[V5,-,Rebased] mm/hotplug: Reorder memblock_[free|remove]() calls in try_remove_memory()
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Message ID 1560252373-3230-1-git-send-email-anshuman.khandual@arm.com
State New
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  • [V5,-,Rebased] mm/hotplug: Reorder memblock_[free|remove]() calls in try_remove_memory()
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Commit Message

Anshuman Khandual June 11, 2019, 11:26 a.m. UTC
Memory hot remove uses get_nid_for_pfn() while tearing down linked sysfs
entries between memory block and node. It first checks pfn validity with
pfn_valid_within() before fetching nid. With CONFIG_HOLES_IN_ZONE config
(arm64 has this enabled) pfn_valid_within() calls pfn_valid().

pfn_valid() is an arch implementation on arm64 (CONFIG_HAVE_ARCH_PFN_VALID)
which scans all mapped memblock regions with memblock_is_map_memory(). This
creates a problem in memory hot remove path which has already removed given
memory range from memory block with memblock_[remove|free] before arriving
at unregister_mem_sect_under_nodes(). Hence get_nid_for_pfn() returns -1
skipping subsequent sysfs_remove_link() calls leaving node <-> memory block
sysfs entries as is. Subsequent memory add operation hits BUG_ON() because
of existing sysfs entries.

[   62.007176] NUMA: Unknown node for memory at 0x680000000, assuming node 0
[   62.052517] ------------[ cut here ]------------
[   62.053211] kernel BUG at mm/memory_hotplug.c:1143!
[   62.053868] Internal error: Oops - BUG: 0 [#1] PREEMPT SMP
[   62.054589] Modules linked in:
[   62.054999] CPU: 19 PID: 3275 Comm: bash Not tainted 5.1.0-rc2-00004-g28cea40b2683 #41
[   62.056274] Hardware name: linux,dummy-virt (DT)
[   62.057166] pstate: 40400005 (nZcv daif +PAN -UAO)
[   62.058083] pc : add_memory_resource+0x1cc/0x1d8
[   62.058961] lr : add_memory_resource+0x10c/0x1d8
[   62.059842] sp : ffff0000168b3ce0
[   62.060477] x29: ffff0000168b3ce0 x28: ffff8005db546c00
[   62.061501] x27: 0000000000000000 x26: 0000000000000000
[   62.062509] x25: ffff0000111ef000 x24: ffff0000111ef5d0
[   62.063520] x23: 0000000000000000 x22: 00000006bfffffff
[   62.064540] x21: 00000000ffffffef x20: 00000000006c0000
[   62.065558] x19: 0000000000680000 x18: 0000000000000024
[   62.066566] x17: 0000000000000000 x16: 0000000000000000
[   62.067579] x15: ffffffffffffffff x14: ffff8005e412e890
[   62.068588] x13: ffff8005d6b105d8 x12: 0000000000000000
[   62.069610] x11: ffff8005d6b10490 x10: 0000000000000040
[   62.070615] x9 : ffff8005e412e898 x8 : ffff8005e412e890
[   62.071631] x7 : ffff8005d6b105d8 x6 : ffff8005db546c00
[   62.072640] x5 : 0000000000000001 x4 : 0000000000000002
[   62.073654] x3 : ffff8005d7049480 x2 : 0000000000000002
[   62.074666] x1 : 0000000000000003 x0 : 00000000ffffffef
[   62.075685] Process bash (pid: 3275, stack limit = 0x00000000d754280f)
[   62.076930] Call trace:
[   62.077411]  add_memory_resource+0x1cc/0x1d8
[   62.078227]  __add_memory+0x70/0xa8
[   62.078901]  probe_store+0xa4/0xc8
[   62.079561]  dev_attr_store+0x18/0x28
[   62.080270]  sysfs_kf_write+0x40/0x58
[   62.080992]  kernfs_fop_write+0xcc/0x1d8
[   62.081744]  __vfs_write+0x18/0x40
[   62.082400]  vfs_write+0xa4/0x1b0
[   62.083037]  ksys_write+0x5c/0xc0
[   62.083681]  __arm64_sys_write+0x18/0x20
[   62.084432]  el0_svc_handler+0x88/0x100
[   62.085177]  el0_svc+0x8/0xc

Re-ordering memblock_[free|remove]() with arch_remove_memory() solves the
problem on arm64 as pfn_valid() behaves correctly and returns positive
as memblock for the address range still exists. arch_remove_memory()
removes applicable memory sections from zone with __remove_pages() and
tears down kernel linear mapping. Removing memblock regions afterwards
is safe because there is no other memblock (bootmem) allocator user that
late. So nobody is going to allocate from the removed range just to blow
up later. Also nobody should be using the bootmem allocated range else
we wouldn't allow to remove it. So reordering is indeed safe.

