Re: [PATCH] mm/migrate: Fix ref-count handling when !hugepage_migration_supported()

[Punit Agrawal]

Naoya Horiguchi  writes:

> On Wed, May 24, 2017 at 04:47:28PM +0100, Punit Agrawal wrote:
>> On failing to migrate a page, soft_offline_huge_page() performs the
>> necessary update to the hugepage ref-count. When
>> !hugepage_migration_supported() , unmap_and_move_hugepage() also
>> decrements the page ref-count for the hugepage. The combined behaviour
>> leaves the ref-count in an inconsistent state.
>> 
>> This leads to soft lockups when running the overcommitted hugepage test
>> from mce-tests suite.
>> 
>> Soft offlining pfn 0x83ed600 at process virtual address 0x4000
>> soft offline: 0x83ed600: migration failed 1, type
>> 1fffc0008008 (uptodate|head)
>> INFO: rcu_preempt detected stalls on CPUs/tasks:
>>  Tasks blocked on level-0 rcu_node (CPUs 0-7): P2715
>>   (detected by 7, t=5254 jiffies, g=963, c=962, q=321)
>>   thugetlb_overco R  running task0  2715   2685 0x0008
>>   Call trace:
>>   [] dump_backtrace+0x0/0x268
>>   [] show_stack+0x24/0x30
>>   [] sched_show_task+0x134/0x180
>>   [] rcu_print_detail_task_stall_rnp+0x54/0x7c
>>   [] rcu_check_callbacks+0xa74/0xb08
>>   [] update_process_times+0x34/0x60
>>   [] tick_sched_handle.isra.7+0x38/0x70
>>   [] tick_sched_timer+0x4c/0x98
>>   [] __hrtimer_run_queues+0xc0/0x300
>>   [] hrtimer_interrupt+0xac/0x228
>>   [] arch_timer_handler_phys+0x3c/0x50
>>   [] handle_percpu_devid_irq+0x8c/0x290
>>   [] generic_handle_irq+0x34/0x50
>>   [] __handle_domain_irq+0x68/0xc0
>>   [] gic_handle_irq+0x5c/0xb0
>> 
>> Fix this by dropping the ref-count decrement in
>> unmap_and_move_hugepage() when !hugepage_migration_supported().
>> 
>> Fixes: 32665f2bbfed ("mm/migrate: correct failure handling if 
>> !hugepage_migration_support()")
>> Reported-by: Manoj Iyer 
>> Signed-off-by: Punit Agrawal 
>> Cc: Joonsoo Kim 
>> Cc: Naoya Horiguchi 
>> Cc: Wanpeng Li 
>> Cc: Christoph Lameter 
>> 
>> --
>> Hi Andrew,
>> 
>> We ran into this bug when working towards enabling memory corruption
>> on arm64. The patch was tested on an arm64 platform running v4.12-rc2
>> with the series to enable memory corruption handling[0].
>> 
>> Please consider merging as a fix for the 4.12 release.
>> 
>> Thanks,
>> Punit
>> 
>> [0] https://www.spinics.net/lists/arm-kernel/msg581657.html
>> ---
>>  mm/migrate.c | 4 +---
>>  1 file changed, 1 insertion(+), 3 deletions(-)
>> 
>> diff --git a/mm/migrate.c b/mm/migrate.c
>> index 89a0a1707f4c..187abd1526df 100644
>> --- a/mm/migrate.c
>> +++ b/mm/migrate.c
>> @@ -1201,10 +1201,8 @@ static int unmap_and_move_huge_page(new_page_t 
>> get_new_page,
>>   * tables or check whether the hugepage is pmd-based or not before
>>   * kicking migration.
>>   */
>> -if (!hugepage_migration_supported(page_hstate(hpage))) {
>> -putback_active_hugepage(hpage);
>
> Thank you for reporting and suggestion, Punit, Manoj.
>
> Simply dropping this putback_active_hugepage() may resume the failure
> counting issue addressed in 32665f2bbfed, so I would recommend to call
> putback_movable_pages() in failure path in soft_offline_huge_page().
>
> @@ -1600,7 +1600,8 @@ static int soft_offline_huge_page(struct page *page, 
> int flags)
>* only one hugepage pointed to by hpage, so we need not
>* run through the pagelist here.
>*/
> - putback_active_hugepage(hpage);
> + if (!list_empty())
> + putback_movable_pages();
>   if (ret > 0)
>   ret = -EIO;
>   } else {
>
> Could you check this works for you?

Using this sequence works as well. I'll send out an update shortly.

