linux-kernel - Re: [PATCH 1/5] jbd: strictly check for write errors on data buffers

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Date:	Thu, 12 Jun 2008 22:19:37 +0900
From:	Hidehiro Kawai <hidehiro.kawai.ez@...achi.com>
To:	Jan Kara <jack@...e.cz>
Cc:	Andreas Dilger <adilger@....com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Theodore Tso <tytso@....edu>, sct@...hat.com,
	linux-kernel@...r.kernel.org, linux-ext4@...r.kernel.org,
	jbacik@...hat.com, cmm@...ibm.com, yumiko.sugita.yf@...achi.com,
	satoshi.oshima.fk@...achi.com
Subject: Re: [PATCH 1/5] jbd: strictly check for write errors on data	buffers

Hi,

Jan Kara wrote:

> On Mon 09-06-08 19:09:25, Hidehiro Kawai wrote:

>>Index: linux-2.6.26-rc4/fs/jbd/commit.c
>>===================================================================
>>--- linux-2.6.26-rc4.orig/fs/jbd/commit.c
>>+++ linux-2.6.26-rc4/fs/jbd/commit.c
>>@@ -432,8 +432,11 @@ void journal_commit_transaction(journal_
>> 			wait_on_buffer(bh);
>> 			spin_lock(&journal->j_list_lock);
>> 		}
>>-		if (unlikely(!buffer_uptodate(bh)))
>>+		if (unlikely(!buffer_uptodate(bh))) {
>>+			set_bit(AS_EIO, &bh->b_page->mapping->flags);
>>+			SetPageError(bh->b_page);
>> 			err = -EIO;
>>+		}
> 
>   Actually, you should be more careful here because if the data buffer has
> been truncated in the currently running transaction, it can happen that
> b_page->mapping is NULL. It is a question how to safely access
> page->mapping - probably you'll need page lock for that...

Thank you for pointing out this problem.  I confirmed that
b_page->mapping can be NULL.  I'm making sure that the locking page
approach works out well.

Thanks,
-- 
Hidehiro Kawai
Hitachi, Systems Development Laboratory
Linux Technology Center

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