Reviewed-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
---
Changes in PATCH V5 - Rebased (from V5)

- Rebased on linux-next (next-20190611)
- s/__remove_memory/try_remove_memory in the subject line
- s/arch_remove_memory/memblock_[free|remove] in the subject line
- A small change in the commit message as re-order happens now for
  memblock remove functions not arch_remove_memory()

 mm/memory_hotplug.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

Comments

Andrew Morton June 11, 2019, 10:19 p.m. UTC | #1
On Tue, 11 Jun 2019 16:56:13 +0530 Anshuman Khandual <anshuman.khandual@arm.com> wrote:

> Memory hot remove uses get_nid_for_pfn() while tearing down linked sysfs
> entries between memory block and node. It first checks pfn validity with
> pfn_valid_within() before fetching nid. With CONFIG_HOLES_IN_ZONE config
> (arm64 has this enabled) pfn_valid_within() calls pfn_valid().
> 
> pfn_valid() is an arch implementation on arm64 (CONFIG_HAVE_ARCH_PFN_VALID)
> which scans all mapped memblock regions with memblock_is_map_memory(). This
> creates a problem in memory hot remove path which has already removed given
> memory range from memory block with memblock_[remove|free] before arriving
> at unregister_mem_sect_under_nodes(). Hence get_nid_for_pfn() returns -1
> skipping subsequent sysfs_remove_link() calls leaving node <-> memory block
> sysfs entries as is. Subsequent memory add operation hits BUG_ON() because
> of existing sysfs entries.
> 
> [   62.007176] NUMA: Unknown node for memory at 0x680000000, assuming node 0
> [   62.052517] ------------[ cut here ]------------
> [   62.053211] kernel BUG at mm/memory_hotplug.c:1143!
> [   62.053868] Internal error: Oops - BUG: 0 [#1] PREEMPT SMP
> [   62.054589] Modules linked in:
> [   62.054999] CPU: 19 PID: 3275 Comm: bash Not tainted 5.1.0-rc2-00004-g28cea40b2683 #41
> [   62.056274] Hardware name: linux,dummy-virt (DT)
> [   62.057166] pstate: 40400005 (nZcv daif +PAN -UAO)
> [   62.058083] pc : add_memory_resource+0x1cc/0x1d8
> [   62.058961] lr : add_memory_resource+0x10c/0x1d8
> [   62.059842] sp : ffff0000168b3ce0
> [   62.060477] x29: ffff0000168b3ce0 x28: ffff8005db546c00
> [   62.061501] x27: 0000000000000000 x26: 0000000000000000
> [   62.062509] x25: ffff0000111ef000 x24: ffff0000111ef5d0
> [   62.063520] x23: 0000000000000000 x22: 00000006bfffffff
> [   62.064540] x21: 00000000ffffffef x20: 00000000006c0000
> [   62.065558] x19: 0000000000680000 x18: 0000000000000024
> [   62.066566] x17: 0000000000000000 x16: 0000000000000000
> [   62.067579] x15: ffffffffffffffff x14: ffff8005e412e890
> [   62.068588] x13: ffff8005d6b105d8 x12: 0000000000000000
> [   62.069610] x11: ffff8005d6b10490 x10: 0000000000000040
> [   62.070615] x9 : ffff8005e412e898 x8 : ffff8005e412e890
> [   62.071631] x7 : ffff8005d6b105d8 x6 : ffff8005db546c00
> [   62.072640] x5 : 0000000000000001 x4 : 0000000000000002
> [   62.073654] x3 : ffff8005d7049480 x2 : 0000000000000002
> [   62.074666] x1 : 0000000000000003 x0 : 00000000ffffffef
> [   62.075685] Process bash (pid: 3275, stack limit = 0x00000000d754280f)
> [   62.076930] Call trace:
> [   62.077411]  add_memory_resource+0x1cc/0x1d8
> [   62.078227]  __add_memory+0x70/0xa8
> [   62.078901]  probe_store+0xa4/0xc8
> [   62.079561]  dev_attr_store+0x18/0x28
> [   62.080270]  sysfs_kf_write+0x40/0x58
> [   62.080992]  kernfs_fop_write+0xcc/0x1d8
> [   62.081744]  __vfs_write+0x18/0x40
> [   62.082400]  vfs_write+0xa4/0x1b0
> [   62.083037]  ksys_write+0x5c/0xc0
> [   62.083681]  __arm64_sys_write+0x18/0x20
> [   62.084432]  el0_svc_handler+0x88/0x100
> [   62.085177]  el0_svc+0x8/0xc

