2023-09-13 21:24:22

by Zi Yan

[permalink] [raw]

Subject: [PATCH v3 5/5] mips: use nth_page() in place of direct struct page manipulation.

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From: Zi Yan <[email protected]>

__flush_dcache_pages() is called during hugetlb migration via
migrate_pages() -> migrate_hugetlbs() -> unmap_and_move_huge_page()
-> move_to_new_folio() -> flush_dcache_folio(). And with hugetlb and
without sparsemem vmemmap, struct page is not guaranteed to be contiguous
beyond a section. Use nth_page() instead.

Fixes: 15fa3e8e3269 ("mips: implement the new page table range API")
Cc: <[email protected]>
Signed-off-by: Zi Yan <[email protected]>
---
arch/mips/mm/cache.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/mips/mm/cache.c b/arch/mips/mm/cache.c
index 02042100e267..7f830634dbe7 100644
--- a/arch/mips/mm/cache.c
+++ b/arch/mips/mm/cache.c
@@ -117,7 +117,7 @@ void __flush_dcache_pages(struct page *page, unsigned int nr)
* get faulted into the tlb (and thus flushed) anyways.
*/
for (i = 0; i < nr; i++) {
- addr = (unsigned long)kmap_local_page(page + i);
+ addr = (unsigned long)kmap_local_page(nth_page(page, i));
flush_data_cache_page(addr);
kunmap_local((void *)addr);
}
--
2.40.1

2023-09-14 04:06:12

by Zi Yan

[permalink] [raw]

Subject: Re: [PATCH v3 5/5] mips: use nth_page() in place of direct struct page manipulation.

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On 13 Sep 2023, at 16:12, Zi Yan wrote:

> From: Zi Yan <[email protected]>
>
> __flush_dcache_pages() is called during hugetlb migration via
> migrate_pages() -> migrate_hugetlbs() -> unmap_and_move_huge_page()
> -> move_to_new_folio() -> flush_dcache_folio(). And with hugetlb and
> without sparsemem vmemmap, struct page is not guaranteed to be contiguous
> beyond a section. Use nth_page() instead.
>
> Fixes: 15fa3e8e3269 ("mips: implement the new page table range API")
> Cc: <[email protected]>
> Signed-off-by: Zi Yan <[email protected]>
> ---
> arch/mips/mm/cache.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/mips/mm/cache.c b/arch/mips/mm/cache.c
> index 02042100e267..7f830634dbe7 100644
> --- a/arch/mips/mm/cache.c
> +++ b/arch/mips/mm/cache.c
> @@ -117,7 +117,7 @@ void __flush_dcache_pages(struct page *page, unsigned int nr)
> * get faulted into the tlb (and thus flushed) anyways.
> */
> for (i = 0; i < nr; i++) {
> - addr = (unsigned long)kmap_local_page(page + i);
> + addr = (unsigned long)kmap_local_page(nth_page(page, i));
> flush_data_cache_page(addr);
> kunmap_local((void *)addr);
> }
> --
> 2.40.1

Without the fix, a wrong address might be used for data cache page flush.
No bug is reported. The fix comes from code inspection.


--
Best Regards,
Yan, Zi

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