On 9/11/23 17:28, Huacai Chen wrote:
> After commit 61167ad5fecdea ("mm: pass nid to reserve_bootmem_region()")
> we get a panic if DEFERRED_STRUCT_PAGE_INIT is enabled:
>
> [snip]
>
> The reason is early memblock_reserve() in memblock_init() set node id
Why is it that only "early" but not "late" memblock_reserve() matters? I
failed to see the reason because the arch-specific memblock_init() isn't
even in the backtrace, which means that *neither* is the culprit.
> to MAX_NUMNODES, which causes NODE_DATA(nid) be a NULL dereference in
"making NODE_DATA(nid) a NULL ..."
> reserve_bootmem_region() -> init_reserved_page(). So set all reserved
> memblocks on Node#0 at initialization to avoid this panic.
>
> Reported-by: WANG Xuerui <[email protected]>
> Signed-off-by: Huacai Chen <[email protected]>
> ---
> arch/loongarch/kernel/mem.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/arch/loongarch/kernel/mem.c b/arch/loongarch/kernel/mem.c
> index 4a4107a6a965..aed901c57fb4 100644
> --- a/arch/loongarch/kernel/mem.c
> +++ b/arch/loongarch/kernel/mem.c
> @@ -50,7 +50,6 @@ void __init memblock_init(void)
> }
>
> memblock_set_current_limit(PFN_PHYS(max_low_pfn));
> - memblock_set_node(0, PHYS_ADDR_MAX, &memblock.memory, 0);
>
> /* Reserve the first 2MB */
> memblock_reserve(PHYS_OFFSET, 0x200000);
> @@ -58,4 +57,7 @@ void __init memblock_init(void)
> /* Reserve the kernel text/data/bss */
> memblock_reserve(__pa_symbol(&_text),
> __pa_symbol(&_end) - __pa_symbol(&_text));
> +
> + memblock_set_node(0, PHYS_ADDR_MAX, &memblock.memory, 0);
> + memblock_set_node(0, PHYS_ADDR_MAX, &memblock.reserved, 0);
So the reordering is for being able to override the newly added
memblocks' nids to 0, and additionally doing the same for
memblock.reserved is the actual fix. Looks okay.
> }
And I've tested the patch on the 2-way 3C5000L server, and it now
correctly boots with deferred struct page init enabled. Thanks for
providing such a quick fix!
Tested-by: WANG Xuerui <[email protected]>
Reviewed-by: WANG Xuerui <[email protected]> # with nits addressed
--
WANG "xen0n" Xuerui
Linux/LoongArch mailing list: https://lore.kernel.org/loongarch/
On Wed, Sep 13, 2023 at 12:08 AM WANG Xuerui <[email protected]> wrote:
>
> On 9/11/23 17:28, Huacai Chen wrote:
> > After commit 61167ad5fecdea ("mm: pass nid to reserve_bootmem_region()")
> > we get a panic if DEFERRED_STRUCT_PAGE_INIT is enabled:
> >
> > [snip]
> >
> > The reason is early memblock_reserve() in memblock_init() set node id
> Why is it that only "early" but not "late" memblock_reserve() matters? I
> failed to see the reason because the arch-specific memblock_init() isn't
> even in the backtrace, which means that *neither* is the culprit.
Late memblock_reserve() operates on subregions of memblock.memory
regions. These reserved regions will be set to the correct node at the
first iteration of memmap_init_reserved_pages().
Huacai
> > to MAX_NUMNODES, which causes NODE_DATA(nid) be a NULL dereference in
> "making NODE_DATA(nid) a NULL ..."
> > reserve_bootmem_region() -> init_reserved_page(). So set all reserved
> > memblocks on Node#0 at initialization to avoid this panic.
> >
> > Reported-by: WANG Xuerui <[email protected]>
> > Signed-off-by: Huacai Chen <[email protected]>
> > ---
> > arch/loongarch/kernel/mem.c | 4 +++-
> > 1 file changed, 3 insertions(+), 1 deletion(-)
> >
> > diff --git a/arch/loongarch/kernel/mem.c b/arch/loongarch/kernel/mem.c
> > index 4a4107a6a965..aed901c57fb4 100644
> > --- a/arch/loongarch/kernel/mem.c
> > +++ b/arch/loongarch/kernel/mem.c
> > @@ -50,7 +50,6 @@ void __init memblock_init(void)
> > }
> >
> > memblock_set_current_limit(PFN_PHYS(max_low_pfn));
> > - memblock_set_node(0, PHYS_ADDR_MAX, &memblock.memory, 0);
> >
> > /* Reserve the first 2MB */
> > memblock_reserve(PHYS_OFFSET, 0x200000);
> > @@ -58,4 +57,7 @@ void __init memblock_init(void)
> > /* Reserve the kernel text/data/bss */
> > memblock_reserve(__pa_symbol(&_text),
> > __pa_symbol(&_end) - __pa_symbol(&_text));
> > +
> > + memblock_set_node(0, PHYS_ADDR_MAX, &memblock.memory, 0);
> > + memblock_set_node(0, PHYS_ADDR_MAX, &memblock.reserved, 0);
> So the reordering is for being able to override the newly added
> memblocks' nids to 0, and additionally doing the same for
> memblock.reserved is the actual fix. Looks okay.
