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[PATCH 2/2] perf/ring_buffer: Fix high-order allocations for AUX space with correct MAX_ORDER limit

Shuai Xue posted 2 patches 2 years, 8 months ago
[PATCH 2/2] perf/ring_buffer: Fix high-order allocations for AUX space with correct MAX_ORDER limit
Posted by Shuai Xue 2 years, 8 months ago 
When perf-record with a large AUX area, e.g 2GB:

    #perf record -C 0 -m ,2G -e arm_spe_0// -- sleep 1

it reveals a WARNING with __alloc_pages:

[   48.888553] ------------[ cut here ]------------
[   48.888559] WARNING: CPU: 39 PID: 17438 at mm/page_alloc.c:5568 __alloc_pages+0x1ec/0x248
[   48.888569] Modules linked in: ip6table_filter(E) ip6_tables(E) iptable_filter(E) ebtable_nat(E) ebtables(E) vfat(E) fat(E) aes_ce_blk(E) aes_ce_cipher(E) crct10dif_ce(E) ghash_ce(E) sm4_ce_cipher(E) sm4(E) sha2_ce(E) sha256_arm64(E) sha1_ce(E) acpi_ipmi(E) sbsa_gwdt(E) sg(E) ipmi_si(E) ipmi_devintf(E) ipmi_msghandler(E) ip_tables(E) sd_mod(E) ast(E) drm_kms_helper(E) syscopyarea(E) sysfillrect(E) nvme(E) sysimgblt(E) i2c_algo_bit(E) nvme_core(E) drm_shmem_helper(E) ahci(E) t10_pi(E) libahci(E) drm(E) crc64_rocksoft(E) i40e(E) crc64(E) libata(E) i2c_core(E)
[   48.888610] CPU: 39 PID: 17438 Comm: perf Kdump: loaded Tainted: G            E      6.3.0-rc4+ #56
[   48.888613] Hardware name: Default Default/Default, BIOS 1.2.M1.AL.P.139.00 03/22/2023
[   48.888614] pstate: 23400009 (nzCv daif +PAN -UAO +TCO +DIT -SSBS BTYPE=--)
[   48.888616] pc : __alloc_pages+0x1ec/0x248
[   48.888619] lr : rb_alloc_aux_page+0x78/0xe0
[   48.888622] sp : ffff800037c5b9e0
[   48.888623] pmr_save: 000000e0
[   48.888624] x29: ffff800037c5b9e0 x28: ffff00082743b800 x27: 0000000000000000
[   48.888627] x26: 0000000000080000 x25: ffff000000000000 x24: ffff000860b21380
[   48.888629] x23: ffff8000093fd3c0 x22: ffff00081a4a2080 x21: 000000000000000b
[   48.888631] x20: 0000000000000000 x19: 000000000000000b x18: 0000000000000020
[   48.888634] x17: 0000000000000000 x16: ffff800008f05be8 x15: ffff00081a4a2610
[   48.888636] x14: 0000000000000000 x13: 323173656761705f x12: ffff00477fffeb90
[   48.888638] x11: 0000000000000000 x10: 0000000000000000 x9 : ffff8000083608a0
[   48.888641] x8 : 0000000000000000 x7 : 0000000000000000 x6 : 0000000000000040
[   48.888643] x5 : 000000000007f400 x4 : 0000000000000000 x3 : 0000000000000000
[   48.888645] x2 : 0000000000000000 x1 : 0000000000000001 x0 : 0000000000012dc0
[   48.888648] Call trace:
[   48.888650]  __alloc_pages+0x1ec/0x248
[   48.888653]  rb_alloc_aux_page+0x78/0xe0
[   48.888654]  rb_alloc_aux+0x13c/0x298
[   48.888656]  perf_mmap+0x468/0x688
[   48.888659]  mmap_region+0x308/0x8a8
[   48.888662]  do_mmap+0x3c0/0x528
[   48.888664]  vm_mmap_pgoff+0xf4/0x1b8
[   48.888666]  ksys_mmap_pgoff+0x18c/0x218
[   48.888668]  __arm64_sys_mmap+0x38/0x58
[   48.888671]  invoke_syscall+0x50/0x128
[   48.888673]  el0_svc_common.constprop.0+0x58/0x188
[   48.888674]  do_el0_svc+0x34/0x50
[   48.888676]  el0_svc+0x34/0x108
[   48.888679]  el0t_64_sync_handler+0xb8/0xc0
[   48.888681]  el0t_64_sync+0x1a4/0x1a8
[   48.888686] ---[ end trace 0000000000000000 ]---

