2014-02-28 02:13:03

by Chao Yu

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

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 <[email protected]>
---
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

2014-03-01 00:26:49

by Dave Chinner

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

On Fri, Feb 28, 2014 at 10:12:05AM +0800, Chao Yu wrote:
> 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 <[email protected]>
> ---
> 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;

redirty_page_for_writepage()?

Cheers,

Dave.
--
Dave Chinner
[email protected]

2014-03-01 02:36:35

by Chao Yu

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

Hi,

> -----Original Message-----
> From: Dave Chinner [mailto:[email protected]]
> Sent: Saturday, March 01, 2014 8:27 AM
> To: Chao Yu
> Cc: ???; [email protected]; [email protected];
> [email protected]
> Subject: Re: [f2fs-dev] [PATCH] f2fs: fix dirty page accounting when redirty
>
> On Fri, Feb 28, 2014 at 10:12:05AM +0800, Chao Yu wrote:
> > 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 <[email protected]>
> > ---
> > 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;
>
> redirty_page_for_writepage()?

set_page_dirty() in a_ops of f2fs not only call __set_page_dirty_nobuffers(),
but also set some private data of page and print trace info.
So it seems we could not easily replace with redirty_page_for_writepage().

Thanks.

>
> Cheers,
>
> Dave.
> --
> Dave Chinner
> [email protected]