linux-kernel - Re: [RFC PATCH 1/2] xfs: free the item in xfs_mru_cache

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Message-ID: <20250502200646.GT25675@frogsfrogsfrogs>
Date: Fri, 2 May 2025 13:06:46 -0700
From: "Darrick J. Wong" <djwong@...nel.org>
To: Hans Holmberg <Hans.Holmberg@....com>
Cc: "linux-xfs@...r.kernel.org" <linux-xfs@...r.kernel.org>,
	Carlos Maiolino <cem@...nel.org>,
	Dave Chinner <david@...morbit.com>, hch <hch@....de>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH 1/2] xfs: free the item in xfs_mru_cache_insert on
 failure

On Wed, Apr 30, 2025 at 08:41:21AM +0000, Hans Holmberg wrote:
> From: Christoph Hellwig <hch@....de>
> 
> Call the provided free_func when xfs_mru_cache_insert as that's what
> the callers need to do anyway.
> 
> Signed-off-by: Christoph Hellwig <hch@....de>
> Signed-off-by: Hans Holmberg <hans.holmberg@....com>
> ---
>  fs/xfs/xfs_filestream.c | 15 ++++-----------
>  fs/xfs/xfs_mru_cache.c  | 15 ++++++++++++---
>  2 files changed, 16 insertions(+), 14 deletions(-)
> 
> diff --git a/fs/xfs/xfs_filestream.c b/fs/xfs/xfs_filestream.c
> index a961aa420c48..044918fbae06 100644
> --- a/fs/xfs/xfs_filestream.c
> +++ b/fs/xfs/xfs_filestream.c
> @@ -304,11 +304,9 @@ xfs_filestream_create_association(
>  	 * for us, so all we need to do here is take another active reference to
>  	 * the perag for the cached association.
>  	 *
> -	 * If we fail to store the association, we need to drop the fstrms
> -	 * counter as well as drop the perag reference we take here for the
> -	 * item. We do not need to return an error for this failure - as long as
> -	 * we return a referenced AG, the allocation can still go ahead just
> -	 * fine.
> +	 * If we fail to store the association, we do not need to return an
> +	 * error for this failure - as long as we return a referenced AG, the
> +	 * allocation can still go ahead just fine.
>  	 */
>  	item = kmalloc(sizeof(*item), GFP_KERNEL | __GFP_RETRY_MAYFAIL);
>  	if (!item)
> @@ -316,14 +314,9 @@ xfs_filestream_create_association(
>  
>  	atomic_inc(&pag_group(args->pag)->xg_active_ref);
>  	item->pag = args->pag;
> -	error = xfs_mru_cache_insert(mp->m_filestream, pino, &item->mru);
> -	if (error)
> -		goto out_free_item;
> +	xfs_mru_cache_insert(mp->m_filestream, pino, &item->mru);

Hmm, don't you still need to check for -ENOMEM returns?  Or if truly
none of the callers care anymore, then can we get rid of the return
value for xfs_mru_cache_insert?

--D

>  	return 0;
>  
> -out_free_item:
> -	xfs_perag_rele(item->pag);
> -	kfree(item);
>  out_put_fstrms:
>  	atomic_dec(&args->pag->pagf_fstrms);
>  	return 0;
> diff --git a/fs/xfs/xfs_mru_cache.c b/fs/xfs/xfs_mru_cache.c
> index d0f5b403bdbe..08443ceec329 100644
> --- a/fs/xfs/xfs_mru_cache.c
> +++ b/fs/xfs/xfs_mru_cache.c
> @@ -414,6 +414,8 @@ xfs_mru_cache_destroy(
>   * To insert an element, call xfs_mru_cache_insert() with the data store, the
>   * element's key and the client data pointer.  This function returns 0 on
>   * success or ENOMEM if memory for the data element couldn't be allocated.
> + *
> + * The passed in elem is freed through the per-cache free_func on failure.
>   */
>  int
>  xfs_mru_cache_insert(
> @@ -421,14 +423,15 @@ xfs_mru_cache_insert(
>  	unsigned long		key,
>  	struct xfs_mru_cache_elem *elem)
>  {
> -	int			error;
> +	int			error = -EINVAL;
>  
>  	ASSERT(mru && mru->lists);
>  	if (!mru || !mru->lists)
> -		return -EINVAL;
> +		goto out_free;
>  
> +	error = -ENOMEM;
>  	if (radix_tree_preload(GFP_KERNEL))
> -		return -ENOMEM;
> +		goto out_free;
>  
>  	INIT_LIST_HEAD(&elem->list_node);
>  	elem->key = key;
> @@ -440,6 +443,12 @@ xfs_mru_cache_insert(
>  		_xfs_mru_cache_list_insert(mru, elem);
>  	spin_unlock(&mru->lock);
>  
> +	if (error)
> +		goto out_free;
> +	return 0;
> +
> +out_free:
> +	mru->free_func(mru->data, elem);
>  	return error;
>  }
>  
> -- 
> 2.34.1
>