[RFC,3/3] mm/memory_hotplug: Remove memory block devices before arch_remove_memory()
diff mbox series

Message ID 20190408101226.20976-4-david@redhat.com
State New
Headers show
Series
  • mm/memory_hotplug: Factor out memory block device handling
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Commit Message

David Hildenbrand April 8, 2019, 10:12 a.m. UTC
Let's factor out removing of memory block devices, which is only
necessary for memory added via add_memory() and friends that created
memory block devices. Remove the devices before calling
arch_remove_memory().

TODO: We should try to get rid of the errors that could be reported by
unregister_memory_block_under_nodes(). Ignoring failures is not that
nice.

Signed-off-by: David Hildenbrand <david@redhat.com>
---
 drivers/base/memory.c  | 41 +++++++++++++++--------------------------
 drivers/base/node.c    |  7 +++----
 include/linux/memory.h |  2 +-
 include/linux/node.h   |  6 ++----
 mm/memory_hotplug.c    | 10 ++++------
 5 files changed, 25 insertions(+), 41 deletions(-)

Comments

Oscar Salvador April 9, 2019, 9:18 a.m. UTC | #1
On Mon, Apr 08, 2019 at 12:12:26PM +0200, David Hildenbrand wrote:
> Let's factor out removing of memory block devices, which is only
> necessary for memory added via add_memory() and friends that created
> memory block devices. Remove the devices before calling
> arch_remove_memory().
> 
> TODO: We should try to get rid of the errors that could be reported by
> unregister_memory_block_under_nodes(). Ignoring failures is not that
> nice.

Hi David,

I am sorry but I will not have to look into this until next week as I am
up to my ears with work plus I am in the middle of a move.

I remember I was once trying to simplify unregister_mem_sect_under_nodes (your
new unregister_memory_block_under_nodes), and I checked whether we could get
rid of the NODEMASK_ALLOC there, something like:

diff --git a/drivers/base/node.c b/drivers/base/node.c
index 8598fcbd2a17..f4294a2928dd 100644
--- a/drivers/base/node.c
+++ b/drivers/base/node.c
@@ -805,16 +805,10 @@ int register_mem_sect_under_node(struct memory_block *mem_blk, void *arg)
 int unregister_mem_sect_under_nodes(struct memory_block *mem_blk,
                                    unsigned long phys_index)
 {
-       NODEMASK_ALLOC(nodemask_t, unlinked_nodes, GFP_KERNEL);
+       nodemask_t unlinked_nodes;
        unsigned long pfn, sect_start_pfn, sect_end_pfn;
 
-       if (!mem_blk) {
-               NODEMASK_FREE(unlinked_nodes);
-               return -EFAULT;
-       }
-       if (!unlinked_nodes)
-               return -ENOMEM;
-       nodes_clear(*unlinked_nodes);
+       nodes_clear(unlinked_nodes);
 
        sect_start_pfn = section_nr_to_pfn(phys_index);
        sect_end_pfn = sect_start_pfn + PAGES_PER_SECTION - 1;
@@ -826,14 +820,13 @@ int unregister_mem_sect_under_nodes(struct memory_block *mem_blk,
                        continue;
                if (!node_online(nid))
                        continue;
-               if (node_test_and_set(nid, *unlinked_nodes))
+               if (node_test_and_set(nid, unlinked_nodes))
                        continue;
                sysfs_remove_link(&node_devices[nid]->dev.kobj,
                         kobject_name(&mem_blk->dev.kobj));
                sysfs_remove_link(&mem_blk->dev.kobj,
                         kobject_name(&node_devices[nid]->dev.kobj));
        }
-       NODEMASK_FREE(unlinked_nodes);
        return 0;
 }


nodemask_t is 128bytes when CONFIG_NODES_SHIFT is 10 , which is the maximum value.
We just need to check whether we can overflow the stack or not.

AFAICS, it is not really a shore stack but it might not be that deep either.

