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mm/hotplug: Only use subsection map for VMEMMAP

PATCH Superseded Baoquan He 5 participants 29 messages Mar 7, 2020 – Mar 11, 2020

Subsystems (3)
Memory management MM core MGLRU

v3 of 4 Superseded 1 of 7 applied Latest is v4 →

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Baoquan He

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#0 lore raw

v3 cover mm/hotplug: Only use subsection map for VMEMMAP

Memory sub-section hotplug was added to fix the issue that nvdimm could be mapped at non-section aligned starting address. A subsection map is added into struct mem_section_usage to implement it.

However, config ZONE_DEVICE depends on SPARSEMEM_VMEMMAP. It means subsection map only makes sense when SPARSEMEM_VMEMMAP enabled. For the classic sparse, subsection map is meaningless and confusing.

About the classic sparse which doesn't support subsection hotplug, Dan said it's more because the effort and maintenance burden outweighs the benefit. Besides, the current 64 bit ARCHes all enable SPARSEMEM_VMEMMAP_ENABLE by default.

In this patchset, the patches 2~4 ares used to make sub-section map and the relevant operation only available for VMEMMAP.

Patch 1 fixes a hot remove failure when the classic sparse is enabled.

Patches 5~7 are for document adding and doc/code cleanup.

Changelog

v2->v3:
David spotted a code bug in the old patch 1, the old local variable subsection_map is invalid once ms->usage is resetting. Add a local variable 'empty' to cache if subsection_map is empty or not.

Remove the kernel-doc comments for the newly added functions fill_subsection_map() and clear_subsection_map(). Michal and David suggested this.

Add a new static function is_subsection_map_empty() to check if the handled section map is empty, but not return the value from clear_subsection_map(). David suggested this.

Add document about only VMEMMAP supporting sub-section hotplug, and check_pfn_span() gating the alignment and size. Michal help rephrase the words.

v1->v2:
Move the hot remove fixing patch to the front so that people can back port it to easier. Suggested by David.

Split the old patch which invalidate the sub-section map in !VMEMMAP case into two patches, patch 4/7, and patch 6/7. This makes patch reviewing easier. Suggested by David.

Take Wei Yang's fixing patch out to post alone, since it has been reviewed and acked by people. Suggested by Andrew.

Fix a code comment mistake in the current patch 2/7. Found out by Wei Yang during reviewing.

Baoquan He (7):
mm/hotplug: fix hot remove failure in SPARSEMEM|!VMEMMAP case mm/sparse.c: introduce new function fill_subsection_map() mm/sparse.c: introduce a new function clear_subsection_map() mm/sparse.c: only use subsection map in VMEMMAP case mm/sparse.c: add note about only VMEMMAP supporting sub-section
support
mm/sparse.c: move subsection_map related codes together mm/sparse.c: Use __get_free_pages() instead in
populate_section_memmap()

 include/linux/mmzone.h |   2 +
 mm/sparse.c            | 159 +++++++++++++++++++++++++++--------------
 2 files changed, 107 insertions(+), 54 deletions(-)
Signature · 1 line
2.17.2
author
#1 lore raw

PATCH v3 1/7 mm/hotplug: fix hot remove failure in SPARSEMEM|!VMEMMAP case

In section_deactivate(), pfn_to_page() doesn't work any more after ms->section_mem_map is resetting to NULL in SPARSEMEM|!VMEMMAP case. It caused hot remove failure:

kernel BUG at mm/page_alloc.c:4806!
invalid opcode: 0000 [#1] SMP PTI

CPU: 3 PID: 8 Comm: kworker/u16:0 Tainted: G        W         5.5.0-next-20200205+ #340
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 0.0.0 02/06/2015
Workqueue: kacpi_hotplug acpi_hotplug_work_fn
RIP: 0010:free_pages+0x85/0xa0
Call Trace:
 __remove_pages+0x99/0xc0
 arch_remove_memory+0x23/0x4d
 try_remove_memory+0xc8/0x130
 ? walk_memory_blocks+0x72/0xa0
 __remove_memory+0xa/0x11
 acpi_memory_device_remove+0x72/0x100
 acpi_bus_trim+0x55/0x90
 acpi_device_hotplug+0x2eb/0x3d0
 acpi_hotplug_work_fn+0x1a/0x30
 process_one_work+0x1a7/0x370
 worker_thread+0x30/0x380
 ? flush_rcu_work+0x30/0x30
 kthread+0x112/0x130
 ? kthread_create_on_node+0x60/0x60
 ret_from_fork+0x35/0x40

Let's move the ->section_mem_map resetting after depopulate_section_memmap() to fix it.

Fixes ba72b4c8cf60 ("mm/sparsemem: support sub-section hotplug")
Signed-off-by Baoquan He <[email protected]>
Cc [email protected]
---
 mm/sparse.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)
mm/sparse.c +6 -2
index 42c18a38ffaa..1b50c15677d7 100644
@@ -734,6 +734,7 @@ static void section_deactivate(unsigned long pfn, unsigned long nr_pages,
 	struct mem_section *ms = __pfn_to_section(pfn);
 	bool section_is_early = early_section(ms);
 	struct page *memmap = NULL;
+	bool empty = false;
 	unsigned long *subsection_map = ms->usage
 		? &ms->usage->subsection_map[0] : NULL;
 

@@ -764,7 +765,8 @@ static void section_deactivate(unsigned long pfn, unsigned long nr_pages,
 	 * For 2/ and 3/ the SPARSEMEM_VMEMMAP={y,n} cases are unified
 	 */
 	bitmap_xor(subsection_map, map, subsection_map, SUBSECTIONS_PER_SECTION);
-	if (bitmap_empty(subsection_map, SUBSECTIONS_PER_SECTION)) {
+	empty = bitmap_empty(subsection_map, SUBSECTIONS_PER_SECTION);
+	if (empty) {
 		unsigned long section_nr = pfn_to_section_nr(pfn);
 
 		/*

@@ -779,13 +781,15 @@ static void section_deactivate(unsigned long pfn, unsigned long nr_pages,
 			ms->usage = NULL;
 		}
 		memmap = sparse_decode_mem_map(ms->section_mem_map, section_nr);
-		ms->section_mem_map = (unsigned long)NULL;
 	}
 
 	if (section_is_early && memmap)
 		free_map_bootmem(memmap);
 	else
 		depopulate_section_memmap(pfn, nr_pages, altmap);
+
+	if (empty)
+		ms->section_mem_map = (unsigned long)NULL;
 }
 
 static struct page * __meminit section_activate(int nid, unsigned long pfn,
Signature · 1 line
2.17.2
maintainer
#2 lore raw

Re: [PATCH v3 1/7] mm/hotplug: fix hot remove failure in SPARSEMEM|!VMEMMAP case

Quoted 27 lines · On Sat, 7 Mar 2020 16:42:23 +0800 Baoquan He <[email protected]> wrote:

In section_deactivate(), pfn_to_page() doesn't work any more after ms->section_mem_map is resetting to NULL in SPARSEMEM|!VMEMMAP case. It caused hot remove failure:

kernel BUG at mm/page_alloc.c:4806!
invalid opcode: 0000 [#1] SMP PTI

CPU: 3 PID: 8 Comm: kworker/u16:0 Tainted: G        W         5.5.0-next-20200205+ #340
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 0.0.0 02/06/2015
Workqueue: kacpi_hotplug acpi_hotplug_work_fn
RIP: 0010:free_pages+0x85/0xa0
Call Trace:
 __remove_pages+0x99/0xc0
 arch_remove_memory+0x23/0x4d
 try_remove_memory+0xc8/0x130
 ? walk_memory_blocks+0x72/0xa0
 __remove_memory+0xa/0x11
 acpi_memory_device_remove+0x72/0x100
 acpi_bus_trim+0x55/0x90
 acpi_device_hotplug+0x2eb/0x3d0
 acpi_hotplug_work_fn+0x1a/0x30
 process_one_work+0x1a7/0x370
 worker_thread+0x30/0x380
 ? flush_rcu_work+0x30/0x30
 kthread+0x112/0x130
 ? kthread_create_on_node+0x60/0x60
 ret_from_fork+0x35/0x40
Quoted 2 lines

Let's move the ->section_mem_map resetting after depopulate_section_memmap() to fix it.

Thanks. I think I'll cherrypick this fix and shall await more review/testing input on the rest of the series.

author
#3 lore raw

Re: [PATCH v3 1/7] mm/hotplug: fix hot remove failure in SPARSEMEM|!VMEMMAP case

Quoted 29 lines · Andrew Morton
Quoted 27 lines · On Sat, 7 Mar 2020 16:42:23 +0800 Baoquan He <[email protected]> wrote:

In section_deactivate(), pfn_to_page() doesn't work any more after ms->section_mem_map is resetting to NULL in SPARSEMEM|!VMEMMAP case. It caused hot remove failure:

kernel BUG at mm/page_alloc.c:4806!
invalid opcode: 0000 [#1] SMP PTI

CPU: 3 PID: 8 Comm: kworker/u16:0 Tainted: G        W         5.5.0-next-20200205+ #340
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 0.0.0 02/06/2015
Workqueue: kacpi_hotplug acpi_hotplug_work_fn
RIP: 0010:free_pages+0x85/0xa0
Call Trace:
 __remove_pages+0x99/0xc0
 arch_remove_memory+0x23/0x4d
 try_remove_memory+0xc8/0x130
 ? walk_memory_blocks+0x72/0xa0
 __remove_memory+0xa/0x11
 acpi_memory_device_remove+0x72/0x100
 acpi_bus_trim+0x55/0x90
 acpi_device_hotplug+0x2eb/0x3d0
 acpi_hotplug_work_fn+0x1a/0x30
 process_one_work+0x1a7/0x370
 worker_thread+0x30/0x380
 ? flush_rcu_work+0x30/0x30
 kthread+0x112/0x130
 ? kthread_create_on_node+0x60/0x60
 ret_from_fork+0x35/0x40
Quoted 5 lines
Quoted 2 lines

Let's move the ->section_mem_map resetting after depopulate_section_memmap() to fix it.

Thanks. I think I'll cherrypick this fix and shall await more review/testing input on the rest of the series.

Sure, thanks.

Reviewed-by on v3 1/7
#4 lore raw

Re: [PATCH v3 1/7] mm/hotplug: fix hot remove failure in SPARSEMEM|!VMEMMAP case

In reply to Baoquan He
Quoted 67 lines · Baoquan He

In section_deactivate(), pfn_to_page() doesn't work any more after ms->section_mem_map is resetting to NULL in SPARSEMEM|!VMEMMAP case. It caused hot remove failure:

kernel BUG at mm/page_alloc.c:4806!
invalid opcode: 0000 [#1] SMP PTI

CPU: 3 PID: 8 Comm: kworker/u16:0 Tainted: G        W         5.5.0-next-20200205+ #340
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 0.0.0 02/06/2015
Workqueue: kacpi_hotplug acpi_hotplug_work_fn
RIP: 0010:free_pages+0x85/0xa0
Call Trace:
 __remove_pages+0x99/0xc0
 arch_remove_memory+0x23/0x4d
 try_remove_memory+0xc8/0x130
 ? walk_memory_blocks+0x72/0xa0
 __remove_memory+0xa/0x11
 acpi_memory_device_remove+0x72/0x100
 acpi_bus_trim+0x55/0x90
 acpi_device_hotplug+0x2eb/0x3d0
 acpi_hotplug_work_fn+0x1a/0x30
 process_one_work+0x1a7/0x370
 worker_thread+0x30/0x380
 ? flush_rcu_work+0x30/0x30
 kthread+0x112/0x130
 ? kthread_create_on_node+0x60/0x60
 ret_from_fork+0x35/0x40

Let's move the ->section_mem_map resetting after depopulate_section_memmap() to fix it.