Thanks

>
> Thanks,
> Naoya Horiguchi
> --
> To unsubscribe, send a message with 'unsubscribe linux-mm' in
> the body to majord...@kvack.org.  For more info on Linux MM,
> see: http://www.linux-mm.org/ .
> Don't email: mailto:"d...@kvack.org;> em...@kvack.org 

Re: [PATCH] mm/migrate: Fix ref-count handling when !hugepage_migration_supported()

[Punit Agrawal]

Naoya Horiguchi  writes:

> On Wed, May 24, 2017 at 04:47:28PM +0100, Punit Agrawal wrote:
>> On failing to migrate a page, soft_offline_huge_page() performs the
>> necessary update to the hugepage ref-count. When
>> !hugepage_migration_supported() , unmap_and_move_hugepage() also
>> decrements the page ref-count for the hugepage. The combined behaviour
>> leaves the ref-count in an inconsistent state.
>> 
>> This leads to soft lockups when running the overcommitted hugepage test
>> from mce-tests suite.
>> 
>> Soft offlining pfn 0x83ed600 at process virtual address 0x4000
>> soft offline: 0x83ed600: migration failed 1, type
>> 1fffc0008008 (uptodate|head)
>> INFO: rcu_preempt detected stalls on CPUs/tasks:
>>  Tasks blocked on level-0 rcu_node (CPUs 0-7): P2715
>>   (detected by 7, t=5254 jiffies, g=963, c=962, q=321)
>>   thugetlb_overco R  running task0  2715   2685 0x0008
>>   Call trace:
>>   [] dump_backtrace+0x0/0x268
>>   [] show_stack+0x24/0x30
>>   [] sched_show_task+0x134/0x180
>>   [] rcu_print_detail_task_stall_rnp+0x54/0x7c
>>   [] rcu_check_callbacks+0xa74/0xb08
>>   [] update_process_times+0x34/0x60
>>   [] tick_sched_handle.isra.7+0x38/0x70
>>   [] tick_sched_timer+0x4c/0x98
>>   [] __hrtimer_run_queues+0xc0/0x300
>>   [] hrtimer_interrupt+0xac/0x228
>>   [] arch_timer_handler_phys+0x3c/0x50
>>   [] handle_percpu_devid_irq+0x8c/0x290
>>   [] generic_handle_irq+0x34/0x50
>>   [] __handle_domain_irq+0x68/0xc0
>>   [] gic_handle_irq+0x5c/0xb0
>> 
>> Fix this by dropping the ref-count decrement in
>> unmap_and_move_hugepage() when !hugepage_migration_supported().
>> 
>> Fixes: 32665f2bbfed ("mm/migrate: correct failure handling if 
>> !hugepage_migration_support()")
>> Reported-by: Manoj Iyer 
>> Signed-off-by: Punit Agrawal 
>> Cc: Joonsoo Kim 
>> Cc: Naoya Horiguchi 
>> Cc: Wanpeng Li 
>> Cc: Christoph Lameter 
>> 
>> --
>> Hi Andrew,
>> 
>> We ran into this bug when working towards enabling memory corruption
>> on arm64. The patch was tested on an arm64 platform running v4.12-rc2
>> with the series to enable memory corruption handling[0].
>> 
>> Please consider merging as a fix for the 4.12 release.
>> 
>> Thanks,
>> Punit
>> 
>> [0] https://www.spinics.net/lists/arm-kernel/msg581657.html
>> ---
>>  mm/migrate.c | 4 +---
>>  1 file changed, 1 insertion(+), 3 deletions(-)
>> 
>> diff --git a/mm/migrate.c b/mm/migrate.c
>> index 89a0a1707f4c..187abd1526df 100644
>> --- a/mm/migrate.c
>> +++ b/mm/migrate.c
>> @@ -1201,10 +1201,8 @@ static int unmap_and_move_huge_page(new_page_t 
>> get_new_page,
>>   * tables or check whether the hugepage is pmd-based or not before
>>   * kicking migration.
>>   */
>> -if (!hugepage_migration_supported(page_hstate(hpage))) {
>> -putback_active_hugepage(hpage);
>
> Thank you for reporting and suggestion, Punit, Manoj.
>
> Simply dropping this putback_active_hugepage() may resume the failure
> counting issue addressed in 32665f2bbfed, so I would recommend to call
> putback_movable_pages() in failure path in soft_offline_huge_page().
>
> @@ -1600,7 +1600,8 @@ static int soft_offline_huge_page(struct page *page, 
> int flags)
>* only one hugepage pointed to by hpage, so we need not
>* run through the pagelist here.
>*/
> - putback_active_hugepage(hpage);
> + if (!list_empty())
> + putback_movable_pages();
>   if (ret > 0)
>   ret = -EIO;
>   } else {
>
> Could you check this works for you?

