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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>

authored by

John David Anglin and committed by
Helge Deller 9ef0f88f 8f5fd927

+32 -9
+32 -9
arch/parisc/kernel/cache.c
··· 543 543 rp3440, etc. So, avoid it if the mm isn't too big. */ 544 544 if ((!IS_ENABLED(CONFIG_SMP) || !arch_irqs_disabled()) && 545 545 mm_total_size(mm) >= parisc_cache_flush_threshold) { 546 - flush_tlb_all(); 546 + if (mm->context) 547 + flush_tlb_all(); 547 548 flush_cache_all(); 548 549 return; 549 550 } ··· 572 571 pfn = pte_pfn(*ptep); 573 572 if (!pfn_valid(pfn)) 574 573 continue; 574 + if (unlikely(mm->context)) 575 + flush_tlb_page(vma, addr); 575 576 __flush_cache_page(vma, addr, PFN_PHYS(pfn)); 576 577 } 577 578 } ··· 582 579 void flush_cache_range(struct vm_area_struct *vma, 583 580 unsigned long start, unsigned long end) 584 581 { 582 + pgd_t *pgd; 583 + unsigned long addr; 584 + 585 585 if ((!IS_ENABLED(CONFIG_SMP) || !arch_irqs_disabled()) && 586 586 end - start >= parisc_cache_flush_threshold) { 587 - flush_tlb_range(vma, start, end); 587 + if (vma->vm_mm->context) 588 + flush_tlb_range(vma, start, end); 588 589 flush_cache_all(); 589 590 return; 590 591 } 591 592 592 - flush_user_dcache_range_asm(start, end); 593 - if (vma->vm_flags & VM_EXEC) 594 - flush_user_icache_range_asm(start, end); 595 - flush_tlb_range(vma, start, end); 593 + if (vma->vm_mm->context == mfsp(3)) { 594 + flush_user_dcache_range_asm(start, end); 595 + if (vma->vm_flags & VM_EXEC) 596 + flush_user_icache_range_asm(start, end); 597 + flush_tlb_range(vma, start, end); 598 + return; 599 + } 600 + 601 + pgd = vma->vm_mm->pgd; 602 + for (addr = vma->vm_start; addr < vma->vm_end; addr += PAGE_SIZE) { 603 + unsigned long pfn; 604 + pte_t *ptep = get_ptep(pgd, addr); 605 + if (!ptep) 606 + continue; 607 + pfn = pte_pfn(*ptep); 608 + if (pfn_valid(pfn)) { 609 + if (unlikely(vma->vm_mm->context)) 610 + flush_tlb_page(vma, addr); 611 + __flush_cache_page(vma, addr, PFN_PHYS(pfn)); 612 + } 613 + } 596 614 } 597 615 598 616 void 599 617 flush_cache_page(struct vm_area_struct *vma, unsigned long vmaddr, unsigned long pfn) 600 618 { 601 - BUG_ON(!vma->vm_mm->context); 602 - 603 619 if (pfn_valid(pfn)) { 604 - flush_tlb_page(vma, vmaddr); 620 + if (likely(vma->vm_mm->context)) 621 + flush_tlb_page(vma, vmaddr); 605 622 __flush_cache_page(vma, vmaddr, PFN_PHYS(pfn)); 606 623 } 607 624 }