mm/slub.c | 13 ++++--------- 1 file changed, 4 insertions(+), 9 deletions(-)
From: Shengming Hu <hu.shengming@zte.com.cn>
Empty sheaves allocated by alloc_empty_sheaf() should be released with
free_empty_sheaf().
Move the empty-sheaf capacity initialization into __alloc_empty_sheaf()
and use it for oversized prefilled sheaves as well.
This keeps the prefill paths consistent: after flushing an oversized or
pfmemalloc sheaf, release the now-empty sheaf through free_empty_sheaf()
instead of kfree().
Signed-off-by: Shengming Hu <hu.shengming@zte.com.cn>
---
Changes in v2:
- Rework the change as suggested by Harry.
- Teach __alloc_empty_sheaf() to initialize capacity and pfmemalloc.
- Allocate oversized prefilled sheaves through __alloc_empty_sheaf().
- Free flushed oversized and pfmemalloc sheaves through free_empty_sheaf().
- Link to v1: https://lore.kernel.org/all/20260521195015105Y4zvKHj0TfPZEujixy9Vo@zte.com.cn/
Changes in v3:
- Address Hao's comments:
- Drop the redundant `pfmemalloc` initialization in
__alloc_empty_sheaf().
- Keep initializing `capacity` and `pfmemalloc` in the normal-sized
prefill path, since the sheaf may be reused rather than freshly
allocated.
- Link to v2: https://lore.kernel.org/all/20260522145900248m-nBcy07_SCDk2ATDWfmg@zte.com.cn/
---
mm/slub.c | 13 ++++---------
1 file changed, 4 insertions(+), 9 deletions(-)
diff --git a/mm/slub.c b/mm/slub.c
index 04692a6f9128..f4c06bf43f2d 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -2782,6 +2782,7 @@ static struct slab_sheaf *__alloc_empty_sheaf(struct kmem_cache *s, gfp_t gfp,
return NULL;
sheaf->cache = s;
+ sheaf->capacity = capacity;
stat(s, SHEAF_ALLOC);
@@ -5015,21 +5016,15 @@ kmem_cache_prefill_sheaf(struct kmem_cache *s, gfp_t gfp, unsigned int size)
if (unlikely(size > s->sheaf_capacity)) {
- sheaf = kzalloc_flex(*sheaf, objects, size, gfp);
+ sheaf = __alloc_empty_sheaf(s, gfp, size);
if (!sheaf)
return NULL;
stat(s, SHEAF_PREFILL_OVERSIZE);
- sheaf->cache = s;
- sheaf->capacity = size;
- /*
- * we do not need to care about pfmemalloc here because oversize
- * sheaves area always flushed and freed when returned
- */
if (!__kmem_cache_alloc_bulk(s, gfp, size,
&sheaf->objects[0])) {
- kfree(sheaf);
+ free_empty_sheaf(s, sheaf);
return NULL;
}
@@ -5097,7 +5092,7 @@ void kmem_cache_return_sheaf(struct kmem_cache *s, gfp_t gfp,
if (unlikely((sheaf->capacity != s->sheaf_capacity)
|| sheaf->pfmemalloc)) {
sheaf_flush_unused(s, sheaf);
- kfree(sheaf);
+ free_empty_sheaf(s, sheaf);
return;
}
--
2.25.1Hi, kernel test robot noticed the following build errors: [auto build test ERROR on akpm-mm/mm-everything] url: https://github.com/intel-lab-lkp/linux/commits/hu-shengming-zte-com-cn/mm-slub-free-prefilled-empty-sheaves-consistently/20260525-211805 base: https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git mm-everything patch link: https://lore.kernel.org/r/20260525211000387LYqTHmxYL900XIB8qwV3h%40zte.com.cn patch subject: [PATCH v3] mm/slub: free prefilled empty sheaves consistently config: powerpc-randconfig-002-20260529 (https://download.01.org/0day-ci/archive/20260529/202605290406.mjAKJqbo-lkp@intel.com/config) compiler: clang version 19.1.7 (https://github.com/llvm/llvm-project cd708029e0b2869e80abe31ddb175f7c35361f90) reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260529/202605290406.mjAKJqbo-lkp@intel.com/reproduce) If you fix the issue in a separate patch/commit (i.e. not just a new version of the same patch/commit), kindly add following tags | Reported-by: kernel test robot <lkp@intel.com> | Closes: https://lore.kernel.org/oe-kbuild-all/202605290406.mjAKJqbo-lkp@intel.com/ All errors (new ones prefixed by >>): >> ld.lld: error: relocation R_PPC_ADDR16_HA cannot be used against symbol 'decrementers_next_tb'; recompile with -fPIC >>> defined in vmlinux.a(arch/powerpc/kernel/time.o) >>> referenced by time.c >>> arch/powerpc/kernel/time.o:(decrementer_set_next_event) in archive vmlinux.a -- >> ld.lld: error: relocation R_PPC_ADDR16_HA cannot be used against symbol 'ppc_emulated'; recompile with -fPIC >>> defined in vmlinux.a(arch/powerpc/kernel/traps.o) >>> referenced by align.c >>> arch/powerpc/kernel/align.o:(fix_alignment) in archive vmlinux.a -- 0-DAY CI Kernel Test Service https://github.com/intel/lkp-tests/wiki
On 5/28/26 22:29, kernel test robot wrote: > Hi, > > kernel test robot noticed the following build errors: > > [auto build test ERROR on akpm-mm/mm-everything] > > url: https://github.com/intel-lab-lkp/linux/commits/hu-shengming-zte-com-cn/mm-slub-free-prefilled-empty-sheaves-consistently/20260525-211805 > base: https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git mm-everything > patch link: https://lore.kernel.org/r/20260525211000387LYqTHmxYL900XIB8qwV3h%40zte.com.cn > patch subject: [PATCH v3] mm/slub: free prefilled empty sheaves consistently > config: powerpc-randconfig-002-20260529 (https://download.01.org/0day-ci/archive/20260529/202605290406.mjAKJqbo-lkp@intel.com/config) > compiler: clang version 19.1.7 (https://github.com/llvm/llvm-project cd708029e0b2869e80abe31ddb175f7c35361f90) > reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260529/202605290406.mjAKJqbo-lkp@intel.com/reproduce) > > If you fix the issue in a separate patch/commit (i.e. not just a new version of > the same patch/commit), kindly add following tags > | Reported-by: kernel test robot <lkp@intel.com> > | Closes: https://lore.kernel.org/oe-kbuild-all/202605290406.mjAKJqbo-lkp@intel.com/ > > All errors (new ones prefixed by >>): > >>> ld.lld: error: relocation R_PPC_ADDR16_HA cannot be used against symbol 'decrementers_next_tb'; recompile with -fPIC > >>> defined in vmlinux.a(arch/powerpc/kernel/time.o) > >>> referenced by time.c > >>> arch/powerpc/kernel/time.o:(decrementer_set_next_event) in archive vmlinux.a > -- >>> ld.lld: error: relocation R_PPC_ADDR16_HA cannot be used against symbol 'ppc_emulated'; recompile with -fPIC > >>> defined in vmlinux.a(arch/powerpc/kernel/traps.o) > >>> referenced by align.c > >>> arch/powerpc/kernel/align.o:(fix_alignment) in archive vmlinux.a Looks like a false positive, the patch didn't touch any of that. > -- > 0-DAY CI Kernel Test Service > https://github.com/intel/lkp-tests/wiki
On 5/25/26 10:10 PM, hu.shengming@zte.com.cn wrote:
> From: Shengming Hu <hu.shengming@zte.com.cn>
>
> Empty sheaves allocated by alloc_empty_sheaf() should be released with
> free_empty_sheaf().
>
> Move the empty-sheaf capacity initialization into __alloc_empty_sheaf()
> and use it for oversized prefilled sheaves as well.
>
> This keeps the prefill paths consistent: after flushing an oversized or
> pfmemalloc sheaf, release the now-empty sheaf through free_empty_sheaf()
> instead of kfree().
>
> Signed-off-by: Shengming Hu <hu.shengming@zte.com.cn>
> ---
> mm/slub.c | 13 ++++---------
> 1 file changed, 4 insertions(+), 9 deletions(-)
>
> diff --git a/mm/slub.c b/mm/slub.c
> index 04692a6f9128..f4c06bf43f2d 100644
> --- a/mm/slub.c
> +++ b/mm/slub.c
> @@ -2782,6 +2782,7 @@ static struct slab_sheaf *__alloc_empty_sheaf(struct kmem_cache *s, gfp_t gfp,
> return NULL;
>
> sheaf->cache = s;
> + sheaf->capacity = capacity;
the capacity field is only used by oversized sheaves (for now).