The problem is that the high-order pages for AUX area is allocated with
an order of MAX_ORDER. Obviously, this is a bogus.

Fix it with an order of MAX_ORDER - 1 at maximum.

Fixes: 0a4e38e64f5e ("perf: Support high-order allocations for AUX space")
Signed-off-by: Shuai Xue <xueshuai@linux.alibaba.com>
---
 kernel/events/ring_buffer.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/events/ring_buffer.c b/kernel/events/ring_buffer.c
index 273a0fe..d6bbdb7 100644
--- a/kernel/events/ring_buffer.c
+++ b/kernel/events/ring_buffer.c
@@ -609,8 +609,8 @@ static struct page *rb_alloc_aux_page(int node, int order)
 {
 	struct page *page;
 
-	if (order > MAX_ORDER)
-		order = MAX_ORDER;
+	if (order >= MAX_ORDER)
+		order = MAX_ORDER - 1;
 
 	do {
 		page = alloc_pages_node(node, PERF_AUX_GFP, order);
-- 
1.8.3.1
Re: [PATCH 2/2] perf/ring_buffer: Fix high-order allocations for AUX space with correct MAX_ORDER limit
Posted by James Clark 2 years, 8 months ago 

On 12/06/2023 06:24, Shuai Xue wrote:
> When perf-record with a large AUX area, e.g 2GB:
> 
>     #perf record -C 0 -m ,2G -e arm_spe_0// -- sleep 1
> 
> it reveals a WARNING with __alloc_pages:
> 
> [   48.888553] ------------[ cut here ]------------
> [   48.888559] WARNING: CPU: 39 PID: 17438 at mm/page_alloc.c:5568 __alloc_pages+0x1ec/0x248
> [   48.888569] Modules linked in: ip6table_filter(E) ip6_tables(E) iptable_filter(E) ebtable_nat(E) ebtables(E) vfat(E) fat(E) aes_ce_blk(E) aes_ce_cipher(E) crct10dif_ce(E) ghash_ce(E) sm4_ce_cipher(E) sm4(E) sha2_ce(E) sha256_arm64(E) sha1_ce(E) acpi_ipmi(E) sbsa_gwdt(E) sg(E) ipmi_si(E) ipmi_devintf(E) ipmi_msghandler(E) ip_tables(E) sd_mod(E) ast(E) drm_kms_helper(E) syscopyarea(E) sysfillrect(E) nvme(E) sysimgblt(E) i2c_algo_bit(E) nvme_core(E) drm_shmem_helper(E) ahci(E) t10_pi(E) libahci(E) drm(E) crc64_rocksoft(E) i40e(E) crc64(E) libata(E) i2c_core(E)
> [   48.888610] CPU: 39 PID: 17438 Comm: perf Kdump: loaded Tainted: G            E      6.3.0-rc4+ #56
> [   48.888613] Hardware name: Default Default/Default, BIOS 1.2.M1.AL.P.139.00 03/22/2023
> [   48.888614] pstate: 23400009 (nzCv daif +PAN -UAO +TCO +DIT -SSBS BTYPE=--)
> [   48.888616] pc : __alloc_pages+0x1ec/0x248
> [   48.888619] lr : rb_alloc_aux_page+0x78/0xe0
> [   48.888622] sp : ffff800037c5b9e0
> [   48.888623] pmr_save: 000000e0
> [   48.888624] x29: ffff800037c5b9e0 x28: ffff00082743b800 x27: 0000000000000000
> [   48.888627] x26: 0000000000080000 x25: ffff000000000000 x24: ffff000860b21380
> [   48.888629] x23: ffff8000093fd3c0 x22: ffff00081a4a2080 x21: 000000000000000b
> [   48.888631] x20: 0000000000000000 x19: 000000000000000b x18: 0000000000000020
