linux-kernel - [patch] mm: task dirty accounting fix

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Date:	Tue, 10 Feb 2009 05:39:53 +0100
From:	Nick Piggin <npiggin@...e.de>
To:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	YAMAMOTO Takashi <yamamoto@...inux.co.jp>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: [patch] mm: task dirty accounting fix

Hi,

This is based from an earlier patch from YAMAMOTO-san which I have
somewhat simplified. What do you think?

Thanks,
Nick

--
YAMAMOTO-san noticed that task_dirty_inc doesn't seem to be called properly for
cases where set_page_dirty is not used to dirty a page (eg. mark_buffer_dirty).

Additionally, there is some inconsistency about when task_dirty_inc is
called. It is used for dirty balancing, however it even gets called for
__set_page_dirty_no_writeback.

So rather than increment it in a set_page_dirty wrapper, move it down to
exactly where the dirty page accounting stats are incremented.

Cc: YAMAMOTO Takashi <yamamoto@...inux.co.jp>
Signed-off-by: Nick Piggin <npiggin@...e.de>
---
 fs/buffer.c         |    1 +
 include/linux/mm.h  |    1 +
 mm/page-writeback.c |   13 +++----------
 3 files changed, 5 insertions(+), 10 deletions(-)

Index: linux-2.6/include/linux/mm.h
===================================================================
--- linux-2.6.orig/include/linux/mm.h
+++ linux-2.6/include/linux/mm.h
@@ -1162,6 +1162,7 @@ extern int filemap_fault(struct vm_area_
 
 /* mm/page-writeback.c */
 int write_one_page(struct page *page, int wait);
+void task_dirty_inc(struct task_struct *tsk);
 
 /* readahead.c */
 #define VM_MAX_READAHEAD	128	/* kbytes */
Index: linux-2.6/mm/page-writeback.c
===================================================================
--- linux-2.6.orig/mm/page-writeback.c
+++ linux-2.6/mm/page-writeback.c
@@ -241,7 +241,7 @@ void bdi_writeout_inc(struct backing_dev
 }
 EXPORT_SYMBOL_GPL(bdi_writeout_inc);
 
-static inline void task_dirty_inc(struct task_struct *tsk)
+void task_dirty_inc(struct task_struct *tsk)
 {
 	prop_inc_single(&vm_dirties, &tsk->dirties);
 }
@@ -1228,6 +1228,7 @@ int __set_page_dirty_nobuffers(struct pa
 				__inc_zone_page_state(page, NR_FILE_DIRTY);
 				__inc_bdi_stat(mapping->backing_dev_info,
 						BDI_RECLAIMABLE);
+				task_dirty_inc(current);
 				task_io_account_write(PAGE_CACHE_SIZE);
 			}
 			radix_tree_tag_set(&mapping->page_tree,
@@ -1263,7 +1264,7 @@ EXPORT_SYMBOL(redirty_page_for_writepage
  * If the mapping doesn't provide a set_page_dirty a_op, then
  * just fall through and assume that it wants buffer_heads.
  */
-static int __set_page_dirty(struct page *page)
+int set_page_dirty(struct page *page)
 {
 	struct address_space *mapping = page_mapping(page);
 
@@ -1281,14 +1282,6 @@ static int __set_page_dirty(struct page
 	}
 	return 0;
 }
-
-int set_page_dirty(struct page *page)
-{
-	int ret = __set_page_dirty(page);
-	if (ret)
-		task_dirty_inc(current);
-	return ret;
-}
 EXPORT_SYMBOL(set_page_dirty);
 
 /*
Index: linux-2.6/fs/buffer.c
===================================================================
--- linux-2.6.orig/fs/buffer.c
+++ linux-2.6/fs/buffer.c
@@ -628,6 +628,7 @@ static int __set_page_dirty(struct page
 			__inc_zone_page_state(page, NR_FILE_DIRTY);
 			__inc_bdi_stat(mapping->backing_dev_info,
 					BDI_RECLAIMABLE);
+			task_dirty_inc(current);
 			task_io_account_write(PAGE_CACHE_SIZE);
 		}
 		radix_tree_tag_set(&mapping->page_tree,
--
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