[PATCH v5 6/7] mm/hotplug: Embed vmem_altmap details in memory block
Aneesh Kumar K.V
aneesh.kumar at linux.ibm.com
Wed Jul 26 20:31:35 AEST 2023
David Hildenbrand <david at redhat.com> writes:
> On 25.07.23 12:02, Aneesh Kumar K.V wrote:
>> With memmap on memory, some architecture needs more details w.r.t altmap
>> such as base_pfn, end_pfn, etc to unmap vmemmap memory. Instead of
>> computing them again when we remove a memory block, embed vmem_altmap
>> details in struct memory_block if we are using memmap on memory block
>> feature.
>>
>> No functional change in this patch
>>
>> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar at linux.ibm.com>
>> ---
>
> [...]
>
>>
>> static int add_memory_block(unsigned long block_id, unsigned long state,
>> - unsigned long nr_vmemmap_pages,
>> + struct vmem_altmap *altmap,
>> struct memory_group *group)
>> {
>> struct memory_block *mem;
>> @@ -744,7 +751,14 @@ static int add_memory_block(unsigned long block_id, unsigned long state,
>> mem->start_section_nr = block_id * sections_per_block;
>> mem->state = state;
>> mem->nid = NUMA_NO_NODE;
>> - mem->nr_vmemmap_pages = nr_vmemmap_pages;
>> + if (altmap) {
>> + mem->altmap = kmalloc(sizeof(struct vmem_altmap), GFP_KERNEL);
>> + if (!mem->altmap) {
>> + kfree(mem);
>> + return -ENOMEM;
>> + }
>> + memcpy(mem->altmap, altmap, sizeof(*altmap));
>> + }
>
> I'm wondering if we should instead let the caller do the alloc/free. So we would alloc
> int the caller and would only store the pointer.
>
> Before removing the memory block, we would clear the pointer and free it in the caller.
>
> IOW, when removing a memory block and we still have an altmap set, something would be wrong.
>
> See below on try_remove_memory() handling.
>
> [...]
>
>> -static int get_nr_vmemmap_pages_cb(struct memory_block *mem, void *arg)
>> +static int get_vmemmap_altmap_cb(struct memory_block *mem, void *arg)
>> {
>> + struct vmem_altmap *altmap = (struct vmem_altmap *)arg;
>> /*
>> - * If not set, continue with the next block.
>> + * If we have any pages allocated from altmap
>> + * return the altmap details and break callback.
>> */
>> - return mem->nr_vmemmap_pages;
>> + if (mem->altmap) {
>> + memcpy(altmap, mem->altmap, sizeof(struct vmem_altmap));
>> + return 1;
>> + }
>> + return 0;
>> }
>>
>> static int check_cpu_on_node(int nid)
>> @@ -2146,9 +2152,8 @@ EXPORT_SYMBOL(try_offline_node);
>>
>> static int __ref try_remove_memory(u64 start, u64 size)
>> {
>> - struct vmem_altmap mhp_altmap = {};
>> - struct vmem_altmap *altmap = NULL;
>> - unsigned long nr_vmemmap_pages;
>> + int ret;
>> + struct vmem_altmap mhp_altmap, *altmap = NULL;
>> int rc = 0, nid = NUMA_NO_NODE;
>>
>> BUG_ON(check_hotplug_memory_range(start, size));
>> @@ -2171,24 +2176,15 @@ static int __ref try_remove_memory(u64 start, u64 size)
>> * the same granularity it was added - a single memory block.
>> */
>> if (mhp_memmap_on_memory()) {
>> - nr_vmemmap_pages = walk_memory_blocks(start, size, NULL,
>> - get_nr_vmemmap_pages_cb);
>> - if (nr_vmemmap_pages) {
>> + ret = walk_memory_blocks(start, size, &mhp_altmap,
>> + get_vmemmap_altmap_cb);
>> + if (ret) {
>> if (size != memory_block_size_bytes()) {
>> pr_warn("Refuse to remove %#llx - %#llx,"
>> "wrong granularity\n",
>> start, start + size);
>> return -EINVAL;
>> }
>> -
>> - /*
>> - * Let remove_pmd_table->free_hugepage_table do the
>> - * right thing if we used vmem_altmap when hot-adding
>> - * the range.
