Re: [PATCH 08/23] parisc: add pte_unmap() to balance get_ptep()

Helge Deller
2023-05-13T21:37:55Z

Hi Hugh,

On 5/10/23 06:52, Hugh Dickins wrote:
> To keep balance in future, remember to pte_unmap() after a successful
> get_ptep(). And (we might as well) pretend that flush_cache_pages()
> really needed a map there, to read the pfn before "unmapping".
>
> Signed-off-by: Hugh Dickins <hughd@google.com>
> ---
> arch/parisc/kernel/cache.c | 26 +++++++++++++++++++++-----
> 1 file changed, 21 insertions(+), 5 deletions(-)
>
> diff --git a/arch/parisc/kernel/cache.c b/arch/parisc/kernel/cache.c
> index 1d3b8bc8a623..b0c969b3a300 100644
> --- a/arch/parisc/kernel/cache.c
> +++ b/arch/parisc/kernel/cache.c
> @@ -425,10 +425,15 @@ void flush_dcache_page(struct page *page)
> offset = (pgoff - mpnt->vm_pgoff) << PAGE_SHIFT;
> addr = mpnt->vm_start + offset;
> if (parisc_requires_coherency()) {
> + bool needs_flush = false;
> pte_t *ptep;
>
> ptep = get_ptep(mpnt->vm_mm, addr);
> - if (ptep && pte_needs_flush(*ptep))
> + if (ptep) {
> + needs_flush = pte_needs_flush(*ptep);
> + pte_unmap(ptep);
> + }
> + if (needs_flush)
> flush_user_cache_page(mpnt, addr);
> } else {
> /*
> @@ -560,14 +565,20 @@ EXPORT_SYMBOL(flush_kernel_dcache_page_addr);
> static void flush_cache_page_if_present(struct vm_area_struct *vma,
> unsigned long vmaddr, unsigned long pfn)
> {
> - pte_t *ptep = get_ptep(vma->vm_mm, vmaddr);
> + bool needs_flush = false;
> + pte_t *ptep;
>
> /*
> * The pte check is racy and sometimes the flush will trigger
> * a non-access TLB miss. Hopefully, the page has already been
> * flushed.
> */
> - if (ptep && pte_needs_flush(*ptep))
> + ptep = get_ptep(vma->vm_mm, vmaddr);
> + if (ptep) {
> + needs_flush = pte_needs_flush(*ptep))

^^^^^
One ")" too much and lacks a trailing ";"
Should be:
needs_flush = pte_needs_flush(*ptep);

With that fixed the kernel compiles and boots sucessfully on parisc.

Helge