h instead, below the slub_def.h includes there.
> is_kmalloc_cache(s) shouldn't have random consumers in the kernel anyway.
> It's fine if kasan includes it, as it's intertwined with slab a lot anyway.
Good suggestion! thanks! This can address Andrew's concern and also
avoid extra cost.
And yes, besides sanity code like kasan/kfence, rare code will care
whether other kmem_cache is a kmalloc cache or not. And kasan code
already includes "../slab.h".
> > Btw, I've worked on some patches related with sl[auo]b recently, and
> > really felt the pain when dealing with 3 allocators, on both reading
> > code and writing patches. And I really like the idea of fading away
> > SLOB as the first step :)
>
> Can't agree more :)
>
> >> If so, that's always best. For (silly) example, consider the behaviour
> >> of
> >>
> >> x = is_kmalloc_cache(s++);
> >>
> >> with and without CONFIG_SLOB.
> >
> > Another solution I can think of is putting the implementation into
> > slab_common.c, like the below?
>
> The overhead of function call between compilation units (sans LTO) is not
> worth it.
Yes. Will send out the v2 patches.
Thanks,
Feng