This is a note to let you know that I've just added the patch titled
parisc: Handle case where flush_cache_range is called with no context
to the 4.15-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...
The filename of the patch is: parisc-handle-case-where-flush_cache_range-is-called-with-no-context.patch and it can be found in the queue-4.15 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.
From 9ef0f88fe5466c2ca1d2975549ba6be502c464c1 Mon Sep 17 00:00:00 2001
From: John David Anglin dave.anglin@bell.net Date: Wed, 7 Mar 2018 08:18:05 -0500 Subject: parisc: Handle case where flush_cache_range is called with no context MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit
From: John David Anglin dave.anglin@bell.net
commit 9ef0f88fe5466c2ca1d2975549ba6be502c464c1 upstream.
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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- arch/parisc/kernel/cache.c | 41 ++++++++++++++++++++++++++++++++--------- 1 file changed, 32 insertions(+), 9 deletions(-)
--- 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)); } }
Patches currently in stable-queue which might be from dave.anglin@bell.net are
queue-4.15/parisc-handle-case-where-flush_cache_range-is-called-with-no-context.patch