Fixes ba72b4c8cf60 ("mm/sparsemem: support sub-section hotplug")
Signed-off-by Baoquan He <[email protected]>
Cc [email protected]
---
 mm/sparse.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)
mm/sparse.c +3 -2
index 42c18a38ffaa..1b50c15677d7 100644
@@ -734,6 +734,7 @@ static void section_deactivate(unsigned long pfn, unsigned long nr_pages,
 	struct mem_section *ms = __pfn_to_section(pfn);
 	bool section_is_early = early_section(ms);
 	struct page *memmap = NULL;
+	bool empty = false;
 	unsigned long *subsection_map = ms->usage
 		? &ms->usage->subsection_map[0] : NULL;
 

@@ -764,7 +765,8 @@ static void section_deactivate(unsigned long pfn, unsigned long nr_pages,
 	 * For 2/ and 3/ the SPARSEMEM_VMEMMAP={y,n} cases are unified
 	 */
 	bitmap_xor(subsection_map, map, subsection_map, SUBSECTIONS_PER_SECTION);
-	if (bitmap_empty(subsection_map, SUBSECTIONS_PER_SECTION)) {
+	empty = bitmap_empty(subsection_map, SUBSECTIONS_PER_SECTION);
+	if (empty) {
 		unsigned long section_nr = pfn_to_section_nr(pfn);
 
 		/*

@@ -779,13 +781,15 @@ static void section_deactivate(unsigned long pfn, unsigned long nr_pages,
 			ms->usage = NULL;
 		}
 		memmap = sparse_decode_mem_map(ms->section_mem_map, section_nr);
-		ms->section_mem_map = (unsigned long)NULL;
 	}

mm/sparse.c static void section_deactivate(unsigned long pfn, unsigned long nr_pages, · line 795

Quoted 10 lines
mm/sparse.c +3 -0
 	if (section_is_early && memmap)
 		free_map_bootmem(memmap);
 	else
 		depopulate_section_memmap(pfn, nr_pages, altmap);
+
+	if (empty)
+		ms->section_mem_map = (unsigned long)NULL;
 }
 
 static struct page * __meminit section_activate(int nid, unsigned long pfn,
Reviewed-by David Hildenbrand <[email protected]>
Signature · 3 lines
Thanks,

David / dhildenb
#5 lore raw

Re: [PATCH v3 1/7] mm/hotplug: fix hot remove failure in SPARSEMEM|!VMEMMAP case

In reply to Baoquan He
Quoted 42 lines · Baoquan He

In section_deactivate(), pfn_to_page() doesn't work any more after ms->section_mem_map is resetting to NULL in SPARSEMEM|!VMEMMAP case. It caused hot remove failure:

kernel BUG at mm/page_alloc.c:4806!
invalid opcode: 0000 [#1] SMP PTI

CPU: 3 PID: 8 Comm: kworker/u16:0 Tainted: G        W         5.5.0-next-20200205+ #340
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 0.0.0 02/06/2015
Workqueue: kacpi_hotplug acpi_hotplug_work_fn
RIP: 0010:free_pages+0x85/0xa0
Call Trace:
 __remove_pages+0x99/0xc0
 arch_remove_memory+0x23/0x4d
 try_remove_memory+0xc8/0x130
 ? walk_memory_blocks+0x72/0xa0
 __remove_memory+0xa/0x11
 acpi_memory_device_remove+0x72/0x100
 acpi_bus_trim+0x55/0x90
 acpi_device_hotplug+0x2eb/0x3d0
 acpi_hotplug_work_fn+0x1a/0x30
 process_one_work+0x1a7/0x370
 worker_thread+0x30/0x380
 ? flush_rcu_work+0x30/0x30
 kthread+0x112/0x130
 ? kthread_create_on_node+0x60/0x60
 ret_from_fork+0x35/0x40

Let's move the ->section_mem_map resetting after depopulate_section_memmap() to fix it.

Fixes ba72b4c8cf60 ("mm/sparsemem: support sub-section hotplug")
Signed-off-by Baoquan He <[email protected]>
Cc [email protected]
---
 mm/sparse.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)
mm/sparse.c +0 -0
index 42c18a38ffaa..1b50c15677d7 100644

mm/sparse.c static void section_deactivate(unsigned long pfn, unsigned long nr_pages, · line 737

Quoted 4 lines
mm/sparse.c +1 -0
@@ -734,6 +734,7 @@ static void section_deactivate(unsigned long pfn, unsigned long nr_pages,
 	struct mem_section *ms = __pfn_to_section(pfn);
 	bool section_is_early = early_section(ms);
 	struct page *memmap = NULL;
+	bool empty = false;

Oh, one NIT: no need to initialize empty to false.

Signature · 3 lines
Thanks,

David / dhildenb
author
#6 lore raw

Re: [PATCH v3 1/7] mm/hotplug: fix hot remove failure in SPARSEMEM|!VMEMMAP case

Quoted 38 lines · David Hildenbrand
Quoted 37 lines · Baoquan He

In section_deactivate(), pfn_to_page() doesn't work any more after ms->section_mem_map is resetting to NULL in SPARSEMEM|!VMEMMAP case. It caused hot remove failure:

kernel BUG at mm/page_alloc.c:4806!
invalid opcode: 0000 [#1] SMP PTI

CPU: 3 PID: 8 Comm: kworker/u16:0 Tainted: G        W         5.5.0-next-20200205+ #340
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 0.0.0 02/06/2015
Workqueue: kacpi_hotplug acpi_hotplug_work_fn
RIP: 0010:free_pages+0x85/0xa0
Call Trace:
 __remove_pages+0x99/0xc0
 arch_remove_memory+0x23/0x4d
 try_remove_memory+0xc8/0x130
 ? walk_memory_blocks+0x72/0xa0
 __remove_memory+0xa/0x11
 acpi_memory_device_remove+0x72/0x100
 acpi_bus_trim+0x55/0x90
 acpi_device_hotplug+0x2eb/0x3d0
 acpi_hotplug_work_fn+0x1a/0x30
 process_one_work+0x1a7/0x370
 worker_thread+0x30/0x380
 ? flush_rcu_work+0x30/0x30
 kthread+0x112/0x130
 ? kthread_create_on_node+0x60/0x60
 ret_from_fork+0x35/0x40

Let's move the ->section_mem_map resetting after depopulate_section_memmap() to fix it.

Fixes ba72b4c8cf60 ("mm/sparsemem: support sub-section hotplug")
Signed-off-by Baoquan He <[email protected]>
Cc [email protected]
---
 mm/sparse.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)
Quoted 11 lines

mm/sparse.c static void section_deactivate(unsigned long pfn, unsigned long nr_pages, · line 737

Quoted 9 lines
mm/sparse.c +1 -0
index 42c18a38ffaa..1b50c15677d7 100644
@@ -734,6 +734,7 @@ static void section_deactivate(unsigned long pfn, unsigned long nr_pages,
 	struct mem_section *ms = __pfn_to_section(pfn);
 	bool section_is_early = early_section(ms);
 	struct page *memmap = NULL;
+	bool empty = false;

Oh, one NIT: no need to initialize empty to false.

Thanks for careful reviewing, David.

Not very sure about this, do you have a doc or discussion thread about not initializing local variable? Maybe Andrew can help update it if this is not suggested.

#7 lore raw

Re: [PATCH v3 1/7] mm/hotplug: fix hot remove failure in SPARSEMEM|!VMEMMAP case

Quoted 51 lines · Baoquan He
Quoted 38 lines · David Hildenbrand
Quoted 37 lines · Baoquan He

In section_deactivate(), pfn_to_page() doesn't work any more after ms->section_mem_map is resetting to NULL in SPARSEMEM|!VMEMMAP case. It caused hot remove failure:

kernel BUG at mm/page_alloc.c:4806!
invalid opcode: 0000 [#1] SMP PTI

CPU: 3 PID: 8 Comm: kworker/u16:0 Tainted: G        W         5.5.0-next-20200205+ #340
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 0.0.0 02/06/2015
Workqueue: kacpi_hotplug acpi_hotplug_work_fn
RIP: 0010:free_pages+0x85/0xa0
Call Trace:
 __remove_pages+0x99/0xc0
 arch_remove_memory+0x23/0x4d
 try_remove_memory+0xc8/0x130
 ? walk_memory_blocks+0x72/0xa0
 __remove_memory+0xa/0x11
 acpi_memory_device_remove+0x72/0x100
 acpi_bus_trim+0x55/0x90
 acpi_device_hotplug+0x2eb/0x3d0
 acpi_hotplug_work_fn+0x1a/0x30
 process_one_work+0x1a7/0x370
 worker_thread+0x30/0x380
 ? flush_rcu_work+0x30/0x30
 kthread+0x112/0x130
 ? kthread_create_on_node+0x60/0x60
 ret_from_fork+0x35/0x40

Let's move the ->section_mem_map resetting after depopulate_section_memmap() to fix it.

Fixes ba72b4c8cf60 ("mm/sparsemem: support sub-section hotplug")
Signed-off-by Baoquan He <[email protected]>
Cc [email protected]
---
 mm/sparse.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)
Quoted 11 lines

mm/sparse.c static void section_deactivate(unsigned long pfn, unsigned long nr_pages, · line 737

Quoted 9 lines
mm/sparse.c +1 -0
index 42c18a38ffaa..1b50c15677d7 100644
@@ -734,6 +734,7 @@ static void section_deactivate(unsigned long pfn, unsigned long nr_pages,
 	struct mem_section *ms = __pfn_to_section(pfn);
 	bool section_is_early = early_section(ms);
 	struct page *memmap = NULL;
+	bool empty = false;

Oh, one NIT: no need to initialize empty to false.

Quoted 5 lines

Thanks for careful reviewing, David.

Not very sure about this, do you have a doc or discussion thread about not initializing local variable? Maybe Andrew can help update it if this is not suggested.

The general rule is to no initialize what will always be initialized later. Compare with most other code in-tree - e.g., sparse_init_nid.

Makes the code usually easier to follow.

Signature · 3 lines
Thanks,

David / dhildenb
Reviewed-by on v3 1/7
#8 lore raw

Re: [PATCH v3 1/7] mm/hotplug: fix hot remove failure in SPARSEMEM|!VMEMMAP case

In reply to Baoquan He
Quoted 68 lines

In section_deactivate(), pfn_to_page() doesn't work any more after ms->section_mem_map is resetting to NULL in SPARSEMEM|!VMEMMAP case. It caused hot remove failure:

kernel BUG at mm/page_alloc.c:4806!
invalid opcode: 0000 [#1] SMP PTI

CPU: 3 PID: 8 Comm: kworker/u16:0 Tainted: G        W         5.5.0-next-20200205+ #340
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 0.0.0 02/06/2015
Workqueue: kacpi_hotplug acpi_hotplug_work_fn
RIP: 0010:free_pages+0x85/0xa0
Call Trace:
 __remove_pages+0x99/0xc0
 arch_remove_memory+0x23/0x4d
 try_remove_memory+0xc8/0x130
 ? walk_memory_blocks+0x72/0xa0
 __remove_memory+0xa/0x11
 acpi_memory_device_remove+0x72/0x100
 acpi_bus_trim+0x55/0x90
 acpi_device_hotplug+0x2eb/0x3d0
 acpi_hotplug_work_fn+0x1a/0x30
 process_one_work+0x1a7/0x370
 worker_thread+0x30/0x380
 ? flush_rcu_work+0x30/0x30
 kthread+0x112/0x130
 ? kthread_create_on_node+0x60/0x60
 ret_from_fork+0x35/0x40

Let's move the ->section_mem_map resetting after depopulate_section_memmap() to fix it.

