s390, thp: remove infrastructure for handling splitting PMDs

With new refcounting we don't need to mark PMDs splitting.  Let's drop
code to handle this.

pmdp_splitting_flush() is not needed too: on splitting PMD we will do
pmdp_clear_flush() + set_pte_at().  pmdp_clear_flush() will do IPI as
needed for fast_gup.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Sasha Levin <sasha.levin@oracle.com>
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Cc: Jerome Marchand <jmarchan@redhat.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Rik van Riel <riel@redhat.com>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Steve Capper <steve.capper@linaro.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Christoph Lameter <cl@linux.com>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 1 insertions, 26 deletions

diff --git a/arch/s390/mm/gup.c b/arch/s390/mm/gup.c
index 1a2cad52babf..13dab0c1645c 100644
--- a/arch/s390/mm/gup.c
+++ b/arch/s390/mm/gup.c
@@ -105,16 +105,7 @@ static inline int gup_pmd_range(pud_t *pudp, pud_t pud, unsigned long addr,
                 pmd = *pmdp;
                 barrier();
                 next = pmd_addr_end(addr, end);
-                /*
-                 * The pmd_trans_splitting() check below explains why
-                 * pmdp_splitting_flush() has to serialize with
-                 * smp_call_function() against our disabled IRQs, to stop
-                 * this gup-fast code from running while we set the
-                 * splitting bit in the pmd. Returning zero will take
-                 * the slow path that will call wait_split_huge_page()
-                 * if the pmd is still in splitting state.
-                 */
-                if (pmd_none(pmd) || pmd_trans_splitting(pmd))
+                if (pmd_none(pmd))
                         return 0;
                 if (unlikely(pmd_large(pmd))) {
                         /*
diff --git a/arch/s390/mm/pgtable.c b/arch/s390/mm/pgtable.c
index aa34af0a0b26..4e54492f463a 100644
--- a/arch/s390/mm/pgtable.c
+++ b/arch/s390/mm/pgtable.c
@@ -1305,22 +1305,6 @@ int pmdp_set_access_flags(struct vm_area_struct *vma,
         return 1;
 }
 
-static void pmdp_splitting_flush_sync(void *arg)
-{
-        /* Simply deliver the interrupt */
-}
-
-void pmdp_splitting_flush(struct vm_area_struct *vma, unsigned long address,
-                          pmd_t *pmdp)
-{
-        VM_BUG_ON(address & ~HPAGE_PMD_MASK);
-        if (!test_and_set_bit(_SEGMENT_ENTRY_SPLIT_BIT,
-                              (unsigned long *) pmdp)) {
-                /* need to serialize against gup-fast (IRQ disabled) */
-                smp_call_function(pmdp_splitting_flush_sync, NULL, 1);
-        }
-}
-
 void pgtable_trans_huge_deposit(struct mm_struct *mm, pmd_t *pmdp,
                                 pgtable_t pgtable)
 {