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From: Anshuman Khandual <anshuman.khandual@arm.com>
To: David Hildenbrand <david@redhat.com>,
	linux-mm@kvack.org, linux-kernel@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org, akpm@linux-foundation.org,
	catalin.marinas@arm.com, will@kernel.org
Cc: mark.rutland@arm.com, mhocko@suse.com, ira.weiny@intel.com,
	cai@lca.pw, logang@deltatee.com, cpandya@codeaurora.org,
	arunks@codeaurora.org, dan.j.williams@intel.com,
	mgorman@techsingularity.net, osalvador@suse.de,
	ard.biesheuvel@arm.com, steve.capper@arm.com, broonie@kernel.org,
	valentin.schneider@arm.com, Robin.Murphy@arm.com,
	steven.price@arm.com, suzuki.poulose@arm.com
Subject: Re: [PATCH V7 1/3] mm/hotplug: Reorder memblock_[free|remove]() calls in try_remove_memory()
Date: Thu, 5 Sep 2019 09:57:23 +0530	[thread overview]
Message-ID: <49c2a682-97c5-5eef-6635-9fe75e4677f7@arm.com> (raw)
In-Reply-To: <e98f2950-bef9-3672-81a8-f9593354fffe@redhat.com>



On 09/04/2019 01:46 PM, David Hildenbrand wrote:
> On 03.09.19 11:45, Anshuman Khandual 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.
> Since
> 
> commit 60bb462fc7adb06ebee3beb5a4af6c7e6182e248
> Author: David Hildenbrand <david@redhat.com>
> Date:   Wed Aug 28 13:57:15 2019 +1000
> 
>     drivers/base/node.c: simplify unregister_memory_block_under_nodes()
> 
> that problem should be gone. There is no get_nid_for_pfn() call anymore.

Yes, the problem is gone. The above commit is still not present on arm64
tree against which this series was rebased and tested while posting.

> 
> So this patch should no longer be necessary - but as I said during
> earlier versions of this patch, the re-ordering might still make sense
> for consistency (removing stuff in the reverse order they were added).
> You'll have to rephrase the description then.

Sure will reword the commit message on these lines.

WARNING: multiple messages have this Message-ID (diff)
From: Anshuman Khandual <anshuman.khandual@arm.com>
To: David Hildenbrand <david@redhat.com>,
	linux-mm@kvack.org, linux-kernel@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org, akpm@linux-foundation.org,
	catalin.marinas@arm.com, will@kernel.org
Cc: mark.rutland@arm.com, mhocko@suse.com, steve.capper@arm.com,
	ira.weiny@intel.com, suzuki.poulose@arm.com,
	mgorman@techsingularity.net, steven.price@arm.com,
	broonie@kernel.org, cai@lca.pw, ard.biesheuvel@arm.com,
	cpandya@codeaurora.org, arunks@codeaurora.org,
	dan.j.williams@intel.com, Robin.Murphy@arm.com,
	logang@deltatee.com, valentin.schneider@arm.com,
	osalvador@suse.de
Subject: Re: [PATCH V7 1/3] mm/hotplug: Reorder memblock_[free|remove]() calls in try_remove_memory()
Date: Thu, 5 Sep 2019 09:57:23 +0530	[thread overview]
Message-ID: <49c2a682-97c5-5eef-6635-9fe75e4677f7@arm.com> (raw)
In-Reply-To: <e98f2950-bef9-3672-81a8-f9593354fffe@redhat.com>



On 09/04/2019 01:46 PM, David Hildenbrand wrote:
> On 03.09.19 11:45, Anshuman Khandual 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.
> Since
> 
> commit 60bb462fc7adb06ebee3beb5a4af6c7e6182e248
> Author: David Hildenbrand <david@redhat.com>
> Date:   Wed Aug 28 13:57:15 2019 +1000
> 
>     drivers/base/node.c: simplify unregister_memory_block_under_nodes()
> 
> that problem should be gone. There is no get_nid_for_pfn() call anymore.

Yes, the problem is gone. The above commit is still not present on arm64
tree against which this series was rebased and tested while posting.

> 
> So this patch should no longer be necessary - but as I said during
> earlier versions of this patch, the re-ordering might still make sense
> for consistency (removing stuff in the reverse order they were added).
> You'll have to rephrase the description then.

Sure will reword the commit message on these lines.

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linux-arm-kernel@lists.infradead.org
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  reply	other threads:[~2019-09-05  4:27 UTC|newest]

Thread overview: 38+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-09-03  9:45 [PATCH V7 0/3] arm64/mm: Enable memory hot remove Anshuman Khandual
2019-09-03  9:45 ` Anshuman Khandual
2019-09-03  9:45 ` [PATCH V7 1/3] mm/hotplug: Reorder memblock_[free|remove]() calls in try_remove_memory() Anshuman Khandual
2019-09-03  9:45   ` Anshuman Khandual
2019-09-04  8:16   ` David Hildenbrand
2019-09-04  8:16     ` David Hildenbrand
2019-09-05  4:27     ` Anshuman Khandual [this message]
2019-09-05  4:27       ` Anshuman Khandual
2019-09-16  1:44   ` Balbir Singh
2019-09-16  1:44     ` Balbir Singh
2019-09-18  9:28     ` Anshuman Khandual
2019-09-18  9:28       ` Anshuman Khandual
2019-09-03  9:45 ` [PATCH V7 2/3] arm64/mm: Hold memory hotplug lock while walking for kernel page table dump Anshuman Khandual
2019-09-03  9:45   ` Anshuman Khandual
2019-09-15  2:35   ` Balbir Singh
2019-09-15  2:35     ` Balbir Singh
2019-09-18  9:12     ` Anshuman Khandual
2019-09-18  9:12       ` Anshuman Khandual
2019-09-03  9:45 ` [PATCH V7 3/3] arm64/mm: Enable memory hot remove Anshuman Khandual
2019-09-03  9:45   ` Anshuman Khandual
2019-09-10 16:17   ` Catalin Marinas
2019-09-10 16:17     ` Catalin Marinas
2019-09-11 10:31     ` David Hildenbrand
2019-09-11 10:31       ` David Hildenbrand
2019-09-12  4:28     ` Anshuman Khandual
2019-09-12  4:28       ` Anshuman Khandual
2019-09-12  8:37       ` Anshuman Khandual
2019-09-12  8:37         ` Anshuman Khandual
2019-09-12 20:15   ` Catalin Marinas
2019-09-12 20:15     ` Catalin Marinas
2019-09-13  5:58     ` Anshuman Khandual
2019-09-13  5:58       ` Anshuman Khandual
2019-09-13 10:09       ` Catalin Marinas
2019-09-13 10:09         ` Catalin Marinas
2019-09-17  4:36         ` Anshuman Khandual
2019-09-17  4:36           ` Anshuman Khandual
2019-09-17 15:08           ` Catalin Marinas
2019-09-17 15:08             ` Catalin Marinas

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