Re: [PATCH 6/6] xfs: cleanup xfs_idestroy_fork

From: Brian Foster <bfoster@redhat.com>
To: Christoph Hellwig <hch@lst.de>
Cc: linux-xfs@vger.kernel.org
Subject: Re: [PATCH 6/6] xfs: cleanup xfs_idestroy_fork
Date: Tue, 12 May 2020 14:54:35 -0400	[thread overview]
Message-ID: <20200512185435.GL37029@bfoster> (raw)
In-Reply-To: <20200510072404.986627-7-hch@lst.de>

On Sun, May 10, 2020 at 09:24:04AM +0200, Christoph Hellwig wrote:
> Move freeing the dynamically allocated attr and COW fork, as well
> as zeroing the pointers where actually needed into the callers, and
> just pass the xfs_ifork structure to xfs_idestroy_fork.  Simplify
> the kmem_free calls by not checking for NULL first, and not zeroing
> the pointers in structure that are about to be freed (either the
> ifork or the containing inode in case of the data fork).
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---
>  fs/xfs/libxfs/xfs_attr_leaf.c  |  7 +++----
>  fs/xfs/libxfs/xfs_inode_buf.c  |  2 +-
>  fs/xfs/libxfs/xfs_inode_fork.c | 36 +++++++++-------------------------
>  fs/xfs/libxfs/xfs_inode_fork.h |  2 +-
>  fs/xfs/xfs_attr_inactive.c     |  7 +++++--
>  fs/xfs/xfs_icache.c            | 15 ++++++++------
>  6 files changed, 28 insertions(+), 41 deletions(-)
> 
...
> diff --git a/fs/xfs/libxfs/xfs_inode_fork.c b/fs/xfs/libxfs/xfs_inode_fork.c
> index 6562f2bcd15cc..577cc20e03170 100644
> --- a/fs/xfs/libxfs/xfs_inode_fork.c
> +++ b/fs/xfs/libxfs/xfs_inode_fork.c
> @@ -495,38 +495,20 @@ xfs_idata_realloc(
>  
>  void
>  xfs_idestroy_fork(
> -	xfs_inode_t	*ip,
> -	int		whichfork)
> +	struct xfs_ifork	*ifp)
>  {
> -	struct xfs_ifork	*ifp;
> -
> -	ifp = XFS_IFORK_PTR(ip, whichfork);
> -	if (ifp->if_broot != NULL) {
> -		kmem_free(ifp->if_broot);
> -		ifp->if_broot = NULL;
> -	}
> +	kmem_free(ifp->if_broot);

I think this function should still reset the pointers within the ifp
that it frees (if_broot and if_data below), particularly as long as
there are multiple callers that pass the data fork because it is not
immediately/independently freed. IOW, it's not clear if something
happens to reset i_mode between when xfs_inode_from_disk() might fail
and destroy the data fork, and when the inode is ultimately freed and we
look at i_mode to determine whether to destroy the data fork.