Fixes ba72b4c8cf60 ("mm/sparsemem: support sub-section hotplug")
Signed-off-by Baoquan He <[email protected]>
Cc [email protected]
---
 mm/sparse.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)
mm/sparse.c +3 -2
index 42c18a38ffaa..1b50c15677d7 100644
@@ -734,6 +734,7 @@ static void section_deactivate(unsigned long pfn, unsigned long nr_pages,
        struct mem_section *ms = __pfn_to_section(pfn);
        bool section_is_early = early_section(ms);
        struct page *memmap = NULL;
+       bool empty = false;
        unsigned long *subsection_map = ms->usage
                ? &ms->usage->subsection_map[0] : NULL;
 

@@ -764,7 +765,8 @@ static void section_deactivate(unsigned long pfn, unsigned long nr_pages,
         * For 2/ and 3/ the SPARSEMEM_VMEMMAP={y,n} cases are unified
         */
        bitmap_xor(subsection_map, map, subsection_map, SUBSECTIONS_PER_SECTION);
-       if (bitmap_empty(subsection_map, SUBSECTIONS_PER_SECTION)) {
+       empty = bitmap_empty(subsection_map, SUBSECTIONS_PER_SECTION);
+       if (empty) {
                unsigned long section_nr = pfn_to_section_nr(pfn);
 
                /*

@@ -779,13 +781,15 @@ static void section_deactivate(unsigned long pfn, unsigned long nr_pages,
                        ms->usage = NULL;
                }
                memmap = sparse_decode_mem_map(ms->section_mem_map, section_nr);
-               ms->section_mem_map = (unsigned long)NULL;
        }
 
        if (section_is_early && memmap)

mm/sparse.c static void section_deactivate(unsigned long pfn, unsigned long nr_pages,

Quoted 10 lines
mm/sparse.c +3 -1
                free_map_bootmem(memmap);
        else
                depopulate_section_memmap(pfn, nr_pages, altmap);
+
+       if (empty)
+               ms->section_mem_map = (unsigned long)NULL;
 }
 
 static struct page * __meminit section_activate(int nid, unsigned long pfn,
--
Reviewed-by Pankaj Gupta <[email protected]>
Quoted 3 lines

2.17.2

Acked-by on v3 1/7
#9 lore raw

Re: [PATCH v3 1/7] mm/hotplug: fix hot remove failure in SPARSEMEM|!VMEMMAP case

In reply to Baoquan He
Quoted 27 lines · Baoquan He

In section_deactivate(), pfn_to_page() doesn't work any more after ms->section_mem_map is resetting to NULL in SPARSEMEM|!VMEMMAP case. It caused hot remove failure:

kernel BUG at mm/page_alloc.c:4806!
invalid opcode: 0000 [#1] SMP PTI

CPU: 3 PID: 8 Comm: kworker/u16:0 Tainted: G        W         5.5.0-next-20200205+ #340
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 0.0.0 02/06/2015
Workqueue: kacpi_hotplug acpi_hotplug_work_fn
RIP: 0010:free_pages+0x85/0xa0
Call Trace:
 __remove_pages+0x99/0xc0
 arch_remove_memory+0x23/0x4d
 try_remove_memory+0xc8/0x130
 ? walk_memory_blocks+0x72/0xa0
 __remove_memory+0xa/0x11
 acpi_memory_device_remove+0x72/0x100
 acpi_bus_trim+0x55/0x90
 acpi_device_hotplug+0x2eb/0x3d0
 acpi_hotplug_work_fn+0x1a/0x30
 process_one_work+0x1a7/0x370
 worker_thread+0x30/0x380
 ? flush_rcu_work+0x30/0x30
 kthread+0x112/0x130
 ? kthread_create_on_node+0x60/0x60
 ret_from_fork+0x35/0x40
Quoted 6 lines

Let's move the ->section_mem_map resetting after depopulate_section_memmap() to fix it.

Fixes ba72b4c8cf60 ("mm/sparsemem: support sub-section hotplug")
Signed-off-by Baoquan He <[email protected]>
Cc [email protected]
Acked-by Michal Hocko <[email protected]>
Quoted 46 lines
---
 mm/sparse.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)
mm/sparse.c +6 -2
index 42c18a38ffaa..1b50c15677d7 100644
@@ -734,6 +734,7 @@ static void section_deactivate(unsigned long pfn, unsigned long nr_pages,
 	struct mem_section *ms = __pfn_to_section(pfn);
 	bool section_is_early = early_section(ms);
 	struct page *memmap = NULL;
+	bool empty = false;
 	unsigned long *subsection_map = ms->usage
 		? &ms->usage->subsection_map[0] : NULL;
 

@@ -764,7 +765,8 @@ static void section_deactivate(unsigned long pfn, unsigned long nr_pages,
 	 * For 2/ and 3/ the SPARSEMEM_VMEMMAP={y,n} cases are unified
 	 */
 	bitmap_xor(subsection_map, map, subsection_map, SUBSECTIONS_PER_SECTION);
-	if (bitmap_empty(subsection_map, SUBSECTIONS_PER_SECTION)) {
+	empty = bitmap_empty(subsection_map, SUBSECTIONS_PER_SECTION);
+	if (empty) {
 		unsigned long section_nr = pfn_to_section_nr(pfn);
 
 		/*

@@ -779,13 +781,15 @@ static void section_deactivate(unsigned long pfn, unsigned long nr_pages,
 			ms->usage = NULL;
 		}
 		memmap = sparse_decode_mem_map(ms->section_mem_map, section_nr);
-		ms->section_mem_map = (unsigned long)NULL;
 	}
 
 	if (section_is_early && memmap)
 		free_map_bootmem(memmap);
 	else
 		depopulate_section_memmap(pfn, nr_pages, altmap);
+
+	if (empty)
+		ms->section_mem_map = (unsigned long)NULL;
 }
 
 static struct page * __meminit section_activate(int nid, unsigned long pfn,
Signature · 1 line
2.17.2
Signature · 2 lines
Michal Hocko
SUSE Labs
author
#10 lore raw

PATCH v3 2/7 mm/sparse.c: introduce new function fill_subsection_map()

In reply to Baoquan He

Factor out the code that fills the subsection map from section_activate() into fill_subsection_map(), this makes section_activate() cleaner and easier to follow.

Signed-off-by Baoquan He <[email protected]>
Reviewed-by Wei Yang <[email protected]>
Reviewed-by David Hildenbrand <[email protected]>
---
 mm/sparse.c | 32 +++++++++++++++++++++-----------
 1 file changed, 21 insertions(+), 11 deletions(-)
mm/sparse.c +21 -11
index 1b50c15677d7..e37c0abcdc89 100644
@@ -792,24 +792,15 @@ static void section_deactivate(unsigned long pfn, unsigned long nr_pages,
 		ms->section_mem_map = (unsigned long)NULL;
 }
 
-static struct page * __meminit section_activate(int nid, unsigned long pfn,
-		unsigned long nr_pages, struct vmem_altmap *altmap)
+static int fill_subsection_map(unsigned long pfn, unsigned long nr_pages)
 {
-	DECLARE_BITMAP(map, SUBSECTIONS_PER_SECTION) = { 0 };
 	struct mem_section *ms = __pfn_to_section(pfn);
-	struct mem_section_usage *usage = NULL;
+	DECLARE_BITMAP(map, SUBSECTIONS_PER_SECTION) = { 0 };
 	unsigned long *subsection_map;
-	struct page *memmap;
 	int rc = 0;
 
 	subsection_mask_set(map, pfn, nr_pages);
 
-	if (!ms->usage) {
-		usage = kzalloc(mem_section_usage_size(), GFP_KERNEL);
-		if (!usage)
-			return ERR_PTR(-ENOMEM);
-		ms->usage = usage;
-	}
 	subsection_map = &ms->usage->subsection_map[0];
 
 	if (bitmap_empty(map, SUBSECTIONS_PER_SECTION))

@@ -820,6 +811,25 @@ static struct page * __meminit section_activate(int nid, unsigned long pfn,
 		bitmap_or(subsection_map, map, subsection_map,
 				SUBSECTIONS_PER_SECTION);
 
+	return rc;
+}
+
+static struct page * __meminit section_activate(int nid, unsigned long pfn,
+		unsigned long nr_pages, struct vmem_altmap *altmap)
+{
+	struct mem_section *ms = __pfn_to_section(pfn);
+	struct mem_section_usage *usage = NULL;
+	struct page *memmap;
+	int rc = 0;
+
+	if (!ms->usage) {
+		usage = kzalloc(mem_section_usage_size(), GFP_KERNEL);
+		if (!usage)
+			return ERR_PTR(-ENOMEM);
+		ms->usage = usage;
+	}
+
+	rc = fill_subsection_map(pfn, nr_pages);
 	if (rc) {
 		if (usage)
 			ms->usage = NULL;
Signature · 1 line
2.17.2
author
#11 lore raw

PATCH v3 3/7 mm/sparse.c: introduce a new function clear_subsection_map()

In reply to Baoquan He

Factor out the code which clear subsection map of one memory region from section_deactivate() into clear_subsection_map().

Signed-off-by Baoquan He <[email protected]>
---
 mm/sparse.c | 31 ++++++++++++++++++++++++-------
 1 file changed, 24 insertions(+), 7 deletions(-)
mm/sparse.c +24 -7
index e37c0abcdc89..d9dcd58d5c1d 100644
@@ -726,15 +726,11 @@ static void free_map_bootmem(struct page *memmap)
 }
 #endif /* CONFIG_SPARSEMEM_VMEMMAP */
 
-static void section_deactivate(unsigned long pfn, unsigned long nr_pages,
-		struct vmem_altmap *altmap)
+static int clear_subsection_map(unsigned long pfn, unsigned long nr_pages)
 {
 	DECLARE_BITMAP(map, SUBSECTIONS_PER_SECTION) = { 0 };
 	DECLARE_BITMAP(tmp, SUBSECTIONS_PER_SECTION) = { 0 };
 	struct mem_section *ms = __pfn_to_section(pfn);
-	bool section_is_early = early_section(ms);
-	struct page *memmap = NULL;
-	bool empty = false;
 	unsigned long *subsection_map = ms->usage
 		? &ms->usage->subsection_map[0] : NULL;
 

@@ -745,8 +741,31 @@ static void section_deactivate(unsigned long pfn, unsigned long nr_pages,
 	if (WARN(!subsection_map || !bitmap_equal(tmp, map, SUBSECTIONS_PER_SECTION),
 				"section already deactivated (%#lx + %ld)\n",
 				pfn, nr_pages))
+		return -EINVAL;
+
+	bitmap_xor(subsection_map, map, subsection_map, SUBSECTIONS_PER_SECTION);
+
+	return 0;
+}
+
+static bool is_subsection_map_empty(struct mem_section *ms)
+{
+	return bitmap_empty(&ms->usage->subsection_map[0],
+			    SUBSECTIONS_PER_SECTION);
+}
+
+static void section_deactivate(unsigned long pfn, unsigned long nr_pages,
+		struct vmem_altmap *altmap)
+{
+	struct mem_section *ms = __pfn_to_section(pfn);
+	bool section_is_early = early_section(ms);
+	struct page *memmap = NULL;
+	bool empty = false;
+
+	if (clear_subsection_map(pfn, nr_pages))
 		return;
 
+	empty = is_subsection_map_empty(ms);
 	/*
 	 * There are 3 cases to handle across two configurations
 	 * (SPARSEMEM_VMEMMAP={y,n}):

@@ -764,8 +783,6 @@ static void section_deactivate(unsigned long pfn, unsigned long nr_pages,
 	 *
 	 * For 2/ and 3/ the SPARSEMEM_VMEMMAP={y,n} cases are unified
 	 */
-	bitmap_xor(subsection_map, map, subsection_map, SUBSECTIONS_PER_SECTION);
-	empty = bitmap_empty(subsection_map, SUBSECTIONS_PER_SECTION);
 	if (empty) {
 		unsigned long section_nr = pfn_to_section_nr(pfn);
Signature · 1 line
2.17.2
Reviewed-by on v3 3/7
#12 lore raw

Re: [PATCH v3 3/7] mm/sparse.c: introduce a new function clear_subsection_map()

Quoted 30 lines · Baoquan He

Factor out the code which clear subsection map of one memory region from section_deactivate() into clear_subsection_map().

