> On Tue 24-09-19 08:46:48, Mircea CIRJALIU - MELIU wrote:
> > Having CONFIG_MEMCG turned off causes these issues:
> > mm/slub.o: In function `slab_pre_alloc_hook':
> > /home/mircea/build/mm/slab.h:425: undefined reference to
> `memcg_kmem_get_cache'
> > mm/slub.o: In function `slab_post_alloc_hook':
> > /home/mircea/build/mm/slab.h:444: undefined reference to
> `memcg_kmem_put_cache'
>
> You should be adding your Sign-off-by to every patch you post to the kernel
> mailing list (see Documentation/SubmittingPatches).
>
> It is also really important to mention which tree does this apply to and ideally
> also note which change has broken the code. In this particular case I have
> tried the current Linus tree (4c07e2ddab5b) and $ grep
> 'CONFIG_SLUB\|CONFIG_MEMCG' .config # CONFIG_MEMCG is not set
> CONFIG_SLUB_DEBUG=y CONFIG_SLUB=y CONFIG_SLUB_CPU_PARTIAL=y
> # CONFIG_SLUB_DEBUG_ON is not set # CONFIG_SLUB_STATS is not set
>
> which means CONFIG_MEMCG_KMEM is not enabled as well. And the
> compilation succeeds. What is your config file?
The config file is not the problem (figured it out).
I am lowering the optimization level on certain files for debug purposes.
In my case: CFLAGS_slub.o += -O1 -fno-inline
The code which causes the problem looks like this:
static inline struct kmem_cache *slab_pre_alloc_hook(struct kmem_cache *s,
gfp_t flags)
{
...
if (memcg_kmem_enabled() &&
((flags & __GFP_ACCOUNT) || (s->flags & SLAB_ACCOUNT)))
return memcg_kmem_get_cache(s);
...
}
Under normal circumstances memcg_kmem_enabled() returns false and the
statement is evaluated as unreachable and removed entirely.
It seems -O1 keeps the call to memcg_kmem_get_cache().
The change that introduced this is here:
commit 452647784b2fccfdeeb976f6f842c6719fb2daac
Author: Vladimir Davydov <vdavydov@xxxxxxxxxxxxx>
Date: Tue Jul 26 15:24:21 2016 -0700
Although I had the same problem before with other header files.
