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

Hugh Dickins
2023-05-10T04:52:43Z

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))
+ pte_unmap(ptep);
+ }
+ if (needs_flush)
flush_cache_page(vma, vmaddr, pfn);
}

@@ -634,17 +645,22 @@ static void flush_cache_pages(struct vm_area_struct *vma, unsigned long start, u
pte_t *ptep;

for (addr = start; addr < end; addr += PAGE_SIZE) {
+ bool needs_flush = false;
/*
* The vma can contain pages that aren't present. Although
* the pte search is expensive, we need the pte to find the
* page pfn and to check whether the page should be flushed.
*/
ptep = get_ptep(vma->vm_mm, addr);
- if (ptep && pte_needs_flush(*ptep)) {
+ if (ptep) {
+ needs_flush = pte_needs_flush(*ptep);
+ pfn = pte_pfn(*ptep);
+ pte_unmap(ptep);
+ }
+ if (needs_flush) {
if (parisc_requires_coherency()) {
flush_user_cache_page(vma, addr);
} else {
- pfn = pte_pfn(*ptep);
if (WARN_ON(!pfn_valid(pfn)))
return;
__flush_cache_page(vma, addr, PFN_PHYS(pfn));
--
2.35.3