Brian

>  
>  	/*
> -	 * If the format is local, then we can't have an extents
> -	 * array so just look for an inline data array.  If we're
> -	 * not local then we may or may not have an extents list,
> -	 * so check and free it up if we do.
> +	 * If the format is local, then we can't have an extents array so just
> +	 * look for an inline data array.  If we're not local then we may or may
> +	 * not have an extents list, so check and free it up if we do.
>  	 */
>  	if (ifp->if_format == XFS_DINODE_FMT_LOCAL) {
> -		if (ifp->if_u1.if_data != NULL) {
> -			kmem_free(ifp->if_u1.if_data);
> -			ifp->if_u1.if_data = NULL;
> -		}
> -	} else if ((ifp->if_flags & XFS_IFEXTENTS) && ifp->if_height) {
> -		xfs_iext_destroy(ifp);
> -	}
> -
> -	if (whichfork == XFS_ATTR_FORK) {
> -		kmem_cache_free(xfs_ifork_zone, ip->i_afp);
> -		ip->i_afp = NULL;
> -	} else if (whichfork == XFS_COW_FORK) {
> -		kmem_cache_free(xfs_ifork_zone, ip->i_cowfp);
> -		ip->i_cowfp = NULL;
> +		kmem_free(ifp->if_u1.if_data);
> +	} else if (ifp->if_flags & XFS_IFEXTENTS) {
> +		if (ifp->if_height)
> +			xfs_iext_destroy(ifp);
>  	}
>  }
>  
> diff --git a/fs/xfs/libxfs/xfs_inode_fork.h b/fs/xfs/libxfs/xfs_inode_fork.h
> index d849cca103edd..a4953e95c4f3f 100644
> --- a/fs/xfs/libxfs/xfs_inode_fork.h
> +++ b/fs/xfs/libxfs/xfs_inode_fork.h
> @@ -86,7 +86,7 @@ int		xfs_iformat_data_fork(struct xfs_inode *, struct xfs_dinode *);
>  int		xfs_iformat_attr_fork(struct xfs_inode *, struct xfs_dinode *);
>  void		xfs_iflush_fork(struct xfs_inode *, struct xfs_dinode *,
>  				struct xfs_inode_log_item *, int);
> -void		xfs_idestroy_fork(struct xfs_inode *, int);
> +void		xfs_idestroy_fork(struct xfs_ifork *ifp);
>  void		xfs_idata_realloc(struct xfs_inode *ip, int64_t byte_diff,
>  				int whichfork);
>  void		xfs_iroot_realloc(struct xfs_inode *, int, int);
> diff --git a/fs/xfs/xfs_attr_inactive.c b/fs/xfs/xfs_attr_inactive.c
> index 00ffc46c0bf71..bfad669e6b2f8 100644
> --- a/fs/xfs/xfs_attr_inactive.c
> +++ b/fs/xfs/xfs_attr_inactive.c
> @@ -388,8 +388,11 @@ xfs_attr_inactive(
>  	xfs_trans_cancel(trans);
>  out_destroy_fork:
>  	/* kill the in-core attr fork before we drop the inode lock */
> -	if (dp->i_afp)
> -		xfs_idestroy_fork(dp, XFS_ATTR_FORK);
> +	if (dp->i_afp) {
> +		xfs_idestroy_fork(dp->i_afp);
> +		kmem_cache_free(xfs_ifork_zone, dp->i_afp);
> +		dp->i_afp = NULL;
> +	}
>  	if (lock_mode)
>  		xfs_iunlock(dp, lock_mode);
>  	return error;
> diff --git a/fs/xfs/xfs_icache.c b/fs/xfs/xfs_icache.c
> index c09b3e9eab1da..d806d3bfa8936 100644
> --- a/fs/xfs/xfs_icache.c
> +++ b/fs/xfs/xfs_icache.c
> @@ -87,15 +87,18 @@ xfs_inode_free_callback(
>  	case S_IFREG:
>  	case S_IFDIR:
>  	case S_IFLNK:
> -		xfs_idestroy_fork(ip, XFS_DATA_FORK);
> +		xfs_idestroy_fork(&ip->i_df);
>  		break;
>  	}
>  
> -	if (ip->i_afp)
> -		xfs_idestroy_fork(ip, XFS_ATTR_FORK);
> -	if (ip->i_cowfp)
> -		xfs_idestroy_fork(ip, XFS_COW_FORK);
> -
> +	if (ip->i_afp) {
> +		xfs_idestroy_fork(ip->i_afp);
> +		kmem_cache_free(xfs_ifork_zone, ip->i_afp);
> +	}
> +	if (ip->i_cowfp) {
> +		xfs_idestroy_fork(ip->i_cowfp);
> +		kmem_cache_free(xfs_ifork_zone, ip->i_cowfp);
> +	}
>  	if (ip->i_itemp) {
>  		ASSERT(!test_bit(XFS_LI_IN_AIL,
>  				 &ip->i_itemp->ili_item.li_flags));
> -- 
> 2.26.2
> 