Patch 1 adds the missing lock in memory hotplug operations,
ensuring that the mem_hotplug_lock is held during critical operations
like mhp_init_memmap_on_memory() and mhp_deinit_memmap_on_memory()
Patch 2 deals with error handling in add_memory_resource() and considers
the possibility of altmap support. This ensures proper deallocation of
struct pages, aligning with the allocation strategy.
Patch 3 relocates the vmem_altmap code to sparse-vmemmap.c, enabling the
utilization of vmem_altmap_free() and vmem_altmap_offset() without the
dependency on CONFIG_ZONE_DEVICE.
v3:
* added Acked-by in patch 3.
* added cc: [email protected] to commit messages (both patch 1 and
patch 2), as reported by patch-bot.
v2:
* cc: [email protected]
* make vmem_altmap_offset()/vmem_altmap_free() inline.
* added Acked-by for patch 1 and patch 2.
v1:
Changes since patch series "implement "memmap on memory" feature on
s390":
Feedback from David:
Patch 1:
* Fixed subject for memory hotplug lock.
* Added locking comments before
memory_block_online()/memory_block_offline().
Patch 2:
* Fixed Fixes-by commit.
lkp report:
Patch 3:
* when CONFIG_SPARSEMEM_VMEMMAP is disabled, resolve
undefined reference to `vmem_altmap_offset' error.
* Request for Reviewed-by once again due to the change in patch3.
Thank you
Sumanth Korikkar (3):
mm/memory_hotplug: add missing mem_hotplug_lock
mm/memory_hotplug: fix error handling in add_memory_resource()
mm: use vmem_altmap code without CONFIG_ZONE_DEVICE
drivers/base/memory.c | 18 +++++++++++++++---
include/linux/memremap.h | 12 ------------
include/linux/mm.h | 26 ++++++++++++++++++++++++++
mm/memory_hotplug.c | 15 +++++++--------
mm/memremap.c | 14 +-------------
5 files changed, 49 insertions(+), 36 deletions(-)
--
2.41.0
vmem_altmap_free() and vmem_altmap_offset() could be utlized without
CONFIG_ZONE_DEVICE enabled. For example,
mm/memory_hotplug.c:__add_pages() relies on that. The altmap is no
longer restricted to ZONE_DEVICE handling, but instead depends on
CONFIG_SPARSEMEM_VMEMMAP.
When CONFIG_SPARSEMEM_VMEMMAP is disabled, these functions are defined
as inline stubs, ensuring compatibility with configurations that do not
use sparsemem vmemmap. Without it, lkp reported the following:
ld: arch/x86/mm/init_64.o: in function `remove_pagetable':
init_64.c:(.meminit.text+0xfc7): undefined reference to
`vmem_altmap_free'
Reported-by: kernel test robot <[email protected]>
Closes: https://lore.kernel.org/oe-kbuild-all/[email protected]/
Reviewed-by: Gerald Schaefer <[email protected]>
Acked-by: David Hildenbrand <[email protected]>
Signed-off-by: Sumanth Korikkar <[email protected]>
---
include/linux/memremap.h | 12 ------------
include/linux/mm.h | 26 ++++++++++++++++++++++++++
mm/memremap.c | 14 +-------------
3 files changed, 27 insertions(+), 25 deletions(-)
diff --git a/include/linux/memremap.h b/include/linux/memremap.h
index 1314d9c5f05b..744c830f4b13 100644
--- a/include/linux/memremap.h
+++ b/include/linux/memremap.h
@@ -196,8 +196,6 @@ struct dev_pagemap *get_dev_pagemap(unsigned long pfn,
struct dev_pagemap *pgmap);
bool pgmap_pfn_valid(struct dev_pagemap *pgmap, unsigned long pfn);
-unsigned long vmem_altmap_offset(struct vmem_altmap *altmap);
