parisc: add pte_unmap() to balance get_ptep()

To keep balance in future, remember to pte_unmap() after a successful
get_ptep().  And act as if flush_cache_pages() really needs a map there,
to read the pfn before "unmapping", to be sure page table is not removed.

Link: https://lkml.kernel.org/r/653369-95ef-acd2-d6ea-e95f5a997493@google.com
Signed-off-by: Hugh Dickins <hughd@google.com>
Cc: Alexander Gordeev <agordeev@linux.ibm.com>
Cc: Alexandre Ghiti <alexghiti@rivosinc.com>
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Christian Borntraeger <borntraeger@linux.ibm.com>
Cc: Chris Zankel <chris@zankel.net>
Cc: Claudio Imbrenda <imbrenda@linux.ibm.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Greg Ungerer <gerg@linux-m68k.org>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Helge Deller <deller@gmx.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: John David Anglin <dave.anglin@bell.net>
Cc: John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Max Filippov <jcmvbkbc@gmail.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Michal Simek <monstr@monstr.eu>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Mike Rapoport (IBM) <rppt@kernel.org>
Cc: Palmer Dabbelt <palmer@dabbelt.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Qi Zheng <zhengqi.arch@bytedance.com>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/arch/parisc/kernel/cache.c b/arch/parisc/kernel/cache.c
index ca4a302..5011602 100644 (file)
--- a/arch/parisc/kernel/cache.c
+++ b/arch/parisc/kernel/cache.c
@@ -426,10 +426,15 @@ 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 {
                        /*
@@ -561,14 +566,20 @@ 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);
 }
 
@@ -635,17 +646,22 @@ 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));