Signed-off-by Baoquan He <[email protected]>
---
 mm/sparse.c | 31 ++++++++++++++++++++++++-------
 1 file changed, 24 insertions(+), 7 deletions(-)
mm/sparse.c +1 -5
index e37c0abcdc89..d9dcd58d5c1d 100644
@@ -726,15 +726,11 @@ static void free_map_bootmem(struct page *memmap)
 }
 #endif /* CONFIG_SPARSEMEM_VMEMMAP */
 
-static void section_deactivate(unsigned long pfn, unsigned long nr_pages,
-		struct vmem_altmap *altmap)
+static int clear_subsection_map(unsigned long pfn, unsigned long nr_pages)
 {
 	DECLARE_BITMAP(map, SUBSECTIONS_PER_SECTION) = { 0 };
 	DECLARE_BITMAP(tmp, SUBSECTIONS_PER_SECTION) = { 0 };
 	struct mem_section *ms = __pfn_to_section(pfn);
-	bool section_is_early = early_section(ms);
-	struct page *memmap = NULL;
-	bool empty = false;
 	unsigned long *subsection_map = ms->usage
 		? &ms->usage->subsection_map[0] : NULL;

mm/sparse.c static void section_deactivate(unsigned long pfn, unsigned long nr_pages, · line 747

Quoted 7 lines
mm/sparse.c +4 -0
@@ -745,8 +741,31 @@ static void section_deactivate(unsigned long pfn, unsigned long nr_pages,
 	if (WARN(!subsection_map || !bitmap_equal(tmp, map, SUBSECTIONS_PER_SECTION),
 				"section already deactivated (%#lx + %ld)\n",
 				pfn, nr_pages))
+		return -EINVAL;
+
+	bitmap_xor(subsection_map, map, subsection_map, SUBSECTIONS_PER_SECTION);
+

Nit: I'd drop this line.

Quoted 6 lines
mm/sparse.c +6 -0
+	return 0;
+}
+
+static bool is_subsection_map_empty(struct mem_section *ms)
+{
+	return bitmap_empty(&ms->usage->subsection_map[0],

mm/sparse.c static void section_deactivate(unsigned long pfn, unsigned long nr_pages, · line 763

Quoted 10 lines
mm/sparse.c +10 -0
+			    SUBSECTIONS_PER_SECTION);
+}
+
+static void section_deactivate(unsigned long pfn, unsigned long nr_pages,
+		struct vmem_altmap *altmap)
+{
+	struct mem_section *ms = __pfn_to_section(pfn);
+	bool section_is_early = early_section(ms);
+	struct page *memmap = NULL;
+	bool empty = false;

Nit: No need to initialize empty.

mm/sparse.c static void section_deactivate(unsigned long pfn, unsigned long nr_pages, · line 767

Quoted 4 lines
mm/sparse.c +2 -0
+
+	if (clear_subsection_map(pfn, nr_pages))
 		return;

Nit: I'd drop this empty line.

mm/sparse.c static void section_deactivate(unsigned long pfn, unsigned long nr_pages, · line 768

Quoted 10 lines
mm/sparse.c +1 -2
+	empty = is_subsection_map_empty(ms);
 	/*
 	 * There are 3 cases to handle across two configurations
 	 * (SPARSEMEM_VMEMMAP={y,n}):

@@ -764,8 +783,6 @@ static void section_deactivate(unsigned long pfn, unsigned long nr_pages,
 	 *
 	 * For 2/ and 3/ the SPARSEMEM_VMEMMAP={y,n} cases are unified
 	 */
-	bitmap_xor(subsection_map, map, subsection_map, SUBSECTIONS_PER_SECTION);
-	empty = bitmap_empty(subsection_map, SUBSECTIONS_PER_SECTION);

I do wonder why you moved this up the comment?

mm/sparse.c static void section_deactivate(unsigned long pfn, unsigned long nr_pages, · line 788

Quoted 4 lines
mm/sparse.c +0 -0
 	if (empty) {
 		unsigned long section_nr = pfn_to_section_nr(pfn);
Reviewed-by David Hildenbrand <[email protected]>
Signature · 3 lines
Thanks,

David / dhildenb
author
#13 lore raw

Re: [PATCH v3 3/7] mm/sparse.c: introduce a new function clear_subsection_map()

Quoted 30 lines · David Hildenbrand
Quoted 29 lines · Baoquan He

Factor out the code which clear subsection map of one memory region from section_deactivate() into clear_subsection_map().

Signed-off-by Baoquan He <[email protected]>
---
 mm/sparse.c | 31 ++++++++++++++++++++++++-------
 1 file changed, 24 insertions(+), 7 deletions(-)
mm/sparse.c +1 -5
index e37c0abcdc89..d9dcd58d5c1d 100644
@@ -726,15 +726,11 @@ static void free_map_bootmem(struct page *memmap)
 }
 #endif /* CONFIG_SPARSEMEM_VMEMMAP */
 
-static void section_deactivate(unsigned long pfn, unsigned long nr_pages,
-		struct vmem_altmap *altmap)
+static int clear_subsection_map(unsigned long pfn, unsigned long nr_pages)
 {
 	DECLARE_BITMAP(map, SUBSECTIONS_PER_SECTION) = { 0 };
 	DECLARE_BITMAP(tmp, SUBSECTIONS_PER_SECTION) = { 0 };
 	struct mem_section *ms = __pfn_to_section(pfn);
-	bool section_is_early = early_section(ms);
-	struct page *memmap = NULL;
-	bool empty = false;
 	unsigned long *subsection_map = ms->usage
 		? &ms->usage->subsection_map[0] : NULL;
Quoted 10 lines

mm/sparse.c static void section_deactivate(unsigned long pfn, unsigned long nr_pages, · line 747

Quoted 8 lines
mm/sparse.c +4 -0
@@ -745,8 +741,31 @@ static void section_deactivate(unsigned long pfn, unsigned long nr_pages,
 	if (WARN(!subsection_map || !bitmap_equal(tmp, map, SUBSECTIONS_PER_SECTION),
 				"section already deactivated (%#lx + %ld)\n",
 				pfn, nr_pages))
+		return -EINVAL;
+
+	bitmap_xor(subsection_map, map, subsection_map, SUBSECTIONS_PER_SECTION);
+

Nit: I'd drop this line.

It's fine to me. I usually keep one line for the returning. I will remove it when update.

Quoted 11 lines
Quoted 11 lines
mm/sparse.c +10 -0
+	return 0;
+}
+
+static bool is_subsection_map_empty(struct mem_section *ms)
+{
+	return bitmap_empty(&ms->usage->subsection_map[0],
+			    SUBSECTIONS_PER_SECTION);
+}
+
+static void section_deactivate(unsigned long pfn, unsigned long nr_pages,
Quoted 8 lines

mm/sparse.c static void section_deactivate(unsigned long pfn, unsigned long nr_pages, · line 763

Quoted 6 lines
mm/sparse.c +6 -0
+		struct vmem_altmap *altmap)
+{
+	struct mem_section *ms = __pfn_to_section(pfn);
+	bool section_is_early = early_section(ms);
+	struct page *memmap = NULL;
+	bool empty = false;

Nit: No need to initialize empty.

This is inherited from patch 1.

Quoted 8 lines

mm/sparse.c static void section_deactivate(unsigned long pfn, unsigned long nr_pages, · line 767

Quoted 5 lines
mm/sparse.c +2 -0
+
+	if (clear_subsection_map(pfn, nr_pages))
 		return;

Nit: I'd drop this empty line.

Quoted 12 lines

mm/sparse.c static void section_deactivate(unsigned long pfn, unsigned long nr_pages, · line 768

Quoted 10 lines
mm/sparse.c +1 -2
+	empty = is_subsection_map_empty(ms);
 	/*
 	 * There are 3 cases to handle across two configurations
 	 * (SPARSEMEM_VMEMMAP={y,n}):

@@ -764,8 +783,6 @@ static void section_deactivate(unsigned long pfn, unsigned long nr_pages,
 	 *
 	 * For 2/ and 3/ the SPARSEMEM_VMEMMAP={y,n} cases are unified
 	 */
-	bitmap_xor(subsection_map, map, subsection_map, SUBSECTIONS_PER_SECTION);
-	empty = bitmap_empty(subsection_map, SUBSECTIONS_PER_SECTION);

I do wonder why you moved this up the comment?

Since this empty will cover two places of handling, so moved it up, seems this is what I was thinking. Can move it back here.

Quoted 12 lines

mm/sparse.c static void section_deactivate(unsigned long pfn, unsigned long nr_pages, · line 788

Quoted 5 lines
mm/sparse.c +0 -0
 	if (empty) {
 		unsigned long section_nr = pfn_to_section_nr(pfn);
Reviewed-by David Hildenbrand <[email protected]>
Signature · 3 lines
Thanks,

David / dhildenb
#14 lore raw

Re: [PATCH v3 3/7] mm/sparse.c: introduce a new function clear_subsection_map()

Quoted 88 lines · Baoquan He
Quoted 30 lines · David Hildenbrand
Quoted 29 lines · Baoquan He

Factor out the code which clear subsection map of one memory region from section_deactivate() into clear_subsection_map().

Signed-off-by Baoquan He <[email protected]>
---
 mm/sparse.c | 31 ++++++++++++++++++++++++-------
 1 file changed, 24 insertions(+), 7 deletions(-)
mm/sparse.c +1 -5
index e37c0abcdc89..d9dcd58d5c1d 100644
@@ -726,15 +726,11 @@ static void free_map_bootmem(struct page *memmap)
 }
 #endif /* CONFIG_SPARSEMEM_VMEMMAP */
 
-static void section_deactivate(unsigned long pfn, unsigned long nr_pages,
-		struct vmem_altmap *altmap)
+static int clear_subsection_map(unsigned long pfn, unsigned long nr_pages)
 {
 	DECLARE_BITMAP(map, SUBSECTIONS_PER_SECTION) = { 0 };
 	DECLARE_BITMAP(tmp, SUBSECTIONS_PER_SECTION) = { 0 };
 	struct mem_section *ms = __pfn_to_section(pfn);
-	bool section_is_early = early_section(ms);
-	struct page *memmap = NULL;
-	bool empty = false;
 	unsigned long *subsection_map = ms->usage
 		? &ms->usage->subsection_map[0] : NULL;
Quoted 10 lines

mm/sparse.c static void section_deactivate(unsigned long pfn, unsigned long nr_pages, · line 747

Quoted 8 lines
mm/sparse.c +4 -0
@@ -745,8 +741,31 @@ static void section_deactivate(unsigned long pfn, unsigned long nr_pages,
 	if (WARN(!subsection_map || !bitmap_equal(tmp, map, SUBSECTIONS_PER_SECTION),
 				"section already deactivated (%#lx + %ld)\n",
 				pfn, nr_pages))
+		return -EINVAL;
+
+	bitmap_xor(subsection_map, map, subsection_map, SUBSECTIONS_PER_SECTION);
+

Nit: I'd drop this line.

It's fine to me. I usually keep one line for the returning. I will remove it when update.

Quoted 11 lines
Quoted 11 lines
mm/sparse.c +10 -0
+	return 0;
+}
+
+static bool is_subsection_map_empty(struct mem_section *ms)
+{
+	return bitmap_empty(&ms->usage->subsection_map[0],
+			    SUBSECTIONS_PER_SECTION);
+}
+
+static void section_deactivate(unsigned long pfn, unsigned long nr_pages,
Quoted 8 lines

mm/sparse.c static void section_deactivate(unsigned long pfn, unsigned long nr_pages, · line 763

Quoted 6 lines
mm/sparse.c +6 -0
+		struct vmem_altmap *altmap)
+{
+	struct mem_section *ms = __pfn_to_section(pfn);
+	bool section_is_early = early_section(ms);
+	struct page *memmap = NULL;
+	bool empty = false;

Nit: No need to initialize empty.

This is inherited from patch 1.