This seems like a serious problem.  Once which should be fixed in 5.2
and perhaps the various -stable kernels as well.

> Re-ordering memblock_[free|remove]() with arch_remove_memory() solves the
> problem on arm64 as pfn_valid() behaves correctly and returns positive
> as memblock for the address range still exists. arch_remove_memory()
> removes applicable memory sections from zone with __remove_pages() and
> tears down kernel linear mapping. Removing memblock regions afterwards
> is safe because there is no other memblock (bootmem) allocator user that
> late. So nobody is going to allocate from the removed range just to blow
> up later. Also nobody should be using the bootmem allocated range else
> we wouldn't allow to remove it. So reordering is indeed safe.
> 
> ...
>
> 
> - Rebased on linux-next (next-20190611)

Yet the patch you've prepared is designed for 5.3.  Was that
deliberate, or should we be targeting earlier kernels?
Anshuman Khandual June 12, 2019, 4:02 a.m. UTC | #2
On 06/12/2019 03:49 AM, Andrew Morton wrote:
> On Tue, 11 Jun 2019 16:56:13 +0530 Anshuman Khandual <anshuman.khandual@arm.com> wrote:
> 
>> Memory hot remove uses get_nid_for_pfn() while tearing down linked sysfs
>> entries between memory block and node. It first checks pfn validity with
>> pfn_valid_within() before fetching nid. With CONFIG_HOLES_IN_ZONE config
>> (arm64 has this enabled) pfn_valid_within() calls pfn_valid().
>>
>> pfn_valid() is an arch implementation on arm64 (CONFIG_HAVE_ARCH_PFN_VALID)
>> which scans all mapped memblock regions with memblock_is_map_memory(). This
>> creates a problem in memory hot remove path which has already removed given
>> memory range from memory block with memblock_[remove|free] before arriving
>> at unregister_mem_sect_under_nodes(). Hence get_nid_for_pfn() returns -1
>> skipping subsequent sysfs_remove_link() calls leaving node <-> memory block
>> sysfs entries as is. Subsequent memory add operation hits BUG_ON() because
>> of existing sysfs entries.
>>
>> [   62.007176] NUMA: Unknown node for memory at 0x680000000, assuming node 0
>> [   62.052517] ------------[ cut here ]------------
>> [   62.053211] kernel BUG at mm/memory_hotplug.c:1143!
>> [   62.053868] Internal error: Oops - BUG: 0 [#1] PREEMPT SMP
>> [   62.054589] Modules linked in:
>> [   62.054999] CPU: 19 PID: 3275 Comm: bash Not tainted 5.1.0-rc2-00004-g28cea40b2683 #41
>> [   62.056274] Hardware name: linux,dummy-virt (DT)
>> [   62.057166] pstate: 40400005 (nZcv daif +PAN -UAO)
>> [   62.058083] pc : add_memory_resource+0x1cc/0x1d8
>> [   62.058961] lr : add_memory_resource+0x10c/0x1d8
>> [   62.059842] sp : ffff0000168b3ce0
>> [   62.060477] x29: ffff0000168b3ce0 x28: ffff8005db546c00
>> [   62.061501] x27: 0000000000000000 x26: 0000000000000000
>> [   62.062509] x25: ffff0000111ef000 x24: ffff0000111ef5d0
>> [   62.063520] x23: 0000000000000000 x22: 00000006bfffffff
>> [   62.064540] x21: 00000000ffffffef x20: 00000000006c0000
>> [   62.065558] x19: 0000000000680000 x18: 0000000000000024
>> [   62.066566] x17: 0000000000000000 x16: 0000000000000000
>> [   62.067579] x15: ffffffffffffffff x14: ffff8005e412e890
>> [   62.068588] x13: ffff8005d6b105d8 x12: 0000000000000000
>> [   62.069610] x11: ffff8005d6b10490 x10: 0000000000000040
>> [   62.070615] x9 : ffff8005e412e898 x8 : ffff8005e412e890
>> [   62.071631] x7 : ffff8005d6b105d8 x6 : ffff8005db546c00
>> [   62.072640] x5 : 0000000000000001 x4 : 0000000000000002
>> [   62.073654] x3 : ffff8005d7049480 x2 : 0000000000000002
>> [   62.074666] x1 : 0000000000000003 x0 : 00000000ffffffef
>> [   62.075685] Process bash (pid: 3275, stack limit = 0x00000000d754280f)
>> [   62.076930] Call trace:
>> [   62.077411]  add_memory_resource+0x1cc/0x1d8
>> [   62.078227]  __add_memory+0x70/0xa8
>> [   62.078901]  probe_store+0xa4/0xc8
>> [   62.079561]  dev_attr_store+0x18/0x28
>> [   62.080270]  sysfs_kf_write+0x40/0x58
>> [   62.080992]  kernfs_fop_write+0xcc/0x1d8
>> [   62.081744]  __vfs_write+0x18/0x40
>> [   62.082400]  vfs_write+0xa4/0x1b0
>> [   62.083037]  ksys_write+0x5c/0xc0
>> [   62.083681]  __arm64_sys_write+0x18/0x20
>> [   62.084432]  el0_svc_handler+0x88/0x100
>> [   62.085177]  el0_svc+0x8/0xc
> 
> This seems like a serious problem.  Once which should be fixed in 5.2
> and perhaps the various -stable kernels as well.

