Re: [PATCH 4/6] libceph: replace message data pointer with list

[Josh Durgin <josh.durgin@inktank.com>]

Reviewed-by: Josh Durgin <josh.durgin@inktank.com>

On 04/05/2013 03:26 PM, Alex Elder wrote:
> In place of the message data pointer, use a list head which links
> through message data items.  For now we only support a single entry
> on that list.
>
> Signed-off-by: Alex Elder <elder@inktank.com>
> ---
>   include/linux/ceph/messenger.h |    3 ++-
>   net/ceph/messenger.c           |   46
> +++++++++++++++++++++++++++-------------
>   2 files changed, 33 insertions(+), 16 deletions(-)
>
> diff --git a/include/linux/ceph/messenger.h b/include/linux/ceph/messenger.h
> index 8846ff6..318da01 100644
> --- a/include/linux/ceph/messenger.h
> +++ b/include/linux/ceph/messenger.h
> @@ -89,6 +89,7 @@ static __inline__ bool ceph_msg_data_type_valid(enum
> ceph_msg_data_type type)
>   }
>
>   struct ceph_msg_data {
> +	struct list_head		links;	/* ceph_msg->data */
>   	enum ceph_msg_data_type		type;
>   	union {
>   #ifdef CONFIG_BLOCK
> @@ -143,7 +144,7 @@ struct ceph_msg {
>   	struct ceph_buffer *middle;
>
>   	size_t				data_length;
> -	struct ceph_msg_data		*data;
> +	struct list_head		data;
>   	struct ceph_msg_data_cursor	cursor;
>
>   	struct ceph_connection *con;
> diff --git a/net/ceph/messenger.c b/net/ceph/messenger.c
> index 50b4093..9ce667e 100644
> --- a/net/ceph/messenger.c
> +++ b/net/ceph/messenger.c
> @@ -985,8 +985,10 @@ static bool ceph_msg_data_pagelist_advance(struct
> ceph_msg_data_cursor *cursor,
>   static void ceph_msg_data_cursor_init(struct ceph_msg *msg, size_t length)
>   {
>   	struct ceph_msg_data_cursor *cursor = &msg->cursor;
> +	struct ceph_msg_data *data;
>
> -	cursor->data = msg->data;
> +	data = list_first_entry(&msg->data, struct ceph_msg_data, links);
> +	cursor->data = data;
>   	switch (cursor->data->type) {
>   	case CEPH_MSG_DATA_PAGELIST:
>   		ceph_msg_data_pagelist_cursor_init(cursor, length);
> @@ -1410,7 +1412,7 @@ static int write_partial_message_data(struct
> ceph_connection *con)
>
>   	dout("%s %p msg %p\n", __func__, con, msg);
>
> -	if (WARN_ON(!msg->data))
> +	if (list_empty(&msg->data))
>   		return -EINVAL;
>
>   	/*
> @@ -2111,7 +2113,7 @@ static int read_partial_msg_data(struct
> ceph_connection *con)
>   	int ret;
>
>   	BUG_ON(!msg);
> -	if (!msg->data)
> +	if (list_empty(&msg->data))
>   		return -EIO;
>
>   	if (do_datacrc)
> @@ -2961,6 +2963,7 @@ static struct ceph_msg_data
> *ceph_msg_data_create(enum ceph_msg_data_type type)
>   	data = kzalloc(sizeof (*data), GFP_NOFS);
>   	if (data)
>   		data->type = type;
> +	INIT_LIST_HEAD(&data->links);
>
>   	return data;
>   }
> @@ -2970,6 +2973,7 @@ static void ceph_msg_data_destroy(struct
> ceph_msg_data *data)
>   	if (!data)
>   		return;
>
> +	WARN_ON(!list_empty(&data->links));
>   	if (data->type == CEPH_MSG_DATA_PAGELIST) {
>   		ceph_pagelist_release(data->pagelist);
>   		kfree(data->pagelist);
> @@ -2985,7 +2989,7 @@ void ceph_msg_data_set_pages(struct ceph_msg *msg,
> struct page **pages,
>   	BUG_ON(!pages);
>   	BUG_ON(!length);
>   	BUG_ON(msg->data_length);
