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From: David Hildenbrand <david@redhat.com>
To: "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>,
	linux-kernel@vger.kernel.org,
	Dan Williams <dan.j.williams@intel.com>
Cc: linux-s390@vger.kernel.org, linux-ia64@vger.kernel.org,
	Ira Weiny <ira.weiny@intel.com>,
	linux-sh@vger.kernel.org, Jason Gunthorpe <jgg@ziepe.ca>,
	Logan Gunthorpe <logang@deltatee.com>,
	Pankaj Gupta <pagupta@redhat.com>,
	linux-mm@kvack.org, Andrew Morton <akpm@linux-foundation.org>,
	linuxppc-dev@lists.ozlabs.org,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v5 01/10] mm/memunmap: Use the correct start and end pfn when removing pages from zone
Date: Sun, 6 Oct 2019 10:13:45 +0200	[thread overview]
Message-ID: <96d3cab9-965d-f363-f3ea-e31e89e2fc01@redhat.com> (raw)
In-Reply-To: <cbb82f0a-a578-5fb0-6b62-00bcd0a09b2e@linux.ibm.com>

On 05.10.19 08:13, Aneesh Kumar K.V wrote:
> On 10/4/19 2:33 PM, David Hildenbrand wrote:
>> On 04.10.19 11:00, David Hildenbrand wrote:
>>> On 03.10.19 18:48, Aneesh Kumar K.V wrote:
>>>> On 10/1/19 8:33 PM, David Hildenbrand wrote:
>>>>> On 01.10.19 16:57, David Hildenbrand wrote:
>>>>>> On 01.10.19 16:40, David Hildenbrand wrote:
>>>>>>> From: "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>
>>>>>>>
>>>>>>> With altmap, all the resource pfns are not initialized. While initializing
>>>>>>> pfn, altmap reserve space is skipped. Hence when removing pfn from zone
>>>>>>> skip pfns that were never initialized.
>>>>>>>
>>>>>>> Update memunmap_pages to calculate start and end pfn based on altmap
>>>>>>> values. This fixes a kernel crash that is observed when destroying
>>>>>>> a namespace.
>>>>>>>
>>>>>>> [   81.356173] kernel BUG at include/linux/mm.h:1107!
>>>>>>> cpu 0x1: Vector: 700 (Program Check) at [c000000274087890]
>>>>>>>       pc: c0000000004b9728: memunmap_pages+0x238/0x340
>>>>>>>       lr: c0000000004b9724: memunmap_pages+0x234/0x340
>>>>>>> ...
>>>>>>>       pid   = 3669, comm = ndctl
>>>>>>> kernel BUG at include/linux/mm.h:1107!
>>>>>>> [c000000274087ba0] c0000000009e3500 devm_action_release+0x30/0x50
>>>>>>> [c000000274087bc0] c0000000009e4758 release_nodes+0x268/0x2d0
>>>>>>> [c000000274087c30] c0000000009dd144 device_release_driver_internal+0x174/0x240
>>>>>>> [c000000274087c70] c0000000009d9dfc unbind_store+0x13c/0x190
>>>>>>> [c000000274087cb0] c0000000009d8a24 drv_attr_store+0x44/0x60
>>>>>>> [c000000274087cd0] c0000000005a7470 sysfs_kf_write+0x70/0xa0
>>>>>>> [c000000274087d10] c0000000005a5cac kernfs_fop_write+0x1ac/0x290
>>>>>>> [c000000274087d60] c0000000004be45c __vfs_write+0x3c/0x70
>>>>>>> [c000000274087d80] c0000000004c26e4 vfs_write+0xe4/0x200
>>>>>>> [c000000274087dd0] c0000000004c2a6c ksys_write+0x7c/0x140
>>>>>>> [c000000274087e20] c00000000000bbd0 system_call+0x5c/0x68
>>>>>>>
>>>>>>> Cc: Dan Williams <dan.j.williams@intel.com>
>>>>>>> Cc: Andrew Morton <akpm@linux-foundation.org>
>>>>>>> Cc: Jason Gunthorpe <jgg@ziepe.ca>
>>>>>>> Cc: Logan Gunthorpe <logang@deltatee.com>
>>>>>>> Cc: Ira Weiny <ira.weiny@intel.com>
>>>>>>> Reviewed-by: Pankaj Gupta <pagupta@redhat.com>
>>>>>>> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
>>>>>>> [ move all pfn-realted declarations into a single line ]
>>>>>>> Signed-off-by: David Hildenbrand <david@redhat.com>
>>>>>>> ---
>>>>>>>    mm/memremap.c | 13 ++++++++-----
>>>>>>>    1 file changed, 8 insertions(+), 5 deletions(-)
>>>>>>>
>>>>>>> diff --git a/mm/memremap.c b/mm/memremap.c
>>>>>>> index 557e53c6fb46..026788b2ac69 100644
>>>>>>> --- a/mm/memremap.c
>>>>>>> +++ b/mm/memremap.c
>>>>>>> @@ -123,7 +123,7 @@ static void dev_pagemap_cleanup(struct dev_pagemap *pgmap)
>>>>>>>    void memunmap_pages(struct dev_pagemap *pgmap)
>>>>>>>    {
>>>>>>>    	struct resource *res = &pgmap->res;
>>>>>>> -	unsigned long pfn;
>>>>>>> +	unsigned long pfn, nr_pages, start_pfn, end_pfn;
>>>>>>>    	int nid;
>>>>>>>    
>>>>>>>    	dev_pagemap_kill(pgmap);
>>>>>>> @@ -131,14 +131,17 @@ void memunmap_pages(struct dev_pagemap *pgmap)
>>>>>>>    		put_page(pfn_to_page(pfn));
>>>>>>>    	dev_pagemap_cleanup(pgmap);
>>>>>>>    
>>>>>>> +	start_pfn = pfn_first(pgmap);
>>>>>>> +	end_pfn = pfn_end(pgmap);
>>>>>>> +	nr_pages = end_pfn - start_pfn;
>>>>>>> +
>>>>>>>    	/* pages are dead and unused, undo the arch mapping */
>>>>>>> -	nid = page_to_nid(pfn_to_page(PHYS_PFN(res->start)));
>>>>>>> +	nid = page_to_nid(pfn_to_page(start_pfn));
>>>>>>>    
>>>>>>>    	mem_hotplug_begin();
>>>>>>>    	if (pgmap->type == MEMORY_DEVICE_PRIVATE) {
>>>>>>> -		pfn = PHYS_PFN(res->start);
>>>>>>> -		__remove_pages(page_zone(pfn_to_page(pfn)), pfn,
