linux-kernel - Re: [PATCH 1/8] f2fs: clear nlink if fail to add

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Date:   Wed, 12 Oct 2016 10:22:44 -0700
From:   Jaegeuk Kim <jaegeuk@...nel.org>
To:     Chao Yu <chao@...nel.org>
Cc:     linux-f2fs-devel@...ts.sourceforge.net,
        linux-kernel@...r.kernel.org, Chao Yu <yuchao0@...wei.com>
Subject: Re: [PATCH 1/8] f2fs: clear nlink if fail to add_link

On Wed, Oct 12, 2016 at 11:24:28PM +0800, Chao Yu wrote:
> Hi Jaegeuk,
> 
> On 2016/10/12 6:19, Jaegeuk Kim wrote:
> > Hi Chao,
> > 
> > On Tue, Oct 11, 2016 at 10:56:59PM +0800, Chao Yu wrote:
> >> From: Chao Yu <yuchao0@...wei.com>
> >>
> >> We don't need to keep incomplete created inode in cache, so if we fail to
> >> add link into directory during new inode creation, it's better to set
> >> nlink of inode to zero, then we can evict inode immediately. Otherwise
> >> release of nid belong to inode will be delayed until inode cache is being
> >> shrunk, it may cause a seemingly endless loop while allocating free nids
> >> in time of testing generic/269 case of fstest suit.
> >>
> >> Signed-off-by: Chao Yu <yuchao0@...wei.com>
> >> ---
> >>  fs/f2fs/inode.c | 8 ++++++++
> >>  1 file changed, 8 insertions(+)
> >>
> >> diff --git a/fs/f2fs/inode.c b/fs/f2fs/inode.c
> >> index d736989..34ae03c 100644
> >> --- a/fs/f2fs/inode.c
> >> +++ b/fs/f2fs/inode.c
> >> @@ -384,6 +384,8 @@ retry:
> >>  		f2fs_lock_op(sbi);
> >>  		err = remove_inode_page(inode);
> >>  		f2fs_unlock_op(sbi);
> >> +		if (err == -ENOENT)
> >> +			err = 0;
> >>  	}
> >>  
> >>  	/* give more chances, if ENOMEM case */
> >> @@ -424,6 +426,12 @@ void handle_failed_inode(struct inode *inode)
> >>  	struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
> >>  	struct node_info ni;
> >>  
> >> +	/*
> >> +	 * clear nlink of inode in order to release resource of inode
> >> +	 * immediately.
> >> +	 */
> >> +	clear_nlink(inode);
> > 
> > We must call update_inode_page() here to avoid kernel panic.
> > Otherwise, this inode is kept in the gdirty list, resulting in kernel panic
> > when flushg dirty inodes, since it was already evicted.
> 
> Thanks for fixing this, is this panic produced with fault injection?

No, it happened xfstests/027 under encrypted mode only.

Thanks,

> 
> Thanks,
> 
> > 
> > I fixed this and started a round of tests.
> > 
> > Thanks,
> > 
> >> +
> >>  	/* don't make bad inode, since it becomes a regular file. */
> >>  	unlock_new_inode(inode);
> >>  
> >> -- 
> >> 2.10.1