> 
> Signed-off-by: David Hildenbrand <david@redhat.com>
> ---
>  drivers/base/memory.c  | 41 +++++++++++++++--------------------------
>  drivers/base/node.c    |  7 +++----
>  include/linux/memory.h |  2 +-
>  include/linux/node.h   |  6 ++----
>  mm/memory_hotplug.c    | 10 ++++------
>  5 files changed, 25 insertions(+), 41 deletions(-)
> 
> diff --git a/drivers/base/memory.c b/drivers/base/memory.c
> index 847b33061e2e..fd8940c37129 100644
> --- a/drivers/base/memory.c
> +++ b/drivers/base/memory.c
> @@ -752,40 +752,29 @@ int hotplug_memory_register(unsigned long start, unsigned long size)
>  }
>  
>  #ifdef CONFIG_MEMORY_HOTREMOVE
> -static int remove_memory_section(struct mem_section *section)
> +void hotplug_memory_unregister(unsigned long start, unsigned long size)
>  {
> +	unsigned long block_nr_pages = memory_block_size_bytes() >> PAGE_SHIFT;
> +	unsigned long start_pfn = PFN_DOWN(start);
> +	unsigned long end_pfn = start_pfn + (size >> PAGE_SHIFT);
>  	struct memory_block *mem;
> +	unsigned long pfn;
>  
> -	mutex_lock(&mem_sysfs_mutex);
> -
> -	/*
> -	 * Some users of the memory hotplug do not want/need memblock to
> -	 * track all sections. Skip over those.
> -	 */
> -	mem = find_memory_block(section);
> -	if (!mem)
> -		goto out_unlock;
> -
> -	unregister_mem_sect_under_nodes(mem, __section_nr(section));
> +	BUG_ON(!IS_ALIGNED(start, memory_block_size_bytes()));
> +	BUG_ON(!IS_ALIGNED(size, memory_block_size_bytes()));
>  
> -	mem->section_count--;
> -	if (mem->section_count == 0)
> +	mutex_lock(&mem_sysfs_mutex);
> +	for (pfn = start_pfn; pfn != end_pfn; pfn += block_nr_pages) {
> +		mem = find_memory_block(__pfn_to_section(pfn));
> +		if (!mem)
> +			continue;
> +		mem->section_count = 0;
> +		unregister_memory_block_under_nodes(mem);
>  		unregister_memory(mem);
> -	else
> -		put_device(&mem->dev);
> -
> -out_unlock:
> +	}
>  	mutex_unlock(&mem_sysfs_mutex);
> -	return 0;
>  }
>  
> -int unregister_memory_section(struct mem_section *section)
> -{
> -	if (!present_section(section))
> -		return -EINVAL;
> -
> -	return remove_memory_section(section);
> -}
>  #endif /* CONFIG_MEMORY_HOTREMOVE */
>  
>  /* return true if the memory block is offlined, otherwise, return false */
> diff --git a/drivers/base/node.c b/drivers/base/node.c
> index 8598fcbd2a17..f9997770ac15 100644
> --- a/drivers/base/node.c
> +++ b/drivers/base/node.c
> @@ -802,8 +802,7 @@ int register_mem_sect_under_node(struct memory_block *mem_blk, void *arg)
>  }
>  
>  /* unregister memory section under all nodes that it spans */
> -int unregister_mem_sect_under_nodes(struct memory_block *mem_blk,
> -				    unsigned long phys_index)
> +int unregister_memory_block_under_nodes(struct memory_block *mem_blk)
>  {
>  	NODEMASK_ALLOC(nodemask_t, unlinked_nodes, GFP_KERNEL);
>  	unsigned long pfn, sect_start_pfn, sect_end_pfn;
> @@ -816,8 +815,8 @@ int unregister_mem_sect_under_nodes(struct memory_block *mem_blk,
>  		return -ENOMEM;
>  	nodes_clear(*unlinked_nodes);
>  
> -	sect_start_pfn = section_nr_to_pfn(phys_index);
> -	sect_end_pfn = sect_start_pfn + PAGES_PER_SECTION - 1;
> +	sect_start_pfn = section_nr_to_pfn(mem_blk->start_section_nr);
> +	sect_end_pfn = section_nr_to_pfn(mem_blk->end_section_nr);
>  	for (pfn = sect_start_pfn; pfn <= sect_end_pfn; pfn++) {
>  		int nid;
>  
