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

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

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.

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?

>  	}
>  got_it:
>  	if (new_i_size && i_size_read(inode) <
> --
> 2.6.3
> 
> 
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