s390/mm: set and get guest storage key mmap locking

Move the mmap semaphore locking out of set_guest_storage_key
and get_guest_storage_key. This makes the two functions more
like the other ptep_xxx operations and allows to avoid repeated
semaphore operations if multiple keys are read or written.

Reviewed-by: David Hildenbrand <dahi@linux.vnet.ibm.com>
Reviewed-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>

1 files changed, 3 insertions, 12 deletions

diff --git a/arch/s390/mm/pgtable.c b/arch/s390/mm/pgtable.c
index 2a23ca96f9c2..7612a7c3a3a8 100644
--- a/arch/s390/mm/pgtable.c
+++ b/arch/s390/mm/pgtable.c
@@ -506,12 +506,9 @@ int set_guest_storage_key(struct mm_struct *mm, unsigned long addr,
         pgste_t old, new;
         pte_t *ptep;
 
-        down_read(&mm->mmap_sem);
         ptep = get_locked_pte(mm, addr, &ptl);
-        if (unlikely(!ptep)) {
-                up_read(&mm->mmap_sem);
+        if (unlikely(!ptep))
                 return -EFAULT;
-        }
 
         new = old = pgste_get_lock(ptep);
         pgste_val(new) &= ~(PGSTE_GR_BIT | PGSTE_GC_BIT |
@@ -538,7 +535,6 @@ int set_guest_storage_key(struct mm_struct *mm, unsigned long addr,
 
         pgste_set_unlock(ptep, new);
         pte_unmap_unlock(ptep, ptl);
-        up_read(&mm->mmap_sem);
         return 0;
 }
 EXPORT_SYMBOL(set_guest_storage_key);
@@ -550,14 +546,11 @@ unsigned long get_guest_storage_key(struct mm_struct *mm, unsigned long addr)
         pgste_t pgste;
         pte_t *ptep;
 
-        down_read(&mm->mmap_sem);
         ptep = get_locked_pte(mm, addr, &ptl);
-        if (unlikely(!ptep)) {
-                up_read(&mm->mmap_sem);
+        if (unlikely(!ptep))
                 return -EFAULT;
-        }
-        pgste = pgste_get_lock(ptep);
 
+        pgste = pgste_get_lock(ptep);
         if (pte_val(*ptep) & _PAGE_INVALID) {
                 key  = (pgste_val(pgste) & PGSTE_ACC_BITS) >> 56;
                 key |= (pgste_val(pgste) & PGSTE_FP_BIT) >> 56;
@@ -572,10 +565,8 @@ unsigned long get_guest_storage_key(struct mm_struct *mm, unsigned long addr)
                 if (pgste_val(pgste) & PGSTE_GC_BIT)
                         key |= _PAGE_CHANGED;
         }
-
         pgste_set_unlock(ptep, pgste);
         pte_unmap_unlock(ptep, ptl);
-        up_read(&mm->mmap_sem);
         return key;
 }
 EXPORT_SYMBOL(get_guest_storage_key);