>>>>>>> -				 PHYS_PFN(resource_size(res)), NULL);
>>>>>>> +		__remove_pages(page_zone(pfn_to_page(start_pfn)), start_pfn,
>>>>>>> +			       nr_pages, NULL);
>>>>>>>    	} else {
>>>>>>>    		arch_remove_memory(nid, res->start, resource_size(res),
>>>>>>>    				pgmap_altmap(pgmap));
>>>>>>>
>>>>>>
>>>>>> Aneesh, I was wondering why the use of "res->start" is correct (and we
>>>>>> shouldn't also witch to start_pfn/nr_pages here. It would be good if Dan
>>>>>> could review.
>>>>>>
>>>>>
>>>>> To be more precise, I wonder if it should actually be
>>>>>
>>>>> __remove_pages(page_zone(pfn_to_page(start_pfn)), res->start,
>>>>>                  resource_size(res))
>>>>>
>>>>
>>>> yes, that would be make it much clear.
>>>>
>>>> But for MEMORY_DEVICE_PRIVATE start_pfn and pfn should be same?
>>>
>>> Okay, let's recap. We should call add_pages()/__remove_pages()
>>> and arch_add_memory()/arch_remove_memory() with the exact same ranges.
>>>
>>> So with PHYS_PFN(res->start) and PHYS_PFN(resource_size(res)
>>>
>>> Now, only a subset of the pages gets actually initialized,
>>> meaning the NID and the ZONE we read could be stale.
>>> That, we have to fix.
>>>
>>> What about something like this (am I missing something?):
>>>
>>>  From d77b5c50f86570819a437517a897cc40ed29eefb Mon Sep 17 00:00:00 2001
>>> From: "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>
>>> Date: Fri, 27 Sep 2019 16:02:24 +0530
>>> Subject: [PATCH] mm/memunmap: Don't access uninitialized memmap in
>>>   memunmap_pages()
>>>
>>> With an altmap, the memmap falling into the reserved altmap space are
>>> not initialized and, therefore, contain a garbage NID and a garbage
>>> zone. Make sure to read the NID/zone from a memmap that was initialzed.
>>>
>>> This fixes a kernel crash that is observed when destroying a namespace:
>>>
>>> [   81.356173] kernel BUG at include/linux/mm.h:1107!
>>> cpu 0x1: Vector: 700 (Program Check) at [c000000274087890]
>>>      pc: c0000000004b9728: memunmap_pages+0x238/0x340
>>>      lr: c0000000004b9724: memunmap_pages+0x234/0x340
>>> ...
>>>      pid   = 3669, comm = ndctl
>>> kernel BUG at include/linux/mm.h:1107!
>>> [c000000274087ba0] c0000000009e3500 devm_action_release+0x30/0x50
>>> [c000000274087bc0] c0000000009e4758 release_nodes+0x268/0x2d0
>>> [c000000274087c30] c0000000009dd144 device_release_driver_internal+0x174/0x240
>>> [c000000274087c70] c0000000009d9dfc unbind_store+0x13c/0x190
>>> [c000000274087cb0] c0000000009d8a24 drv_attr_store+0x44/0x60
>>> [c000000274087cd0] c0000000005a7470 sysfs_kf_write+0x70/0xa0
>>> [c000000274087d10] c0000000005a5cac kernfs_fop_write+0x1ac/0x290
>>> [c000000274087d60] c0000000004be45c __vfs_write+0x3c/0x70
>>> [c000000274087d80] c0000000004c26e4 vfs_write+0xe4/0x200
>>> [c000000274087dd0] c0000000004c2a6c ksys_write+0x7c/0x140
>>> [c000000274087e20] c00000000000bbd0 system_call+0x5c/0x68
>>>
>>> Cc: Dan Williams <dan.j.williams@intel.com>
>>> Cc: Andrew Morton <akpm@linux-foundation.org>
>>> Cc: Jason Gunthorpe <jgg@ziepe.ca>
>>> Cc: Logan Gunthorpe <logang@deltatee.com>
>>> Cc: Ira Weiny <ira.weiny@intel.com>
>>> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
>>> [ minimze code changes, rephrase description ]
>>> Signed-off-by: David Hildenbrand <david@redhat.com>
>>> ---
>>>   mm/memremap.c | 11 +++++++----
>>>   1 file changed, 7 insertions(+), 4 deletions(-)
>>>
>>> diff --git a/mm/memremap.c b/mm/memremap.c
>>> index 557e53c6fb46..8b11c0da345c 100644
>>> --- a/mm/memremap.c
>>> +++ b/mm/memremap.c
>>> @@ -123,6 +123,7 @@ static void dev_pagemap_cleanup(struct dev_pagemap *pgmap)
>>>   void memunmap_pages(struct dev_pagemap *pgmap)
>>>   {
>>>   	struct resource *res = &pgmap->res;
>>> +	struct page *first_page;
>>>   	unsigned long pfn;
>>>   	int nid;
>>>   
>>> @@ -131,14 +132,16 @@ void memunmap_pages(struct dev_pagemap *pgmap)
>>>   		put_page(pfn_to_page(pfn));
>>>   	dev_pagemap_cleanup(pgmap);
>>>   
>>> +	/* make sure to access a memmap that was actually initialized */
>>> +	first_page = pfn_to_page(pfn_first(pgmap));
>>> +
>>>   	/* pages are dead and unused, undo the arch mapping */
>>> -	nid = page_to_nid(pfn_to_page(PHYS_PFN(res->start)));
>>> +	nid = page_to_nid(first_page);
>>>   
>>>   	mem_hotplug_begin();
>>>   	if (pgmap->type == MEMORY_DEVICE_PRIVATE) {
>>> -		pfn = PHYS_PFN(res->start);
>>> -		__remove_pages(page_zone(pfn_to_page(pfn)), pfn,
>>> -				 PHYS_PFN(resource_size(res)), NULL);
>>> +		__remove_pages(page_zone(first_page), res->start,
>>> +			       resource_size(res), NULL);
>>
>> Keeping the PHYS_PFN() calls of course ...
>>
> 
> 
> That is not different from what I posted right?  For MEMORY_DEVICE_PRIVATE