-void vmem_altmap_free(struct vmem_altmap *altmap, unsigned long nr_pfns);
unsigned long memremap_compat_align(void);
#else
static inline void *devm_memremap_pages(struct device *dev,
@@ -228,16 +226,6 @@ static inline bool pgmap_pfn_valid(struct dev_pagemap *pgmap, unsigned long pfn)
return false;
}
-static inline unsigned long vmem_altmap_offset(struct vmem_altmap *altmap)
-{
- return 0;
-}
-
-static inline void vmem_altmap_free(struct vmem_altmap *altmap,
- unsigned long nr_pfns)
-{
-}
-
/* when memremap_pages() is disabled all archs can remap a single page */
static inline unsigned long memremap_compat_align(void)
{
diff --git a/include/linux/mm.h b/include/linux/mm.h
index bf5d0b1b16f4..f2344fd8acbe 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -3786,6 +3786,32 @@ void vmemmap_free(unsigned long start, unsigned long end,
struct vmem_altmap *altmap);
#endif
+#ifdef CONFIG_SPARSEMEM_VMEMMAP
+static inline unsigned long vmem_altmap_offset(struct vmem_altmap *altmap)
+{
+ /* number of pfns from base where pfn_to_page() is valid */
+ if (altmap)
+ return altmap->reserve + altmap->free;
+ return 0;
+}
+
+static inline void vmem_altmap_free(struct vmem_altmap *altmap,
+ unsigned long nr_pfns)
+{
+ altmap->alloc -= nr_pfns;
+}
+#else
+static inline unsigned long vmem_altmap_offset(struct vmem_altmap *altmap)
+{
+ return 0;
+}
+
+static inline void vmem_altmap_free(struct vmem_altmap *altmap,
+ unsigned long nr_pfns)
+{
+}
+#endif
+
#define VMEMMAP_RESERVE_NR 2
#ifdef CONFIG_ARCH_WANT_OPTIMIZE_DAX_VMEMMAP
static inline bool __vmemmap_can_optimize(struct vmem_altmap *altmap,
diff --git a/mm/memremap.c b/mm/memremap.c
index bee85560a243..9531faa92a7c 100644
--- a/mm/memremap.c
+++ b/mm/memremap.c
@@ -7,6 +7,7 @@
#include <linux/memremap.h>
#include <linux/pfn_t.h>
#include <linux/swap.h>
+#include <linux/mm.h>
#include <linux/mmzone.h>
#include <linux/swapops.h>
#include <linux/types.h>
@@ -422,19 +423,6 @@ void devm_memunmap_pages(struct device *dev, struct dev_pagemap *pgmap)
}
EXPORT_SYMBOL_GPL(devm_memunmap_pages);
-unsigned long vmem_altmap_offset(struct vmem_altmap *altmap)
-{
- /* number of pfns from base where pfn_to_page() is valid */
- if (altmap)
- return altmap->reserve + altmap->free;
- return 0;
-}
-
-void vmem_altmap_free(struct vmem_altmap *altmap, unsigned long nr_pfns)
-{
- altmap->alloc -= nr_pfns;
-}
-
/**
* get_dev_pagemap() - take a new live reference on the dev_pagemap for @pfn
* @pfn: page frame number to lookup page_map
--
2.41.0
From Documentation/core-api/memory-hotplug.rst:
When adding/removing/onlining/offlining memory or adding/removing
heterogeneous/device memory, we should always hold the mem_hotplug_lock
in write mode to serialise memory hotplug (e.g. access to global/zone
variables).
mhp_(de)init_memmap_on_memory() functions can change zone stats and
struct page content, but they are currently called w/o the
mem_hotplug_lock.
When memory block is being offlined and when kmemleak goes through each
populated zone, the following theoretical race conditions could occur:
CPU 0: | CPU 1:
memory_offline() |
-> offline_pages() |
-> mem_hotplug_begin() |
... |
-> mem_hotplug_done() |
| kmemleak_scan()
| -> get_online_mems()
| ...
