[patch 4/8] mm: allow not updating BDI stats in end_page_writeback()

[Miklos Szeredi <miklos@szeredi.hu>]

[-- Attachment #1: end_page_writeback_nobdi.patch --]
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Fuse's writepage will need to clear page writeback separately from
updating the per BDI counters.

This patch renames end_page_writeback() to __end_page_writeback() and
adds a boolean parameter to indicate if the per BDI stats need to be
updated.

Regular callers get an inline end_page_writeback() without the boolean
parameter.

Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
---
 include/linux/page-flags.h |    2 +-
 include/linux/pagemap.h    |    7 ++++++-
 mm/filemap.c               |    7 ++++---
 mm/page-writeback.c        |    4 ++--
 4 files changed, 13 insertions(+), 7 deletions(-)

Index: linux/include/linux/page-flags.h
===================================================================
--- linux.orig/include/linux/page-flags.h	2008-03-17 18:24:13.000000000 +0100
+++ linux/include/linux/page-flags.h	2008-03-17 18:25:53.000000000 +0100
@@ -300,7 +300,7 @@ struct page;	/* forward declaration */
 
 extern void cancel_dirty_page(struct page *page, unsigned int account_size);
 
-int test_clear_page_writeback(struct page *page);
+int test_clear_page_writeback(struct page *page, bool bdi_stats);
 int test_set_page_writeback(struct page *page);
 
 static inline void set_page_writeback(struct page *page)
Index: linux/include/linux/pagemap.h
===================================================================
--- linux.orig/include/linux/pagemap.h	2008-03-17 18:24:13.000000000 +0100
+++ linux/include/linux/pagemap.h	2008-03-17 18:25:53.000000000 +0100
@@ -223,7 +223,12 @@ static inline void wait_on_page_writebac
 		wait_on_page_bit(page, PG_writeback);
 }
 
-extern void end_page_writeback(struct page *page);
+extern void __end_page_writeback(struct page *page, bool bdi_stats);
+
+static inline void end_page_writeback(struct page *page)
+{
+	__end_page_writeback(page, true);
+}
 
 /*
  * Fault a userspace page into pagetables.  Return non-zero on a fault.
Index: linux/mm/filemap.c
===================================================================
--- linux.orig/mm/filemap.c	2008-03-17 18:25:38.000000000 +0100
+++ linux/mm/filemap.c	2008-03-17 18:25:53.000000000 +0100
@@ -574,19 +574,20 @@ EXPORT_SYMBOL(unlock_page);
 /**
  * end_page_writeback - end writeback against a page
  * @page: the page
+ * @bdi_stats: update the per-bdi writeback counter
  */
-void end_page_writeback(struct page *page)
+void __end_page_writeback(struct page *page, bool bdi_stats)
 {
 	if (TestClearPageReclaim(page))
 		rotate_reclaimable_page(page);
 
-	if (!test_clear_page_writeback(page))
+	if (!test_clear_page_writeback(page, bdi_stats))
 		BUG();
 
 	smp_mb__after_clear_bit();
 	wake_up_page(page, PG_writeback);
 }
-EXPORT_SYMBOL(end_page_writeback);
+EXPORT_SYMBOL(__end_page_writeback);
 
 /**
  * __lock_page - get a lock on the page, assuming we need to sleep to get it
Index: linux/mm/page-writeback.c
===================================================================
--- linux.orig/mm/page-writeback.c	2008-03-17 18:25:17.000000000 +0100
+++ linux/mm/page-writeback.c	2008-03-17 18:25:53.000000000 +0100
@@ -1242,7 +1242,7 @@ int clear_page_dirty_for_io(struct page 
 }
 EXPORT_SYMBOL(clear_page_dirty_for_io);
 
-int test_clear_page_writeback(struct page *page)
+int test_clear_page_writeback(struct page *page, bool bdi_stats)
 {
 	struct address_space *mapping = page_mapping(page);
 	int ret;
@@ -1257,7 +1257,7 @@ int test_clear_page_writeback(struct pag
 			radix_tree_tag_clear(&mapping->page_tree,
 						page_index(page),
 						PAGECACHE_TAG_WRITEBACK);
-			if (bdi_cap_writeback_dirty(bdi)) {
+			if (bdi_stats && bdi_cap_writeback_dirty(bdi)) {
 				__dec_bdi_stat(bdi, BDI_WRITEBACK);
 				__bdi_writeout_inc(bdi);
 			}

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