Re: [PATCH v3 09/11] mm/memory_hotplug: Remove memory block devices before arch_remove_memory()

[Wei Yang]

On Mon, May 27, 2019 at 01:11:50PM +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().
>
>This finishes factoring out memory block device handling from
>arch_add_memory() and arch_remove_memory().
>
>Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
>Cc: "Rafael J. Wysocki" <rafael@xxxxxxxxxx>
>Cc: David Hildenbrand <david@xxxxxxxxxx>
>Cc: "mike.travis@xxxxxxx" <mike.travis@xxxxxxx>
>Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
>Cc: Andrew Banman <andrew.banman@xxxxxxx>
>Cc: Ingo Molnar <mingo@xxxxxxxxxx>
>Cc: Alex Deucher <alexander.deucher@xxxxxxx>
>Cc: "David S. Miller" <davem@xxxxxxxxxxxxx>
>Cc: Mark Brown <broonie@xxxxxxxxxx>
>Cc: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
>Cc: Oscar Salvador <osalvador@xxxxxxx>
>Cc: Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx>
>Cc: Michal Hocko <mhocko@xxxxxxxx>
>Cc: Pavel Tatashin <pavel.tatashin@xxxxxxxxxxxxx>
>Cc: Arun KS <arunks@xxxxxxxxxxxxxx>
>Cc: Mathieu Malaterre <malat@xxxxxxxxxx>
>Reviewed-by: Dan Williams <dan.j.williams@xxxxxxxxx>
>Signed-off-by: David Hildenbrand <david@xxxxxxxxxx>
>---
> drivers/base/memory.c  | 37 ++++++++++++++++++-------------------
> drivers/base/node.c    | 11 ++++++-----
> include/linux/memory.h |  2 +-
> include/linux/node.h   |  6 ++----
> mm/memory_hotplug.c    |  5 +++--
> 5 files changed, 30 insertions(+), 31 deletions(-)
>
>diff --git a/drivers/base/memory.c b/drivers/base/memory.c
>index 5a0370f0c506..f28efb0bf5c7 100644
>--- a/drivers/base/memory.c
>+++ b/drivers/base/memory.c
>@@ -763,32 +763,31 @@ int create_memory_block_devices(unsigned long start, unsigned long size)
> 	return ret;
> }
> 
>-void unregister_memory_section(struct mem_section *section)
>+/*
>+ * Remove memory block devices for the given memory area. Start and size
>+ * have to be aligned to memory block granularity. Memory block devices
>+ * have to be offline.
>+ */
>+void remove_memory_block_devices(unsigned long start, unsigned long size)
> {
>+	const int start_block_id = pfn_to_block_id(PFN_DOWN(start));
>+	const int end_block_id = pfn_to_block_id(PFN_DOWN(start + size));
> 	struct memory_block *mem;
>+	int block_id;
> 
>-	if (WARN_ON_ONCE(!present_section(section)))
>+	if (WARN_ON_ONCE(!IS_ALIGNED(start, memory_block_size_bytes()) ||
>+			 !IS_ALIGNED(size, memory_block_size_bytes())))
> 		return;
> 
> 	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));
>-
>-	mem->section_count--;
>-	if (mem->section_count == 0)
>+	for (block_id = start_block_id; block_id != end_block_id; block_id++) {
>+		mem = find_memory_block_by_id(block_id, NULL);
>+		if (WARN_ON_ONCE(!mem))
>+			continue;
>+		mem->section_count = 0;

Is this step necessary?

>+		unregister_memory_block_under_nodes(mem);
> 		unregister_memory(mem);
>-	else
>-		put_device(&mem->dev);
>-
>-out_unlock:
>+	}
> 	mutex_unlock(&mem_sysfs_mutex);
> }
> 
>diff --git a/drivers/base/node.c b/drivers/base/node.c
>index 8598fcbd2a17..04fdfa99b8bc 100644
>--- a/drivers/base/node.c
>+++ b/drivers/base/node.c
>@@ -801,9 +801,10 @@ int register_mem_sect_under_node(struct memory_block *mem_blk, void *arg)
> 	return 0;
> }
> 
>-/* unregister memory section under all nodes that it spans */
>-int unregister_mem_sect_under_nodes(struct memory_block *mem_blk,
>-				    unsigned long phys_index)
>+/*
>+ * Unregister memory block device under all nodes that it spans.
>+ */
>+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 +817,8 @@ 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 db3e8567f900..f26a5417ec5d 100644
>--- a/include/linux/memory.h
>+++ b/include/linux/memory.h
>@@ -112,7 +112,7 @@ extern void unregister_memory_notifier(struct notifier_block *nb);
> extern int register_memory_isolate_notifier(struct notifier_block *nb);
> extern void unregister_memory_isolate_notifier(struct notifier_block *nb);
> int create_memory_block_devices(unsigned long start, unsigned long size);
>-extern void unregister_memory_section(struct mem_section *);
>+void remove_memory_block_devices(unsigned long start, unsigned long size);
> extern int memory_dev_init(void);
> extern int memory_notify(unsigned long val, void *v);
> extern int memory_isolate_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 9a92549ef23b..82136c5b4c5f 100644
>--- a/mm/memory_hotplug.c
>+++ b/mm/memory_hotplug.c
>@@ -520,8 +520,6 @@ static void __remove_section(struct zone *zone, struct mem_section *ms,
> 	if (WARN_ON_ONCE(!valid_section(ms)))
> 		return;
> 
>-	unregister_memory_section(ms);
>-
> 	scn_nr = __section_nr(ms);
> 	start_pfn = section_nr_to_pfn((unsigned long)scn_nr);
> 	__remove_zone(zone, start_pfn);
>@@ -1845,6 +1843,9 @@ 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 */
>+	remove_memory_block_devices(start, size);
>+
> 	arch_remove_memory(nid, start, size, NULL);
> 	__release_memory_resource(start, size);
> 
>-- 
>2.20.1

-- 
Wei Yang
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