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>

1 files changed, 21 insertions, 33 deletions

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index addfe4accc07..524c078ce67b 100644
--- 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);