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

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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@xxxxxxxxxx>
---
  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





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