> diff --git a/include/linux/memory.h b/include/linux/memory.h
> index e275dc775834..414e43ab0881 100644
> --- a/include/linux/memory.h
> +++ b/include/linux/memory.h
> @@ -113,7 +113,7 @@ extern int register_memory_isolate_notifier(struct notifier_block *nb);
>  extern void unregister_memory_isolate_notifier(struct notifier_block *nb);
>  int hotplug_memory_register(unsigned long start, unsigned long size);
>  #ifdef CONFIG_MEMORY_HOTREMOVE
> -extern int unregister_memory_section(struct mem_section *);
> +void hotplug_memory_unregister(unsigned long start, unsigned long size);
>  #endif
>  extern int memory_dev_init(void);
>  extern int memory_notify(unsigned long val, void *v);
> diff --git a/include/linux/node.h b/include/linux/node.h
> index 1a557c589ecb..02a29e71b175 100644
> --- a/include/linux/node.h
> +++ b/include/linux/node.h
> @@ -139,8 +139,7 @@ extern int register_cpu_under_node(unsigned int cpu, unsigned int nid);
>  extern int unregister_cpu_under_node(unsigned int cpu, unsigned int nid);
>  extern int register_mem_sect_under_node(struct memory_block *mem_blk,
>  						void *arg);
> -extern int unregister_mem_sect_under_nodes(struct memory_block *mem_blk,
> -					   unsigned long phys_index);
> +extern int unregister_memory_block_under_nodes(struct memory_block *mem_blk);
>  
>  extern int register_memory_node_under_compute_node(unsigned int mem_nid,
>  						   unsigned int cpu_nid,
> @@ -176,8 +175,7 @@ static inline int register_mem_sect_under_node(struct memory_block *mem_blk,
>  {
>  	return 0;
>  }
> -static inline int unregister_mem_sect_under_nodes(struct memory_block *mem_blk,
> -						  unsigned long phys_index)
> +static inline int unregister_memory_block_under_nodes(struct memory_block *mem_blk)
>  {
>  	return 0;
>  }
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index 13ee0a26e034..041b93c5eede 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -518,14 +518,9 @@ static int __remove_section(struct zone *zone, struct mem_section *ms,
>  {
>  	unsigned long start_pfn;
>  	int scn_nr;
> -	int ret = -EINVAL;
>  
>  	if (!valid_section(ms))
> -		return ret;
> -
> -	ret = unregister_memory_section(ms);
> -	if (ret)
> -		return ret;
> +		return -EINVAL;
>  
>  	scn_nr = __section_nr(ms);
>  	start_pfn = section_nr_to_pfn((unsigned long)scn_nr);
> @@ -1875,6 +1870,9 @@ void __ref __remove_memory(int nid, u64 start, u64 size)
>  	memblock_free(start, size);
>  	memblock_remove(start, size);
>  
> +	/* remove memory block devices before removing memory */
> +	hotplug_memory_unregister(start, size);
> +
>  	arch_remove_memory(nid, start, size, NULL);
>  
>  	try_offline_node(nid);
> -- 
> 2.17.2
>
David Hildenbrand April 9, 2019, 9:25 a.m. UTC | #2
On 09.04.19 11:18, Oscar Salvador wrote:
> On Mon, Apr 08, 2019 at 12:12:26PM +0200, David Hildenbrand wrote:
>> Let's factor out removing of memory block devices, which is only
>> necessary for memory added via add_memory() and friends that created
>> memory block devices. Remove the devices before calling
>> arch_remove_memory().
>>
>> TODO: We should try to get rid of the errors that could be reported by
>> unregister_memory_block_under_nodes(). Ignoring failures is not that
>> nice.
> 
> Hi David,
> 
> I am sorry but I will not have to look into this until next week as I am
> up to my ears with work plus I am in the middle of a move.