But the problem does not exist in the current kernel as yet till the reworked
versions of the other two patches in this series get merged. This patch was
after arm64 hot-remove enablement in V1 (https://lkml.org/lkml/2019/4/3/28)
but after some discussions it was decided to be moved before hot-remove from
V2 (https://lkml.org/lkml/2019/4/14/5) onwards as a prerequisite patch instead.

> 
>> Re-ordering memblock_[free|remove]() with arch_remove_memory() solves the
>> problem on arm64 as pfn_valid() behaves correctly and returns positive
>> as memblock for the address range still exists. arch_remove_memory()
>> removes applicable memory sections from zone with __remove_pages() and
>> tears down kernel linear mapping. Removing memblock regions afterwards
>> is safe because there is no other memblock (bootmem) allocator user that
>> late. So nobody is going to allocate from the removed range just to blow
>> up later. Also nobody should be using the bootmem allocated range else
>> we wouldn't allow to remove it. So reordering is indeed safe.
>>
>> ...
>>
>>
>> - Rebased on linux-next (next-20190611)
> 
> Yet the patch you've prepared is designed for 5.3.  Was that
> deliberate, or should we be targeting earlier kernels?

It was deliberate for 5.3 as a preparation for upcoming reworked arm64 hot-remove.
David Hildenbrand June 12, 2019, 6:53 a.m. UTC | #3
On 12.06.19 06:02, Anshuman Khandual wrote:
> 
> 
> On 06/12/2019 03:49 AM, Andrew Morton wrote:
>> On Tue, 11 Jun 2019 16:56:13 +0530 Anshuman Khandual <anshuman.khandual@arm.com> wrote:
>>
>>> Memory hot remove uses get_nid_for_pfn() while tearing down linked sysfs
>>> entries between memory block and node. It first checks pfn validity with
>>> pfn_valid_within() before fetching nid. With CONFIG_HOLES_IN_ZONE config
>>> (arm64 has this enabled) pfn_valid_within() calls pfn_valid().
>>>
>>> pfn_valid() is an arch implementation on arm64 (CONFIG_HAVE_ARCH_PFN_VALID)
>>> which scans all mapped memblock regions with memblock_is_map_memory(). This
>>> creates a problem in memory hot remove path which has already removed given
>>> memory range from memory block with memblock_[remove|free] before arriving
>>> at unregister_mem_sect_under_nodes(). Hence get_nid_for_pfn() returns -1
>>> skipping subsequent sysfs_remove_link() calls leaving node <-> memory block
>>> sysfs entries as is. Subsequent memory add operation hits BUG_ON() because
>>> of existing sysfs entries.
>>>
>>> [   62.007176] NUMA: Unknown node for memory at 0x680000000, assuming node 0
>>> [   62.052517] ------------[ cut here ]------------
>>> [   62.053211] kernel BUG at mm/memory_hotplug.c:1143!
>>> [   62.053868] Internal error: Oops - BUG: 0 [#1] PREEMPT SMP
>>> [   62.054589] Modules linked in:
>>> [   62.054999] CPU: 19 PID: 3275 Comm: bash Not tainted 5.1.0-rc2-00004-g28cea40b2683 #41
>>> [   62.056274] Hardware name: linux,dummy-virt (DT)
>>> [   62.057166] pstate: 40400005 (nZcv daif +PAN -UAO)
>>> [   62.058083] pc : add_memory_resource+0x1cc/0x1d8
>>> [   62.058961] lr : add_memory_resource+0x10c/0x1d8