Using this sequence works as well. I'll send out an update shortly.

Thanks

>
> Thanks,
> Naoya Horiguchi
> --
> To unsubscribe, send a message with 'unsubscribe linux-mm' in
> the body to majord...@kvack.org.  For more info on Linux MM,
> see: http://www.linux-mm.org/ .
> Don't email: mailto:"d...@kvack.org;> em...@kvack.org 

Re: [PATCH] mm/migrate: Fix ref-count handling when !hugepage_migration_supported()

[Punit Agrawal]

Andrew Morton  writes:

> On Wed, 24 May 2017 16:47:28 +0100 Punit Agrawal  
> wrote:
>
>> On failing to migrate a page, soft_offline_huge_page() performs the
>> necessary update to the hugepage ref-count. When
>> !hugepage_migration_supported() , unmap_and_move_hugepage() also
>> decrements the page ref-count for the hugepage. The combined behaviour
>> leaves the ref-count in an inconsistent state.
>> 
>> This leads to soft lockups when running the overcommitted hugepage test
>> from mce-tests suite.
>> 
>> Soft offlining pfn 0x83ed600 at process virtual address 0x4000
>> soft offline: 0x83ed600: migration failed 1, type
>> 1fffc0008008 (uptodate|head)
>> INFO: rcu_preempt detected stalls on CPUs/tasks:
>>  Tasks blocked on level-0 rcu_node (CPUs 0-7): P2715
>>   (detected by 7, t=5254 jiffies, g=963, c=962, q=321)
>>   thugetlb_overco R  running task0  2715   2685 0x0008
>>   Call trace:
>>   [] dump_backtrace+0x0/0x268
>>   [] show_stack+0x24/0x30
>>   [] sched_show_task+0x134/0x180
>>   [] rcu_print_detail_task_stall_rnp+0x54/0x7c
>>   [] rcu_check_callbacks+0xa74/0xb08
>>   [] update_process_times+0x34/0x60
>>   [] tick_sched_handle.isra.7+0x38/0x70
>>   [] tick_sched_timer+0x4c/0x98
>>   [] __hrtimer_run_queues+0xc0/0x300
>>   [] hrtimer_interrupt+0xac/0x228
>>   [] arch_timer_handler_phys+0x3c/0x50
>>   [] handle_percpu_devid_irq+0x8c/0x290
>>   [] generic_handle_irq+0x34/0x50
>>   [] __handle_domain_irq+0x68/0xc0
>>   [] gic_handle_irq+0x5c/0xb0
>> 
>> Fix this by dropping the ref-count decrement in
>> unmap_and_move_hugepage() when !hugepage_migration_supported().
>> 
>> Fixes: 32665f2bbfed ("mm/migrate: correct failure handling if 
>> !hugepage_migration_support()")
>> Reported-by: Manoj Iyer 
>> Signed-off-by: Punit Agrawal 
>> Cc: Joonsoo Kim 
>> Cc: Naoya Horiguchi 
>> Cc: Wanpeng Li 
>> Cc: Christoph Lameter 
>
> 32665f2bbfed was three years ago.  Do you have any theory as to why
> this took so long to be detected?

This only triggers on systems that enable memory failure handling
(ARCH_SUPPORTS_MEMORY_FAILURE) but not hugepage migration
(!ARCH_ENABLE_HUGEPAGE_MIGRATION).

I imagine this wasn't triggered as there aren't many systems running
this configuration.

> And do you believe a -stable backport is warranted?

I'll defer to Horiguchi-san's judgement here.

>
> --
> To unsubscribe, send a message with 'unsubscribe linux-mm' in
> the body to majord...@kvack.org.  For more info on Linux MM,
> see: http://www.linux-mm.org/ .
> Don't email: mailto:"d...@kvack.org;> em...@kvack.org 

Re: [PATCH] mm/migrate: Fix ref-count handling when !hugepage_migration_supported()

[Punit Agrawal]

Andrew Morton  writes:

> On Wed, 24 May 2017 16:47:28 +0100 Punit Agrawal  
> wrote:
>
>> On failing to migrate a page, soft_offline_huge_page() performs the
>> necessary update to the hugepage ref-count. When
>> !hugepage_migration_supported() , unmap_and_move_hugepage() also
>> decrements the page ref-count for the hugepage. The combined behaviour
>> leaves the ref-count in an inconsistent state.
>> 
>> This leads to soft lockups when running the overcommitted hugepage test
>> from mce-tests suite.
>> 
>> Soft offlining pfn 0x83ed600 at process virtual address 0x4000
>> soft offline: 0x83ed600: migration failed 1, type
>> 1fffc0008008 (uptodate|head)
>> INFO: rcu_preempt detected stalls on CPUs/tasks:
>>  Tasks blocked on level-0 rcu_node (CPUs 0-7): P2715
>>   (detected by 7, t=5254 jiffies, g=963, c=962, q=321)
>>   thugetlb_overco R  running task0  2715   2685 0x0008
>>   Call trace:
>>   [] dump_backtrace+0x0/0x268
>>   [] show_stack+0x24/0x30
>>   [] sched_show_task+0x134/0x180
>>   [] rcu_print_detail_task_stall_rnp+0x54/0x7c
>>   [] rcu_check_callbacks+0xa74/0xb08
>>   [] update_process_times+0x34/0x60
>>   [] tick_sched_handle.isra.7+0x38/0x70
>>   [] tick_sched_timer+0x4c/0x98
>>   [] __hrtimer_run_queues+0xc0/0x300
>>   [] hrtimer_interrupt+0xac/0x228
>>   [] arch_timer_handler_phys+0x3c/0x50
>>   [] handle_percpu_devid_irq+0x8c/0x290
>>   [] generic_handle_irq+0x34/0x50
>>   [] __handle_domain_irq+0x68/0xc0
>>   [] gic_handle_irq+0x5c/0xb0
>> 
>> Fix this by dropping the ref-count decrement in
>> unmap_and_move_hugepage() when !hugepage_migration_supported().
>> 
>> Fixes: 32665f2bbfed ("mm/migrate: correct failure handling if 
>> !hugepage_migration_support()")
>> Reported-by: Manoj Iyer 
>> Signed-off-by: Punit Agrawal 
>> Cc: Joonsoo Kim 
>> Cc: Naoya Horiguchi 
>> Cc: Wanpeng Li 
>> Cc: Christoph Lameter 
>
> 32665f2bbfed was three years ago.  Do you have any theory as to why
> this took so long to be detected?

This only triggers on systems that enable memory failure handling
(ARCH_SUPPORTS_MEMORY_FAILURE) but not hugepage migration
(!ARCH_ENABLE_HUGEPAGE_MIGRATION).

I imagine this wasn't triggered as there aren't many systems running
this configuration.

> And do you believe a -stable backport is warranted?

I'll defer to Horiguchi-san's judgement here.

>
> --
> To unsubscribe, send a message with 'unsubscribe linux-mm' in
> the body to majord...@kvack.org.  For more info on Linux MM,
> see: http://www.linux-mm.org/ .
> Don't email: mailto:"d...@kvack.org;> em...@kvack.org 

Re: [PATCH] mm/migrate: Fix ref-count handling when !hugepage_migration_supported()

[Naoya Horiguchi]

On Wed, May 24, 2017 at 12:56:10PM -0700, Andrew Morton wrote:
> On Wed, 24 May 2017 16:47:28 +0100 Punit Agrawal  
> wrote:
> 
> > On failing to migrate a page, soft_offline_huge_page() performs the
> > necessary update to the hugepage ref-count. When
> > !hugepage_migration_supported() , unmap_and_move_hugepage() also
> > decrements the page ref-count for the hugepage. The combined behaviour
> > leaves the ref-count in an inconsistent state.
> > 
> > This leads to soft lockups when running the overcommitted hugepage test
> > from mce-tests suite.
> > 
> > Soft offlining pfn 0x83ed600 at process virtual address 0x4000
> > soft offline: 0x83ed600: migration failed 1, type
> > 1fffc0008008 (uptodate|head)
> > INFO: rcu_preempt detected stalls on CPUs/tasks:
> >  Tasks blocked on level-0 rcu_node (CPUs 0-7): P2715
> >   (detected by 7, t=5254 jiffies, g=963, c=962, q=321)
> >   thugetlb_overco R  running task0  2715   2685 0x0008
> >   Call trace:
> >   [] dump_backtrace+0x0/0x268
> >   [] show_stack+0x24/0x30
> >   [] sched_show_task+0x134/0x180
> >   [] rcu_print_detail_task_stall_rnp+0x54/0x7c
> >   [] rcu_check_callbacks+0xa74/0xb08
> >   [] update_process_times+0x34/0x60
> >   [] tick_sched_handle.isra.7+0x38/0x70
> >   [] tick_sched_timer+0x4c/0x98
> >   [] __hrtimer_run_queues+0xc0/0x300
> >   [] hrtimer_interrupt+0xac/0x228
> >   [] arch_timer_handler_phys+0x3c/0x50
> >   [] handle_percpu_devid_irq+0x8c/0x290
> >   [] generic_handle_irq+0x34/0x50
> >   [] __handle_domain_irq+0x68/0xc0
> >   [] gic_handle_irq+0x5c/0xb0
> > 
> > Fix this by dropping the ref-count decrement in
> > unmap_and_move_hugepage() when !hugepage_migration_supported().
> > 
> > Fixes: 32665f2bbfed ("mm/migrate: correct failure handling if 
> > !hugepage_migration_support()")
> > Reported-by: Manoj Iyer 
> > Signed-off-by: Punit Agrawal 
> > Cc: Joonsoo Kim 
> > Cc: Naoya Horiguchi 
> > Cc: Wanpeng Li 
> > Cc: Christoph Lameter 
> 
> 32665f2bbfed was three years ago.  Do you have any theory as to why
> this took so long to be detected?