-> mhp_deinit_memmap_on_memory() |
[not protected by mem_hotplug_begin/done()]|
Marks memory section as offline, | Retrieves zone_start_pfn
poisons vmemmap struct pages and updates | and struct page members.
the zone related data |
| ...
| -> put_online_mems()
Fix this by ensuring mem_hotplug_lock is taken before performing
mhp_init_memmap_on_memory(). Also ensure that
mhp_deinit_memmap_on_memory() holds the lock.
online/offline_pages() are currently only called from
memory_block_online/offline(), so it is safe to move the locking there.
Fixes: a08a2ae34613 ("mm,memory_hotplug: allocate memmap from the added memory range")
Cc: [email protected] # 5.15+
Reviewed-by: Gerald Schaefer <[email protected]>
Acked-by: David Hildenbrand <[email protected]>
Signed-off-by: Sumanth Korikkar <[email protected]>
---
drivers/base/memory.c | 18 +++++++++++++++---
mm/memory_hotplug.c | 13 ++++++-------
2 files changed, 21 insertions(+), 10 deletions(-)
diff --git a/drivers/base/memory.c b/drivers/base/memory.c
index f3b9a4d0fa3b..8a13babd826c 100644
--- a/drivers/base/memory.c
+++ b/drivers/base/memory.c
@@ -180,6 +180,9 @@ static inline unsigned long memblk_nr_poison(struct memory_block *mem)
}
#endif
+/*
+ * Must acquire mem_hotplug_lock in write mode.
+ */
static int memory_block_online(struct memory_block *mem)
{
unsigned long start_pfn = section_nr_to_pfn(mem->start_section_nr);
@@ -204,10 +207,11 @@ static int memory_block_online(struct memory_block *mem)
if (mem->altmap)
nr_vmemmap_pages = mem->altmap->free;
+ mem_hotplug_begin();
if (nr_vmemmap_pages) {
ret = mhp_init_memmap_on_memory(start_pfn, nr_vmemmap_pages, zone);
if (ret)
- return ret;
+ goto out;
}
ret = online_pages(start_pfn + nr_vmemmap_pages,
@@ -215,7 +219,7 @@ static int memory_block_online(struct memory_block *mem)
if (ret) {
if (nr_vmemmap_pages)
mhp_deinit_memmap_on_memory(start_pfn, nr_vmemmap_pages);
- return ret;
+ goto out;
}
/*
@@ -227,9 +231,14 @@ static int memory_block_online(struct memory_block *mem)
nr_vmemmap_pages);
mem->zone = zone;
+out:
+ mem_hotplug_done();
return ret;
}
+/*
+ * Must acquire mem_hotplug_lock in write mode.
+ */
static int memory_block_offline(struct memory_block *mem)
{
unsigned long start_pfn = section_nr_to_pfn(mem->start_section_nr);
@@ -247,6 +256,7 @@ static int memory_block_offline(struct memory_block *mem)
if (mem->altmap)
nr_vmemmap_pages = mem->altmap->free;
+ mem_hotplug_begin();
if (nr_vmemmap_pages)
adjust_present_page_count(pfn_to_page(start_pfn), mem->group,
-nr_vmemmap_pages);
@@ -258,13 +268,15 @@ static int memory_block_offline(struct memory_block *mem)
if (nr_vmemmap_pages)
adjust_present_page_count(pfn_to_page(start_pfn),
mem->group, nr_vmemmap_pages);
- return ret;
+ goto out;
}
if (nr_vmemmap_pages)
mhp_deinit_memmap_on_memory(start_pfn, nr_vmemmap_pages);
mem->zone = NULL;
+out:
+ mem_hotplug_done();
return ret;
}
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 1b03f4ec6fd2..c8238fc5edcb 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -1129,6 +1129,9 @@ void mhp_deinit_memmap_on_memory(unsigned long pfn, unsigned long nr_pages)
kasan_remove_zero_shadow(__va(PFN_PHYS(pfn)), PFN_PHYS(nr_pages));
}
+/*
+ * Must be called with mem_hotplug_lock in write mode.