No worries, I have plenty of other stuff to do as well and this is only
an RFC that will require other refactorings and maybe discussions first
- one of these, I will send out shortly so we can discuss.

Happy moving :)

> 
> I remember I was once trying to simplify unregister_mem_sect_under_nodes (your
> new unregister_memory_block_under_nodes), and I checked whether we could get
> rid of the NODEMASK_ALLOC there, something like:

Yeah, something like that makes perfect sense. Thanks!

> 
> diff --git a/drivers/base/node.c b/drivers/base/node.c
> index 8598fcbd2a17..f4294a2928dd 100644
> --- a/drivers/base/node.c
> +++ b/drivers/base/node.c
> @@ -805,16 +805,10 @@ int register_mem_sect_under_node(struct memory_block *mem_blk, void *arg)
>  int unregister_mem_sect_under_nodes(struct memory_block *mem_blk,
>                                     unsigned long phys_index)
>  {
> -       NODEMASK_ALLOC(nodemask_t, unlinked_nodes, GFP_KERNEL);
> +       nodemask_t unlinked_nodes;
>         unsigned long pfn, sect_start_pfn, sect_end_pfn;
>  
> -       if (!mem_blk) {
> -               NODEMASK_FREE(unlinked_nodes);
> -               return -EFAULT;
> -       }
> -       if (!unlinked_nodes)
> -               return -ENOMEM;
> -       nodes_clear(*unlinked_nodes);
> +       nodes_clear(unlinked_nodes);
>  
>         sect_start_pfn = section_nr_to_pfn(phys_index);
>         sect_end_pfn = sect_start_pfn + PAGES_PER_SECTION - 1;
> @@ -826,14 +820,13 @@ int unregister_mem_sect_under_nodes(struct memory_block *mem_blk,
>                         continue;
>                 if (!node_online(nid))
>                         continue;
> -               if (node_test_and_set(nid, *unlinked_nodes))
> +               if (node_test_and_set(nid, unlinked_nodes))
>                         continue;
>                 sysfs_remove_link(&node_devices[nid]->dev.kobj,
>                          kobject_name(&mem_blk->dev.kobj));
>                 sysfs_remove_link(&mem_blk->dev.kobj,
>                          kobject_name(&node_devices[nid]->dev.kobj));
>         }
> -       NODEMASK_FREE(unlinked_nodes);
>         return 0;
>  }
> 
> 
> nodemask_t is 128bytes when CONFIG_NODES_SHIFT is 10 , which is the maximum value.
> We just need to check whether we can overflow the stack or not.
> 
> AFAICS, it is not really a shore stack but it might not be that deep either.

Patch
diff mbox series

diff --git a/drivers/base/memory.c b/drivers/base/memory.c
index 847b33061e2e..fd8940c37129 100644
--- a/drivers/base/memory.c
+++ b/drivers/base/memory.c
@@ -752,40 +752,29 @@  int hotplug_memory_register(unsigned long start, unsigned long size)
 }
 
 #ifdef CONFIG_MEMORY_HOTREMOVE
-static int remove_memory_section(struct mem_section *section)
+void hotplug_memory_unregister(unsigned long start, unsigned long size)
 {
+	unsigned long block_nr_pages = memory_block_size_bytes() >> PAGE_SHIFT;
+	unsigned long start_pfn = PFN_DOWN(start);
+	unsigned long end_pfn = start_pfn + (size >> PAGE_SHIFT);
 	struct memory_block *mem;
+	unsigned long pfn;
 
-	mutex_lock(&mem_sysfs_mutex);
-
-	/*
-	 * Some users of the memory hotplug do not want/need memblock to
-	 * track all sections. Skip over those.
-	 */
-	mem = find_memory_block(section);
-	if (!mem)
-		goto out_unlock;
-
-	unregister_mem_sect_under_nodes(mem, __section_nr(section));
+	BUG_ON(!IS_ALIGNED(start, memory_block_size_bytes()));
+	BUG_ON(!IS_ALIGNED(size, memory_block_size_bytes()));
 
-	mem->section_count--;
-	if (mem->section_count == 0)
+	mutex_lock(&mem_sysfs_mutex);
+	for (pfn = start_pfn; pfn != end_pfn; pfn += block_nr_pages) {
+		mem = find_memory_block(__pfn_to_section(pfn));
+		if (!mem)
+			continue;
+		mem->section_count = 0;
+		unregister_memory_block_under_nodes(mem);
 		unregister_memory(mem);
-	else
-		put_device(&mem->dev);
-
-out_unlock:
+	}
 	mutex_unlock(&mem_sysfs_mutex);
-	return 0;
 }
 
-int unregister_memory_section(struct mem_section *section)
-{
-	if (!present_section(section))
-		return -EINVAL;
-
-	return remove_memory_section(section);
-}
 #endif /* CONFIG_MEMORY_HOTREMOVE */
 