Quoted 8 lines

mm/sparse.c static void section_deactivate(unsigned long pfn, unsigned long nr_pages, · line 767

Quoted 5 lines
mm/sparse.c +2 -0
+
+	if (clear_subsection_map(pfn, nr_pages))
 		return;

Nit: I'd drop this empty line.

Quoted 12 lines

mm/sparse.c static void section_deactivate(unsigned long pfn, unsigned long nr_pages, · line 768

Quoted 10 lines
mm/sparse.c +1 -2
+	empty = is_subsection_map_empty(ms);
 	/*
 	 * There are 3 cases to handle across two configurations
 	 * (SPARSEMEM_VMEMMAP={y,n}):

@@ -764,8 +783,6 @@ static void section_deactivate(unsigned long pfn, unsigned long nr_pages,
 	 *
 	 * For 2/ and 3/ the SPARSEMEM_VMEMMAP={y,n} cases are unified
 	 */
-	bitmap_xor(subsection_map, map, subsection_map, SUBSECTIONS_PER_SECTION);
-	empty = bitmap_empty(subsection_map, SUBSECTIONS_PER_SECTION);

I do wonder why you moved this up the comment?

Quoted 2 lines

Since this empty will cover two places of handling, so moved it up, seems this is what I was thinking. Can move it back here.

You're moving the whole comment later, was just wondering (makes it slightly harder to review).

Signature · 3 lines
Thanks,

David / dhildenb
author
#15 lore raw

Re: [PATCH v3 3/7] mm/sparse.c: introduce a new function clear_subsection_map()

Quoted 89 lines · David Hildenbrand
Quoted 88 lines · Baoquan He
Quoted 30 lines · David Hildenbrand
Quoted 29 lines · Baoquan He

Factor out the code which clear subsection map of one memory region from section_deactivate() into clear_subsection_map().

Signed-off-by Baoquan He <[email protected]>
---
 mm/sparse.c | 31 ++++++++++++++++++++++++-------
 1 file changed, 24 insertions(+), 7 deletions(-)
mm/sparse.c +1 -5
index e37c0abcdc89..d9dcd58d5c1d 100644
@@ -726,15 +726,11 @@ static void free_map_bootmem(struct page *memmap)
 }
 #endif /* CONFIG_SPARSEMEM_VMEMMAP */
 
-static void section_deactivate(unsigned long pfn, unsigned long nr_pages,
-		struct vmem_altmap *altmap)
+static int clear_subsection_map(unsigned long pfn, unsigned long nr_pages)
 {
 	DECLARE_BITMAP(map, SUBSECTIONS_PER_SECTION) = { 0 };
 	DECLARE_BITMAP(tmp, SUBSECTIONS_PER_SECTION) = { 0 };
 	struct mem_section *ms = __pfn_to_section(pfn);
-	bool section_is_early = early_section(ms);
-	struct page *memmap = NULL;
-	bool empty = false;
 	unsigned long *subsection_map = ms->usage
 		? &ms->usage->subsection_map[0] : NULL;
Quoted 10 lines

mm/sparse.c static void section_deactivate(unsigned long pfn, unsigned long nr_pages, · line 747

Quoted 8 lines
mm/sparse.c +4 -0
@@ -745,8 +741,31 @@ static void section_deactivate(unsigned long pfn, unsigned long nr_pages,
 	if (WARN(!subsection_map || !bitmap_equal(tmp, map, SUBSECTIONS_PER_SECTION),
 				"section already deactivated (%#lx + %ld)\n",
 				pfn, nr_pages))
+		return -EINVAL;
+
+	bitmap_xor(subsection_map, map, subsection_map, SUBSECTIONS_PER_SECTION);
+

Nit: I'd drop this line.

It's fine to me. I usually keep one line for the returning. I will remove it when update.

Quoted 11 lines
Quoted 11 lines
mm/sparse.c +10 -0
+	return 0;
+}
+
+static bool is_subsection_map_empty(struct mem_section *ms)
+{
+	return bitmap_empty(&ms->usage->subsection_map[0],
+			    SUBSECTIONS_PER_SECTION);
+}
+
+static void section_deactivate(unsigned long pfn, unsigned long nr_pages,
Quoted 8 lines

mm/sparse.c static void section_deactivate(unsigned long pfn, unsigned long nr_pages, · line 763

Quoted 6 lines
mm/sparse.c +6 -0
+		struct vmem_altmap *altmap)
+{
+	struct mem_section *ms = __pfn_to_section(pfn);
+	bool section_is_early = early_section(ms);
+	struct page *memmap = NULL;
+	bool empty = false;

Nit: No need to initialize empty.

This is inherited from patch 1.

Quoted 20 lines

mm/sparse.c static void section_deactivate(unsigned long pfn, unsigned long nr_pages, · line 767

Quoted 5 lines
mm/sparse.c +2 -0
+
+	if (clear_subsection_map(pfn, nr_pages))
 		return;

Nit: I'd drop this empty line.

mm/sparse.c static void section_deactivate(unsigned long pfn, unsigned long nr_pages, · line 768

Quoted 10 lines
mm/sparse.c +1 -2
+	empty = is_subsection_map_empty(ms);
 	/*
 	 * There are 3 cases to handle across two configurations
 	 * (SPARSEMEM_VMEMMAP={y,n}):

@@ -764,8 +783,6 @@ static void section_deactivate(unsigned long pfn, unsigned long nr_pages,
 	 *
 	 * For 2/ and 3/ the SPARSEMEM_VMEMMAP={y,n} cases are unified
 	 */
-	bitmap_xor(subsection_map, map, subsection_map, SUBSECTIONS_PER_SECTION);
-	empty = bitmap_empty(subsection_map, SUBSECTIONS_PER_SECTION);

I do wonder why you moved this up the comment?

Quoted 5 lines
Quoted 2 lines

Since this empty will cover two places of handling, so moved it up, seems this is what I was thinking. Can move it back here.

You're moving the whole comment later, was just wondering (makes it slightly harder to review).

I see, sorry for the confusion. I will move it back when repost.

author
#16 lore raw

PATCH v3 4/7 mm/sparse.c: only use subsection map in VMEMMAP case

In reply to Baoquan He

Currently, to support subsection aligned memory region adding for pmem, subsection map is added to track which subsection is present.

However, config ZONE_DEVICE depends on SPARSEMEM_VMEMMAP. It means subsection map only makes sense when SPARSEMEM_VMEMMAP enabled. For the classic sparse, subsection map is meaningless and confusing.

About the classic sparse which doesn't support subsection hotplug, Dan said it's more because the effort and maintenance burden outweighs the benefit. Besides, the current 64 bit ARCHes all enable SPARSEMEM_VMEMMAP_ENABLE by default.

Combining the above reasons, no need to provide subsection map and the relevant handling for the classic sparse. Handle it with this patch.

Signed-off-by Baoquan He <[email protected]>
---
 include/linux/mmzone.h |  2 ++
 mm/sparse.c            | 25 +++++++++++++++++++++++++
 2 files changed, 27 insertions(+)
include/linux/mmzone.h +2 -0
index 42b77d3b68e8..f3f264826423 100644
@@ -1143,7 +1143,9 @@ static inline unsigned long section_nr_to_pfn(unsigned long sec)
 #define SUBSECTION_ALIGN_DOWN(pfn) ((pfn) & PAGE_SUBSECTION_MASK)
 
 struct mem_section_usage {
+#ifdef CONFIG_SPARSEMEM_VMEMMAP
 	DECLARE_BITMAP(subsection_map, SUBSECTIONS_PER_SECTION);
+#endif
 	/* See declaration of similar field in struct zone */
 	unsigned long pageblock_flags[0];
 };
mm/sparse.c +25 -0
index d9dcd58d5c1d..2142045ab5c5 100644
@@ -209,6 +209,7 @@ static inline unsigned long first_present_section_nr(void)
 	return next_present_section_nr(-1);
 }
 
+#ifdef CONFIG_SPARSEMEM_VMEMMAP
 static void subsection_mask_set(unsigned long *map, unsigned long pfn,
 		unsigned long nr_pages)
 {

@@ -243,6 +244,11 @@ void __init subsection_map_init(unsigned long pfn, unsigned long nr_pages)
 		nr_pages -= pfns;
 	}
 }
+#else
+void __init subsection_map_init(unsigned long pfn, unsigned long nr_pages)
+{
+}
+#endif
 
 /* Record a memory area against a node. */
 void __init memory_present(int nid, unsigned long start, unsigned long end)

@@ -726,6 +732,7 @@ static void free_map_bootmem(struct page *memmap)
 }
 #endif /* CONFIG_SPARSEMEM_VMEMMAP */
 
+#ifdef CONFIG_SPARSEMEM_VMEMMAP
 static int clear_subsection_map(unsigned long pfn, unsigned long nr_pages)
 {
 	DECLARE_BITMAP(map, SUBSECTIONS_PER_SECTION) = { 0 };

@@ -753,6 +760,17 @@ static bool is_subsection_map_empty(struct mem_section *ms)
 	return bitmap_empty(&ms->usage->subsection_map[0],
 			    SUBSECTIONS_PER_SECTION);
 }
+#else
+static int clear_subsection_map(unsigned long pfn, unsigned long nr_pages)
+{
+	return 0;
+}
+
+static bool is_subsection_map_empty(struct mem_section *ms)
+{
+	return true;
+}
+#endif
 
 static void section_deactivate(unsigned long pfn, unsigned long nr_pages,
 		struct vmem_altmap *altmap)

@@ -809,6 +827,7 @@ static void section_deactivate(unsigned long pfn, unsigned long nr_pages,
 		ms->section_mem_map = (unsigned long)NULL;
 }
 
+#ifdef CONFIG_SPARSEMEM_VMEMMAP
 static int fill_subsection_map(unsigned long pfn, unsigned long nr_pages)
 {
 	struct mem_section *ms = __pfn_to_section(pfn);

@@ -830,6 +849,12 @@ static int fill_subsection_map(unsigned long pfn, unsigned long nr_pages)
 
 	return rc;
 }
+#else
+static int fill_subsection_map(unsigned long pfn, unsigned long nr_pages)
+{
+	return 0;
+}
+#endif
 
 static struct page * __meminit section_activate(int nid, unsigned long pfn,
 		unsigned long nr_pages, struct vmem_altmap *altmap)
Signature · 1 line
2.17.2
Reviewed-by on v3 4/7
#17 lore raw

Re: [PATCH v3 4/7] mm/sparse.c: only use subsection map in VMEMMAP case

Quoted 97 lines · Baoquan He

Currently, to support subsection aligned memory region adding for pmem, subsection map is added to track which subsection is present.

However, config ZONE_DEVICE depends on SPARSEMEM_VMEMMAP. It means subsection map only makes sense when SPARSEMEM_VMEMMAP enabled. For the classic sparse, subsection map is meaningless and confusing.

About the classic sparse which doesn't support subsection hotplug, Dan said it's more because the effort and maintenance burden outweighs the benefit. Besides, the current 64 bit ARCHes all enable SPARSEMEM_VMEMMAP_ENABLE by default.

Combining the above reasons, no need to provide subsection map and the relevant handling for the classic sparse. Handle it with this patch.