I'll go with this modified patch for now, which does not change the ranges
passed to  __remove_pages(), because that looked like a unrelated change to me.
__remove_ages() has to be called with the same range as add_pages().


commit f66c2fa09293ae0f99afc4363146941579152409 (HEAD)
Author: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Date:   Fri Sep 27 16:02:24 2019 +0530

    mm/memunmap: Don't access uninitialized memmap in memunmap_pages()
    
    With an altmap, the memmap falling into the reserved altmap space are
    not initialized and, therefore, contain a garbage NID and a garbage
    zone. Make sure to read the NID/zone from a memmap that was initialzed.
    
    This fixes a kernel crash that is observed when destroying a namespace:
    
    [   81.356173] kernel BUG at include/linux/mm.h:1107!
    cpu 0x1: Vector: 700 (Program Check) at [c000000274087890]
        pc: c0000000004b9728: memunmap_pages+0x238/0x340
        lr: c0000000004b9724: memunmap_pages+0x234/0x340
    ...
        pid   = 3669, comm = ndctl
    kernel BUG at include/linux/mm.h:1107!
    [c000000274087ba0] c0000000009e3500 devm_action_release+0x30/0x50
    [c000000274087bc0] c0000000009e4758 release_nodes+0x268/0x2d0
    [c000000274087c30] c0000000009dd144 device_release_driver_internal+0x174/0x240
    [c000000274087c70] c0000000009d9dfc unbind_store+0x13c/0x190
    [c000000274087cb0] c0000000009d8a24 drv_attr_store+0x44/0x60
    [c000000274087cd0] c0000000005a7470 sysfs_kf_write+0x70/0xa0
    [c000000274087d10] c0000000005a5cac kernfs_fop_write+0x1ac/0x290
    [c000000274087d60] c0000000004be45c __vfs_write+0x3c/0x70
    [c000000274087d80] c0000000004c26e4 vfs_write+0xe4/0x200
    [c000000274087dd0] c0000000004c2a6c ksys_write+0x7c/0x140
    [c000000274087e20] c00000000000bbd0 system_call+0x5c/0x68
    
