[f2fs-dev] [PATCH] f2fs: fix dirty page accounting when redirty

[Chao Yu <chao2.yu@samsung.com>]

We should de-account dirty counters for page when redirty in ->writepage().

Wu Fengguang described in 'commit 971767caf632190f77a40b4011c19948232eed75':
"writeback: fix dirtied pages accounting on redirty
De-account the accumulative dirty counters on page redirty.

Page redirties (very common in ext4) will introduce mismatch between
counters (a) and (b)

a) NR_DIRTIED, BDI_DIRTIED, tsk->nr_dirtied
b) NR_WRITTEN, BDI_WRITTEN

This will introduce systematic errors in balanced_rate and result in
dirty page position errors (ie. the dirty pages are no longer balanced
around the global/bdi setpoints)."

Signed-off-by: Chao Yu <chao2.yu@samsung.com>
---
 fs/f2fs/checkpoint.c |    1 +
 fs/f2fs/data.c       |    1 +
 fs/f2fs/node.c       |    1 +
 3 files changed, 3 insertions(+)

diff --git a/fs/f2fs/checkpoint.c b/fs/f2fs/checkpoint.c
index c8516ee..f069249 100644
--- a/fs/f2fs/checkpoint.c
+++ b/fs/f2fs/checkpoint.c
@@ -178,6 +178,7 @@ no_write:
 redirty_out:
 	dec_page_count(sbi, F2FS_DIRTY_META);
 	wbc->pages_skipped++;
+	account_page_redirty(page);
 	set_page_dirty(page);
 	return AOP_WRITEPAGE_ACTIVATE;
 }
diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
index 93d80ea..101b4cd 100644
--- a/fs/f2fs/data.c
+++ b/fs/f2fs/data.c
@@ -839,6 +839,7 @@ out:
 
 redirty_out:
 	wbc->pages_skipped++;
+	account_page_redirty(page);
 	set_page_dirty(page);
 	return AOP_WRITEPAGE_ACTIVATE;
 }
diff --git a/fs/f2fs/node.c b/fs/f2fs/node.c
index 1f9cf21..8c14110 100644
--- a/fs/f2fs/node.c
+++ b/fs/f2fs/node.c
@@ -1193,6 +1193,7 @@ static int f2fs_write_node_page(struct page *page,
 redirty_out:
 	dec_page_count(sbi, F2FS_DIRTY_NODES);
 	wbc->pages_skipped++;
+	account_page_redirty(page);
 	set_page_dirty(page);
 	return AOP_WRITEPAGE_ACTIVATE;
 }
-- 
1.7.9.5