>> - */
>> - mhp_altmap.base_pfn = PHYS_PFN(start);
>> - mhp_altmap.free = nr_vmemmap_pages;
>> - mhp_altmap.alloc = nr_vmemmap_pages;
>> altmap = &mhp_altmap;
>> }
>
>
> Instead of that, I suggest (whitespace damage expected):
>
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index 3f231cf1b410..f6860df64549 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -1956,12 +1956,19 @@ static int check_memblock_offlined_cb(struct memory_block *mem, void *arg)
> return 0;
> }
>
> -static int get_nr_vmemmap_pages_cb(struct memory_block *mem, void *arg)
> +static int test_has_altmap_cb(struct memory_block *mem, void *arg)
> {
> - /*
> - * If not set, continue with the next block.
> - */
> - return mem->nr_vmemmap_pages;
> + struct memory_block **mem_ptr = (struct memory_block **)arg;
> +
> + if (mem->altmap) {
> + /*
> + * We're not taking a reference on the memory block; it
> + * it cannot vanish while we're about to that memory ourselves.
> + */
> + *mem_ptr = mem;
> + return 1;
> + }
> + return 0;
> }
>
> static int check_cpu_on_node(int nid)
> @@ -2036,9 +2043,7 @@ EXPORT_SYMBOL(try_offline_node);
>
> static int __ref try_remove_memory(u64 start, u64 size)
> {
> - struct vmem_altmap mhp_altmap = {};
> struct vmem_altmap *altmap = NULL;
> - unsigned long nr_vmemmap_pages;
> int rc = 0, nid = NUMA_NO_NODE;
>
> BUG_ON(check_hotplug_memory_range(start, size));
> @@ -2061,9 +2066,9 @@ static int __ref try_remove_memory(u64 start, u64 size)
> * the same granularity it was added - a single memory block.
> */
> if (mhp_memmap_on_memory()) {
> - nr_vmemmap_pages = walk_memory_blocks(start, size, NULL,
> - get_nr_vmemmap_pages_cb);
> - if (nr_vmemmap_pages) {
> + struct memory_block *mem;
> +
> + if (walk_memory_blocks(start, size, &mem, test_has_altmap_cb)) {
> if (size != memory_block_size_bytes()) {
> pr_warn("Refuse to remove %#llx - %#llx,"
> "wrong granularity\n",
> @@ -2072,12 +2077,11 @@ static int __ref try_remove_memory(u64 start, u64 size)
> }
>
> /*
> - * Let remove_pmd_table->free_hugepage_table do the
> - * right thing if we used vmem_altmap when hot-adding
> - * the range.
> + * Clear the altmap from the memory block before we
> + * remove it; we'll take care of freeing the altmap.
> */
> - mhp_altmap.alloc = nr_vmemmap_pages;
> - altmap = &mhp_altmap;
> + altmap = mem->altmap;
> + mem->altmap = NULL;
> }
> }
>
> @@ -2094,6 +2098,9 @@ static int __ref try_remove_memory(u64 start, u64 size)
>
> arch_remove_memory(start, size, altmap);
>
> + if (altmap)
> + kfree(altmap);
> +
> if (IS_ENABLED(CONFIG_ARCH_KEEP_MEMBLOCK)) {
> memblock_phys_free(start, size);
> memblock_remove(start, size);
>
Is this any better. Any specific reason we want the alloc and free in
the caller?
