mm/hugetlb: simplify hugetlb unmap

For hugetlb like THP (and unlike regular page), we do tlb flush after
dropping ptl.  Because of the above, we don't need to track force_flush
like we do now.  Instead we can simply call tlb_remove_page() which will
do the flush if needed.

No functionality change in this patch.

Link: http://lkml.kernel.org/r/1465049193-22197-1-git-send-email-aneesh.kumar@linux.vnet.ibm.com
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: "Kirill A. Shutemov" <kirill@shutemov.name>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index addfe4accc076817cdbc4009bb9f44d5e61315d4..524c078ce67b2708c10de1504d279159420256d6 100644 (file)
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -3177,7 +3177,6 @@ void __unmap_hugepage_range(struct mmu_gather *tlb, struct vm_area_struct *vma,
                            unsigned long start, unsigned long end,
                            struct page *ref_page)
 {
-       int force_flush = 0;
        struct mm_struct *mm = vma->vm_mm;
        unsigned long address;
        pte_t *ptep;
@@ -3196,19 +3195,22 @@ void __unmap_hugepage_range(struct mmu_gather *tlb, struct vm_area_struct *vma,
        tlb_start_vma(tlb, vma);
        mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
        address = start;
-again:
        for (; address < end; address += sz) {
                ptep = huge_pte_offset(mm, address);
                if (!ptep)
                        continue;
 
                ptl = huge_pte_lock(h, mm, ptep);
-               if (huge_pmd_unshare(mm, &address, ptep))
-                       goto unlock;
+               if (huge_pmd_unshare(mm, &address, ptep)) {
+                       spin_unlock(ptl);
+                       continue;
+               }
 
                pte = huge_ptep_get(ptep);
-               if (huge_pte_none(pte))
-                       goto unlock;
+               if (huge_pte_none(pte)) {
+                       spin_unlock(ptl);
+                       continue;
+               }
 
                /*
                 * Migrating hugepage or HWPoisoned hugepage is already
@@ -3216,7 +3218,8 @@ again:
                 */
                if (unlikely(!pte_present(pte))) {
                        huge_pte_clear(mm, address, ptep);
-                       goto unlock;
+                       spin_unlock(ptl);
+                       continue;
                }
 
                page = pte_page(pte);
@@ -3226,9 +3229,10 @@ again:
                 * are about to unmap is the actual page of interest.
                 */
                if (ref_page) {
-                       if (page != ref_page)
-                               goto unlock;
-
+                       if (page != ref_page) {
+                               spin_unlock(ptl);
+                               continue;
+                       }
                        /*
                         * Mark the VMA as having unmapped its page so that
                         * future faults in this VMA will fail rather than
@@ -3244,30 +3248,14 @@ again:
 
                hugetlb_count_sub(pages_per_huge_page(h), mm);
                page_remove_rmap(page, true);
-               force_flush = !__tlb_remove_page(tlb, page);
-               if (force_flush) {
-                       address += sz;
-                       spin_unlock(ptl);
-                       break;
-               }
-               /* Bail out after unmapping reference page if supplied */
-               if (ref_page) {
-                       spin_unlock(ptl);
-                       break;
-               }
-unlock:
+
                spin_unlock(ptl);
-       }
-       /*
-        * mmu_gather ran out of room to batch pages, we break out of
-        * the PTE lock to avoid doing the potential expensive TLB invalidate
-        * and page-free while holding it.
-        */
-       if (force_flush) {
-               force_flush = 0;
-               tlb_flush_mmu(tlb);
-               if (address < end && !ref_page)
-                       goto again;
+               tlb_remove_page(tlb, page);
+               /*
+                * Bail out after unmapping reference page if supplied
+                */
+               if (ref_page)
+                       break;
        }
        mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
        tlb_end_vma(tlb, vma);