[PATCH v8 04/20] powerpc/mm: Avoid useless lock with single page fragments

[Christophe Leroy]

There is no point in taking the page table lock as pte_frag or
pmd_frag are always NULL when we have only one fragment.

Reviewed-by: Aneesh Kumar K.V <aneesh.ku...@linux.ibm.com>
Signed-off-by: Christophe Leroy <christophe.le...@c-s.fr>
---
 arch/powerpc/mm/pgtable-book3s64.c | 3 +++
 arch/powerpc/mm/pgtable-frag.c     | 3 +++
 2 files changed, 6 insertions(+)

diff --git a/arch/powerpc/mm/pgtable-book3s64.c 
b/arch/powerpc/mm/pgtable-book3s64.c
index 0c0fd173208a..f3c31f5e1026 100644
--- a/arch/powerpc/mm/pgtable-book3s64.c
+++ b/arch/powerpc/mm/pgtable-book3s64.c
@@ -244,6 +244,9 @@ static pmd_t *get_pmd_from_cache(struct mm_struct *mm)
 {
        void *pmd_frag, *ret;
 
+       if (PMD_FRAG_NR == 1)
+               return NULL;
+
        spin_lock(&mm->page_table_lock);
        ret = mm->context.pmd_frag;
        if (ret) {
diff --git a/arch/powerpc/mm/pgtable-frag.c b/arch/powerpc/mm/pgtable-frag.c
index d61e7c2a9a79..7544d0d7177d 100644
--- a/arch/powerpc/mm/pgtable-frag.c
+++ b/arch/powerpc/mm/pgtable-frag.c
@@ -34,6 +34,9 @@ static pte_t *get_pte_from_cache(struct mm_struct *mm)
 {
        void *pte_frag, *ret;
 
+       if (PTE_FRAG_NR == 1)
+               return NULL;
+
        spin_lock(&mm->page_table_lock);
        ret = mm->context.pte_frag;
        if (ret) {
-- 
2.13.3