It should be outside __alloc_empty_sheaf().
> stat(s, SHEAF_ALLOC);
>
> @@ -5015,21 +5016,15 @@ kmem_cache_prefill_sheaf(struct kmem_cache *s, gfp_t gfp, unsigned int size)
>
> if (unlikely(size > s->sheaf_capacity)) {
>
> - sheaf = kzalloc_flex(*sheaf, objects, size, gfp);
> + sheaf = __alloc_empty_sheaf(s, gfp, size);
> if (!sheaf)
> return NULL;
>
> stat(s, SHEAF_PREFILL_OVERSIZE);
So now SHEAF_ALLOC and SHEAF_FREE include oversized sheaves.
I think that's fine, but can we update the commit message and the comment?
the comment:
SHEAF_ALLOC, /* Allocation of an empty sheaf including oversized ones */
SHEAF_FREE, /* Freeing of an empty sheaf including oversized ones */
> - sheaf->cache = s;
> - sheaf->capacity = size;
> - /*
> - * we do not need to care about pfmemalloc here because oversize
> - * sheaves area always flushed and freed when returned
> - */
the comment is still worth having?
> if (!__kmem_cache_alloc_bulk(s, gfp, size,
> &sheaf->objects[0])) {
> - kfree(sheaf);
> + free_empty_sheaf(s, sheaf);
> return NULL;
> }
--
Cheers,
Harry / Hyeonggon
Harry worte:
> On 5/25/26 10:10 PM, hu.shengming@zte.com.cn wrote:
> > From: Shengming Hu <hu.shengming@zte.com.cn>
> >
> > Empty sheaves allocated by alloc_empty_sheaf() should be released with
> > free_empty_sheaf().
> >
> > Move the empty-sheaf capacity initialization into __alloc_empty_sheaf()
> > and use it for oversized prefilled sheaves as well.
> >
> > This keeps the prefill paths consistent: after flushing an oversized or
> > pfmemalloc sheaf, release the now-empty sheaf through free_empty_sheaf()
> > instead of kfree().
> >
> > Signed-off-by: Shengming Hu <hu.shengming@zte.com.cn>
> > ---
> > mm/slub.c | 13 ++++---------
> > 1 file changed, 4 insertions(+), 9 deletions(-)
> >
> > diff --git a/mm/slub.c b/mm/slub.c
> > index 04692a6f9128..f4c06bf43f2d 100644
> > --- a/mm/slub.c
> > +++ b/mm/slub.c
> > @@ -2782,6 +2782,7 @@ static struct slab_sheaf *__alloc_empty_sheaf(struct kmem_cache *s, gfp_t gfp,
> > return NULL;
> >
> > sheaf->cache = s;
> > + sheaf->capacity = capacity;
>
> the capacity field is only used by oversized sheaves (for now).
> It should be outside __alloc_empty_sheaf().
>
Thanks for the review.
That makes sense. I will keep the capacity initialization in the
oversized prefill path.
> > stat(s, SHEAF_ALLOC);
> >
> > @@ -5015,21 +5016,15 @@ kmem_cache_prefill_sheaf(struct kmem_cache *s, gfp_t gfp, unsigned int size)
> >
> > if (unlikely(size > s->sheaf_capacity)) {
> >
> > - sheaf = kzalloc_flex(*sheaf, objects, size, gfp);
> > + sheaf = __alloc_empty_sheaf(s, gfp, size);
> > if (!sheaf)
> > return NULL;
> >
> > stat(s, SHEAF_PREFILL_OVERSIZE);
>
> So now SHEAF_ALLOC and SHEAF_FREE include oversized sheaves.
> I think that's fine, but can we update the commit message and the comment?
>
> the comment:
> SHEAF_ALLOC, /* Allocation of an empty sheaf including oversized ones */
> SHEAF_FREE, /* Freeing of an empty sheaf including oversized ones */
>
Yes, I will update the stat comments and mention this in the commit message.
