Re: [f2fs-dev] [PATCH 1/3] f2fs: check the page status filled from disk

[Jaegeuk Kim <jaegeuk@kernel.org>]

Hi Chao,

On Tue, Jan 05, 2016 at 05:31:51PM +0800, Chao Yu wrote:
> Hi Jaegeuk,
> 
> > -----Original Message-----
> > From: Jaegeuk Kim [mailto:jaegeuk@kernel.org]
> > Sent: Sunday, January 03, 2016 9:26 AM
> > To: linux-kernel@vger.kernel.org; linux-fsdevel@vger.kernel.org;
> > linux-f2fs-devel@lists.sourceforge.net
> > Cc: Jaegeuk Kim
> > Subject: [f2fs-dev] [PATCH 1/3] f2fs: check the page status filled from disk
> > 
> > After reading a page, we need to check whether there is any error.
> > 
> > Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
> > ---
> >  fs/f2fs/data.c | 8 ++++++++
> >  1 file changed, 8 insertions(+)
> > 
> > diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
> > index 89a978c..11b2111 100644
> > --- a/fs/f2fs/data.c
> > +++ b/fs/f2fs/data.c
> > @@ -448,6 +448,14 @@ repeat:
> > 
> >  		/* wait for read completion */
> >  		lock_page(page);
> > +		if (unlikely(!PageUptodate(page))) {
> > +			f2fs_put_page(page, 1);
> > +			return ERR_PTR(-EIO);
> 
> There is a convention in get_new_data_page, anyway we should release ipage
> if there is any error occurs, but I think it will be ok to return directly
> since it seems impossible the new dentry page has its real block address.

Makes sense, but definitely ipage should be put. :)

> 
> To avoid any bug here or wrong usage, how about add bug_on as following patch?
> 
> >From d92f0f34493b27ef28da67c446d552ce721b5d6f Mon Sep 17 00:00:00 2001
> From: Chao Yu <chao2.yu@samsung.com>
> Date: Tue, 5 Jan 2016 15:28:56 +0800
> Subject: [PATCH] f2fs: add f2fs_bug_on in get_new_data_page
> 
> In get_new_data_page, locked inode page should not be hold before
> get_read_data_page, this patch adds f2fs_bug_on to detect this
> condition.
> 
> Signed-off-by: Chao Yu <chao2.yu@samsung.com>
> ---
>  fs/f2fs/data.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
> index 48f0bd3..2c5e3f6 100644
> --- a/fs/f2fs/data.c
> +++ b/fs/f2fs/data.c
> @@ -440,6 +440,8 @@ repeat:
>  		zero_user_segment(page, 0, PAGE_CACHE_SIZE);
>  		SetPageUptodate(page);
>  	} else {
> +		f2fs_bug_on(F2FS_I_SB(inode), ipage);
> +
>  		f2fs_put_page(page, 1);
>  
>  		page = get_read_data_page(inode, index, READ_SYNC, true);
> -- 
> 2.6.3
> 
> 
> > +		}
> > +		if (unlikely(page->mapping != mapping)) {
> > +			f2fs_put_page(page, 1);
> > +			goto repeat;
> > +		}
> 
> How about use get_lock_data_page to avoid duplicated code?

Agreed.

How about this?

>From fef77fb244a706491e8e4c46cb245e99e22003c3 Mon Sep 17 00:00:00 2001
From: Jaegeuk Kim <jaegeuk@kernel.org>
Date: Fri, 1 Jan 2016 22:03:47 -0800
Subject: [PATCH] f2fs: check the page status filled from disk

After reading a page, we need to check whether there is any error.

Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
---
 fs/f2fs/data.c | 14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
index 89a978c..89d633a 100644
--- a/fs/f2fs/data.c
+++ b/fs/f2fs/data.c
@@ -442,12 +442,16 @@ repeat:
 	} else {
 		f2fs_put_page(page, 1);
 
-		page = get_read_data_page(inode, index, READ_SYNC, true);
-		if (IS_ERR(page))
-			goto repeat;
+		f2fs_bug_on(F2FS_I_SB(inode), ipage);
 
-		/* wait for read completion */
-		lock_page(page);
+		page = get_lock_data_page(inode, index, true);
+		if (IS_ERR(page)) {
+			if (PTR_ERR(page) == -EIO) {
+				f2fs_put_page(ipage, 1);
+				return page;
+			}
+			goto repeat;
+		}
 	}
 got_it:
 	if (new_i_size && i_size_read(inode) <
-- 
2.6.3