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[RFC v3 03/17] mm: Introduce pte_spinlock

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This is needed because in handle_pte_fault() pte_offset_map() is
called and then fe->ptl is fetched and spin_locked.

This was previously embedded in the call to pte_offset_map_lock().

Signed-off-by: Laurent Dufour <ldufour@linux.vnet.ibm.com>
---
 mm/memory.c | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/mm/memory.c b/mm/memory.c
index bce32c9d73c2..441c0e3f3a0f 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -2100,6 +2100,13 @@ static inline void wp_page_reuse(struct vm_fault *vmf)
 	pte_unmap_unlock(vmf->pte, vmf->ptl);
 }
 
+static bool pte_spinlock(struct vm_fault *vmf)
+{
+	vmf->ptl = pte_lockptr(vmf->vma->vm_mm, vmf->pmd);
+	spin_lock(vmf->ptl);
+	return true;
+}
+
 static bool pte_map_lock(struct vm_fault *vmf)
 {
 	vmf->pte = pte_offset_map_lock(vmf->vma->vm_mm, vmf->pmd, vmf->address, &vmf->ptl);
@@ -3398,8 +3405,8 @@ static int do_numa_page(struct vm_fault *vmf)
 	* page table entry is not accessible, so there would be no
 	* concurrent hardware modifications to the PTE.
 	*/
-	vmf->ptl = pte_lockptr(vma->vm_mm, vmf->pmd);
-	spin_lock(vmf->ptl);
+	if (!pte_spinlock(vmf))
+		return VM_FAULT_RETRY;
 	if (unlikely(!pte_same(*vmf->pte, pte))) {
 		pte_unmap_unlock(vmf->pte, vmf->ptl);
 		goto out;
@@ -3566,8 +3573,8 @@ static int handle_pte_fault(struct vm_fault *vmf)
 	if (pte_protnone(vmf->orig_pte) && vma_is_accessible(vmf->vma))
 		return do_numa_page(vmf);
 
-	vmf->ptl = pte_lockptr(vmf->vma->vm_mm, vmf->pmd);
-	spin_lock(vmf->ptl);
+	if (!pte_spinlock(vmf))
+		return VM_FAULT_RETRY;
 	entry = vmf->orig_pte;
 	if (unlikely(!pte_same(*vmf->pte, entry)))
 		goto unlock;
-- 
2.7.4

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[RFC v3 00/17] Speculative page faults Laurent Dufour <ldufour@linux.vnet.ibm.com> - 2017-04-27 18:00 +0200
  [RFC v3 03/17] mm: Introduce pte_spinlock Laurent Dufour <ldufour@linux.vnet.ibm.com> - 2017-04-27 18:00 +0200
    Re: [RFC v3 03/17] mm: Introduce pte_spinlock Matthew Wilcox <willy@infradead.org> - 2017-04-30 06:50 +0200
      Re: [RFC v3 03/17] mm: Introduce pte_spinlock Laurent Dufour <ldufour@linux.vnet.ibm.com> - 2017-05-03 15:10 +0200
  [RFC v3 13/17] mm/spf Protect vm_policy's changes against speculative pf Laurent Dufour <ldufour@linux.vnet.ibm.com> - 2017-04-27 18:00 +0200
  [RFC v3 04/17] mm: VMA sequence count Laurent Dufour <ldufour@linux.vnet.ibm.com> - 2017-04-27 18:00 +0200
  [RFC v3 02/17] mm: Prepare for FAULT_FLAG_SPECULATIVE Laurent Dufour <ldufour@linux.vnet.ibm.com> - 2017-04-27 18:00 +0200
  [RFC v3 12/17] mm/spf: Protect changes to vm_flags Laurent Dufour <ldufour@linux.vnet.ibm.com> - 2017-04-27 18:00 +0200
  [RFC v3 14/17] x86/mm: Update the handle_speculative_fault's path Laurent Dufour <ldufour@linux.vnet.ibm.com> - 2017-04-27 18:00 +0200
  [RFC v3 06/17] mm: Provide speculative fault infrastructure Laurent Dufour <ldufour@linux.vnet.ibm.com> - 2017-04-27 18:00 +0200
  [RFC v3 16/17] mm: protect madvise vs speculative pf Laurent Dufour <ldufour@linux.vnet.ibm.com> - 2017-04-27 18:00 +0200
  [RFC v3 09/17] mm/spf: Fix fe.sequence init in __handle_mm_fault() Laurent Dufour <ldufour@linux.vnet.ibm.com> - 2017-04-27 18:00 +0200
  [RFC v3 08/17] mm/spf: Try spin lock in speculative path Laurent Dufour <ldufour@linux.vnet.ibm.com> - 2017-04-27 18:00 +0200

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