> [   48.888634] x17: 0000000000000000 x16: ffff800008f05be8 x15: ffff00081a4a2610
> [   48.888636] x14: 0000000000000000 x13: 323173656761705f x12: ffff00477fffeb90
> [   48.888638] x11: 0000000000000000 x10: 0000000000000000 x9 : ffff8000083608a0
> [   48.888641] x8 : 0000000000000000 x7 : 0000000000000000 x6 : 0000000000000040
> [   48.888643] x5 : 000000000007f400 x4 : 0000000000000000 x3 : 0000000000000000
> [   48.888645] x2 : 0000000000000000 x1 : 0000000000000001 x0 : 0000000000012dc0
> [   48.888648] Call trace:
> [   48.888650]  __alloc_pages+0x1ec/0x248
> [   48.888653]  rb_alloc_aux_page+0x78/0xe0
> [   48.888654]  rb_alloc_aux+0x13c/0x298
> [   48.888656]  perf_mmap+0x468/0x688
> [   48.888659]  mmap_region+0x308/0x8a8
> [   48.888662]  do_mmap+0x3c0/0x528
> [   48.888664]  vm_mmap_pgoff+0xf4/0x1b8
> [   48.888666]  ksys_mmap_pgoff+0x18c/0x218
> [   48.888668]  __arm64_sys_mmap+0x38/0x58
> [   48.888671]  invoke_syscall+0x50/0x128
> [   48.888673]  el0_svc_common.constprop.0+0x58/0x188
> [   48.888674]  do_el0_svc+0x34/0x50
> [   48.888676]  el0_svc+0x34/0x108
> [   48.888679]  el0t_64_sync_handler+0xb8/0xc0
> [   48.888681]  el0t_64_sync+0x1a4/0x1a8
> [   48.888686] ---[ end trace 0000000000000000 ]---
> 
> The problem is that the high-order pages for AUX area is allocated with
> an order of MAX_ORDER. Obviously, this is a bogus.
> 
> Fix it with an order of MAX_ORDER - 1 at maximum.
> 
> Fixes: 0a4e38e64f5e ("perf: Support high-order allocations for AUX space")
> Signed-off-by: Shuai Xue <xueshuai@linux.alibaba.com>
> ---
>  kernel/events/ring_buffer.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/kernel/events/ring_buffer.c b/kernel/events/ring_buffer.c
> index 273a0fe..d6bbdb7 100644
> --- a/kernel/events/ring_buffer.c
> +++ b/kernel/events/ring_buffer.c
> @@ -609,8 +609,8 @@ static struct page *rb_alloc_aux_page(int node, int order)
>  {
>  	struct page *page;
>  
> -	if (order > MAX_ORDER)
> -		order = MAX_ORDER;
> +	if (order >= MAX_ORDER)
> +		order = MAX_ORDER - 1;
>  
>  	do {
>  		page = alloc_pages_node(node, PERF_AUX_GFP, order);


It seems like this was only just recently changed with this as the
commit message (23baf83):

   mm, treewide: redefine MAX_ORDER sanely

  MAX_ORDER currently defined as number of orders page allocator
  supports: user can ask buddy allocator for page order between 0 and
  MAX_ORDER-1.

  This definition is counter-intuitive and lead to number of bugs all
  over the kernel.

  Change the definition of MAX_ORDER to be inclusive: the range of
  orders user can ask from buddy allocator is 0..MAX_ORDER now.

