Commit b035f5a6d852 ("mm: slab: reduce the kmalloc() minimum alignment
if DMA bouncing possible") allows architectures with non-coherent DMA to
define a small ARCH_KMALLOC_MINALIGN (e.g. sizeof(unsigned long long))
and this has been enabled on arm64. With KASAN_HW_TAGS enabled, however,
ARCH_SLAB_MINALIGN becomes 16 on arm64 (arch_slab_minalign() dynamically
selects it since commit d949a8155d13 ("mm: make minimum slab alignment a
runtime property")). This can lead to a situation where kmalloc-8 caches
are attempted to be created with a kmem_caches.size aligned to 16. When
the cache is mergeable, it can lead to kernel warnings like:
sysfs: cannot create duplicate filename '/kernel/slab/:d-0000016'
CPU: 0 PID: 1 Comm: swapper/0 Not tainted 6.6.0-rc1-00001-gda98843cd306-dirty #5
Hardware name: QEMU QEMU Virtual Machine, BIOS 0.0.0 02/06/2015
Call trace:
dump_backtrace+0x90/0xe8
show_stack+0x18/0x24
dump_stack_lvl+0x48/0x60
dump_stack+0x18/0x24
sysfs_warn_dup+0x64/0x80
sysfs_create_dir_ns+0xe8/0x108
kobject_add_internal+0x98/0x264
kobject_init_and_add+0x8c/0xd8
sysfs_slab_add+0x12c/0x248
slab_sysfs_init+0x98/0x14c
do_one_initcall+0x6c/0x1b0
kernel_init_freeable+0x1c0/0x288
kernel_init+0x24/0x1e0
ret_from_fork+0x10/0x20
kobject: kobject_add_internal failed for :d-0000016 with -EEXIST, don't try to register things with the same name in the same directory.
SLUB: Unable to add boot slab dma-kmalloc-8 to sysfs
Limit the __kmalloc_minalign() return value (used to create the
kmalloc-* caches) to arch_slab_minalign() so that kmalloc-8 caches are
skipped when KASAN_HW_TAGS is enabled (both config and runtime).
Fixes: b035f5a6d852 ("mm: slab: reduce the kmalloc() minimum alignment if DMA bouncing possible")
Signed-off-by: Catalin Marinas <[email protected]>
Reported-by: Mark Rutland <[email protected]>
Cc: Andrew Morton <[email protected]>
Cc: Vlastimil Babka <[email protected]>
Cc: Peter Collingbourne <[email protected]>
Cc: <[email protected]> # 6.5.x
---
The previous post was messed up by my git send-email configuration, so
sending it again. Also cc'ing Vlastimil since he reviewed the previous
slab changes for ARCH_KMALLOC_MINALIGN. Thanks.
mm/slab_common.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)
diff --git a/mm/slab_common.c b/mm/slab_common.c
index cd71f9581e67..8b45922ed295 100644
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@ -895,10 +895,13 @@ void __init setup_kmalloc_cache_index_table(void)
static unsigned int __kmalloc_minalign(void)
{
+ unsigned int minalign = dma_get_cache_alignment();
+
if (IS_ENABLED(CONFIG_DMA_BOUNCE_UNALIGNED_KMALLOC) &&
is_swiotlb_allocated())
- return ARCH_KMALLOC_MINALIGN;
- return dma_get_cache_alignment();
+ minalign = ARCH_KMALLOC_MINALIGN;
+
+ return ALIGN(minalign, arch_slab_minalign());
}
void __init
On 10/6/23 18:39, Catalin Marinas wrote:
> Commit b035f5a6d852 ("mm: slab: reduce the kmalloc() minimum alignment
> if DMA bouncing possible") allows architectures with non-coherent DMA to
> define a small ARCH_KMALLOC_MINALIGN (e.g. sizeof(unsigned long long))
> and this has been enabled on arm64. With KASAN_HW_TAGS enabled, however,
> ARCH_SLAB_MINALIGN becomes 16 on arm64 (arch_slab_minalign() dynamically
> selects it since commit d949a8155d13 ("mm: make minimum slab alignment a
> runtime property")). This can lead to a situation where kmalloc-8 caches
> are attempted to be created with a kmem_caches.size aligned to 16. When
> the cache is mergeable, it can lead to kernel warnings like:
>
> sysfs: cannot create duplicate filename '/kernel/slab/:d-0000016'
> CPU: 0 PID: 1 Comm: swapper/0 Not tainted 6.6.0-rc1-00001-gda98843cd306-dirty #5
> Hardware name: QEMU QEMU Virtual Machine, BIOS 0.0.0 02/06/2015
> Call trace:
> dump_backtrace+0x90/0xe8
> show_stack+0x18/0x24
> dump_stack_lvl+0x48/0x60
> dump_stack+0x18/0x24
> sysfs_warn_dup+0x64/0x80
> sysfs_create_dir_ns+0xe8/0x108
> kobject_add_internal+0x98/0x264
> kobject_init_and_add+0x8c/0xd8
> sysfs_slab_add+0x12c/0x248
> slab_sysfs_init+0x98/0x14c
> do_one_initcall+0x6c/0x1b0
> kernel_init_freeable+0x1c0/0x288
> kernel_init+0x24/0x1e0
> ret_from_fork+0x10/0x20
> kobject: kobject_add_internal failed for :d-0000016 with -EEXIST, don't try to register things with the same name in the same directory.
