Re: [PATCH v2 3/3] mm: don't panic when links can't be created in sysfs

Laurent Dufour
2020-09-15T07:27:07Z

Le 15/09/2020 à 09:23, David Hildenbrand a écrit :
> On 14.09.20 18:50, Laurent Dufour wrote:
>> At boot time, or when doing memory hot-add operations, if the links in
>> sysfs can't be created, the system is still able to run, so just report the
>> error in the kernel log rather than BUG_ON and potentially make system
>> unusable because the callpath can be called with locks held.
>>
>> Since the number of memory blocks managed could be high, the messages are
>> rate limited.
>>
>> As a consequence, link_mem_sections() has no status to report anymore.
>>
>> Signed-off-by: Laurent Dufour <ldufour@linux.ibm.com>
>> Acked-by: Michal Hocko <mhocko@suse.com>
>> Cc: David Hildenbrand <david@redhat.com>
>> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
>> ---
>> drivers/base/node.c | 33 +++++++++++++++++++++------------
>> include/linux/node.h | 16 +++++++---------
>> mm/memory_hotplug.c | 5 ++---
>> 3 files changed, 30 insertions(+), 24 deletions(-)
>>
>> diff --git a/drivers/base/node.c b/drivers/base/node.c
>> index 01ee73c9d675..249b2ba6dc81 100644
>> --- a/drivers/base/node.c
>> +++ b/drivers/base/node.c
>> @@ -761,8 +761,8 @@ static int __ref get_nid_for_pfn(unsigned long pfn)
>> return pfn_to_nid(pfn);
>> }
>>
>> -static int do_register_memory_block_under_node(int nid,
>> - struct memory_block *mem_blk)
>> +static void do_register_memory_block_under_node(int nid,
>> + struct memory_block *mem_blk)
>> {
>> int ret;
>>
>> @@ -775,12 +775,19 @@ static int do_register_memory_block_under_node(int nid,
>> ret = sysfs_create_link_nowarn(&node_devices[nid]->dev.kobj,
>> &mem_blk->dev.kobj,
>> kobject_name(&mem_blk->dev.kobj));
>> - if (ret)
>> - return ret;
>> + if (ret && ret != -EEXIST)
>> + dev_err_ratelimited(&node_devices[nid]->dev,
>> + "can't create link to %s in sysfs (%d)\n",
>> + kobject_name(&mem_blk->dev.kobj), ret);
>>
>> - return sysfs_create_link_nowarn(&mem_blk->dev.kobj,
>> + ret = sysfs_create_link_nowarn(&mem_blk->dev.kobj,
>> &node_devices[nid]->dev.kobj,
>> kobject_name(&node_devices[nid]->dev.kobj));
>> + if (ret && ret != -EEXIST)
>> + dev_err_ratelimited(&mem_blk->dev,
>> + "can't create link to %s in sysfs (%d)\n",
>> + kobject_name(&node_devices[nid]->dev.kobj),
>> + ret);
>> }
>>
>> /* register memory section under specified node if it spans that node */
>> @@ -817,7 +824,8 @@ static int register_mem_block_under_node_early(struct memory_block *mem_blk,
>> continue;
>>
>> /* The memory block is registered to the first matching node */
>> - return do_register_memory_block_under_node(nid, mem_blk);
>> + do_register_memory_block_under_node(nid, mem_blk);
>> + return 0;
>> }
>> /* mem section does not span the specified node */
>> return 0;
>> @@ -832,7 +840,8 @@ static int register_mem_block_under_node_hotplug(struct memory_block *mem_blk,
>> {
>> int nid = *(int *)arg;
>>
>> - return do_register_memory_block_under_node(nid, mem_blk);
>> + do_register_memory_block_under_node(nid, mem_blk);
>> + return 0;
>> }
>>
>> /*
>> @@ -850,8 +859,8 @@ void unregister_memory_block_under_nodes(struct memory_block *mem_blk)
>> kobject_name(&node_devices[mem_blk->nid]->dev.kobj));
>> }
>>
>> -int link_mem_sections(int nid, unsigned long start_pfn, unsigned long end_pfn,
>> - enum meminit_context context)
>> +void link_mem_sections(int nid, unsigned long start_pfn, unsigned long end_pfn,
>> + enum meminit_context context)
>> {
>> walk_memory_blocks_func_t func;
>>
>> @@ -860,9 +869,9 @@ int link_mem_sections(int nid, unsigned long start_pfn, unsigned long end_pfn,
>> else
>> func = register_mem_block_under_node_early;
>>
>> - return walk_memory_blocks(PFN_PHYS(start_pfn),
>> - PFN_PHYS(end_pfn - start_pfn), (void *)&nid,
>> - func);
>> + walk_memory_blocks(PFN_PHYS(start_pfn), PFN_PHYS(end_pfn - start_pfn),
>> + (void *)&nid, func);
>> + return;
>> }
>>
>> #ifdef CONFIG_HUGETLBFS
>> diff --git a/include/linux/node.h b/include/linux/node.h
>> index 014ba3ab2efd..8e5a29897936 100644
>> --- a/include/linux/node.h
>> +++ b/include/linux/node.h
>> @@ -99,15 +99,14 @@ extern struct node *node_devices[];
>> typedef void (*node_registration_func_t)(struct node *);
>>
>> #if defined(CONFIG_MEMORY_HOTPLUG_SPARSE) && defined(CONFIG_NUMA)
>> -int link_mem_sections(int nid, unsigned long start_pfn,
>> - unsigned long end_pfn,
>> - enum meminit_context context);
>> +void link_mem_sections(int nid, unsigned long start_pfn,
>> + unsigned long end_pfn,
>> + enum meminit_context context);
>> #else
>> -static inline int link_mem_sections(int nid, unsigned long start_pfn,
>> - unsigned long end_pfn,
>> - enum meminit_context context)
>> +static inline void link_mem_sections(int nid, unsigned long start_pfn,
>> + unsigned long end_pfn,
>> + enum meminit_context context)
>> {
>> - return 0;
>> }
>> #endif
>>
>> @@ -130,8 +129,7 @@ static inline int register_one_node(int nid)
>> if (error)
>> return error;
>> /* link memory sections under this node */
>> - error = link_mem_sections(nid, start_pfn, end_pfn,
>> - MEMINIT_EARLY);
>> + link_mem_sections(nid, start_pfn, end_pfn, MEMINIT_EARLY);
>> }
>>
>> return error;
>> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
>> index 03df20078827..01e01a530d38 100644
>> --- a/mm/memory_hotplug.c
>> +++ b/mm/memory_hotplug.c
>> @@ -1080,9 +1080,8 @@ int __ref add_memory_resource(int nid, struct resource *res)
>> }
>>
>> /* link memory sections under this node.*/
>> - ret = link_mem_sections(nid, PFN_DOWN(start), PFN_UP(start + size - 1),
>> - MEMINIT_HOTPLUG);
>> - BUG_ON(ret);
>> + link_mem_sections(nid, PFN_DOWN(start), PFN_UP(start + size - 1),
>> + MEMINIT_HOTPLUG);
>>
>> /* create new memmap entry */
>> if (!strcmp(res->name, "System RAM"))
>>
>
> I just remember that I still have some cleanup patches lying around that
> rework the whole node onlining on the add_memory() path, being able to
> fail in a nice way rather than ignoring errors. Anyhow, this is good
> enough for now
>
> Acked-by: David Hildenbrand <david@redhat.com>
>

Thanks David.