linux-kernel - Re: [PATCH 3/5] f2fs: move f2fs_balance

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Date:	Fri, 08 Mar 2013 11:33:05 +0900
From:	Jaegeuk Kim <jaegeuk.kim@...sung.com>
To:	Namjae Jeon <linkinjeon@...il.com>
Cc:	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-f2fs-devel@...ts.sourceforge.net,
	Namjae Jeon <namjae.jeon@...sung.com>,
	Amit Sahrawat <a.sahrawat@...sung.com>
Subject: Re: [PATCH 3/5] f2fs: move f2fs_balance_fs to correct place in unlink

2013-03-04 (월), 15:10 +0900, Namjae Jeon:
> 2013/3/3, Jaegeuk Kim <jaegeuk.kim@...sung.com>:
> > 2013-03-02 (토), 12:41 +0900, Namjae Jeon:
> >> From: Namjae Jeon <namjae.jeon@...sung.com>
> >>
> >> Actual dirty of pages will occur in f2fs_delete_entry so move the
> >> f2fs_balance_fs just before deletion.
> >>
> >> Signed-off-by: Namjae Jeon <namjae.jeon@...sung.com>
> >> Signed-off-by: Amit Sahrawat <a.sahrawat@...sung.com>
> >> ---
> >>  fs/f2fs/namei.c |    4 ++--
> >>  1 file changed, 2 insertions(+), 2 deletions(-)
> >>
> >> diff --git a/fs/f2fs/namei.c b/fs/f2fs/namei.c
> >> index 1a49b88..eaa86f5 100644
> >> --- a/fs/f2fs/namei.c
> >> +++ b/fs/f2fs/namei.c
> >> @@ -223,8 +223,6 @@ static int f2fs_unlink(struct inode *dir, struct
> >> dentry *dentry)
> >>  	struct page *page;
> >>  	int err = -ENOENT;
> >>
> >> -	f2fs_balance_fs(sbi);
> >> -
> >>  	de = f2fs_find_entry(dir, &dentry->d_name, &page);
> >>  	if (!de)
> >>  		goto fail;
> >> @@ -236,6 +234,8 @@ static int f2fs_unlink(struct inode *dir, struct
> >> dentry *dentry)
> >>  		goto fail;
> >>  	}
> >>
> >> +	f2fs_balance_fs(sbi);
> >> +
> >
> > I think we don't need to do this because of no issues on performance and
> > reliability.
> > In addition, it would be better to call f2fs_balance_fs without any
> > dentry page.
> Regarding moving “f2fs_balance_fs” in unlink part– we considered one scenario.
> Suppose – when the disk is full and it really needed to trigger the
> Garbage collection. But in this we considered one scenario. Let’s say
> the ‘name’ being passed is for invalid file i.e., the file does not
> exist. So, primarily in this case – I think it should return
> immediately.
> In such cases it actually results in wrong timing results for the
> non-existence files.
> For this observation we thought that f2fs_balance_fs be instead called
> at a proper place i.e., after there is no lookup-failure.

If so, could you check all the locations of f2fs_balance_fs and write
one patch for whole things?
I suspect that many directory operations are exposed to this issue.
Thanks,

> 
> Let me know your opinion.
> Thanks.
> >
> >>  	f2fs_delete_entry(de, page, inode);
> >>
> >>  	/* In order to evict this inode,  we set it dirty */
> >
> > --
> > Jaegeuk Kim
> > Samsung
> >
> --
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-- 
Jaegeuk Kim
Samsung

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