powerpc/mm: Move around testing of _PAGE_PRESENT in hash code

Instead of adding _PAGE_PRESENT to the access permission mask
in each low level routine independently, we add it once from
hash_page().

We also move the preliminary access check (the racy one before
the PTE is locked) up so it applies to the huge page case. This
duplicates code in __hash_page_huge() which we'll remove in a
subsequent patch to fix a race in there.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

2 files changed, 11 insertions, 17 deletions

diff --git a/arch/powerpc/mm/hash_low_64.S b/arch/powerpc/mm/hash_low_64.S
index a719f53921a5..3079f6b44cf5 100644
--- a/arch/powerpc/mm/hash_low_64.S
+++ b/arch/powerpc/mm/hash_low_64.S
@@ -68,9 +68,6 @@ _GLOBAL(__hash_page_4K)
         std     r8,STK_PARM(r8)(r1)
         std     r9,STK_PARM(r9)(r1)
         
-        /* Add _PAGE_PRESENT to access */
-        ori     r4,r4,_PAGE_PRESENT
-
         /* Save non-volatile registers.
          * r31 will hold "old PTE"
          * r30 is "new PTE"
@@ -347,9 +344,6 @@ _GLOBAL(__hash_page_4K)
         std     r8,STK_PARM(r8)(r1)
         std     r9,STK_PARM(r9)(r1)
 
-        /* Add _PAGE_PRESENT to access */
-        ori     r4,r4,_PAGE_PRESENT
-
         /* Save non-volatile registers.
          * r31 will hold "old PTE"
          * r30 is "new PTE"
@@ -687,9 +681,6 @@ _GLOBAL(__hash_page_64K)
         std     r8,STK_PARM(r8)(r1)
         std     r9,STK_PARM(r9)(r1)
 
-        /* Add _PAGE_PRESENT to access */
-        ori     r4,r4,_PAGE_PRESENT
-
         /* Save non-volatile registers.
          * r31 will hold "old PTE"
          * r30 is "new PTE"
diff --git a/arch/powerpc/mm/hash_utils_64.c b/arch/powerpc/mm/hash_utils_64.c
index 98f262de5585..40847a9dd6db 100644
--- a/arch/powerpc/mm/hash_utils_64.c
+++ b/arch/powerpc/mm/hash_utils_64.c
@@ -955,6 +955,17 @@ int hash_page(unsigned long ea, unsigned long access, unsigned long trap)
                 return 1;
         }
 
+        /* Add _PAGE_PRESENT to the required access perm */
+        access |= _PAGE_PRESENT;
+
+        /* Pre-check access permissions (will be re-checked atomically
+         * in __hash_page_XX but this pre-check is a fast path
+         */
+        if (access & ~pte_val(*ptep)) {
+                DBG_LOW(" no access !\n");
+                return 1;
+        }
+
 #ifdef CONFIG_HUGETLB_PAGE
         if (hugeshift)
                 return __hash_page_huge(ea, access, vsid, ptep, trap, local,
@@ -967,14 +978,6 @@ int hash_page(unsigned long ea, unsigned long access, unsigned long trap)
         DBG_LOW(" i-pte: %016lx %016lx\n", pte_val(*ptep),
                 pte_val(*(ptep + PTRS_PER_PTE)));
 #endif
-        /* Pre-check access permissions (will be re-checked atomically
-         * in __hash_page_XX but this pre-check is a fast path
-         */
-        if (access & ~pte_val(*ptep)) {
-                DBG_LOW(" no access !\n");
-                return 1;
-        }
-
         /* Do actual hashing */
 #ifdef CONFIG_PPC_64K_PAGES
         /* If _PAGE_4K_PFN is set, make sure this is a 4k segment */