Signed-off-by Baoquan He <[email protected]>
---
 include/linux/mmzone.h |  2 ++
 mm/sparse.c            | 25 +++++++++++++++++++++++++
 2 files changed, 27 insertions(+)
include/linux/mmzone.h +2 -0
index 42b77d3b68e8..f3f264826423 100644
@@ -1143,7 +1143,9 @@ static inline unsigned long section_nr_to_pfn(unsigned long sec)
 #define SUBSECTION_ALIGN_DOWN(pfn) ((pfn) & PAGE_SUBSECTION_MASK)
 
 struct mem_section_usage {
+#ifdef CONFIG_SPARSEMEM_VMEMMAP
 	DECLARE_BITMAP(subsection_map, SUBSECTIONS_PER_SECTION);
+#endif
 	/* See declaration of similar field in struct zone */
 	unsigned long pageblock_flags[0];
 };
mm/sparse.c +19 -0
index d9dcd58d5c1d..2142045ab5c5 100644
@@ -209,6 +209,7 @@ static inline unsigned long first_present_section_nr(void)
 	return next_present_section_nr(-1);
 }
 
+#ifdef CONFIG_SPARSEMEM_VMEMMAP
 static void subsection_mask_set(unsigned long *map, unsigned long pfn,
 		unsigned long nr_pages)
 {

@@ -243,6 +244,11 @@ void __init subsection_map_init(unsigned long pfn, unsigned long nr_pages)
 		nr_pages -= pfns;
 	}
 }
+#else
+void __init subsection_map_init(unsigned long pfn, unsigned long nr_pages)
+{
+}
+#endif
 
 /* Record a memory area against a node. */
 void __init memory_present(int nid, unsigned long start, unsigned long end)

@@ -726,6 +732,7 @@ static void free_map_bootmem(struct page *memmap)
 }
 #endif /* CONFIG_SPARSEMEM_VMEMMAP */
 
+#ifdef CONFIG_SPARSEMEM_VMEMMAP
 static int clear_subsection_map(unsigned long pfn, unsigned long nr_pages)
 {
 	DECLARE_BITMAP(map, SUBSECTIONS_PER_SECTION) = { 0 };

@@ -753,6 +760,17 @@ static bool is_subsection_map_empty(struct mem_section *ms)
 	return bitmap_empty(&ms->usage->subsection_map[0],
 			    SUBSECTIONS_PER_SECTION);
 }
+#else
+static int clear_subsection_map(unsigned long pfn, unsigned long nr_pages)
+{
+	return 0;
+}
+
+static bool is_subsection_map_empty(struct mem_section *ms)
+{
+	return true;
+}
+#endif
 
 static void section_deactivate(unsigned long pfn, unsigned long nr_pages,
 		struct vmem_altmap *altmap)

@@ -809,6 +827,7 @@ static void section_deactivate(unsigned long pfn, unsigned long nr_pages,
 		ms->section_mem_map = (unsigned long)NULL;
 }
 
+#ifdef CONFIG_SPARSEMEM_VMEMMAP
 static int fill_subsection_map(unsigned long pfn, unsigned long nr_pages)
 {
 	struct mem_section *ms = __pfn_to_section(pfn);

@@ -830,6 +849,12 @@ static int fill_subsection_map(unsigned long pfn, unsigned long nr_pages)
 
 	return rc;

mm/sparse.c static int fill_subsection_map(unsigned long pfn, unsigned long nr_pages) · line 860

Quoted 10 lines
mm/sparse.c +6 -0
 }
+#else
+static int fill_subsection_map(unsigned long pfn, unsigned long nr_pages)
+{
+	return 0;
+}
+#endif
 
 static struct page * __meminit section_activate(int nid, unsigned long pfn,
 		unsigned long nr_pages, struct vmem_altmap *altmap)
Reviewed-by David Hildenbrand <[email protected]>
Signature · 3 lines
Thanks,

David / dhildenb
author
#18 lore raw

PATCH v3 5/7 mm/sparse.c: add note about only VMEMMAP supporting sub-section support

In reply to Baoquan He

And tell check_pfn_span() gating the porper alignment and size of hot added memory region.

And also move the code comments from inside section_deactivate() to being above it. The code comments are reasonable for the whole function, and the moving makes code cleaner.

Signed-off-by Baoquan He <[email protected]>
---
 mm/sparse.c | 37 ++++++++++++++++++++-----------------
 1 file changed, 20 insertions(+), 17 deletions(-)
mm/sparse.c +20 -17
index 2142045ab5c5..0fbd79c4ad81 100644
@@ -772,6 +772,22 @@ static bool is_subsection_map_empty(struct mem_section *ms)
 }
 #endif
 
+/*
+ * To deactivate a memory region, there are 3 cases to handle across
+ * two configurations (SPARSEMEM_VMEMMAP={y,n}):
+ *
+ * 1. deactivation of a partial hot-added section (only possible in
+ *    the SPARSEMEM_VMEMMAP=y case).
+ *      a) section was present at memory init.
+ *      b) section was hot-added post memory init.
+ * 2. deactivation of a complete hot-added section.
+ * 3. deactivation of a complete section from memory init.
+ *
+ * For 1, when subsection_map does not empty we will not be freeing the
+ * usage map, but still need to free the vmemmap range.
+ *
+ * For 2 and 3, the SPARSEMEM_VMEMMAP={y,n} cases are unified
+ */
 static void section_deactivate(unsigned long pfn, unsigned long nr_pages,
 		struct vmem_altmap *altmap)
 {

@@ -784,23 +800,6 @@ static void section_deactivate(unsigned long pfn, unsigned long nr_pages,
 		return;
 
 	empty = is_subsection_map_empty(ms);
-	/*
-	 * There are 3 cases to handle across two configurations
-	 * (SPARSEMEM_VMEMMAP={y,n}):
-	 *
-	 * 1/ deactivation of a partial hot-added section (only possible
-	 * in the SPARSEMEM_VMEMMAP=y case).
-	 *    a/ section was present at memory init
-	 *    b/ section was hot-added post memory init
-	 * 2/ deactivation of a complete hot-added section
-	 * 3/ deactivation of a complete section from memory init
-	 *
-	 * For 1/, when subsection_map does not empty we will not be
-	 * freeing the usage map, but still need to free the vmemmap
-	 * range.
-	 *
-	 * For 2/ and 3/ the SPARSEMEM_VMEMMAP={y,n} cases are unified
-	 */
 	if (empty) {
 		unsigned long section_nr = pfn_to_section_nr(pfn);
 

@@ -907,6 +906,10 @@ static struct page * __meminit section_activate(int nid, unsigned long pfn,
  *
  * This is only intended for hotplug.
  *
+ * Note that only VMEMMAP supports sub-section aligned hotplug,
+ * the proper alignment and size are gated by check_pfn_span().
+ *
+ *
  * Return:
  * * 0		- On success.
  * * -EEXIST	- Section has been present.
Signature · 1 line
2.17.2
author
#19 lore raw

Re: [PATCH v3 5/7] mm/sparse.c: add note about only VMEMMAP supporting sub-section support

On 03/07/20 at 04:42pm, Baoquan He wrote:

Sorry, the subject should be:

mm/sparse.c: add note about only VMEMMAP supporting sub-section hotplug

Quoted 77 lines

And tell check_pfn_span() gating the porper alignment and size of hot added memory region.

And also move the code comments from inside section_deactivate() to being above it. The code comments are reasonable for the whole function, and the moving makes code cleaner.

Signed-off-by Baoquan He <[email protected]>
---
 mm/sparse.c | 37 ++++++++++++++++++++-----------------
 1 file changed, 20 insertions(+), 17 deletions(-)
mm/sparse.c +20 -17
index 2142045ab5c5..0fbd79c4ad81 100644
@@ -772,6 +772,22 @@ static bool is_subsection_map_empty(struct mem_section *ms)
 }
 #endif
 
+/*
+ * To deactivate a memory region, there are 3 cases to handle across
+ * two configurations (SPARSEMEM_VMEMMAP={y,n}):
+ *
+ * 1. deactivation of a partial hot-added section (only possible in
+ *    the SPARSEMEM_VMEMMAP=y case).
+ *      a) section was present at memory init.
+ *      b) section was hot-added post memory init.
+ * 2. deactivation of a complete hot-added section.
+ * 3. deactivation of a complete section from memory init.
+ *
+ * For 1, when subsection_map does not empty we will not be freeing the
+ * usage map, but still need to free the vmemmap range.
+ *
+ * For 2 and 3, the SPARSEMEM_VMEMMAP={y,n} cases are unified
+ */
 static void section_deactivate(unsigned long pfn, unsigned long nr_pages,
 		struct vmem_altmap *altmap)
 {

@@ -784,23 +800,6 @@ static void section_deactivate(unsigned long pfn, unsigned long nr_pages,
 		return;
 
 	empty = is_subsection_map_empty(ms);
-	/*
-	 * There are 3 cases to handle across two configurations
-	 * (SPARSEMEM_VMEMMAP={y,n}):
-	 *
-	 * 1/ deactivation of a partial hot-added section (only possible
-	 * in the SPARSEMEM_VMEMMAP=y case).
-	 *    a/ section was present at memory init
-	 *    b/ section was hot-added post memory init
-	 * 2/ deactivation of a complete hot-added section
-	 * 3/ deactivation of a complete section from memory init
-	 *
-	 * For 1/, when subsection_map does not empty we will not be
-	 * freeing the usage map, but still need to free the vmemmap
-	 * range.
-	 *
-	 * For 2/ and 3/ the SPARSEMEM_VMEMMAP={y,n} cases are unified
-	 */
 	if (empty) {
 		unsigned long section_nr = pfn_to_section_nr(pfn);
 

@@ -907,6 +906,10 @@ static struct page * __meminit section_activate(int nid, unsigned long pfn,
  *
  * This is only intended for hotplug.
  *
+ * Note that only VMEMMAP supports sub-section aligned hotplug,
+ * the proper alignment and size are gated by check_pfn_span().
+ *
+ *
  * Return:
  * * 0		- On success.
  * * -EEXIST	- Section has been present.
Signature · 1 line
2.17.2
Acked-by on v3 5/7
#20 lore raw

Re: [PATCH v3 5/7] mm/sparse.c: add note about only VMEMMAP supporting sub-section support

In reply to Baoquan He
Quoted 8 lines · Baoquan He

And tell check_pfn_span() gating the porper alignment and size of hot added memory region.

And also move the code comments from inside section_deactivate() to being above it. The code comments are reasonable for the whole function, and the moving makes code cleaner.

Signed-off-by Baoquan He <[email protected]>
Acked-by Michal Hocko <[email protected]>

I have glanced through other patches and they seem sane but I do not have time to go deeper to give an ack. I like this one though because it really makes the intention clearer.

Quoted 69 lines
---
 mm/sparse.c | 37 ++++++++++++++++++++-----------------
 1 file changed, 20 insertions(+), 17 deletions(-)
mm/sparse.c +20 -17
index 2142045ab5c5..0fbd79c4ad81 100644
@@ -772,6 +772,22 @@ static bool is_subsection_map_empty(struct mem_section *ms)
 }
 #endif
 
+/*
+ * To deactivate a memory region, there are 3 cases to handle across
+ * two configurations (SPARSEMEM_VMEMMAP={y,n}):
+ *
+ * 1. deactivation of a partial hot-added section (only possible in
+ *    the SPARSEMEM_VMEMMAP=y case).
+ *      a) section was present at memory init.
+ *      b) section was hot-added post memory init.
+ * 2. deactivation of a complete hot-added section.
+ * 3. deactivation of a complete section from memory init.
+ *
+ * For 1, when subsection_map does not empty we will not be freeing the
+ * usage map, but still need to free the vmemmap range.
+ *
+ * For 2 and 3, the SPARSEMEM_VMEMMAP={y,n} cases are unified
+ */
 static void section_deactivate(unsigned long pfn, unsigned long nr_pages,
 		struct vmem_altmap *altmap)
 {

@@ -784,23 +800,6 @@ static void section_deactivate(unsigned long pfn, unsigned long nr_pages,
 		return;
 
 	empty = is_subsection_map_empty(ms);
-	/*
-	 * There are 3 cases to handle across two configurations
-	 * (SPARSEMEM_VMEMMAP={y,n}):
-	 *
-	 * 1/ deactivation of a partial hot-added section (only possible
-	 * in the SPARSEMEM_VMEMMAP=y case).
-	 *    a/ section was present at memory init
-	 *    b/ section was hot-added post memory init
-	 * 2/ deactivation of a complete hot-added section
-	 * 3/ deactivation of a complete section from memory init
-	 *
-	 * For 1/, when subsection_map does not empty we will not be
-	 * freeing the usage map, but still need to free the vmemmap
-	 * range.
-	 *
-	 * For 2/ and 3/ the SPARSEMEM_VMEMMAP={y,n} cases are unified
-	 */
 	if (empty) {
 		unsigned long section_nr = pfn_to_section_nr(pfn);
 

@@ -907,6 +906,10 @@ static struct page * __meminit section_activate(int nid, unsigned long pfn,
  *
  * This is only intended for hotplug.
  *
+ * Note that only VMEMMAP supports sub-section aligned hotplug,
+ * the proper alignment and size are gated by check_pfn_span().
+ *
+ *
  * Return:
  * * 0		- On success.
  * * -EEXIST	- Section has been present.
Signature · 1 line
2.17.2
Signature · 2 lines
Michal Hocko
SUSE Labs
author
#21 lore raw

Re: [PATCH v3 5/7] mm/sparse.c: add note about only VMEMMAP supporting sub-section support

Quoted 8 lines · Michal Hocko
Quoted 7 lines · Baoquan He

And tell check_pfn_span() gating the porper alignment and size of hot added memory region.

