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mm: hugetlb_vmemmap: move PageVmemmapSelfHosted() check to split_vmemmap_huge_pmd()

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To check a page whether it is self-hosted needs to traverse the page table
(e.g.  pmd_off_k()), however, we already have done this in the next
calling of vmemmap_remap_range().  Moving PageVmemmapSelfHosted() check to
vmemmap_pmd_entry() could simplify the code a bit.

Link: https://lkml.kernel.org/r/20231127084645.27017-4-songmuchun@bytedance.com
Signed-off-by: Muchun Song <songmuchun@bytedance.com>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Kefeng Wang <wangkefeng.wang@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Muchun Song 2023-11-27 16:46:44 +08:00 committed by Andrew Morton
parent fb93ed6334
commit be035a2acf
1 changed files with 24 additions and 46 deletions
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70
mm/hugetlb_vmemmap.c
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@ -95,6 +95,7 @@ static int vmemmap_split_pmd(pmd_t *pmd, struct page *head, unsigned long start,
static int vmemmap_pmd_entry(pmd_t *pmd, unsigned long addr, static int vmemmap_pmd_entry(pmd_t *pmd, unsigned long addr,
unsigned long next, struct mm_walk *walk) unsigned long next, struct mm_walk *walk)
{ {
int ret = 0;
struct page *head; struct page *head;
struct vmemmap_remap_walk *vmemmap_walk = walk->private; struct vmemmap_remap_walk *vmemmap_walk = walk->private;
@ -104,9 +105,30 @@ static int vmemmap_pmd_entry(pmd_t *pmd, unsigned long addr,
spin_lock(&init_mm.page_table_lock); spin_lock(&init_mm.page_table_lock);
head = pmd_leaf(*pmd) ? pmd_page(*pmd) : NULL; head = pmd_leaf(*pmd) ? pmd_page(*pmd) : NULL;
/*
* Due to HugeTLB alignment requirements and the vmemmap
* pages being at the start of the hotplugged memory
* region in memory_hotplug.memmap_on_memory case. Checking
* the vmemmap page associated with the first vmemmap page
* if it is self-hosted is sufficient.
*
* [ hotplugged memory ]
* [ section ][...][ section ]
* [ vmemmap ][ usable memory ]
* ^ | ^ |
* +--+ | |
* +------------------------+
*/
if (unlikely(!vmemmap_walk->nr_walked)) {
struct page *page = head ? head + pte_index(addr) :
pte_page(ptep_get(pte_offset_kernel(pmd, addr)));
if (PageVmemmapSelfHosted(page))
ret = -ENOTSUPP;
}
spin_unlock(&init_mm.page_table_lock); spin_unlock(&init_mm.page_table_lock);
if (!head) if (!head || ret)
return 0; return ret;
return vmemmap_split_pmd(pmd, head, addr & PMD_MASK, vmemmap_walk); return vmemmap_split_pmd(pmd, head, addr & PMD_MASK, vmemmap_walk);
} }
@ -524,50 +546,6 @@ static bool vmemmap_should_optimize(const struct hstate *h, const struct page *h
if (!hugetlb_vmemmap_optimizable(h)) if (!hugetlb_vmemmap_optimizable(h))
return false; return false;
if (IS_ENABLED(CONFIG_MEMORY_HOTPLUG)) {
pmd_t *pmdp, pmd;
struct page *vmemmap_page;
unsigned long vaddr = (unsigned long)head;
/*
* Only the vmemmap page's vmemmap page can be self-hosted.
* Walking the page tables to find the backing page of the
* vmemmap page.
*/
pmdp = pmd_off_k(vaddr);
/*
* The READ_ONCE() is used to stabilize *pmdp in a register or
* on the stack so that it will stop changing under the code.
* The only concurrent operation where it can be changed is
* split_vmemmap_huge_pmd() (*pmdp will be stable after this
* operation).
*/
pmd = READ_ONCE(*pmdp);
if (pmd_leaf(pmd))
vmemmap_page = pmd_page(pmd) + pte_index(vaddr);
else
vmemmap_page = pte_page(*pte_offset_kernel(pmdp, vaddr));
/*
* Due to HugeTLB alignment requirements and the vmemmap pages
* being at the start of the hotplugged memory region in
* memory_hotplug.memmap_on_memory case. Checking any vmemmap
* page's vmemmap page if it is marked as VmemmapSelfHosted is
* sufficient.
*
* [ hotplugged memory ]
* [ section ][...][ section ]
* [ vmemmap ][ usable memory ]
* ^ | | |
* +---+ | |
* ^ | |
* +-------+ |
* ^ |
* +-------------------------------------------+
*/
if (PageVmemmapSelfHosted(vmemmap_page))
return false;
}
return true; return true;
} }