libceph: replace message data pointer with list

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

diff --git a/include/linux/ceph/messenger.h b/include/linux/ceph/messenger.h
index 8846ff6..318da01 100644 (file)
--- 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 3aa0f30..8bfe7d3 100644 (file)
--- 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)
@@ -2963,6 +2965,7 @@ 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;
 }
@@ -2972,6 +2975,7 @@ 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);
@@ -2987,7 +2991,7 @@ 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);
@@ -2995,8 +2999,9 @@ 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);
 
@@ -3008,14 +3013,14 @@ 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);
 
@@ -3027,15 +3032,15 @@ 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 */
@@ -3059,6 +3064,7 @@ 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;
@@ -3204,6 +3210,9 @@ 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));
@@ -3213,8 +3222,15 @@ 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)
@@ -3227,7 +3243,7 @@ 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);