> SLUB: Unable to add boot slab dma-kmalloc-8 to sysfs
>
> Limit the __kmalloc_minalign() return value (used to create the
> kmalloc-* caches) to arch_slab_minalign() so that kmalloc-8 caches are
> skipped when KASAN_HW_TAGS is enabled (both config and runtime).
>
> Fixes: b035f5a6d852 ("mm: slab: reduce the kmalloc() minimum alignment if DMA bouncing possible")
> Signed-off-by: Catalin Marinas <[email protected]>
> Reported-by: Mark Rutland <[email protected]>
> Cc: Andrew Morton <[email protected]>
> Cc: Vlastimil Babka <[email protected]>
> Cc: Peter Collingbourne <[email protected]>
> Cc: <[email protected]> # 6.5.x
> ---
>
> The previous post was messed up by my git send-email configuration, so
> sending it again. Also cc'ing Vlastimil since he reviewed the previous
> slab changes for ARCH_KMALLOC_MINALIGN. Thanks.
It also touches only slab files so I can take it via slab tree.
> mm/slab_common.c | 7 +++++--
> 1 file changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/mm/slab_common.c b/mm/slab_common.c
> index cd71f9581e67..8b45922ed295 100644
> --- a/mm/slab_common.c
> +++ b/mm/slab_common.c
> @@ -895,10 +895,13 @@ void __init setup_kmalloc_cache_index_table(void)
>
> static unsigned int __kmalloc_minalign(void)
> {
> + unsigned int minalign = dma_get_cache_alignment();
> +
> if (IS_ENABLED(CONFIG_DMA_BOUNCE_UNALIGNED_KMALLOC) &&
> is_swiotlb_allocated())
> - return ARCH_KMALLOC_MINALIGN;
> - return dma_get_cache_alignment();
> + minalign = ARCH_KMALLOC_MINALIGN;
> +
> + return ALIGN(minalign, arch_slab_minalign());
Could it be max() instead of ALIGN()? It would be more obvious, at least to
me :)
> }
>
> void __init
On Mon, Oct 09, 2023 at 10:22:52AM +0200, Vlastimil Babka wrote:
> On 10/6/23 18:39, Catalin Marinas wrote:
> > Commit b035f5a6d852 ("mm: slab: reduce the kmalloc() minimum alignment
> > if DMA bouncing possible") allows architectures with non-coherent DMA to
> > define a small ARCH_KMALLOC_MINALIGN (e.g. sizeof(unsigned long long))
> > and this has been enabled on arm64. With KASAN_HW_TAGS enabled, however,
> > ARCH_SLAB_MINALIGN becomes 16 on arm64 (arch_slab_minalign() dynamically
> > selects it since commit d949a8155d13 ("mm: make minimum slab alignment a
> > runtime property")). This can lead to a situation where kmalloc-8 caches
> > are attempted to be created with a kmem_caches.size aligned to 16. When
> > the cache is mergeable, it can lead to kernel warnings like:
> >
> > sysfs: cannot create duplicate filename '/kernel/slab/:d-0000016'
> > CPU: 0 PID: 1 Comm: swapper/0 Not tainted 6.6.0-rc1-00001-gda98843cd306-dirty #5
> > Hardware name: QEMU QEMU Virtual Machine, BIOS 0.0.0 02/06/2015
> > Call trace:
> > dump_backtrace+0x90/0xe8
> > show_stack+0x18/0x24
> > dump_stack_lvl+0x48/0x60
> > dump_stack+0x18/0x24
> > sysfs_warn_dup+0x64/0x80
> > sysfs_create_dir_ns+0xe8/0x108
> > kobject_add_internal+0x98/0x264
> > kobject_init_and_add+0x8c/0xd8
> > sysfs_slab_add+0x12c/0x248
> > slab_sysfs_init+0x98/0x14c
> > do_one_initcall+0x6c/0x1b0
> > kernel_init_freeable+0x1c0/0x288
> > kernel_init+0x24/0x1e0
> > ret_from_fork+0x10/0x20
> > kobject: kobject_add_internal failed for :d-0000016 with -EEXIST, don't try to register things with the same name in the same directory.
