linux-kernel - Re: [f2fs-dev] [PATCH] f2fs: get parent inode when recovering pino

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Date:   Tue, 5 May 2020 12:08:30 -0700
From:   Jaegeuk Kim <jaegeuk@...nel.org>
To:     Eric Biggers <ebiggers@...nel.org>
Cc:     linux-kernel@...r.kernel.org,
        linux-f2fs-devel@...ts.sourceforge.net, kernel-team@...roid.com
Subject: Re: [f2fs-dev] [PATCH] f2fs: get parent inode when recovering pino

On 05/05, Eric Biggers wrote:
> On Tue, May 05, 2020 at 11:49:32AM -0700, Jaegeuk Kim wrote:
> > How about this?
> > 
> > From 2a6b0e53e592854306062a2dc35db2d8f79062f2 Mon Sep 17 00:00:00 2001
> > From: Jaegeuk Kim <jaegeuk@...nel.org>
> > Date: Tue, 5 May 2020 11:33:29 -0700
> > Subject: [PATCH] f2fs: find a living dentry when finding parent ino
> > 
> > We need to check any dentry still alive to get parent inode number.
> > 
> > Suggested-by: Eric Biggers <ebiggers@...nel.org>
> > Signed-off-by: Jaegeuk Kim <jaegeuk@...nel.org>
> > ---
> >  fs/f2fs/file.c | 5 ++---
> >  1 file changed, 2 insertions(+), 3 deletions(-)
> > 
> > diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
> > index a0a4413d6083b..95139cb85faca 100644
> > --- a/fs/f2fs/file.c
> > +++ b/fs/f2fs/file.c
> > @@ -169,9 +169,8 @@ static int get_parent_ino(struct inode *inode, nid_t *pino)
> >  {
> >  	struct dentry *dentry;
> >  
> > -	inode = igrab(inode);
> > -	dentry = d_find_any_alias(inode);
> > -	iput(inode);
> > +	/* Need to check if valid dentry still exists. */
> > +	dentry = d_find_alias(inode);
> >  	if (!dentry)
> >  		return 0;
> >  
> 
> It's fine, but it could use some more explanation.  (What's a "valid dentry"?)
> How about the following?

Cool, I took this. Thanks,

> 
> >From f8fe7d57eead1423e8548ac7a5ec881d701466a5 Mon Sep 17 00:00:00 2001
> From: Eric Biggers <ebiggers@...gle.com>
> Date: Tue, 5 May 2020 11:41:11 -0700
> Subject: [PATCH] f2fs: correctly fix the parent inode number during fsync()
> 
> fsync() may be called on a deleted file that's still open.  So when
> fsync() tries to set the parent inode number when the inode has
> LOST_PINO and i_nlink == 1 (to avoid later checkpoints), it needs to
> make sure to get the parent directory via a non-deleted alias.
> 
> Also remove the unnecessary igrab() and iput(), as the caller already
> holds a reference to the inode.
> 
> Signed-off-by: Eric Biggers <ebiggers@...gle.com>
> ---
>  fs/f2fs/file.c | 8 +++++---
>  1 file changed, 5 insertions(+), 3 deletions(-)
> 
> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
> index 6ab8f621a3c5a2..b3069188fd3478 100644
> --- a/fs/f2fs/file.c
> +++ b/fs/f2fs/file.c
> @@ -165,9 +165,11 @@ static int get_parent_ino(struct inode *inode, nid_t *pino)
>  {
>  	struct dentry *dentry;
>  
> -	inode = igrab(inode);
> -	dentry = d_find_any_alias(inode);
> -	iput(inode);
> +	/*
> +	 * Make sure to get the non-deleted alias.  The alias associated with
> +	 * the open file descriptor being fsync()'ed may be deleted already.
> +	 */
> +	dentry = d_find_alias(inode);
>  	if (!dentry)
>  		return 0;
>  
> -- 
> 2.26.2