    Cc: Dan Williams <dan.j.williams@intel.com>
    Cc: Andrew Morton <akpm@linux-foundation.org>
    Cc: Jason Gunthorpe <jgg@ziepe.ca>
    Cc: Logan Gunthorpe <logang@deltatee.com>
    Cc: Ira Weiny <ira.weiny@intel.com>
    Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
    [ minimze code changes, rephrase description ]
    Signed-off-by: David Hildenbrand <david@redhat.com>

diff --git a/mm/memremap.c b/mm/memremap.c
index 557e53c6fb46..8c2fb44c3b4d 100644
--- a/mm/memremap.c
+++ b/mm/memremap.c
@@ -123,6 +123,7 @@ static void dev_pagemap_cleanup(struct dev_pagemap *pgmap)
 void memunmap_pages(struct dev_pagemap *pgmap)
 {
        struct resource *res = &pgmap->res;
+       struct page *first_page;
        unsigned long pfn;
        int nid;
 
@@ -131,14 +132,16 @@ void memunmap_pages(struct dev_pagemap *pgmap)
                put_page(pfn_to_page(pfn));
        dev_pagemap_cleanup(pgmap);
 
+       /* make sure to access a memmap that was actually initialized */
+       first_page = pfn_to_page(pfn_first(pgmap));
+
        /* pages are dead and unused, undo the arch mapping */
-       nid = page_to_nid(pfn_to_page(PHYS_PFN(res->start)));
+       nid = page_to_nid(first_page);
 
        mem_hotplug_begin();
        if (pgmap->type == MEMORY_DEVICE_PRIVATE) {
-               pfn = PHYS_PFN(res->start);
-               __remove_pages(page_zone(pfn_to_page(pfn)), pfn,
-                                PHYS_PFN(resource_size(res)), NULL);
+               __remove_pages(page_zone(first_page), PHYS_PFN(res->start),
+                              PHYS_PFN(resource_size(res)), NULL);
        } else {
                arch_remove_memory(nid, res->start, resource_size(res),
                                pgmap_altmap(pgmap));



As Andrew wants to give this some testing, I'll send out a new version
shortly, then we can discuss there.


-- 

Thanks,

David / dhildenb

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  reply	other threads:[~2019-10-06  8:13 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <20191001144011.3801-1-david@redhat.com>
2019-10-01 14:40 ` [PATCH v5 01/10] mm/memunmap: Use the correct start and end pfn when removing pages from zone David Hildenbrand
2019-10-01 14:57   ` David Hildenbrand
2019-10-01 15:03     ` David Hildenbrand
2019-10-03 16:48       ` Aneesh Kumar K.V
2019-10-04  9:00         ` David Hildenbrand
2019-10-04  9:03           ` David Hildenbrand
2019-10-04  9:33             ` David Hildenbrand
2019-10-05  6:13             ` Aneesh Kumar K.V
2019-10-06  8:13               ` David Hildenbrand [this message]
2019-10-01 14:40 ` [PATCH v5 02/10] mm/memmap_init: Update variable name in memmap_init_zone David Hildenbrand
2019-10-01 14:40 ` [PATCH v5 03/10] mm/memory_hotplug: Don't access uninitialized memmaps in shrink_pgdat_span() David Hildenbrand
2019-10-01 14:40 ` [PATCH v5 04/10] mm/memory_hotplug: Don't access uninitialized memmaps in shrink_zone_span() David Hildenbrand
2019-10-01 23:47   ` kbuild test robot
2019-10-02  0:06   ` kbuild test robot
2019-10-02  7:05     ` David Hildenbrand
2019-10-01 14:40 ` [PATCH v5 06/10] mm/memory_hotplug: Poison memmap in remove_pfn_range_from_zone() David Hildenbrand
2019-10-01 14:40 ` [PATCH v5 07/10] mm/memory_hotplug: We always have a zone in find_(smallest|biggest)_section_pfn David Hildenbrand
2019-10-01 14:40 ` [PATCH v5 08/10] mm/memory_hotplug: Don't check for "all holes" in shrink_zone_span() David Hildenbrand
2019-10-01 14:40 ` [PATCH v5 09/10] mm/memory_hotplug: Drop local variables " David Hildenbrand
2019-10-01 14:40 ` [PATCH v5 10/10] mm/memory_hotplug: Cleanup __remove_pages() David Hildenbrand

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