It might be worth referring to this in the commit message or adding a
fixes: reference. Or maybe this new change isn't quite right?

James
Re: [PATCH 2/2] perf/ring_buffer: Fix high-order allocations for AUX space with correct MAX_ORDER limit
Posted by Leo Yan 2 years, 8 months ago 
On Mon, Jun 12, 2023 at 09:45:38AM +0100, James Clark wrote:

[...]

> > @@ -609,8 +609,8 @@ static struct page *rb_alloc_aux_page(int node, int order)
> >  {
> >  	struct page *page;
> >  
> > -	if (order > MAX_ORDER)
> > -		order = MAX_ORDER;
> > +	if (order >= MAX_ORDER)
> > +		order = MAX_ORDER - 1;
> >  
> >  	do {
> >  		page = alloc_pages_node(node, PERF_AUX_GFP, order);
> 
> 
> It seems like this was only just recently changed with this as the
> commit message (23baf83):
> 
>    mm, treewide: redefine MAX_ORDER sanely
> 
>   MAX_ORDER currently defined as number of orders page allocator
>   supports: user can ask buddy allocator for page order between 0 and
>   MAX_ORDER-1.
> 
>   This definition is counter-intuitive and lead to number of bugs all
>   over the kernel.
> 
>   Change the definition of MAX_ORDER to be inclusive: the range of
>   orders user can ask from buddy allocator is 0..MAX_ORDER now.
> 
> It might be worth referring to this in the commit message or adding a
> fixes: reference. Or maybe this new change isn't quite right?

Good point.  If so, we don't need this patch anymore.

Thanks for reminding, James.

Leo
Re: [PATCH 2/2] perf/ring_buffer: Fix high-order allocations for AUX space with correct MAX_ORDER limit
Posted by Shuai Xue 2 years, 8 months ago 

On 2023/6/12 17:09, Leo Yan wrote:
> On Mon, Jun 12, 2023 at 09:45:38AM +0100, James Clark wrote:
> 
> [...]
> 
>>> @@ -609,8 +609,8 @@ static struct page *rb_alloc_aux_page(int node, int order)
>>>  {
>>>  	struct page *page;
>>>  
>>> -	if (order > MAX_ORDER)
>>> -		order = MAX_ORDER;
>>> +	if (order >= MAX_ORDER)
>>> +		order = MAX_ORDER - 1;
>>>  
>>>  	do {
>>>  		page = alloc_pages_node(node, PERF_AUX_GFP, order);
>>
>>
>> It seems like this was only just recently changed with this as the
>> commit message (23baf83):
>>
>>    mm, treewide: redefine MAX_ORDER sanely
>>
>>   MAX_ORDER currently defined as number of orders page allocator
>>   supports: user can ask buddy allocator for page order between 0 and
>>   MAX_ORDER-1.
>>
>>   This definition is counter-intuitive and lead to number of bugs all
>>   over the kernel.
>>
>>   Change the definition of MAX_ORDER to be inclusive: the range of
>>   orders user can ask from buddy allocator is 0..MAX_ORDER now.
>>
>> It might be worth referring to this in the commit message or adding a
>> fixes: reference. Or maybe this new change isn't quite right?
> 
> Good point.  If so, we don't need this patch anymore.
> 
> Thanks for reminding, James.
> 
> Leo

Hi, Leo and James,

I tested on the Linus master tree, the mentioned commit 23baf83 ("mm, treewide: redefine MAX_ORDER sanely")
has fix this oops.

