[PATCH] mm: arches skip ptlock

Convert those few architectures which are calling pud_alloc, pmd_alloc,
pte_alloc_map on a user mm, not to take the page_table_lock first, nor drop it
after.  Each of these can continue to use pte_alloc_map, no need to change
over to pte_alloc_map_lock, they're neither racy nor swappable.

In the sparc64 io_remap_pfn_range, flush_tlb_range then falls outside of the
page_table_lock: that's okay, on sparc64 it's like flush_tlb_mm, and that has
always been called from outside of page_table_lock in dup_mmap.

Signed-off-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

5 files changed, 3 insertions, 39 deletions

diff --git a/arch/arm/mm/mm-armv.c b/arch/arm/mm/mm-armv.c
index 61bc2fa051..60f3e039ba 100644
--- a/arch/arm/mm/mm-armv.c
+++ b/arch/arm/mm/mm-armv.c
@@ -180,11 +180,6 @@ pgd_t *get_pgd_slow(struct mm_struct *mm)
 
         if (!vectors_high()) {
                 /*
-                 * This lock is here just to satisfy pmd_alloc and pte_lock
-                 */
-                spin_lock(&mm->page_table_lock);
-
-                /*
                  * On ARM, first page must always be allocated since it
                  * contains the machine vectors.
                  */
@@ -201,23 +196,14 @@ pgd_t *get_pgd_slow(struct mm_struct *mm)
                 set_pte(new_pte, *init_pte);
                 pte_unmap_nested(init_pte);
                 pte_unmap(new_pte);
-
-                spin_unlock(&mm->page_table_lock);
         }
 
         return new_pgd;
 
 no_pte:
-        spin_unlock(&mm->page_table_lock);
         pmd_free(new_pmd);
-        free_pages((unsigned long)new_pgd, 2);
-        return NULL;
-
 no_pmd:
-        spin_unlock(&mm->page_table_lock);
         free_pages((unsigned long)new_pgd, 2);
-        return NULL;
-
 no_pgd:
         return NULL;
 }
diff --git a/arch/arm26/mm/memc.c b/arch/arm26/mm/memc.c
index d6b008b8db..34def6397c 100644
--- a/arch/arm26/mm/memc.c
+++ b/arch/arm26/mm/memc.c
@@ -79,12 +79,6 @@ pgd_t *get_pgd_slow(struct mm_struct *mm)
                 goto no_pgd;
 
         /*
-         * This lock is here just to satisfy pmd_alloc and pte_lock
-         * FIXME: I bet we could avoid taking it pretty much altogether
-         */
-        spin_lock(&mm->page_table_lock);
-
-        /*
          * On ARM, first page must always be allocated since it contains
          * the machine vectors.
          */
@@ -113,23 +107,14 @@ pgd_t *get_pgd_slow(struct mm_struct *mm)
         memcpy(new_pgd + FIRST_KERNEL_PGD_NR, init_pgd + FIRST_KERNEL_PGD_NR,
                 (PTRS_PER_PGD - FIRST_KERNEL_PGD_NR) * sizeof(pgd_t));
 
-        spin_unlock(&mm->page_table_lock);
-
         /* update MEMC tables */
         cpu_memc_update_all(new_pgd);
         return new_pgd;
 
 no_pte:
-        spin_unlock(&mm->page_table_lock);
         pmd_free(new_pmd);
-        free_pgd_slow(new_pgd);
-        return NULL;
-
 no_pmd:
-        spin_unlock(&mm->page_table_lock);
         free_pgd_slow(new_pgd);
-        return NULL;
-
 no_pgd:
         return NULL;
 }
diff --git a/arch/sparc/mm/generic.c b/arch/sparc/mm/generic.c
index 659c9a71f8..9604893ffd 100644
--- a/arch/sparc/mm/generic.c
+++ b/arch/sparc/mm/generic.c
@@ -81,9 +81,8 @@ int io_remap_pfn_range(struct vm_area_struct *vma, unsigned long from,
         dir = pgd_offset(mm, from);
         flush_cache_range(vma, beg, end);
 
-        spin_lock(&mm->page_table_lock);
         while (from < end) {
-                pmd_t *pmd = pmd_alloc(current->mm, dir, from);
+                pmd_t *pmd = pmd_alloc(mm, dir, from);
                 error = -ENOMEM;
                 if (!pmd)
                         break;
@@ -93,7 +92,6 @@ int io_remap_pfn_range(struct vm_area_struct *vma, unsigned long from,
                 from = (from + PGDIR_SIZE) & PGDIR_MASK;
                 dir++;
         }
-        spin_unlock(&mm->page_table_lock);
 
         flush_tlb_range(vma, beg, end);
         return error;
diff --git a/arch/sparc64/mm/generic.c b/arch/sparc64/mm/generic.c
index afc01cec70..112c316e7c 100644
--- a/arch/sparc64/mm/generic.c
+++ b/arch/sparc64/mm/generic.c
@@ -135,9 +135,8 @@ int io_remap_pfn_range(struct vm_area_struct *vma, unsigned long from,
         dir = pgd_offset(mm, from);
         flush_cache_range(vma, beg, end);
 
-        spin_lock(&mm->page_table_lock);
         while (from < end) {
-                pud_t *pud = pud_alloc(current->mm, dir, from);
+                pud_t *pud = pud_alloc(mm, dir, from);
                 error = -ENOMEM;
                 if (!pud)
                         break;
@@ -147,8 +146,7 @@ int io_remap_pfn_range(struct vm_area_struct *vma, unsigned long from,
                 from = (from + PGDIR_SIZE) & PGDIR_MASK;
                 dir++;
         }
-        flush_tlb_range(vma, beg, end);
-        spin_unlock(&mm->page_table_lock);
 
+        flush_tlb_range(vma, beg, end);
         return error;
 }
diff --git a/arch/um/kernel/skas/mmu.c b/arch/um/kernel/skas/mmu.c
index 240143b616..02cf36e033 100644
--- a/arch/um/kernel/skas/mmu.c
+++ b/arch/um/kernel/skas/mmu.c
@@ -28,7 +28,6 @@ static int init_stub_pte(struct mm_struct *mm, unsigned long proc,
         pmd_t *pmd;
         pte_t *pte;
 
-        spin_lock(&mm->page_table_lock);
         pgd = pgd_offset(mm, proc);
         pud = pud_alloc(mm, pgd, proc);
         if (!pud)
@@ -63,7 +62,6 @@ static int init_stub_pte(struct mm_struct *mm, unsigned long proc,
         *pte = mk_pte(virt_to_page(kernel), __pgprot(_PAGE_PRESENT));
         *pte = pte_mkexec(*pte);
         *pte = pte_wrprotect(*pte);
-        spin_unlock(&mm->page_table_lock);
         return(0);
 
  out_pmd:
@@ -71,7 +69,6 @@ static int init_stub_pte(struct mm_struct *mm, unsigned long proc,
  out_pte:
         pmd_free(pmd);
  out:
-        spin_unlock(&mm->page_table_lock);
         return(-ENOMEM);
 }