diff --git a/drivers/base/memory.c b/drivers/base/memory.c
index 0210ed7b7696..271cfdf8f6b6 100644
--- a/drivers/base/memory.c
+++ b/drivers/base/memory.c
@@ -106,7 +106,7 @@ static void memory_block_release(struct device *dev)
{
struct memory_block *mem = to_memory_block(dev);
- kfree(mem->altmap);
+ WARN_ON(mem->altmap);
kfree(mem);
}
@@ -751,14 +751,8 @@ static int add_memory_block(unsigned long block_id, unsigned long state,
mem->start_section_nr = block_id * sections_per_block;
mem->state = state;
mem->nid = NUMA_NO_NODE;
- if (altmap) {
- mem->altmap = kmalloc(sizeof(struct vmem_altmap), GFP_KERNEL);
- if (!mem->altmap) {
- kfree(mem);
- return -ENOMEM;
- }
- memcpy(mem->altmap, altmap, sizeof(*altmap));
- }
+ if (altmap)
+ mem->altmap = altmap;
INIT_LIST_HEAD(&mem->group_next);
#ifndef CONFIG_NUMA
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 2bad1bf0e9e3..1c7d88332e0e 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -1445,8 +1445,13 @@ int __ref add_memory_resource(int nid, struct resource *res, mhp_t mhp_flags)
*/
if (mhp_flags & MHP_MEMMAP_ON_MEMORY) {
if (mhp_supports_memmap_on_memory(size)) {
+
mhp_altmap.free = memory_block_memmap_on_memory_pages();
- params.altmap = &mhp_altmap;
+ params.altmap = kzalloc(sizeof(struct vmem_altmap), GFP_KERNEL);
+ if (!params.altmap)
+ goto error;
+
+ memcpy(params.altmap, &mhp_altmap, sizeof(mhp_altmap));
}
/* fallback to not using altmap */
}
@@ -2067,13 +2072,14 @@ static int check_memblock_offlined_cb(struct memory_block *mem, void *arg)
static int get_vmemmap_altmap_cb(struct memory_block *mem, void *arg)
{
- struct vmem_altmap *altmap = (struct vmem_altmap *)arg;
+ struct vmem_altmap **altmap = (struct vmem_altmap **)arg;
/*
* If we have any pages allocated from altmap
* return the altmap details and break callback.
*/
if (mem->altmap) {
- memcpy(altmap, mem->altmap, sizeof(struct vmem_altmap));
+ *altmap = mem->altmap;
+ mem->altmap = NULL;
return 1;
}
return 0;
@@ -2152,7 +2158,7 @@ EXPORT_SYMBOL(try_offline_node);
static int __ref try_remove_memory(u64 start, u64 size)
{
int ret;
- struct vmem_altmap mhp_altmap, *altmap = NULL;
+ struct vmem_altmap *altmap = NULL;
int rc = 0, nid = NUMA_NO_NODE;
BUG_ON(check_hotplug_memory_range(start, size));
@@ -2174,7 +2180,7 @@ static int __ref try_remove_memory(u64 start, u64 size)
* We only support removing memory added with MHP_MEMMAP_ON_MEMORY in
* the same granularity it was added - a single memory block.
*/
- ret = walk_memory_blocks(start, size, &mhp_altmap,
+ ret = walk_memory_blocks(start, size, &altmap,
get_vmemmap_altmap_cb);
if (ret) {
if (size != memory_block_size_bytes()) {
@@ -2183,7 +2189,6 @@ static int __ref try_remove_memory(u64 start, u64 size)
start, start + size);
return -EINVAL;
}
- altmap = &mhp_altmap;
}
/* remove memmap entry */
@@ -2203,8 +2208,10 @@ static int __ref try_remove_memory(u64 start, u64 size)
* Now that we are tracking alloc and free correctly
* we can add check to verify altmap free pages.
*/
- if (altmap)
+ if (altmap) {
WARN(altmap->alloc, "Altmap not fully unmapped");
+ kfree(altmap);
+ }
if (IS_ENABLED(CONFIG_ARCH_KEEP_MEMBLOCK)) {
memblock_phys_free(start, size);
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