[PATCH] mm: msync_pte_range progress

Use latency breaking in msync_pte_range like that in copy_pte_range, instead
of the ugly CONFIG_PREEMPT filemap_msync alternatives.

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

1 files changed, 14 insertions, 24 deletions

diff --git a/mm/msync.c b/mm/msync.c
index 9cab3f2d58..3b5f1c521d 100644
--- a/mm/msync.c
+++ b/mm/msync.c
@@ -26,12 +26,21 @@ static void msync_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
                                 unsigned long addr, unsigned long end)
 {
         pte_t *pte;
+        int progress = 0;
 
+again:
         pte = pte_offset_map(pmd, addr);
         do {
                 unsigned long pfn;
                 struct page *page;
 
+                if (progress >= 64) {
+                        progress = 0;
+                        if (need_resched() ||
+                            need_lockbreak(&vma->vm_mm->page_table_lock))
+                                break;
+                }
+                progress++;
                 if (!pte_present(*pte))
                         continue;
                 if (!pte_maybe_dirty(*pte))
@@ -46,8 +55,12 @@ static void msync_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
                 if (ptep_clear_flush_dirty(vma, addr, pte) ||
                     page_test_and_clear_dirty(page))
                         set_page_dirty(page);
+                progress += 3;
         } while (pte++, addr += PAGE_SIZE, addr != end);
         pte_unmap(pte - 1);
+        cond_resched_lock(&vma->vm_mm->page_table_lock);
+        if (addr != end)
+                goto again;
 }
 
 static inline void msync_pmd_range(struct vm_area_struct *vma, pud_t *pud,
@@ -106,29 +119,6 @@ static void msync_page_range(struct vm_area_struct *vma,
         spin_unlock(&mm->page_table_lock);
 }
 
-#ifdef CONFIG_PREEMPT
-static inline void filemap_msync(struct vm_area_struct *vma,
-                                 unsigned long addr, unsigned long end)
-{
-        const size_t chunk = 64 * 1024; /* bytes */
-        unsigned long next;
-
-        do {
-                next = addr + chunk;
-                if (next > end || next < addr)
-                        next = end;
-                msync_page_range(vma, addr, next);
-                cond_resched();
-        } while (addr = next, addr != end);
-}
-#else
-static inline void filemap_msync(struct vm_area_struct *vma,
-                                 unsigned long addr, unsigned long end)
-{
-        msync_page_range(vma, addr, end);
-}
-#endif
-
 /*
  * MS_SYNC syncs the entire file - including mappings.
  *
@@ -150,7 +140,7 @@ static int msync_interval(struct vm_area_struct *vma,
                 return -EBUSY;
 
         if (file && (vma->vm_flags & VM_SHARED)) {
-                filemap_msync(vma, addr, end);
+                msync_page_range(vma, addr, end);
 
                 if (flags & MS_SYNC) {
                         struct address_space *mapping = file->f_mapping;