>>> [   62.059842] sp : ffff0000168b3ce0
>>> [   62.060477] x29: ffff0000168b3ce0 x28: ffff8005db546c00
>>> [   62.061501] x27: 0000000000000000 x26: 0000000000000000
>>> [   62.062509] x25: ffff0000111ef000 x24: ffff0000111ef5d0
>>> [   62.063520] x23: 0000000000000000 x22: 00000006bfffffff
>>> [   62.064540] x21: 00000000ffffffef x20: 00000000006c0000
>>> [   62.065558] x19: 0000000000680000 x18: 0000000000000024
>>> [   62.066566] x17: 0000000000000000 x16: 0000000000000000
>>> [   62.067579] x15: ffffffffffffffff x14: ffff8005e412e890
>>> [   62.068588] x13: ffff8005d6b105d8 x12: 0000000000000000
>>> [   62.069610] x11: ffff8005d6b10490 x10: 0000000000000040
>>> [   62.070615] x9 : ffff8005e412e898 x8 : ffff8005e412e890
>>> [   62.071631] x7 : ffff8005d6b105d8 x6 : ffff8005db546c00
>>> [   62.072640] x5 : 0000000000000001 x4 : 0000000000000002
>>> [   62.073654] x3 : ffff8005d7049480 x2 : 0000000000000002
>>> [   62.074666] x1 : 0000000000000003 x0 : 00000000ffffffef
>>> [   62.075685] Process bash (pid: 3275, stack limit = 0x00000000d754280f)
>>> [   62.076930] Call trace:
>>> [   62.077411]  add_memory_resource+0x1cc/0x1d8
>>> [   62.078227]  __add_memory+0x70/0xa8
>>> [   62.078901]  probe_store+0xa4/0xc8
>>> [   62.079561]  dev_attr_store+0x18/0x28
>>> [   62.080270]  sysfs_kf_write+0x40/0x58
>>> [   62.080992]  kernfs_fop_write+0xcc/0x1d8
>>> [   62.081744]  __vfs_write+0x18/0x40
>>> [   62.082400]  vfs_write+0xa4/0x1b0
>>> [   62.083037]  ksys_write+0x5c/0xc0
>>> [   62.083681]  __arm64_sys_write+0x18/0x20
>>> [   62.084432]  el0_svc_handler+0x88/0x100
>>> [   62.085177]  el0_svc+0x8/0xc
>>
>> This seems like a serious problem.  Once which should be fixed in 5.2
>> and perhaps the various -stable kernels as well.
> 
> But the problem does not exist in the current kernel as yet till the reworked
> versions of the other two patches in this series get merged. This patch was
> after arm64 hot-remove enablement in V1 (https://lkml.org/lkml/2019/4/3/28)
> but after some discussions it was decided to be moved before hot-remove from
> V2 (https://lkml.org/lkml/2019/4/14/5) onwards as a prerequisite patch instead.
> 
>>
>>> Re-ordering memblock_[free|remove]() with arch_remove_memory() solves the
>>> problem on arm64 as pfn_valid() behaves correctly and returns positive
>>> as memblock for the address range still exists. arch_remove_memory()
>>> removes applicable memory sections from zone with __remove_pages() and
>>> tears down kernel linear mapping. Removing memblock regions afterwards
>>> is safe because there is no other memblock (bootmem) allocator user that
>>> late. So nobody is going to allocate from the removed range just to blow
>>> up later. Also nobody should be using the bootmem allocated range else
>>> we wouldn't allow to remove it. So reordering is indeed safe.
>>>
>>> ...
>>>
>>>
>>> - Rebased on linux-next (next-20190611)
>>
>> Yet the patch you've prepared is designed for 5.3.  Was that
>> deliberate, or should we be targeting earlier kernels?
> 
> It was deliberate for 5.3 as a preparation for upcoming reworked arm64 hot-remove.
> 