My per-release testing only ran for "hugepage_migration_supported() == true"
setting (i.e. x86 with CONFIG_HUGETLB_PAGE=y). I need extend the coverage.
And other arch's developers recently have come to have interest in hugepage
migration.

>  And do you believe a -stable
> backport is warranted?

I agree to send the fix to stable, so the stable tag is wanted.

Cc: sta...@kernel.org   # v3.14+

Thanks,
Naoya Horiguchi

Re: [PATCH] mm/migrate: Fix ref-count handling when !hugepage_migration_supported()

[Naoya Horiguchi]

On Wed, May 24, 2017 at 12:56:10PM -0700, Andrew Morton wrote:
> On Wed, 24 May 2017 16:47:28 +0100 Punit Agrawal  
> wrote:
> 
> > On failing to migrate a page, soft_offline_huge_page() performs the
> > necessary update to the hugepage ref-count. When
> > !hugepage_migration_supported() , unmap_and_move_hugepage() also
> > decrements the page ref-count for the hugepage. The combined behaviour
> > leaves the ref-count in an inconsistent state.
> > 
> > This leads to soft lockups when running the overcommitted hugepage test
> > from mce-tests suite.
> > 
> > Soft offlining pfn 0x83ed600 at process virtual address 0x4000
> > soft offline: 0x83ed600: migration failed 1, type
> > 1fffc0008008 (uptodate|head)
> > INFO: rcu_preempt detected stalls on CPUs/tasks:
> >  Tasks blocked on level-0 rcu_node (CPUs 0-7): P2715
> >   (detected by 7, t=5254 jiffies, g=963, c=962, q=321)
> >   thugetlb_overco R  running task0  2715   2685 0x0008
> >   Call trace:
> >   [] dump_backtrace+0x0/0x268
> >   [] show_stack+0x24/0x30
> >   [] sched_show_task+0x134/0x180
> >   [] rcu_print_detail_task_stall_rnp+0x54/0x7c
> >   [] rcu_check_callbacks+0xa74/0xb08
> >   [] update_process_times+0x34/0x60
> >   [] tick_sched_handle.isra.7+0x38/0x70
> >   [] tick_sched_timer+0x4c/0x98
> >   [] __hrtimer_run_queues+0xc0/0x300
> >   [] hrtimer_interrupt+0xac/0x228
> >   [] arch_timer_handler_phys+0x3c/0x50
> >   [] handle_percpu_devid_irq+0x8c/0x290
> >   [] generic_handle_irq+0x34/0x50
> >   [] __handle_domain_irq+0x68/0xc0
> >   [] gic_handle_irq+0x5c/0xb0
> > 
> > Fix this by dropping the ref-count decrement in
> > unmap_and_move_hugepage() when !hugepage_migration_supported().
> > 
> > Fixes: 32665f2bbfed ("mm/migrate: correct failure handling if 
> > !hugepage_migration_support()")
> > Reported-by: Manoj Iyer 
> > Signed-off-by: Punit Agrawal 
> > Cc: Joonsoo Kim 
> > Cc: Naoya Horiguchi 
> > Cc: Wanpeng Li 
> > Cc: Christoph Lameter 
> 
> 32665f2bbfed was three years ago.  Do you have any theory as to why
> this took so long to be detected?

My per-release testing only ran for "hugepage_migration_supported() == true"
setting (i.e. x86 with CONFIG_HUGETLB_PAGE=y). I need extend the coverage.
And other arch's developers recently have come to have interest in hugepage
migration.

>  And do you believe a -stable
> backport is warranted?

I agree to send the fix to stable, so the stable tag is wanted.