> > }
>
> And I've tested the patch on the 2-way 3C5000L server, and it now
> correctly boots with deferred struct page init enabled. Thanks for
> providing such a quick fix!
>
> Tested-by: WANG Xuerui <[email protected]>
> Reviewed-by: WANG Xuerui <[email protected]> # with nits addressed
>
> --
> WANG "xen0n" Xuerui
>
> Linux/LoongArch mailing list: https://lore.kernel.org/loongarch/
>
>
On 9/13/23 08:49, Huacai Chen wrote:
> On Wed, Sep 13, 2023 at 12:08 AM WANG Xuerui <[email protected]> wrote:
>> On 9/11/23 17:28, Huacai Chen wrote:
>>> After commit 61167ad5fecdea ("mm: pass nid to reserve_bootmem_region()")
>>> we get a panic if DEFERRED_STRUCT_PAGE_INIT is enabled:
>>>
>>> [snip]
>>>
>>> The reason is early memblock_reserve() in memblock_init() set node id
>> Why is it that only "early" but not "late" memblock_reserve() matters? I
>> failed to see the reason because the arch-specific memblock_init() isn't
>> even in the backtrace, which means that *neither* is the culprit.
> Late memblock_reserve() operates on subregions of memblock.memory
> regions. These reserved regions will be set to the correct node at the
> first iteration of memmap_init_reserved_pages().
Thanks for the clarification. According to the code behavior (and the
comment I left on the reordering change below) I'm now sure the intended
meaning is "calling memblock_reserve() after memblock_set_node() is
effectively leaving those regions with nid=MAX_NUMNODES" (or something
like that, pointing out that the memblock_set_node() call actually had
no effect in this case). "Early" and "late" in the context of init code
can be especially confusing IMO :-)
>
> Huacai
>
>>> to MAX_NUMNODES, which causes NODE_DATA(nid) be a NULL dereference in
>> "making NODE_DATA(nid) a NULL ..."
>>> reserve_bootmem_region() -> init_reserved_page(). So set all reserved
>>> memblocks on Node#0 at initialization to avoid this panic.
>>>
>>> Reported-by: WANG Xuerui <[email protected]>
>>> Signed-off-by: Huacai Chen <[email protected]>
>>> ---
>>> arch/loongarch/kernel/mem.c | 4 +++-
>>> 1 file changed, 3 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/arch/loongarch/kernel/mem.c b/arch/loongarch/kernel/mem.c
>>> index 4a4107a6a965..aed901c57fb4 100644
>>> --- a/arch/loongarch/kernel/mem.c
>>> +++ b/arch/loongarch/kernel/mem.c
>>> @@ -50,7 +50,6 @@ void __init memblock_init(void)
>>> }
>>>
>>> memblock_set_current_limit(PFN_PHYS(max_low_pfn));
>>> - memblock_set_node(0, PHYS_ADDR_MAX, &memblock.memory, 0);
>>>
>>> /* Reserve the first 2MB */
>>> memblock_reserve(PHYS_OFFSET, 0x200000);
>>> @@ -58,4 +57,7 @@ void __init memblock_init(void)
>>> /* Reserve the kernel text/data/bss */
>>> memblock_reserve(__pa_symbol(&_text),
>>> __pa_symbol(&_end) - __pa_symbol(&_text));
>>> +
>>> + memblock_set_node(0, PHYS_ADDR_MAX, &memblock.memory, 0);
>>> + memblock_set_node(0, PHYS_ADDR_MAX, &memblock.reserved, 0);
>> So the reordering is for being able to override the newly added
>> memblocks' nids to 0, and additionally doing the same for
>> memblock.reserved is the actual fix. Looks okay.
>>> }
>> And I've tested the patch on the 2-way 3C5000L server, and it now
>> correctly boots with deferred struct page init enabled. Thanks for
>> providing such a quick fix!
>>
>> Tested-by: WANG Xuerui <[email protected]>
>> Reviewed-by: WANG Xuerui <[email protected]> # with nits addressed
>>
>> --
>> WANG "xen0n" Xuerui
>>
>> Linux/LoongArch mailing list: https://lore.kernel.org/loongarch/
>>
>>
--
WANG "xen0n" Xuerui
Linux/LoongArch mailing list: https://lore.kernel.org/loongarch/