 /* return true if the memory block is offlined, otherwise, return false */
diff --git a/drivers/base/node.c b/drivers/base/node.c
index 8598fcbd2a17..f9997770ac15 100644
--- a/drivers/base/node.c
+++ b/drivers/base/node.c
@@ -802,8 +802,7 @@  int register_mem_sect_under_node(struct memory_block *mem_blk, void *arg)
 }
 
 /* unregister memory section under all nodes that it spans */
-int unregister_mem_sect_under_nodes(struct memory_block *mem_blk,
-				    unsigned long phys_index)
+int unregister_memory_block_under_nodes(struct memory_block *mem_blk)
 {
 	NODEMASK_ALLOC(nodemask_t, unlinked_nodes, GFP_KERNEL);
 	unsigned long pfn, sect_start_pfn, sect_end_pfn;
@@ -816,8 +815,8 @@  int unregister_mem_sect_under_nodes(struct memory_block *mem_blk,
 		return -ENOMEM;
 	nodes_clear(*unlinked_nodes);
 
-	sect_start_pfn = section_nr_to_pfn(phys_index);
-	sect_end_pfn = sect_start_pfn + PAGES_PER_SECTION - 1;
+	sect_start_pfn = section_nr_to_pfn(mem_blk->start_section_nr);
+	sect_end_pfn = section_nr_to_pfn(mem_blk->end_section_nr);
 	for (pfn = sect_start_pfn; pfn <= sect_end_pfn; pfn++) {
 		int nid;
 
diff --git a/include/linux/memory.h b/include/linux/memory.h
index e275dc775834..414e43ab0881 100644
--- a/include/linux/memory.h
+++ b/include/linux/memory.h
@@ -113,7 +113,7 @@  extern int register_memory_isolate_notifier(struct notifier_block *nb);
 extern void unregister_memory_isolate_notifier(struct notifier_block *nb);
 int hotplug_memory_register(unsigned long start, unsigned long size);
 #ifdef CONFIG_MEMORY_HOTREMOVE
-extern int unregister_memory_section(struct mem_section *);
+void hotplug_memory_unregister(unsigned long start, unsigned long size);
 #endif
 extern int memory_dev_init(void);
 extern int memory_notify(unsigned long val, void *v);
diff --git a/include/linux/node.h b/include/linux/node.h
index 1a557c589ecb..02a29e71b175 100644
--- a/include/linux/node.h
+++ b/include/linux/node.h
@@ -139,8 +139,7 @@  extern int register_cpu_under_node(unsigned int cpu, unsigned int nid);
 extern int unregister_cpu_under_node(unsigned int cpu, unsigned int nid);
 extern int register_mem_sect_under_node(struct memory_block *mem_blk,
 						void *arg);
-extern int unregister_mem_sect_under_nodes(struct memory_block *mem_blk,
-					   unsigned long phys_index);
+extern int unregister_memory_block_under_nodes(struct memory_block *mem_blk);
 
 extern int register_memory_node_under_compute_node(unsigned int mem_nid,
 						   unsigned int cpu_nid,
@@ -176,8 +175,7 @@  static inline int register_mem_sect_under_node(struct memory_block *mem_blk,
 {
 	return 0;
 }
-static inline int unregister_mem_sect_under_nodes(struct memory_block *mem_blk,
-						  unsigned long phys_index)
+static inline int unregister_memory_block_under_nodes(struct memory_block *mem_blk)
 {
 	return 0;
 }
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 13ee0a26e034..041b93c5eede 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -518,14 +518,9 @@  static int __remove_section(struct zone *zone, struct mem_section *ms,
 {
 	unsigned long start_pfn;
 	int scn_nr;
-	int ret = -EINVAL;
 
 	if (!valid_section(ms))
-		return ret;
-
-	ret = unregister_memory_section(ms);
-	if (ret)
-		return ret;
+		return -EINVAL;
 
 	scn_nr = __section_nr(ms);
 	start_pfn = section_nr_to_pfn((unsigned long)scn_nr);
@@ -1875,6 +1870,9 @@  void __ref __remove_memory(int nid, u64 start, u64 size)
 	memblock_free(start, size);
 	memblock_remove(start, size);
 
+	/* remove memory block devices before removing memory */
+	hotplug_memory_unregister(start, size);
+
 	arch_remove_memory(nid, start, size, NULL);
 
 	try_offline_node(nid);