I will drop out this patch, thank you :)

Cheers,
Shuai
Re: [PATCH 2/2] perf/ring_buffer: Fix high-order allocations for AUX space with correct MAX_ORDER limit
Posted by Leo Yan 2 years, 8 months ago 
On Mon, Jun 12, 2023 at 01:24:52PM +0800, Shuai Xue wrote:
> When perf-record with a large AUX area, e.g 2GB:
> 
>     #perf record -C 0 -m ,2G -e arm_spe_0// -- sleep 1
> 
> it reveals a WARNING with __alloc_pages:
> 
> [   48.888553] ------------[ cut here ]------------
> [   48.888559] WARNING: CPU: 39 PID: 17438 at mm/page_alloc.c:5568 __alloc_pages+0x1ec/0x248
> [   48.888569] Modules linked in: ip6table_filter(E) ip6_tables(E) iptable_filter(E) ebtable_nat(E) ebtables(E) vfat(E) fat(E) aes_ce_blk(E) aes_ce_cipher(E) crct10dif_ce(E) ghash_ce(E) sm4_ce_cipher(E) sm4(E) sha2_ce(E) sha256_arm64(E) sha1_ce(E) acpi_ipmi(E) sbsa_gwdt(E) sg(E) ipmi_si(E) ipmi_devintf(E) ipmi_msghandler(E) ip_tables(E) sd_mod(E) ast(E) drm_kms_helper(E) syscopyarea(E) sysfillrect(E) nvme(E) sysimgblt(E) i2c_algo_bit(E) nvme_core(E) drm_shmem_helper(E) ahci(E) t10_pi(E) libahci(E) drm(E) crc64_rocksoft(E) i40e(E) crc64(E) libata(E) i2c_core(E)
> [   48.888610] CPU: 39 PID: 17438 Comm: perf Kdump: loaded Tainted: G            E      6.3.0-rc4+ #56
> [   48.888613] Hardware name: Default Default/Default, BIOS 1.2.M1.AL.P.139.00 03/22/2023
> [   48.888614] pstate: 23400009 (nzCv daif +PAN -UAO +TCO +DIT -SSBS BTYPE=--)
> [   48.888616] pc : __alloc_pages+0x1ec/0x248
> [   48.888619] lr : rb_alloc_aux_page+0x78/0xe0
> [   48.888622] sp : ffff800037c5b9e0
> [   48.888623] pmr_save: 000000e0
> [   48.888624] x29: ffff800037c5b9e0 x28: ffff00082743b800 x27: 0000000000000000
> [   48.888627] x26: 0000000000080000 x25: ffff000000000000 x24: ffff000860b21380
> [   48.888629] x23: ffff8000093fd3c0 x22: ffff00081a4a2080 x21: 000000000000000b
> [   48.888631] x20: 0000000000000000 x19: 000000000000000b x18: 0000000000000020
> [   48.888634] x17: 0000000000000000 x16: ffff800008f05be8 x15: ffff00081a4a2610
> [   48.888636] x14: 0000000000000000 x13: 323173656761705f x12: ffff00477fffeb90
> [   48.888638] x11: 0000000000000000 x10: 0000000000000000 x9 : ffff8000083608a0
> [   48.888641] x8 : 0000000000000000 x7 : 0000000000000000 x6 : 0000000000000040
> [   48.888643] x5 : 000000000007f400 x4 : 0000000000000000 x3 : 0000000000000000
> [   48.888645] x2 : 0000000000000000 x1 : 0000000000000001 x0 : 0000000000012dc0
> [   48.888648] Call trace:
> [   48.888650]  __alloc_pages+0x1ec/0x248
> [   48.888653]  rb_alloc_aux_page+0x78/0xe0
> [   48.888654]  rb_alloc_aux+0x13c/0x298
> [   48.888656]  perf_mmap+0x468/0x688
> [   48.888659]  mmap_region+0x308/0x8a8
> [   48.888662]  do_mmap+0x3c0/0x528
> [   48.888664]  vm_mmap_pgoff+0xf4/0x1b8
> [   48.888666]  ksys_mmap_pgoff+0x18c/0x218
> [   48.888668]  __arm64_sys_mmap+0x38/0x58
> [   48.888671]  invoke_syscall+0x50/0x128
> [   48.888673]  el0_svc_common.constprop.0+0x58/0x188
> [   48.888674]  do_el0_svc+0x34/0x50
> [   48.888676]  el0_svc+0x34/0x108
> [   48.888679]  el0t_64_sync_handler+0xb8/0xc0
> [   48.888681]  el0t_64_sync+0x1a4/0x1a8
> [   48.888686] ---[ end trace 0000000000000000 ]---
> 
> The problem is that the high-order pages for AUX area is allocated with
> an order of MAX_ORDER. Obviously, this is a bogus.
> 
> Fix it with an order of MAX_ORDER - 1 at maximum.
> 
> Fixes: 0a4e38e64f5e ("perf: Support high-order allocations for AUX space")
> Signed-off-by: Shuai Xue <xueshuai@linux.alibaba.com>

