[PATCH] truncate: clear page dirtiness before running try_to_free_buffers()

truncate presently invalidates the dirty page's buffer_heads then shoots down
the page.  But try_to_free_buffers() will now bale out because the page is
dirty.

Net effect: the LRU gets filled with dirty pages which have invalidated
buffer_heads attached.  They have no ->mapping and hence cannot be cleaned.
The machine leaks memory at an enormous rate.

Fix this by cleaning the page before running try_to_free_buffers(), so
try_to_free_buffers() can do its work.

Also, remember to do dirty-page-acoounting in cancel_dirty_page() so the
machine won't wedge up trying to write non-existent dirty pages.

Probably still wrong, but now less so.

Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

diff --git a/mm/truncate.c b/mm/truncate.c
index bf9e2965d6664dacec17094162d20772433923d3..89a5c359b6e821ec00e0fd8e8d189f3d9152e45a 100644 (file)
--- a/mm/truncate.c
+++ b/mm/truncate.c
@@ -60,11 +60,12 @@ void cancel_dirty_page(struct page *page, unsigned int account_size)
                WARN_ON(++warncount < 5);
        }
                
-       if (TestClearPageDirty(page) && account_size)
+       if (TestClearPageDirty(page) && account_size) {
+               dec_zone_page_state(page, NR_FILE_DIRTY);
                task_io_account_cancelled_write(account_size);
+       }
 }
 
-
 /*
  * If truncate cannot remove the fs-private metadata from the page, the page
  * becomes anonymous.  It will be left on the LRU and may even be mapped into
@@ -81,11 +82,11 @@ truncate_complete_page(struct address_space *mapping, struct page *page)
        if (page->mapping != mapping)
                return;
 
+       cancel_dirty_page(page, PAGE_CACHE_SIZE);
+
        if (PagePrivate(page))
                do_invalidatepage(page, 0);
 
-       cancel_dirty_page(page, PAGE_CACHE_SIZE);
-
        ClearPageUptodate(page);
        ClearPageMappedToDisk(page);
        remove_from_page_cache(page);