> > - sheaf->cache = s;
> > - sheaf->capacity = size;
> > - /*
> > - * we do not need to care about pfmemalloc here because oversize
> > - * sheaves area always flushed and freed when returned
> > - */
>
> the comment is still worth having?
>
The pfmemalloc comment is still useful as well. I dropped it too
aggressively, so I will restore it in v4.
> > if (!__kmem_cache_alloc_bulk(s, gfp, size,
> > &sheaf->objects[0])) {
> > - kfree(sheaf);
> > + free_empty_sheaf(s, sheaf);
> > return NULL;
> > }
>
> --
> Cheers,
> Harry / Hyeonggon
--
With Best Regards,
Shengming
On Mon, May 25, 2026 at 09:10:00PM +0800, hu.shengming@zte.com.cn wrote:
> From: Shengming Hu <hu.shengming@zte.com.cn>
>
> Empty sheaves allocated by alloc_empty_sheaf() should be released with
> free_empty_sheaf().
>
> Move the empty-sheaf capacity initialization into __alloc_empty_sheaf()
> and use it for oversized prefilled sheaves as well.
>
> This keeps the prefill paths consistent: after flushing an oversized or
> pfmemalloc sheaf, release the now-empty sheaf through free_empty_sheaf()
> instead of kfree().
>
> Signed-off-by: Shengming Hu <hu.shengming@zte.com.cn>
> ---
> Changes in v2:
> - Rework the change as suggested by Harry.
> - Teach __alloc_empty_sheaf() to initialize capacity and pfmemalloc.
> - Allocate oversized prefilled sheaves through __alloc_empty_sheaf().
> - Free flushed oversized and pfmemalloc sheaves through free_empty_sheaf().
> - Link to v1: https://lore.kernel.org/all/20260521195015105Y4zvKHj0TfPZEujixy9Vo@zte.com.cn/
>
> Changes in v3:
> - Address Hao's comments:
> - Drop the redundant `pfmemalloc` initialization in
> __alloc_empty_sheaf().
> - Keep initializing `capacity` and `pfmemalloc` in the normal-sized
> prefill path, since the sheaf may be reused rather than freshly
> allocated.
> - Link to v2: https://lore.kernel.org/all/20260522145900248m-nBcy07_SCDk2ATDWfmg@zte.com.cn/
>
> ---
> mm/slub.c | 13 ++++---------
> 1 file changed, 4 insertions(+), 9 deletions(-)
>
> diff --git a/mm/slub.c b/mm/slub.c
> index 04692a6f9128..f4c06bf43f2d 100644
> --- a/mm/slub.c
> +++ b/mm/slub.c
> @@ -2782,6 +2782,7 @@ static struct slab_sheaf *__alloc_empty_sheaf(struct kmem_cache *s, gfp_t gfp,
> return NULL;
>
> sheaf->cache = s;
> + sheaf->capacity = capacity;
>
> stat(s, SHEAF_ALLOC);
>
> @@ -5015,21 +5016,15 @@ kmem_cache_prefill_sheaf(struct kmem_cache *s, gfp_t gfp, unsigned int size)
>
> if (unlikely(size > s->sheaf_capacity)) {
>
> - sheaf = kzalloc_flex(*sheaf, objects, size, gfp);
> + sheaf = __alloc_empty_sheaf(s, gfp, size);
> if (!sheaf)
> return NULL;
>
> stat(s, SHEAF_PREFILL_OVERSIZE);
> - sheaf->cache = s;
> - sheaf->capacity = size;
>
> - /*
> - * we do not need to care about pfmemalloc here because oversize
> - * sheaves area always flushed and freed when returned
> - */
just a bit curious, why did you decide to delete these comments?
> if (!__kmem_cache_alloc_bulk(s, gfp, size,
> &sheaf->objects[0])) {
> - kfree(sheaf);
> + free_empty_sheaf(s, sheaf);
> return NULL;
> }
>
> @@ -5097,7 +5092,7 @@ void kmem_cache_return_sheaf(struct kmem_cache *s, gfp_t gfp,
> if (unlikely((sheaf->capacity != s->sheaf_capacity)
> || sheaf->pfmemalloc)) {
> sheaf_flush_unused(s, sheaf);
> - kfree(sheaf);
> + free_empty_sheaf(s, sheaf);
> return;
> }
>
> --
> 2.25.1
Hao wrote:
> On Mon, May 25, 2026 at 09:10:00PM +0800, hu.shengming@zte.com.cn wrote:
> > From: Shengming Hu <hu.shengming@zte.com.cn>
> >
> > Empty sheaves allocated by alloc_empty_sheaf() should be released with
> > free_empty_sheaf().
