parisc: Handle case where flush_cache_range is called with no context

Just when I had decided that flush_cache_range() was always called with
a valid context, Helge reported two cases where the
"BUG_ON(!vma->vm_mm->context);" was hit on the phantom buildd:

 kernel BUG at /mnt/sdb6/linux/linux-4.15.4/arch/parisc/kernel/cache.c:587!
 CPU: 1 PID: 3254 Comm: kworker/1:2 Tainted: G D 4.15.0-1-parisc64-smp #1 Debian 4.15.4-1+b1
 Workqueue: events free_ioctx
  IAOQ[0]: flush_cache_range+0x164/0x168
  IAOQ[1]: flush_cache_page+0x0/0x1c8
  RP(r2): unmap_page_range+0xae8/0xb88
 Backtrace:
  [<00000000404a6980>] unmap_page_range+0xae8/0xb88
  [<00000000404a6ae0>] unmap_single_vma+0xc0/0x188
  [<00000000404a6cdc>] zap_page_range_single+0x134/0x1f8
  [<00000000404a702c>] unmap_mapping_range+0x1cc/0x208
  [<0000000040461518>] truncate_pagecache+0x98/0x108
  [<0000000040461624>] truncate_setsize+0x9c/0xb8
  [<00000000405d7f30>] put_aio_ring_file+0x80/0x100
  [<00000000405d803c>] aio_free_ring+0x8c/0x290
  [<00000000405d82c0>] free_ioctx+0x80/0x180
  [<0000000040284e6c>] process_one_work+0x21c/0x668
  [<00000000402854c4>] worker_thread+0x20c/0x778
  [<0000000040291d44>] kthread+0x2d4/0x2e0
  [<0000000040204020>] end_fault_vector+0x20/0xc0

This indicates that we need to handle the no context case in
flush_cache_range() as we do in flush_cache_mm().

In thinking about this, I realized that we don't need to flush the TLB
when there is no context.  So, I added context checks to the large flush
cases in flush_cache_mm() and flush_cache_range().  The large flush case
occurs frequently in flush_cache_mm() and the change should improve fork
performance.

The v2 version of this change removes the BUG_ON from flush_cache_page()
by skipping the TLB flush when there is no context.  I also added code
to flush the TLB in flush_cache_mm() and flush_cache_range() when we
have a context that's not current.  Now all three routines handle TLB
flushes in a similar manner.

Signed-off-by: John David Anglin <dave.anglin@bell.net>
Cc: stable@vger.kernel.org # 4.9+
Signed-off-by: Helge Deller <deller@gmx.de>

diff --git a/arch/parisc/kernel/cache.c b/arch/parisc/kernel/cache.c
index 7908977..e3b4554 100644 (file)
--- a/arch/parisc/kernel/cache.c
+++ b/arch/parisc/kernel/cache.c
@@ -543,7 +543,8 @@ void flush_cache_mm(struct mm_struct *mm)
           rp3440, etc.  So, avoid it if the mm isn't too big.  */
        if ((!IS_ENABLED(CONFIG_SMP) || !arch_irqs_disabled()) &&
            mm_total_size(mm) >= parisc_cache_flush_threshold) {
-               flush_tlb_all();
+               if (mm->context)
+                       flush_tlb_all();
                flush_cache_all();
                return;
        }
@@ -571,6 +572,8 @@ void flush_cache_mm(struct mm_struct *mm)
                        pfn = pte_pfn(*ptep);
                        if (!pfn_valid(pfn))
                                continue;
+                       if (unlikely(mm->context))
+                               flush_tlb_page(vma, addr);
                        __flush_cache_page(vma, addr, PFN_PHYS(pfn));
                }
        }
@@ -579,26 +582,46 @@ void flush_cache_mm(struct mm_struct *mm)
 void flush_cache_range(struct vm_area_struct *vma,
                unsigned long start, unsigned long end)
 {
+       pgd_t *pgd;
+       unsigned long addr;
+
        if ((!IS_ENABLED(CONFIG_SMP) || !arch_irqs_disabled()) &&
            end - start >= parisc_cache_flush_threshold) {
-               flush_tlb_range(vma, start, end);
+               if (vma->vm_mm->context)
+                       flush_tlb_range(vma, start, end);
                flush_cache_all();
                return;
        }
 
-       flush_user_dcache_range_asm(start, end);
-       if (vma->vm_flags & VM_EXEC)
-               flush_user_icache_range_asm(start, end);
-       flush_tlb_range(vma, start, end);
+       if (vma->vm_mm->context == mfsp(3)) {
+               flush_user_dcache_range_asm(start, end);
+               if (vma->vm_flags & VM_EXEC)
+                       flush_user_icache_range_asm(start, end);
+               flush_tlb_range(vma, start, end);
+               return;
+       }
+
+       pgd = vma->vm_mm->pgd;
+       for (addr = vma->vm_start; addr < vma->vm_end; addr += PAGE_SIZE) {
+               unsigned long pfn;
+               pte_t *ptep = get_ptep(pgd, addr);
+               if (!ptep)
+                       continue;
+               pfn = pte_pfn(*ptep);
+               if (pfn_valid(pfn)) {
+                       if (unlikely(vma->vm_mm->context))
+                               flush_tlb_page(vma, addr);
+                       __flush_cache_page(vma, addr, PFN_PHYS(pfn));
+               }
+       }
 }
 
 void
 flush_cache_page(struct vm_area_struct *vma, unsigned long vmaddr, unsigned long pfn)
 {
-       BUG_ON(!vma->vm_mm->context);
-
        if (pfn_valid(pfn)) {
-               flush_tlb_page(vma, vmaddr);
+               if (likely(vma->vm_mm->context))
+                       flush_tlb_page(vma, vmaddr);
                __flush_cache_page(vma, vmaddr, PFN_PHYS(pfn));
        }
 }