Cc: sta...@kernel.org   # v3.14+

Thanks,
Naoya Horiguchi

Re: [PATCH] mm/migrate: Fix ref-count handling when !hugepage_migration_supported()

[Naoya Horiguchi]

On Wed, May 24, 2017 at 04:47:28PM +0100, Punit Agrawal wrote:
> On failing to migrate a page, soft_offline_huge_page() performs the
> necessary update to the hugepage ref-count. When
> !hugepage_migration_supported() , unmap_and_move_hugepage() also
> decrements the page ref-count for the hugepage. The combined behaviour
> leaves the ref-count in an inconsistent state.
> 
> This leads to soft lockups when running the overcommitted hugepage test
> from mce-tests suite.
> 
> Soft offlining pfn 0x83ed600 at process virtual address 0x4000
> soft offline: 0x83ed600: migration failed 1, type
> 1fffc0008008 (uptodate|head)
> INFO: rcu_preempt detected stalls on CPUs/tasks:
>  Tasks blocked on level-0 rcu_node (CPUs 0-7): P2715
>   (detected by 7, t=5254 jiffies, g=963, c=962, q=321)
>   thugetlb_overco R  running task0  2715   2685 0x0008
>   Call trace:
>   [] dump_backtrace+0x0/0x268
>   [] show_stack+0x24/0x30
>   [] sched_show_task+0x134/0x180
>   [] rcu_print_detail_task_stall_rnp+0x54/0x7c
>   [] rcu_check_callbacks+0xa74/0xb08
>   [] update_process_times+0x34/0x60
>   [] tick_sched_handle.isra.7+0x38/0x70
>   [] tick_sched_timer+0x4c/0x98
>   [] __hrtimer_run_queues+0xc0/0x300
>   [] hrtimer_interrupt+0xac/0x228
>   [] arch_timer_handler_phys+0x3c/0x50
>   [] handle_percpu_devid_irq+0x8c/0x290
>   [] generic_handle_irq+0x34/0x50
>   [] __handle_domain_irq+0x68/0xc0
>   [] gic_handle_irq+0x5c/0xb0
> 
> Fix this by dropping the ref-count decrement in
> unmap_and_move_hugepage() when !hugepage_migration_supported().
> 
> Fixes: 32665f2bbfed ("mm/migrate: correct failure handling if 
> !hugepage_migration_support()")
> Reported-by: Manoj Iyer 
> Signed-off-by: Punit Agrawal 
> Cc: Joonsoo Kim 
> Cc: Naoya Horiguchi 
> Cc: Wanpeng Li 
> Cc: Christoph Lameter 
> 
> --
> Hi Andrew,
> 
> We ran into this bug when working towards enabling memory corruption
> on arm64. The patch was tested on an arm64 platform running v4.12-rc2
> with the series to enable memory corruption handling[0].
> 
> Please consider merging as a fix for the 4.12 release.
> 
> Thanks,
> Punit
> 
> [0] https://www.spinics.net/lists/arm-kernel/msg581657.html
> ---
>  mm/migrate.c | 4 +---
>  1 file changed, 1 insertion(+), 3 deletions(-)
> 
> diff --git a/mm/migrate.c b/mm/migrate.c
> index 89a0a1707f4c..187abd1526df 100644
> --- a/mm/migrate.c
> +++ b/mm/migrate.c
> @@ -1201,10 +1201,8 @@ static int unmap_and_move_huge_page(new_page_t 
> get_new_page,
>* tables or check whether the hugepage is pmd-based or not before
>* kicking migration.
>*/
> - if (!hugepage_migration_supported(page_hstate(hpage))) {
> - putback_active_hugepage(hpage);

Thank you for reporting and suggestion, Punit, Manoj.

Simply dropping this putback_active_hugepage() may resume the failure
counting issue addressed in 32665f2bbfed, so I would recommend to call
putback_movable_pages() in failure path in soft_offline_huge_page().

@@ -1600,7 +1600,8 @@ static int soft_offline_huge_page(struct page *page, int 
flags)
 * only one hugepage pointed to by hpage, so we need not
 * run through the pagelist here.
 */
-   putback_active_hugepage(hpage);
+   if (!list_empty())
+   putback_movable_pages();
if (ret > 0)
ret = -EIO;
} else {

Could you check this works for you?