We should probably add to the patch description something like "This is
a preparation for arm64 memory hotremove. The described issue is not
relevant on other architectures."
Andrew Morton June 13, 2019, 1:54 a.m. UTC | #4
On Wed, 12 Jun 2019 08:53:33 +0200 David Hildenbrand <david@redhat.com> wrote:

> >>> ...
> >>>
> >>>
> >>> - Rebased on linux-next (next-20190611)
> >>
> >> Yet the patch you've prepared is designed for 5.3.  Was that
> >> deliberate, or should we be targeting earlier kernels?
> > 
> > It was deliberate for 5.3 as a preparation for upcoming reworked arm64 hot-remove.
> > 
> 
> We should probably add to the patch description something like "This is
> a preparation for arm64 memory hotremove. The described issue is not
> relevant on other architectures."

Please.  And is there any reason to merge it separately?  Can it be
[patch 1/3] in the "arm64/mm: Enable memory hot remove" series?
Anshuman Khandual June 13, 2019, 5:37 a.m. UTC | #5
On 06/13/2019 07:24 AM, Andrew Morton wrote:
> On Wed, 12 Jun 2019 08:53:33 +0200 David Hildenbrand <david@redhat.com> wrote:
> 
>>>>> ...
>>>>>
>>>>>
>>>>> - Rebased on linux-next (next-20190611)
>>>>
>>>> Yet the patch you've prepared is designed for 5.3.  Was that
>>>> deliberate, or should we be targeting earlier kernels?
>>>
>>> It was deliberate for 5.3 as a preparation for upcoming reworked arm64 hot-remove.
>>>
>>
>> We should probably add to the patch description something like "This is
>> a preparation for arm64 memory hotremove. The described issue is not
>> relevant on other architectures."
> 
> Please.  And is there any reason to merge it separately?  Can it be
> [patch 1/3] in the "arm64/mm: Enable memory hot remove" series?

Sure it can be. I will make this [patch 1/3] in the next version for
"arm64/mm: Enable memory hot remove". Apologies for the noise here.
David Hildenbrand June 13, 2019, 6:14 a.m. UTC | #6
On 13.06.19 03:54, Andrew Morton wrote:
> On Wed, 12 Jun 2019 08:53:33 +0200 David Hildenbrand <david@redhat.com> wrote:
> 
>>>>> ...
>>>>>
>>>>>
>>>>> - Rebased on linux-next (next-20190611)
>>>>
>>>> Yet the patch you've prepared is designed for 5.3.  Was that
>>>> deliberate, or should we be targeting earlier kernels?
>>>
>>> It was deliberate for 5.3 as a preparation for upcoming reworked arm64 hot-remove.
>>>
>>
>> We should probably add to the patch description something like "This is
>> a preparation for arm64 memory hotremove. The described issue is not
>> relevant on other architectures."
> 
> Please.  And is there any reason to merge it separately?  Can it be
> [patch 1/3] in the "arm64/mm: Enable memory hot remove" series?
> 

Nothing that the patch can be considered a cleanup:

"
mm/hotplug: Reorder memblock_[free|remove]() calls in try_remove_memory()

In add_memory_resource() we have:

	memblock_add_node(start, size, nid)
	...
	arch_add_memory(nid, start, size, &restrictions);
	...
	create_memory_block_devices(start, size);

While in try_remove_memory() we have:

	memblock_free(start, size);
	memblock_remove(start, size);
	...
	remove_memory_block_devices(start, size);
	arch_remove_memory(nid, start, size, NULL);

Let's restore the correct order by removing the memblock after
arch_remove_memory().
"

I think with such a description, we can include it now. Andrew?

Patch
diff mbox series

diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index a88c5f334e5a..cfa5facf1b38 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -1831,13 +1831,13 @@  static int __ref try_remove_memory(int nid, u64 start, u64 size)
 
 	/* remove memmap entry */
 	firmware_map_remove(start, start + size, "System RAM");
-	memblock_free(start, size);
-	memblock_remove(start, size);
 
 	/* remove memory block devices before removing memory */
 	remove_memory_block_devices(start, size);
 
 	arch_remove_memory(nid, start, size, NULL);
+	memblock_free(start, size);
+	memblock_remove(start, size);
 	__release_memory_resource(start, size);
 
 	try_offline_node(nid);