Re: [PATCH v4 14/17] xfs: mount-api - add xfs_fc_free()

[Brian Foster <bfoster@redhat.com>]

On Thu, Oct 03, 2019 at 06:26:32PM +0800, Ian Kent wrote:
> Add the fs_context_operations method .free that performs fs
> context cleanup on context release.
> 
> Signed-off-by: Ian Kent <raven@themaw.net>
> ---
>  fs/xfs/xfs_super.c |   26 ++++++++++++++++++++++++++
>  1 file changed, 26 insertions(+)
> 
> diff --git a/fs/xfs/xfs_super.c b/fs/xfs/xfs_super.c
> index 06f650fb3a8c..4f2963ff9e06 100644
> --- a/fs/xfs/xfs_super.c
> +++ b/fs/xfs/xfs_super.c
> @@ -2133,10 +2133,36 @@ static const struct super_operations xfs_super_operations = {
>  	.free_cached_objects	= xfs_fs_free_cached_objects,
>  };
>  
> +static void xfs_fc_free(struct fs_context *fc)
> +{
> +	struct xfs_fs_context	*ctx = fc->fs_private;
> +	struct xfs_mount	*mp = fc->s_fs_info;
> +
> +	/*
> +	 * When the mount context is initialized the private
> +	 * struct xfs_mount info (mp) is allocated and stored in
> +	 * the fs context along with the struct xfs_fs_context
> +	 * (ctx) mount context working working storage.
> +	 *

"working working storage" ?

> +	 * On super block allocation the mount info struct, mp,
> +	 * is moved into private super block info field ->s_fs_info
> +	 * of the newly allocated super block. But if an error occurs
> +	 * before this happens it's the responsibility of the fs
> +	 * context to release the mount info struct.
> +	 */

I like the comment here, but it seems it could be simplified. E.g:

	/*
	 * mp and ctx are stored in the fs_context when it is initialized. mp is
	 * transferred to the superblock on a successful mount, but if an error
	 * occurs before the transfer we have to free it here.
	 */

> +	if (mp) {
> +		kfree(mp->m_logname);
> +		kfree(mp->m_rtname);

Also, can we just call xfs_free_fsname() here to be safe/consisent? With
those nits fixed up, this seems fine to me.

Brian

> +		kfree(mp);
> +	}
> +	kfree(ctx);
> +}
> +
>  static const struct fs_context_operations xfs_context_ops = {
>  	.parse_param = xfs_parse_param,
>  	.get_tree    = xfs_get_tree,
>  	.reconfigure = xfs_reconfigure,
> +	.free        = xfs_fc_free,
>  };
>  
>  static struct file_system_type xfs_fs_type = {
>