LGTM:

Reviewed-by: Leo Yan <leo.yan@linaro.org>

> ---
>  kernel/events/ring_buffer.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/kernel/events/ring_buffer.c b/kernel/events/ring_buffer.c
> index 273a0fe..d6bbdb7 100644
> --- a/kernel/events/ring_buffer.c
> +++ b/kernel/events/ring_buffer.c
> @@ -609,8 +609,8 @@ static struct page *rb_alloc_aux_page(int node, int order)
>  {
>  	struct page *page;
>  
> -	if (order > MAX_ORDER)
> -		order = MAX_ORDER;
> +	if (order >= MAX_ORDER)
> +		order = MAX_ORDER - 1;
>  
>  	do {
>  		page = alloc_pages_node(node, PERF_AUX_GFP, order);
> -- 
> 1.8.3.1
>
Re: [PATCH 2/2] perf/ring_buffer: Fix high-order allocations for AUX space with correct MAX_ORDER limit
Posted by Shuai Xue 2 years, 8 months ago 

On 2023/6/12 16:30, Leo Yan wrote:
> On Mon, Jun 12, 2023 at 01:24:52PM +0800, Shuai Xue wrote:
>> When perf-record with a large AUX area, e.g 2GB:
>>
>>     #perf record -C 0 -m ,2G -e arm_spe_0// -- sleep 1
>>
>> it reveals a WARNING with __alloc_pages:
>>
>> [   48.888553] ------------[ cut here ]------------
>> [   48.888559] WARNING: CPU: 39 PID: 17438 at mm/page_alloc.c:5568 __alloc_pages+0x1ec/0x248
>> [   48.888569] Modules linked in: ip6table_filter(E) ip6_tables(E) iptable_filter(E) ebtable_nat(E) ebtables(E) vfat(E) fat(E) aes_ce_blk(E) aes_ce_cipher(E) crct10dif_ce(E) ghash_ce(E) sm4_ce_cipher(E) sm4(E) sha2_ce(E) sha256_arm64(E) sha1_ce(E) acpi_ipmi(E) sbsa_gwdt(E) sg(E) ipmi_si(E) ipmi_devintf(E) ipmi_msghandler(E) ip_tables(E) sd_mod(E) ast(E) drm_kms_helper(E) syscopyarea(E) sysfillrect(E) nvme(E) sysimgblt(E) i2c_algo_bit(E) nvme_core(E) drm_shmem_helper(E) ahci(E) t10_pi(E) libahci(E) drm(E) crc64_rocksoft(E) i40e(E) crc64(E) libata(E) i2c_core(E)
>> [   48.888610] CPU: 39 PID: 17438 Comm: perf Kdump: loaded Tainted: G            E      6.3.0-rc4+ #56
>> [   48.888613] Hardware name: Default Default/Default, BIOS 1.2.M1.AL.P.139.00 03/22/2023
>> [   48.888614] pstate: 23400009 (nzCv daif +PAN -UAO +TCO +DIT -SSBS BTYPE=--)
>> [   48.888616] pc : __alloc_pages+0x1ec/0x248
>> [   48.888619] lr : rb_alloc_aux_page+0x78/0xe0
>> [   48.888622] sp : ffff800037c5b9e0
>> [   48.888623] pmr_save: 000000e0
>> [   48.888624] x29: ffff800037c5b9e0 x28: ffff00082743b800 x27: 0000000000000000
>> [   48.888627] x26: 0000000000080000 x25: ffff000000000000 x24: ffff000860b21380
>> [   48.888629] x23: ffff8000093fd3c0 x22: ffff00081a4a2080 x21: 000000000000000b