> -	BUG_ON(msg->data != NULL);
> +	BUG_ON(!list_empty(&msg->data));
>
>   	data = ceph_msg_data_create(CEPH_MSG_DATA_PAGES);
>   	BUG_ON(!data);
> @@ -2993,8 +2997,9 @@ void ceph_msg_data_set_pages(struct ceph_msg *msg,
> struct page **pages,
>   	data->length = length;
>   	data->alignment = alignment & ~PAGE_MASK;
>
> -	msg->data = data;
> -	msg->data_length = length;
> +	BUG_ON(!list_empty(&msg->data));
> +	list_add_tail(&data->links, &msg->data);
> +	msg->data_length += length;
>   }
>   EXPORT_SYMBOL(ceph_msg_data_set_pages);
>
> @@ -3006,14 +3011,14 @@ void ceph_msg_data_set_pagelist(struct ceph_msg
> *msg,
>   	BUG_ON(!pagelist);
>   	BUG_ON(!pagelist->length);
>   	BUG_ON(msg->data_length);
> -	BUG_ON(msg->data != NULL);
> +	BUG_ON(!list_empty(&msg->data));
>
>   	data = ceph_msg_data_create(CEPH_MSG_DATA_PAGELIST);
>   	BUG_ON(!data);
>   	data->pagelist = pagelist;
>
> -	msg->data = data;
> -	msg->data_length = pagelist->length;
> +	list_add_tail(&data->links, &msg->data);
> +	msg->data_length += pagelist->length;
>   }
>   EXPORT_SYMBOL(ceph_msg_data_set_pagelist);
>
> @@ -3025,15 +3030,15 @@ void ceph_msg_data_set_bio(struct ceph_msg *msg,
> struct bio *bio,
>
>   	BUG_ON(!bio);
>   	BUG_ON(msg->data_length);
> -	BUG_ON(msg->data != NULL);
> +	BUG_ON(!list_empty(&msg->data));
>
>   	data = ceph_msg_data_create(CEPH_MSG_DATA_BIO);
>   	BUG_ON(!data);
>   	data->bio = bio;
>   	data->bio_length = length;
>
> -	msg->data = data;
> -	msg->data_length = length;
> +	list_add_tail(&data->links, &msg->data);
> +	msg->data_length += length;
>   }
>   EXPORT_SYMBOL(ceph_msg_data_set_bio);
>   #endif	/* CONFIG_BLOCK */
> @@ -3057,6 +3062,7 @@ struct ceph_msg *ceph_msg_new(int type, int
> front_len, gfp_t flags,
>
>   	INIT_LIST_HEAD(&m->list_head);
>   	kref_init(&m->kref);
> +	INIT_LIST_HEAD(&m->data);
>
>   	/* front */
>   	m->front_max = front_len;
> @@ -3202,6 +3208,9 @@ void ceph_msg_kfree(struct ceph_msg *m)
>   void ceph_msg_last_put(struct kref *kref)
>   {
>   	struct ceph_msg *m = container_of(kref, struct ceph_msg, kref);
> +	LIST_HEAD(data);
> +	struct list_head *links;
> +	struct list_head *next;
>
>   	dout("ceph_msg_put last one on %p\n", m);
>   	WARN_ON(!list_empty(&m->list_head));
> @@ -3211,8 +3220,15 @@ void ceph_msg_last_put(struct kref *kref)
>   		ceph_buffer_put(m->middle);
>   		m->middle = NULL;
>   	}
> -	ceph_msg_data_destroy(m->data);
> -	m->data = NULL;
> +
> +	list_splice_init(&m->data, &data);
> +	list_for_each_safe(links, next, &data) {
> +		struct ceph_msg_data *data;
> +
> +		data = list_entry(links, struct ceph_msg_data, links);
> +		list_del_init(links);
> +		ceph_msg_data_destroy(data);
> +	}
>   	m->data_length = 0;
>
>   	if (m->pool)
> @@ -3225,7 +3241,7 @@ EXPORT_SYMBOL(ceph_msg_last_put);
>   void ceph_msg_dump(struct ceph_msg *msg)
>   {
>   	pr_debug("msg_dump %p (front_max %d length %zd)\n", msg,
> -		 msg->front_max, msg->data->length);
> +		 msg->front_max, msg->data_length);
>   	print_hex_dump(KERN_DEBUG, "header: ",
>   		       DUMP_PREFIX_OFFSET, 16, 1,
>   		       &msg->hdr, sizeof(msg->hdr), true);
>