And also move the code comments from inside section_deactivate() to being above it. The code comments are reasonable for the whole function, and the moving makes code cleaner.

Quoted 7 lines
Quoted 1 line
Signed-off-by Baoquan He <[email protected]>
Acked-by Michal Hocko <[email protected]>

I have glanced through other patches and they seem sane but I do not have time to go deeper to give an ack. I like this one though because it really makes the intention clearer.

Thanks for your reviewing and providing ack on this patch.

I will post a new version to rebase on the top of patch 1 and its appended fix, then address those concerns from David.

author
#22 lore raw

PATCH v3 6/7 mm/sparse.c: move subsection_map related codes together

In reply to Baoquan He

No functional change.

Signed-off-by Baoquan He <[email protected]>
---
 mm/sparse.c | 134 +++++++++++++++++++++++++---------------------------
 1 file changed, 65 insertions(+), 69 deletions(-)
mm/sparse.c +65 -69
index 0fbd79c4ad81..fde651ab8741 100644
@@ -244,10 +244,75 @@ void __init subsection_map_init(unsigned long pfn, unsigned long nr_pages)
 		nr_pages -= pfns;
 	}
 }
+
+static int clear_subsection_map(unsigned long pfn, unsigned long nr_pages)
+{
+	DECLARE_BITMAP(map, SUBSECTIONS_PER_SECTION) = { 0 };
+	DECLARE_BITMAP(tmp, SUBSECTIONS_PER_SECTION) = { 0 };
+	struct mem_section *ms = __pfn_to_section(pfn);
+	unsigned long *subsection_map = ms->usage
+		? &ms->usage->subsection_map[0] : NULL;
+
+	subsection_mask_set(map, pfn, nr_pages);
+	if (subsection_map)
+		bitmap_and(tmp, map, subsection_map, SUBSECTIONS_PER_SECTION);
+
+	if (WARN(!subsection_map || !bitmap_equal(tmp, map, SUBSECTIONS_PER_SECTION),
+				"section already deactivated (%#lx + %ld)\n",
+				pfn, nr_pages))
+		return -EINVAL;
+
+	bitmap_xor(subsection_map, map, subsection_map, SUBSECTIONS_PER_SECTION);
+
+	return 0;
+}
+
+static bool is_subsection_map_empty(struct mem_section *ms)
+{
+	return bitmap_empty(&ms->usage->subsection_map[0],
+			    SUBSECTIONS_PER_SECTION);
+}
+
+static int fill_subsection_map(unsigned long pfn, unsigned long nr_pages)
+{
+	struct mem_section *ms = __pfn_to_section(pfn);
+	DECLARE_BITMAP(map, SUBSECTIONS_PER_SECTION) = { 0 };
+	unsigned long *subsection_map;
+	int rc = 0;
+
+	subsection_mask_set(map, pfn, nr_pages);
+
+	subsection_map = &ms->usage->subsection_map[0];
+
+	if (bitmap_empty(map, SUBSECTIONS_PER_SECTION))
+		rc = -EINVAL;
+	else if (bitmap_intersects(map, subsection_map, SUBSECTIONS_PER_SECTION))
+		rc = -EEXIST;
+	else
+		bitmap_or(subsection_map, map, subsection_map,
+				SUBSECTIONS_PER_SECTION);
+
+	return rc;
+}
 #else
 void __init subsection_map_init(unsigned long pfn, unsigned long nr_pages)
 {
 }
+
+static int clear_subsection_map(unsigned long pfn, unsigned long nr_pages)
+{
+	return 0;
+}
+
+static bool is_subsection_map_empty(struct mem_section *ms)
+{
+	return true;
+}
+
+static int fill_subsection_map(unsigned long pfn, unsigned long nr_pages)
+{
+	return 0;
+}
 #endif
 
 /* Record a memory area against a node. */

@@ -732,46 +797,6 @@ static void free_map_bootmem(struct page *memmap)
 }
 #endif /* CONFIG_SPARSEMEM_VMEMMAP */
 
-#ifdef CONFIG_SPARSEMEM_VMEMMAP
-static int clear_subsection_map(unsigned long pfn, unsigned long nr_pages)
-{
-	DECLARE_BITMAP(map, SUBSECTIONS_PER_SECTION) = { 0 };
-	DECLARE_BITMAP(tmp, SUBSECTIONS_PER_SECTION) = { 0 };
-	struct mem_section *ms = __pfn_to_section(pfn);
-	unsigned long *subsection_map = ms->usage
-		? &ms->usage->subsection_map[0] : NULL;
-
-	subsection_mask_set(map, pfn, nr_pages);
-	if (subsection_map)
-		bitmap_and(tmp, map, subsection_map, SUBSECTIONS_PER_SECTION);
-
-	if (WARN(!subsection_map || !bitmap_equal(tmp, map, SUBSECTIONS_PER_SECTION),
-				"section already deactivated (%#lx + %ld)\n",
-				pfn, nr_pages))
-		return -EINVAL;
-
-	bitmap_xor(subsection_map, map, subsection_map, SUBSECTIONS_PER_SECTION);
-
-	return 0;
-}
-
-static bool is_subsection_map_empty(struct mem_section *ms)
-{
-	return bitmap_empty(&ms->usage->subsection_map[0],
-			    SUBSECTIONS_PER_SECTION);
-}
-#else
-static int clear_subsection_map(unsigned long pfn, unsigned long nr_pages)
-{
-	return 0;
-}
-
-static bool is_subsection_map_empty(struct mem_section *ms)
-{
-	return true;
-}
-#endif
-
 /*
  * To deactivate a memory region, there are 3 cases to handle across
  * two configurations (SPARSEMEM_VMEMMAP={y,n}):

@@ -826,35 +851,6 @@ static void section_deactivate(unsigned long pfn, unsigned long nr_pages,
 		ms->section_mem_map = (unsigned long)NULL;
 }
 
-#ifdef CONFIG_SPARSEMEM_VMEMMAP
-static int fill_subsection_map(unsigned long pfn, unsigned long nr_pages)
-{
-	struct mem_section *ms = __pfn_to_section(pfn);
-	DECLARE_BITMAP(map, SUBSECTIONS_PER_SECTION) = { 0 };
-	unsigned long *subsection_map;
-	int rc = 0;
-
-	subsection_mask_set(map, pfn, nr_pages);
-
-	subsection_map = &ms->usage->subsection_map[0];
-
-	if (bitmap_empty(map, SUBSECTIONS_PER_SECTION))
-		rc = -EINVAL;
-	else if (bitmap_intersects(map, subsection_map, SUBSECTIONS_PER_SECTION))
-		rc = -EEXIST;
-	else
-		bitmap_or(subsection_map, map, subsection_map,
-				SUBSECTIONS_PER_SECTION);
-
-	return rc;
-}
-#else
-static int fill_subsection_map(unsigned long pfn, unsigned long nr_pages)
-{
-	return 0;
-}
-#endif
-
 static struct page * __meminit section_activate(int nid, unsigned long pfn,
 		unsigned long nr_pages, struct vmem_altmap *altmap)
 {
Signature · 1 line
2.17.2
#23 lore raw

Re: [PATCH v3 6/7] mm/sparse.c: move subsection_map related codes together

Quoted 161 lines · Baoquan He

No functional change.

Signed-off-by Baoquan He <[email protected]>
---
 mm/sparse.c | 134 +++++++++++++++++++++++++---------------------------
 1 file changed, 65 insertions(+), 69 deletions(-)
mm/sparse.c +65 -62
index 0fbd79c4ad81..fde651ab8741 100644
@@ -244,10 +244,75 @@ void __init subsection_map_init(unsigned long pfn, unsigned long nr_pages)
 		nr_pages -= pfns;
 	}
 }
+
+static int clear_subsection_map(unsigned long pfn, unsigned long nr_pages)
+{
+	DECLARE_BITMAP(map, SUBSECTIONS_PER_SECTION) = { 0 };
+	DECLARE_BITMAP(tmp, SUBSECTIONS_PER_SECTION) = { 0 };
+	struct mem_section *ms = __pfn_to_section(pfn);
+	unsigned long *subsection_map = ms->usage
+		? &ms->usage->subsection_map[0] : NULL;
+
+	subsection_mask_set(map, pfn, nr_pages);
+	if (subsection_map)
+		bitmap_and(tmp, map, subsection_map, SUBSECTIONS_PER_SECTION);
+
+	if (WARN(!subsection_map || !bitmap_equal(tmp, map, SUBSECTIONS_PER_SECTION),
+				"section already deactivated (%#lx + %ld)\n",
+				pfn, nr_pages))
+		return -EINVAL;
+
+	bitmap_xor(subsection_map, map, subsection_map, SUBSECTIONS_PER_SECTION);
+
+	return 0;
+}
+
+static bool is_subsection_map_empty(struct mem_section *ms)
+{
+	return bitmap_empty(&ms->usage->subsection_map[0],
+			    SUBSECTIONS_PER_SECTION);
+}
+
+static int fill_subsection_map(unsigned long pfn, unsigned long nr_pages)
+{
+	struct mem_section *ms = __pfn_to_section(pfn);
+	DECLARE_BITMAP(map, SUBSECTIONS_PER_SECTION) = { 0 };
+	unsigned long *subsection_map;
+	int rc = 0;
+
+	subsection_mask_set(map, pfn, nr_pages);
+
+	subsection_map = &ms->usage->subsection_map[0];
+
+	if (bitmap_empty(map, SUBSECTIONS_PER_SECTION))
+		rc = -EINVAL;
+	else if (bitmap_intersects(map, subsection_map, SUBSECTIONS_PER_SECTION))
+		rc = -EEXIST;
+	else
+		bitmap_or(subsection_map, map, subsection_map,
+				SUBSECTIONS_PER_SECTION);
+
+	return rc;
+}
 #else
 void __init subsection_map_init(unsigned long pfn, unsigned long nr_pages)
 {
 }
+
+static int clear_subsection_map(unsigned long pfn, unsigned long nr_pages)
+{
+	return 0;
+}
+
+static bool is_subsection_map_empty(struct mem_section *ms)
+{
+	return true;
+}
+
+static int fill_subsection_map(unsigned long pfn, unsigned long nr_pages)
+{
+	return 0;
+}
 #endif
 
 /* Record a memory area against a node. */

@@ -732,46 +797,6 @@ static void free_map_bootmem(struct page *memmap)
 }
 #endif /* CONFIG_SPARSEMEM_VMEMMAP */
 
