On 4/22/21 11:13 AM, Aneesh Kumar K.V wrote:
Move TLB flush outside page table lock so that kernel does
less with page table lock held. Releasing the ptl with old
TLB contents still valid will behave such that such access
happened before the level3 or level2 entry update.
Ok this break the page lifetime rule
commit: eb66ae030829 ("mremap: properly flush TLB before releasing the
page")
I will respin dropping this change and add a comment around explaining
why we need to do tlb flush before dropping ptl.
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxx>
---
mm/mremap.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/mm/mremap.c b/mm/mremap.c
index 109560977944..9effca76bf17 100644
--- a/mm/mremap.c
+++ b/mm/mremap.c
@@ -258,7 +258,7 @@ static bool move_normal_pmd(struct vm_area_struct *vma, unsigned long old_addr,
* We don't have to worry about the ordering of src and dst
* ptlocks because exclusive mmap_lock prevents deadlock.
*/
- old_ptl = pmd_lock(vma->vm_mm, old_pmd);
+ old_ptl = pmd_lock(mm, old_pmd);
new_ptl = pmd_lockptr(mm, new_pmd);
if (new_ptl != old_ptl)
spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING);
@@ -270,11 +270,11 @@ static bool move_normal_pmd(struct vm_area_struct *vma, unsigned long old_addr,
VM_BUG_ON(!pmd_none(*new_pmd));
pmd_populate(mm, new_pmd, (pgtable_t)pmd_page_vaddr(pmd));
- flush_pte_tlb_pwc_range(vma, old_addr, old_addr + PMD_SIZE);
if (new_ptl != old_ptl)
spin_unlock(new_ptl);
spin_unlock(old_ptl);
+ flush_pte_tlb_pwc_range(vma, old_addr, old_addr + PMD_SIZE);
return true;
}
#else
@@ -305,7 +305,7 @@ static bool move_normal_pud(struct vm_area_struct *vma, unsigned long old_addr,
* We don't have to worry about the ordering of src and dst
* ptlocks because exclusive mmap_lock prevents deadlock.
*/
- old_ptl = pud_lock(vma->vm_mm, old_pud);
+ old_ptl = pud_lock(mm, old_pud);
new_ptl = pud_lockptr(mm, new_pud);
if (new_ptl != old_ptl)
spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING);
@@ -317,11 +317,11 @@ static bool move_normal_pud(struct vm_area_struct *vma, unsigned long old_addr,
VM_BUG_ON(!pud_none(*new_pud));
pud_populate(mm, new_pud, (pmd_t *)pud_page_vaddr(pud));
- flush_pte_tlb_pwc_range(vma, old_addr, old_addr + PUD_SIZE);
if (new_ptl != old_ptl)
spin_unlock(new_ptl);
spin_unlock(old_ptl);
+ flush_pte_tlb_pwc_range(vma, old_addr, old_addr + PUD_SIZE);
return true;
}
#else
