mm: set_page_dirty_balance() vs ->page_mkwrite()

All the current page_mkwrite() implementations also set the page dirty. Which
results in the set_page_dirty_balance() call to _not_ call balance, because the
page is already found dirty.

This allows us to dirty a _lot_ of pages without ever hitting
balance_dirty_pages().  Not good (tm).

Force a balance call if ->page_mkwrite() was successful.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/include/linux/writeback.h b/include/linux/writeback.h
index 4ef4d22..b4af6bc 100644 (file)
--- a/include/linux/writeback.h
+++ b/include/linux/writeback.h
@@ -127,7 +127,7 @@ int sync_page_range(struct inode *inode, struct address_space *mapping,
                        loff_t pos, loff_t count);
 int sync_page_range_nolock(struct inode *inode, struct address_space *mapping,
                           loff_t pos, loff_t count);
-void set_page_dirty_balance(struct page *page);
+void set_page_dirty_balance(struct page *page, int page_mkwrite);
 void writeback_set_ratelimit(void);
 
 /* pdflush.c */

diff --git a/mm/memory.c b/mm/memory.c
index c0e7741..f82b359 100644 (file)
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1639,6 +1639,7 @@ static int do_wp_page(struct mm_struct *mm, struct vm_area_struct *vma,
        struct page *old_page, *new_page;
        pte_t entry;
        int reuse = 0, ret = 0;
+       int page_mkwrite = 0;
        struct page *dirty_page = NULL;
 
        old_page = vm_normal_page(vma, address, orig_pte);
@@ -1687,6 +1688,8 @@ static int do_wp_page(struct mm_struct *mm, struct vm_area_struct *vma,
                        page_cache_release(old_page);
                        if (!pte_same(*page_table, orig_pte))
                                goto unlock;
+
+                       page_mkwrite = 1;
                }
                dirty_page = old_page;
                get_page(dirty_page);
@@ -1774,7 +1777,7 @@ unlock:
                 * do_no_page is protected similarly.
                 */
                wait_on_page_locked(dirty_page);
-               set_page_dirty_balance(dirty_page);
+               set_page_dirty_balance(dirty_page, page_mkwrite);
                put_page(dirty_page);
        }
        return ret;
@@ -2322,6 +2325,7 @@ static int __do_fault(struct mm_struct *mm, struct vm_area_struct *vma,
        struct page *dirty_page = NULL;
        struct vm_fault vmf;
        int ret;
+       int page_mkwrite = 0;
 
        vmf.virtual_address = (void __user *)(address & PAGE_MASK);
        vmf.pgoff = pgoff;
@@ -2398,6 +2402,7 @@ static int __do_fault(struct mm_struct *mm, struct vm_area_struct *vma,
                                        anon = 1; /* no anon but release vmf.page */
                                        goto out;
                                }
+                               page_mkwrite = 1;
                        }
                }
 
@@ -2453,7 +2458,7 @@ out_unlocked:
        if (anon)
                page_cache_release(vmf.page);
        else if (dirty_page) {
-               set_page_dirty_balance(dirty_page);
+               set_page_dirty_balance(dirty_page, page_mkwrite);
                put_page(dirty_page);
        }
 

diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 63512a9..4472036 100644 (file)
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -274,9 +274,9 @@ static void balance_dirty_pages(struct address_space *mapping)
                pdflush_operation(background_writeout, 0);
 }
 
-void set_page_dirty_balance(struct page *page)
+void set_page_dirty_balance(struct page *page, int page_mkwrite)
 {
-       if (set_page_dirty(page)) {
+       if (set_page_dirty(page) || page_mkwrite) {
                struct address_space *mapping = page_mapping(page);
 
                if (mapping)