>> [   48.888631] x20: 0000000000000000 x19: 000000000000000b x18: 0000000000000020
>> [   48.888634] x17: 0000000000000000 x16: ffff800008f05be8 x15: ffff00081a4a2610
>> [   48.888636] x14: 0000000000000000 x13: 323173656761705f x12: ffff00477fffeb90
>> [   48.888638] x11: 0000000000000000 x10: 0000000000000000 x9 : ffff8000083608a0
>> [   48.888641] x8 : 0000000000000000 x7 : 0000000000000000 x6 : 0000000000000040
>> [   48.888643] x5 : 000000000007f400 x4 : 0000000000000000 x3 : 0000000000000000
>> [   48.888645] x2 : 0000000000000000 x1 : 0000000000000001 x0 : 0000000000012dc0
>> [   48.888648] Call trace:
>> [   48.888650]  __alloc_pages+0x1ec/0x248
>> [   48.888653]  rb_alloc_aux_page+0x78/0xe0
>> [   48.888654]  rb_alloc_aux+0x13c/0x298
>> [   48.888656]  perf_mmap+0x468/0x688
>> [   48.888659]  mmap_region+0x308/0x8a8
>> [   48.888662]  do_mmap+0x3c0/0x528
>> [   48.888664]  vm_mmap_pgoff+0xf4/0x1b8
>> [   48.888666]  ksys_mmap_pgoff+0x18c/0x218
>> [   48.888668]  __arm64_sys_mmap+0x38/0x58
>> [   48.888671]  invoke_syscall+0x50/0x128
>> [   48.888673]  el0_svc_common.constprop.0+0x58/0x188
>> [   48.888674]  do_el0_svc+0x34/0x50
>> [   48.888676]  el0_svc+0x34/0x108
>> [   48.888679]  el0t_64_sync_handler+0xb8/0xc0
>> [   48.888681]  el0t_64_sync+0x1a4/0x1a8
>> [   48.888686] ---[ end trace 0000000000000000 ]---
>>
>> The problem is that the high-order pages for AUX area is allocated with
>> an order of MAX_ORDER. Obviously, this is a bogus.
>>
>> Fix it with an order of MAX_ORDER - 1 at maximum.
>>
>> Fixes: 0a4e38e64f5e ("perf: Support high-order allocations for AUX space")
>> Signed-off-by: Shuai Xue <xueshuai@linux.alibaba.com>
> 
> LGTM:
> 
> Reviewed-by: Leo Yan <leo.yan@linaro.org>

Thank you :)

Cheers
Shuai

> 
>> ---
>>  kernel/events/ring_buffer.c | 4 ++--
>>  1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/kernel/events/ring_buffer.c b/kernel/events/ring_buffer.c
>> index 273a0fe..d6bbdb7 100644
>> --- a/kernel/events/ring_buffer.c
>> +++ b/kernel/events/ring_buffer.c
>> @@ -609,8 +609,8 @@ static struct page *rb_alloc_aux_page(int node, int order)
>>  {
>>  	struct page *page;
>>  
>> -	if (order > MAX_ORDER)
>> -		order = MAX_ORDER;
>> +	if (order >= MAX_ORDER)
>> +		order = MAX_ORDER - 1;
>>  
>>  	do {
>>  		page = alloc_pages_node(node, PERF_AUX_GFP, order);
>> -- 
>> 1.8.3.1
>>

Patchew 2.1-devel-b67e4c2

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