Thanks,
Naoya Horiguchi

Re: [PATCH] mm/migrate: Fix ref-count handling when !hugepage_migration_supported()

[Naoya Horiguchi]

On Wed, May 24, 2017 at 04:47:28PM +0100, Punit Agrawal wrote:
> On failing to migrate a page, soft_offline_huge_page() performs the
> necessary update to the hugepage ref-count. When
> !hugepage_migration_supported() , unmap_and_move_hugepage() also
> decrements the page ref-count for the hugepage. The combined behaviour
> leaves the ref-count in an inconsistent state.
> 
> This leads to soft lockups when running the overcommitted hugepage test
> from mce-tests suite.
> 
> Soft offlining pfn 0x83ed600 at process virtual address 0x4000
> soft offline: 0x83ed600: migration failed 1, type
> 1fffc0008008 (uptodate|head)
> INFO: rcu_preempt detected stalls on CPUs/tasks:
>  Tasks blocked on level-0 rcu_node (CPUs 0-7): P2715
>   (detected by 7, t=5254 jiffies, g=963, c=962, q=321)
>   thugetlb_overco R  running task0  2715   2685 0x0008
>   Call trace:
>   [] dump_backtrace+0x0/0x268
>   [] show_stack+0x24/0x30
>   [] sched_show_task+0x134/0x180
>   [] rcu_print_detail_task_stall_rnp+0x54/0x7c
>   [] rcu_check_callbacks+0xa74/0xb08
>   [] update_process_times+0x34/0x60
>   [] tick_sched_handle.isra.7+0x38/0x70
>   [] tick_sched_timer+0x4c/0x98
>   [] __hrtimer_run_queues+0xc0/0x300
>   [] hrtimer_interrupt+0xac/0x228
>   [] arch_timer_handler_phys+0x3c/0x50
>   [] handle_percpu_devid_irq+0x8c/0x290
>   [] generic_handle_irq+0x34/0x50
>   [] __handle_domain_irq+0x68/0xc0
>   [] gic_handle_irq+0x5c/0xb0
> 
> Fix this by dropping the ref-count decrement in
> unmap_and_move_hugepage() when !hugepage_migration_supported().
> 
> Fixes: 32665f2bbfed ("mm/migrate: correct failure handling if 
> !hugepage_migration_support()")
> Reported-by: Manoj Iyer 
> Signed-off-by: Punit Agrawal 
> Cc: Joonsoo Kim 
> Cc: Naoya Horiguchi 
> Cc: Wanpeng Li 
> Cc: Christoph Lameter 
> 
> --
> Hi Andrew,
> 
> We ran into this bug when working towards enabling memory corruption
> on arm64. The patch was tested on an arm64 platform running v4.12-rc2
> with the series to enable memory corruption handling[0].
> 
> Please consider merging as a fix for the 4.12 release.
> 
> Thanks,
> Punit
> 
> [0] https://www.spinics.net/lists/arm-kernel/msg581657.html
> ---
>  mm/migrate.c | 4 +---
>  1 file changed, 1 insertion(+), 3 deletions(-)
> 
> diff --git a/mm/migrate.c b/mm/migrate.c
> index 89a0a1707f4c..187abd1526df 100644
> --- a/mm/migrate.c
> +++ b/mm/migrate.c
> @@ -1201,10 +1201,8 @@ static int unmap_and_move_huge_page(new_page_t 
> get_new_page,
>* tables or check whether the hugepage is pmd-based or not before
>* kicking migration.
>*/
> - if (!hugepage_migration_supported(page_hstate(hpage))) {
> - putback_active_hugepage(hpage);

Thank you for reporting and suggestion, Punit, Manoj.

Simply dropping this putback_active_hugepage() may resume the failure
counting issue addressed in 32665f2bbfed, so I would recommend to call
putback_movable_pages() in failure path in soft_offline_huge_page().

@@ -1600,7 +1600,8 @@ static int soft_offline_huge_page(struct page *page, int 
flags)
 * only one hugepage pointed to by hpage, so we need not
 * run through the pagelist here.
 */
-   putback_active_hugepage(hpage);
+   if (!list_empty())
+   putback_movable_pages();
if (ret > 0)
ret = -EIO;
} else {

Could you check this works for you?