-#ifdef CONFIG_SPARSEMEM_VMEMMAP
-static int clear_subsection_map(unsigned long pfn, unsigned long nr_pages)
-{
-	DECLARE_BITMAP(map, SUBSECTIONS_PER_SECTION) = { 0 };
-	DECLARE_BITMAP(tmp, SUBSECTIONS_PER_SECTION) = { 0 };
-	struct mem_section *ms = __pfn_to_section(pfn);
-	unsigned long *subsection_map = ms->usage
-		? &ms->usage->subsection_map[0] : NULL;
-
-	subsection_mask_set(map, pfn, nr_pages);
-	if (subsection_map)
-		bitmap_and(tmp, map, subsection_map, SUBSECTIONS_PER_SECTION);
-
-	if (WARN(!subsection_map || !bitmap_equal(tmp, map, SUBSECTIONS_PER_SECTION),
-				"section already deactivated (%#lx + %ld)\n",
-				pfn, nr_pages))
-		return -EINVAL;
-
-	bitmap_xor(subsection_map, map, subsection_map, SUBSECTIONS_PER_SECTION);
-
-	return 0;
-}
-
-static bool is_subsection_map_empty(struct mem_section *ms)
-{
-	return bitmap_empty(&ms->usage->subsection_map[0],
-			    SUBSECTIONS_PER_SECTION);
-}
-#else
-static int clear_subsection_map(unsigned long pfn, unsigned long nr_pages)
-{
-	return 0;
-}
-
-static bool is_subsection_map_empty(struct mem_section *ms)
-{
-	return true;
-}
-#endif
-
 /*
  * To deactivate a memory region, there are 3 cases to handle across
  * two configurations (SPARSEMEM_VMEMMAP={y,n}):

@@ -826,35 +851,6 @@ static void section_deactivate(unsigned long pfn, unsigned long nr_pages,
 		ms->section_mem_map = (unsigned long)NULL;
 }
 
-#ifdef CONFIG_SPARSEMEM_VMEMMAP
-static int fill_subsection_map(unsigned long pfn, unsigned long nr_pages)
-{
-	struct mem_section *ms = __pfn_to_section(pfn);
-	DECLARE_BITMAP(map, SUBSECTIONS_PER_SECTION) = { 0 };
-	unsigned long *subsection_map;
-	int rc = 0;
-
-	subsection_mask_set(map, pfn, nr_pages);
-
-	subsection_map = &ms->usage->subsection_map[0];
-
-	if (bitmap_empty(map, SUBSECTIONS_PER_SECTION))
-		rc = -EINVAL;
-	else if (bitmap_intersects(map, subsection_map, SUBSECTIONS_PER_SECTION))
-		rc = -EEXIST;
-	else
-		bitmap_or(subsection_map, map, subsection_map,
-				SUBSECTIONS_PER_SECTION);
-
-	return rc;
-}

mm/sparse.c static void section_deactivate(unsigned long pfn, unsigned long nr_pages, · line 856

Quoted 10 lines
mm/sparse.c +0 -7
-#else
-static int fill_subsection_map(unsigned long pfn, unsigned long nr_pages)
-{
-	return 0;
-}
-#endif
-
 static struct page * __meminit section_activate(int nid, unsigned long pfn,
 		unsigned long nr_pages, struct vmem_altmap *altmap)
 {

IMHO, we don't need this patch - but just my personal opinion. Change itself looks good on a quick glance.

Signature · 3 lines
Thanks,

David / dhildenb
author
#24 lore raw

Re: [PATCH v3 6/7] mm/sparse.c: move subsection_map related codes together

Quoted 11 lines · David Hildenbrand
Quoted 6 lines · Baoquan He

No functional change.

Signed-off-by Baoquan He <[email protected]>
---
 mm/sparse.c | 134 +++++++++++++++++++++++++---------------------------
 1 file changed, 65 insertions(+), 69 deletions(-)

IMHO, we don't need this patch - but just my personal opinion. Change itself looks good on a quick glance.

I personally like seeing function set operating on one data structure being put together. To me, I use vi+ctags+cscope to jump to called funtion easily. When try to get a picture of a data and handling, e.g here the subsection map and the relevant functions, putting them together is better to understand code. I am also fine to discard this patch, no patch has dependency on this one in this series, it's easy to not pick it if no one like it.

author
#25 lore raw

PATCH v3 7/7 mm/sparse.c: Use __get_free_pages() instead in populate_section_memmap()

In reply to Baoquan He

This removes the unnecessary goto, and simplify codes.

Signed-off-by Baoquan He <[email protected]>
Reviewed-by Wei Yang <[email protected]>
---
 mm/sparse.c | 16 ++++++----------
 1 file changed, 6 insertions(+), 10 deletions(-)
mm/sparse.c +6 -10
index fde651ab8741..266f7f5040fb 100644
@@ -735,23 +735,19 @@ static void free_map_bootmem(struct page *memmap)
 struct page * __meminit populate_section_memmap(unsigned long pfn,
 		unsigned long nr_pages, int nid, struct vmem_altmap *altmap)
 {
-	struct page *page, *ret;
+	struct page *ret;
 	unsigned long memmap_size = sizeof(struct page) * PAGES_PER_SECTION;
 
-	page = alloc_pages(GFP_KERNEL|__GFP_NOWARN, get_order(memmap_size));
-	if (page)
-		goto got_map_page;
+	ret = (void*)__get_free_pages(GFP_KERNEL|__GFP_NOWARN,
+				get_order(memmap_size));
+	if (ret)
+		return ret;
 
 	ret = vmalloc(memmap_size);
 	if (ret)
-		goto got_map_ptr;
+		return ret;
 
 	return NULL;
-got_map_page:
-	ret = (struct page *)pfn_to_kaddr(page_to_pfn(page));
-got_map_ptr:
-
-	return ret;
 }
 
 static void depopulate_section_memmap(unsigned long pfn, unsigned long nr_pages,
Signature · 1 line
2.17.2
#26 lore raw

Re: [PATCH v3 7/7] mm/sparse.c: Use __get_free_pages() instead in populate_section_memmap()

Quoted 30 lines · Baoquan He

This removes the unnecessary goto, and simplify codes.

Signed-off-by Baoquan He <[email protected]>
Reviewed-by Wei Yang <[email protected]>
---
 mm/sparse.c | 16 ++++++----------
 1 file changed, 6 insertions(+), 10 deletions(-)
mm/sparse.c +5 -4
index fde651ab8741..266f7f5040fb 100644
@@ -735,23 +735,19 @@ static void free_map_bootmem(struct page *memmap)
 struct page * __meminit populate_section_memmap(unsigned long pfn,
 		unsigned long nr_pages, int nid, struct vmem_altmap *altmap)
 {
-	struct page *page, *ret;
+	struct page *ret;
 	unsigned long memmap_size = sizeof(struct page) * PAGES_PER_SECTION;
 
-	page = alloc_pages(GFP_KERNEL|__GFP_NOWARN, get_order(memmap_size));
-	if (page)
-		goto got_map_page;
+	ret = (void*)__get_free_pages(GFP_KERNEL|__GFP_NOWARN,
+				get_order(memmap_size));
+	if (ret)
+		return ret;
 
 	ret = vmalloc(memmap_size);
 	if (ret)

mm/sparse.c static void free_map_bootmem(struct page *memmap) · line 751

Quoted 10 lines
mm/sparse.c +1 -6
-		goto got_map_ptr;
+		return ret;
 
 	return NULL;
-got_map_page:
-	ret = (struct page *)pfn_to_kaddr(page_to_pfn(page));
-got_map_ptr:
-
-	return ret;
 }

Boy this code is ugly. Is there any reason we cannot simply use kvmalloc_array(PAGES_PER_SECTION, sizeof(struct page), GFP_KERNEL | __GFP_NOWARN)

And if we care about locality then go even one step further kvmalloc_node(PAGES_PER_SECTION * sizeof(struct page), GFP_KERNEL | __GFP_NOWARN, nid)

Signature · 2 lines
Michal Hocko
SUSE Labs
#27 lore raw

Re: [PATCH v3 7/7] mm/sparse.c: Use __get_free_pages() instead in populate_section_memmap()

Quoted 45 lines · Michal Hocko
Quoted 30 lines · Baoquan He

This removes the unnecessary goto, and simplify codes.

Signed-off-by Baoquan He <[email protected]>
Reviewed-by Wei Yang <[email protected]>
---
 mm/sparse.c | 16 ++++++----------
 1 file changed, 6 insertions(+), 10 deletions(-)
mm/sparse.c +5 -4
index fde651ab8741..266f7f5040fb 100644
@@ -735,23 +735,19 @@ static void free_map_bootmem(struct page *memmap)
 struct page * __meminit populate_section_memmap(unsigned long pfn,
 		unsigned long nr_pages, int nid, struct vmem_altmap *altmap)
 {
-	struct page *page, *ret;
+	struct page *ret;
 	unsigned long memmap_size = sizeof(struct page) * PAGES_PER_SECTION;
 
-	page = alloc_pages(GFP_KERNEL|__GFP_NOWARN, get_order(memmap_size));
-	if (page)
-		goto got_map_page;
+	ret = (void*)__get_free_pages(GFP_KERNEL|__GFP_NOWARN,
+				get_order(memmap_size));
+	if (ret)
+		return ret;
 
 	ret = vmalloc(memmap_size);
 	if (ret)

mm/sparse.c static void free_map_bootmem(struct page *memmap) · line 751

Quoted 10 lines
mm/sparse.c +1 -6
-		goto got_map_ptr;
+		return ret;
 
 	return NULL;
-got_map_page:
-	ret = (struct page *)pfn_to_kaddr(page_to_pfn(page));
-got_map_ptr:
-
-	return ret;
 }

Boy this code is ugly. Is there any reason we cannot simply use kvmalloc_array(PAGES_PER_SECTION, sizeof(struct page), GFP_KERNEL | __GFP_NOWARN)

Quoted 3 lines

And if we care about locality then go even one step further kvmalloc_node(PAGES_PER_SECTION * sizeof(struct page), GFP_KERNEL | __GFP_NOWARN, nid)

Makes perfect sense to me.

Signature · 3 lines
Thanks,

David / dhildenb
author
#28 lore raw

Re: [PATCH v3 7/7] mm/sparse.c: Use __get_free_pages() instead in populate_section_memmap()

In reply to Michal Hocko
Quoted 45 lines · Michal Hocko
Quoted 30 lines · Baoquan He

This removes the unnecessary goto, and simplify codes.

Signed-off-by Baoquan He <[email protected]>
Reviewed-by Wei Yang <[email protected]>
---
 mm/sparse.c | 16 ++++++----------
 1 file changed, 6 insertions(+), 10 deletions(-)
mm/sparse.c +5 -4
index fde651ab8741..266f7f5040fb 100644
@@ -735,23 +735,19 @@ static void free_map_bootmem(struct page *memmap)
 struct page * __meminit populate_section_memmap(unsigned long pfn,
 		unsigned long nr_pages, int nid, struct vmem_altmap *altmap)
 {
-	struct page *page, *ret;
+	struct page *ret;
 	unsigned long memmap_size = sizeof(struct page) * PAGES_PER_SECTION;
 
-	page = alloc_pages(GFP_KERNEL|__GFP_NOWARN, get_order(memmap_size));
-	if (page)
-		goto got_map_page;
+	ret = (void*)__get_free_pages(GFP_KERNEL|__GFP_NOWARN,
+				get_order(memmap_size));
+	if (ret)
+		return ret;
 
 	ret = vmalloc(memmap_size);
 	if (ret)

mm/sparse.c static void free_map_bootmem(struct page *memmap) · line 751

Quoted 10 lines
mm/sparse.c +1 -6
-		goto got_map_ptr;
+		return ret;
 
 	return NULL;
-got_map_page:
-	ret = (struct page *)pfn_to_kaddr(page_to_pfn(page));
-got_map_ptr:
-
-	return ret;
 }

Boy this code is ugly. Is there any reason we cannot simply use kvmalloc_array(PAGES_PER_SECTION, sizeof(struct page), GFP_KERNEL | __GFP_NOWARN)

Quoted 2 lines

And if we care about locality then go even one step further kvmalloc_node(PAGES_PER_SECTION * sizeof(struct page), GFP_KERNEL | __GFP_NOWARN, nid)

Yes, this looks better. I will use this to make a new version. Thanks.