[Devel] Re: [PATCH 1/2] Add socket list helper functions

[Oren Laadan]

Dan Smith wrote:
> The INET patch needs to maintain a list of listening sockets in order to
> support post-restart socket hashing.  The ckpt_ctx_free() function thus
> needs to clean up that list after processing the deferqueue, and needs to
> know something about what is on that list.  Instead of calling into a
> single cleanup function in the checkpoint code, I decided to just make
> the list itself a little more abstract and separate it here.

IMHO this is over-engineered. This way, you place net-related knowledge
in ckpt_ctx_free(), instead of isolating that sort of smarts under net/
subdir. I'd rather see the clean-up logic near the "litter" logic, so
to speak.

Or, make it entirely generic, use container_of etc and put in, for
instance, in include/linux/list2.h. Anyway, I don't think it belongs
in checkpoint.h.

Thanks,

Oren.

> 
> Signed-off-by: Dan Smith <danms at us.ibm.com>
> ---
>  include/linux/checkpoint.h |    5 +++++
>  net/checkpoint.c           |   42 ++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 47 insertions(+), 0 deletions(-)
> 
> diff --git a/include/linux/checkpoint.h b/include/linux/checkpoint.h
> index dd75bc2..89e41c2 100644
> --- a/include/linux/checkpoint.h
> +++ b/include/linux/checkpoint.h
> @@ -100,6 +100,11 @@ extern int ckpt_sock_getnames(struct ckpt_ctx *ctx,
>  			      struct socket *socket,
>  			      struct sockaddr *loc, unsigned *loc_len,
>  			      struct sockaddr *rem, unsigned *rem_len);
> +int sock_list_add(struct list_head *list, struct sock *sk);
> +typedef int (*sock_compare_fn)(struct sock *, struct sock *);
> +struct sock *sock_list_find(struct list_head *list, struct sock *sk,
> +			    sock_compare_fn cmp);
> +void sock_list_free(struct list_head *list);
>  
>  /* ckpt kflags */
>  #define ckpt_set_ctx_kflag(__ctx, __kflag)  \
> diff --git a/net/checkpoint.c b/net/checkpoint.c
> index 9a72aae..e7e8e75 100644
> --- a/net/checkpoint.c
> +++ b/net/checkpoint.c
> @@ -758,3 +758,45 @@ struct file *sock_file_restore(struct ckpt_ctx *ctx, struct ckpt_hdr_file *ptr)
>  
>  	return file;
>  }
> +
> +struct ckpt_sock_list_item {
> +       struct sock *sk;
> +       struct list_head list;
> +};
> +
> +int sock_list_add(struct list_head *list, struct sock *sk)
> +{
> +	struct ckpt_sock_list_item *item;
> +
> +	item = kmalloc(sizeof(*item), GFP_KERNEL);
> +	if (!item)
> +		return -ENOMEM;
> +
> +	item->sk = sk;
> +	list_add(&item->list, list);
> +
> +	return 0;
> +}
> +
> +void sock_list_free(struct list_head *list)
> +{
> +	struct ckpt_sock_list_item *item, *tmp;
> +
> +	list_for_each_entry_safe(item, tmp, list, list) {
> +		list_del(&item->list);
> +		kfree(item);
> +	}
> +}
> +
> +struct sock *sock_list_find(struct list_head *list, struct sock *sk,
> +			    sock_compare_fn cmp)
> +{
> +	struct ckpt_sock_list_item *item;
> +
> +	list_for_each_entry(item, list, list) {
> +		if (cmp(sk, item->sk))
> +			return item->sk;
> +	}
> +
> +	return NULL;
> +}
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