Thanks,
Naoya Horiguchi

Re: [PATCH] mm/migrate: Fix ref-count handling when !hugepage_migration_supported()

[Andrew Morton]

On Wed, 24 May 2017 16:47:28 +0100 Punit Agrawal  wrote:

> On failing to migrate a page, soft_offline_huge_page() performs the
> necessary update to the hugepage ref-count. When
> !hugepage_migration_supported() , unmap_and_move_hugepage() also
> decrements the page ref-count for the hugepage. The combined behaviour
> leaves the ref-count in an inconsistent state.
> 
> This leads to soft lockups when running the overcommitted hugepage test
> from mce-tests suite.
> 
> Soft offlining pfn 0x83ed600 at process virtual address 0x4000
> soft offline: 0x83ed600: migration failed 1, type
> 1fffc0008008 (uptodate|head)
> INFO: rcu_preempt detected stalls on CPUs/tasks:
>  Tasks blocked on level-0 rcu_node (CPUs 0-7): P2715
>   (detected by 7, t=5254 jiffies, g=963, c=962, q=321)
>   thugetlb_overco R  running task0  2715   2685 0x0008
>   Call trace:
>   [] dump_backtrace+0x0/0x268
>   [] show_stack+0x24/0x30
>   [] sched_show_task+0x134/0x180
>   [] rcu_print_detail_task_stall_rnp+0x54/0x7c
>   [] rcu_check_callbacks+0xa74/0xb08
>   [] update_process_times+0x34/0x60
>   [] tick_sched_handle.isra.7+0x38/0x70
>   [] tick_sched_timer+0x4c/0x98
>   [] __hrtimer_run_queues+0xc0/0x300
>   [] hrtimer_interrupt+0xac/0x228
>   [] arch_timer_handler_phys+0x3c/0x50
>   [] handle_percpu_devid_irq+0x8c/0x290
>   [] generic_handle_irq+0x34/0x50
>   [] __handle_domain_irq+0x68/0xc0
>   [] gic_handle_irq+0x5c/0xb0
> 
> Fix this by dropping the ref-count decrement in
> unmap_and_move_hugepage() when !hugepage_migration_supported().
> 
> Fixes: 32665f2bbfed ("mm/migrate: correct failure handling if 
> !hugepage_migration_support()")
> Reported-by: Manoj Iyer 
> Signed-off-by: Punit Agrawal 
> Cc: Joonsoo Kim 
> Cc: Naoya Horiguchi 
> Cc: Wanpeng Li 
> Cc: Christoph Lameter 

32665f2bbfed was three years ago.  Do you have any theory as to why
this took so long to be detected?  And do you believe a -stable
backport is warranted?

Re: [PATCH] mm/migrate: Fix ref-count handling when !hugepage_migration_supported()

[Andrew Morton]

On Wed, 24 May 2017 16:47:28 +0100 Punit Agrawal  wrote:

> On failing to migrate a page, soft_offline_huge_page() performs the
> necessary update to the hugepage ref-count. When
> !hugepage_migration_supported() , unmap_and_move_hugepage() also
> decrements the page ref-count for the hugepage. The combined behaviour
> leaves the ref-count in an inconsistent state.
> 
> This leads to soft lockups when running the overcommitted hugepage test
> from mce-tests suite.
> 
> Soft offlining pfn 0x83ed600 at process virtual address 0x4000
> soft offline: 0x83ed600: migration failed 1, type
> 1fffc0008008 (uptodate|head)
> INFO: rcu_preempt detected stalls on CPUs/tasks:
>  Tasks blocked on level-0 rcu_node (CPUs 0-7): P2715
>   (detected by 7, t=5254 jiffies, g=963, c=962, q=321)
>   thugetlb_overco R  running task0  2715   2685 0x0008
>   Call trace:
>   [] dump_backtrace+0x0/0x268
>   [] show_stack+0x24/0x30
>   [] sched_show_task+0x134/0x180
>   [] rcu_print_detail_task_stall_rnp+0x54/0x7c
>   [] rcu_check_callbacks+0xa74/0xb08
>   [] update_process_times+0x34/0x60
>   [] tick_sched_handle.isra.7+0x38/0x70
>   [] tick_sched_timer+0x4c/0x98
>   [] __hrtimer_run_queues+0xc0/0x300
>   [] hrtimer_interrupt+0xac/0x228
>   [] arch_timer_handler_phys+0x3c/0x50
>   [] handle_percpu_devid_irq+0x8c/0x290
>   [] generic_handle_irq+0x34/0x50
>   [] __handle_domain_irq+0x68/0xc0
>   [] gic_handle_irq+0x5c/0xb0
> 
> Fix this by dropping the ref-count decrement in
> unmap_and_move_hugepage() when !hugepage_migration_supported().
> 
> Fixes: 32665f2bbfed ("mm/migrate: correct failure handling if 
> !hugepage_migration_support()")
> Reported-by: Manoj Iyer 
> Signed-off-by: Punit Agrawal 
> Cc: Joonsoo Kim 
> Cc: Naoya Horiguchi 
> Cc: Wanpeng Li 
> Cc: Christoph Lameter 

32665f2bbfed was three years ago.  Do you have any theory as to why
this took so long to be detected?  And do you believe a -stable
backport is warranted?