+ */
int __ref online_pages(unsigned long pfn, unsigned long nr_pages,
struct zone *zone, struct memory_group *group)
{
@@ -1149,7 +1152,6 @@ int __ref online_pages(unsigned long pfn, unsigned long nr_pages,
!IS_ALIGNED(pfn + nr_pages, PAGES_PER_SECTION)))
return -EINVAL;
- mem_hotplug_begin();
/* associate pfn range with the zone */
move_pfn_range_to_zone(zone, pfn, nr_pages, NULL, MIGRATE_ISOLATE);
@@ -1208,7 +1210,6 @@ int __ref online_pages(unsigned long pfn, unsigned long nr_pages,
writeback_set_ratelimit();
memory_notify(MEM_ONLINE, &arg);
- mem_hotplug_done();
return 0;
failed_addition:
@@ -1217,7 +1218,6 @@ int __ref online_pages(unsigned long pfn, unsigned long nr_pages,
(((unsigned long long) pfn + nr_pages) << PAGE_SHIFT) - 1);
memory_notify(MEM_CANCEL_ONLINE, &arg);
remove_pfn_range_from_zone(zone, pfn, nr_pages);
- mem_hotplug_done();
return ret;
}
@@ -1863,6 +1863,9 @@ static int count_system_ram_pages_cb(unsigned long start_pfn,
return 0;
}
+/*
+ * Must be called with mem_hotplug_lock in write mode.
+ */
int __ref offline_pages(unsigned long start_pfn, unsigned long nr_pages,
struct zone *zone, struct memory_group *group)
{
@@ -1885,8 +1888,6 @@ int __ref offline_pages(unsigned long start_pfn, unsigned long nr_pages,
!IS_ALIGNED(start_pfn + nr_pages, PAGES_PER_SECTION)))
return -EINVAL;
- mem_hotplug_begin();
-
/*
* Don't allow to offline memory blocks that contain holes.
* Consequently, memory blocks with holes can never get onlined
@@ -2027,7 +2028,6 @@ int __ref offline_pages(unsigned long start_pfn, unsigned long nr_pages,
memory_notify(MEM_OFFLINE, &arg);
remove_pfn_range_from_zone(zone, start_pfn, nr_pages);
- mem_hotplug_done();
return 0;
failed_removal_isolated:
@@ -2042,7 +2042,6 @@ int __ref offline_pages(unsigned long start_pfn, unsigned long nr_pages,
(unsigned long long) start_pfn << PAGE_SHIFT,
((unsigned long long) end_pfn << PAGE_SHIFT) - 1,
reason);
- mem_hotplug_done();
return ret;
}
--
2.41.0
In add_memory_resource(), creation of memory block devices occurs after
successful call to arch_add_memory(). However, creation of memory block
devices could fail. In that case, arch_remove_memory() is called to
perform necessary cleanup.
Currently with or without altmap support, arch_remove_memory() is always
passed with altmap set to NULL during error handling. This leads to
freeing of struct pages using free_pages(), eventhough the allocation
might have been performed with altmap support via
altmap_alloc_block_buf().
Fix the error handling by passing altmap in arch_remove_memory(). This
ensures the following:
* When altmap is disabled, deallocation of the struct pages array occurs
via free_pages().
* When altmap is enabled, deallocation occurs via vmem_altmap_free().
Fixes: a08a2ae34613 ("mm,memory_hotplug: allocate memmap from the added memory range")
Cc: [email protected] # 5.15+
Reviewed-by: Gerald Schaefer <[email protected]>
Acked-by: David Hildenbrand <[email protected]>
Signed-off-by: Sumanth Korikkar <[email protected]>
---
mm/memory_hotplug.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index c8238fc5edcb..4f476a970e84 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -1458,7 +1458,7 @@ int __ref add_memory_resource(int nid, struct resource *res, mhp_t mhp_flags)
/* create memory block devices after memory was added */
ret = create_memory_block_devices(start, size, params.altmap, group);
if (ret) {
- arch_remove_memory(start, size, NULL);
+ arch_remove_memory(start, size, params.altmap);
goto error_free;
}
--
2.41.0