> >
> > Move the empty-sheaf capacity initialization into __alloc_empty_sheaf()
> > and use it for oversized prefilled sheaves as well.
> >
> > This keeps the prefill paths consistent: after flushing an oversized or
> > pfmemalloc sheaf, release the now-empty sheaf through free_empty_sheaf()
> > instead of kfree().
> >
> > Signed-off-by: Shengming Hu <hu.shengming@zte.com.cn>
> > ---
> > Changes in v2:
> > - Rework the change as suggested by Harry.
> > - Teach __alloc_empty_sheaf() to initialize capacity and pfmemalloc.
> > - Allocate oversized prefilled sheaves through __alloc_empty_sheaf().
> > - Free flushed oversized and pfmemalloc sheaves through free_empty_sheaf().
> > - Link to v1: https://lore.kernel.org/all/20260521195015105Y4zvKHj0TfPZEujixy9Vo@zte.com.cn/
> >
> > Changes in v3:
> > - Address Hao's comments:
> > - Drop the redundant `pfmemalloc` initialization in
> > __alloc_empty_sheaf().
> > - Keep initializing `capacity` and `pfmemalloc` in the normal-sized
> > prefill path, since the sheaf may be reused rather than freshly
> > allocated.
> > - Link to v2: https://lore.kernel.org/all/20260522145900248m-nBcy07_SCDk2ATDWfmg@zte.com.cn/
> >
> > ---
> > mm/slub.c | 13 ++++---------
> > 1 file changed, 4 insertions(+), 9 deletions(-)
> >
> > diff --git a/mm/slub.c b/mm/slub.c
> > index 04692a6f9128..f4c06bf43f2d 100644
> > --- a/mm/slub.c
> > +++ b/mm/slub.c
> > @@ -2782,6 +2782,7 @@ static struct slab_sheaf *__alloc_empty_sheaf(struct kmem_cache *s, gfp_t gfp,
> > return NULL;
> >
> > sheaf->cache = s;
> > + sheaf->capacity = capacity;
> >
> > stat(s, SHEAF_ALLOC);
> >
> > @@ -5015,21 +5016,15 @@ kmem_cache_prefill_sheaf(struct kmem_cache *s, gfp_t gfp, unsigned int size)
> >
> > if (unlikely(size > s->sheaf_capacity)) {
> >
> > - sheaf = kzalloc_flex(*sheaf, objects, size, gfp);
> > + sheaf = __alloc_empty_sheaf(s, gfp, size);
> > if (!sheaf)
> > return NULL;
> >
> > stat(s, SHEAF_PREFILL_OVERSIZE);
> > - sheaf->cache = s;
> > - sheaf->capacity = size;
> >
> > - /*
> > - * we do not need to care about pfmemalloc here because oversize
> > - * sheaves area always flushed and freed when returned
> > - */
>
> just a bit curious, why did you decide to delete these comments?
>
Sorry about that.
I removed the comment while moving the oversized sheaf allocation to
__alloc_empty_sheaf(), because the local cache/capacity initialization was
removed from this path. However, looking at it again, the comment is still
worth.
I will restore it in v4.
Thanks a lot.
> > if (!__kmem_cache_alloc_bulk(s, gfp, size,
> > &sheaf->objects[0])) {
> > - kfree(sheaf);
> > + free_empty_sheaf(s, sheaf);
> > return NULL;
> > }
> >
> > @@ -5097,7 +5092,7 @@ void kmem_cache_return_sheaf(struct kmem_cache *s, gfp_t gfp,
> > if (unlikely((sheaf->capacity != s->sheaf_capacity)
> > || sheaf->pfmemalloc)) {
> > sheaf_flush_unused(s, sheaf);
> > - kfree(sheaf);
> > + free_empty_sheaf(s, sheaf);
> > return;
> > }
> >
> > --
> > 2.25.1
--
With Best Regards,
Shengming
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