> > SLUB: Unable to add boot slab dma-kmalloc-8 to sysfs
> >
> > Limit the __kmalloc_minalign() return value (used to create the
> > kmalloc-* caches) to arch_slab_minalign() so that kmalloc-8 caches are
> > skipped when KASAN_HW_TAGS is enabled (both config and runtime).
> >
> > Fixes: b035f5a6d852 ("mm: slab: reduce the kmalloc() minimum alignment if DMA bouncing possible")
> > Signed-off-by: Catalin Marinas <[email protected]>
> > Reported-by: Mark Rutland <[email protected]>
> > Cc: Andrew Morton <[email protected]>
> > Cc: Vlastimil Babka <[email protected]>
> > Cc: Peter Collingbourne <[email protected]>
> > Cc: <[email protected]> # 6.5.x
> > ---
> >
> > The previous post was messed up by my git send-email configuration, so
> > sending it again. Also cc'ing Vlastimil since he reviewed the previous
> > slab changes for ARCH_KMALLOC_MINALIGN. Thanks.
>
> It also touches only slab files so I can take it via slab tree.
Thanks.
> > mm/slab_common.c | 7 +++++--
> > 1 file changed, 5 insertions(+), 2 deletions(-)
> >
> > diff --git a/mm/slab_common.c b/mm/slab_common.c
> > index cd71f9581e67..8b45922ed295 100644
> > --- a/mm/slab_common.c
> > +++ b/mm/slab_common.c
> > @@ -895,10 +895,13 @@ void __init setup_kmalloc_cache_index_table(void)
> >
> > static unsigned int __kmalloc_minalign(void)
> > {
> > + unsigned int minalign = dma_get_cache_alignment();
> > +
> > if (IS_ENABLED(CONFIG_DMA_BOUNCE_UNALIGNED_KMALLOC) &&
> > is_swiotlb_allocated())
> > - return ARCH_KMALLOC_MINALIGN;
> > - return dma_get_cache_alignment();
> > + minalign = ARCH_KMALLOC_MINALIGN;
> > +
> > + return ALIGN(minalign, arch_slab_minalign());
>
> Could it be max() instead of ALIGN()? It would be more obvious, at least to
> me :)
Yeah, max() would do since they are all a power of two. Do you want me
to repost?
--
Catalin
On 10/9/23 13:20, Catalin Marinas wrote:
>> > mm/slab_common.c | 7 +++++--
>> > 1 file changed, 5 insertions(+), 2 deletions(-)
>> >
>> > diff --git a/mm/slab_common.c b/mm/slab_common.c
>> > index cd71f9581e67..8b45922ed295 100644
>> > --- a/mm/slab_common.c
>> > +++ b/mm/slab_common.c
>> > @@ -895,10 +895,13 @@ void __init setup_kmalloc_cache_index_table(void)
>> >
>> > static unsigned int __kmalloc_minalign(void)
>> > {
>> > + unsigned int minalign = dma_get_cache_alignment();
>> > +
>> > if (IS_ENABLED(CONFIG_DMA_BOUNCE_UNALIGNED_KMALLOC) &&
>> > is_swiotlb_allocated())
>> > - return ARCH_KMALLOC_MINALIGN;
>> > - return dma_get_cache_alignment();
>> > + minalign = ARCH_KMALLOC_MINALIGN;
>> > +
>> > + return ALIGN(minalign, arch_slab_minalign());
>>
>> Could it be max() instead of ALIGN()? It would be more obvious, at least to
>> me :)
>
> Yeah, max() would do since they are all a power of two. Do you want me
> to repost?
No need, picked up and changed locally. Thanks!