[Sheepdog] [PATCH v2 2/3] cluster: add blocking mechanism to notification
Liu Yuan
namei.unix at gmail.com
Mon Oct 10 11:29:06 CEST 2011
On 10/10/2011 04:44 PM, MORITA Kazutaka wrote:
> Currently Sheepdog vdi operations (create/delete/lookup/...) are
> processed in two phase multicasting:
>
> 1. multicasts a vdi request
> 2. only the master node handles the request and multicasts the
> response
>
> During this two phase, we cannot allow any other vdi operations and
> membership changes, and this makes sheep/group.c a bit hard to read.
>
> This patch simplifies this by adding a blocking callback to the
> notification function in the cluster driver. If the caller of
> cdrv->notify() sets 'block_cb' as an argument, block_cb() is called
> from the cluster driver before the message is notified to any node.
> All the cluster events are blocked in every nodes until the caller
> finishes the vdi operation in block_cb().
>
> With this change, the master node is no longer in charge of vdi
> operations, but this is a good change to make Sheepdog more symmetric.
>
> Signed-off-by: MORITA Kazutaka<morita.kazutaka at lab.ntt.co.jp>
> ---
> sheep/cluster.h | 10 ++-
> sheep/cluster/corosync.c | 211 +++++++++++++++++++++++++++++++++++++++-------
> sheep/group.c | 12 ++--
> 3 files changed, 195 insertions(+), 38 deletions(-)
>
> diff --git a/sheep/cluster.h b/sheep/cluster.h
> index 43f4575..25b2d48 100644
> --- a/sheep/cluster.h
> +++ b/sheep/cluster.h
> @@ -71,11 +71,17 @@ struct cluster_driver {
> *
> * This function sends 'msg' to all the nodes. The notified
> * messages can be read through notify_handler() in
> - * cdrv_handlers.
> + * cdrv_handlers. If 'block_cb' is specified, block_cb() is
> + * called before 'msg' is notified to all the nodes. All the
> + * cluster events including this notification are blocked
> + * until block_cb() returns or this blocking node leaves the
> + * cluster. The sheep daemon can sleep in block_cb(), so this
> + * callback must be called from other than the dispatch
> + * thread.
from other than? I don't get it. Did you mean from worker thread other
than main thread?
> *
> * Returns zero on success, -1 on error
> */
> - int (*notify)(void *msg, size_t msg_len);
> + int (*notify)(void *msg, size_t msg_len, void (*block_cb)(void *arg));
>
> /*
> * Dispatch handlers
> diff --git a/sheep/cluster/corosync.c b/sheep/cluster/corosync.c
> index ff52525..629e8a9 100644
> --- a/sheep/cluster/corosync.c
> +++ b/sheep/cluster/corosync.c
> @@ -14,22 +14,35 @@
> #include<corosync/cfg.h>
>
> #include "cluster.h"
> +#include "work.h"
>
> static cpg_handle_t cpg_handle;
> static struct cpg_name cpg_group = { 9, "sheepdog" };
>
> static corosync_cfg_handle_t cfg_handle;
> +static struct sheepid this_sheepid;
> +
> +static struct work_queue *corosync_block_wq;
>
> static struct cdrv_handlers corosync_handlers;
>
> static LIST_HEAD(corosync_event_list);
> +static LIST_HEAD(corosync_block_list);
>
> +/* event types which are dispatched in corosync_dispatch() */
> enum corosync_event_type {
> COROSYNC_EVENT_TYPE_JOIN,
> COROSYNC_EVENT_TYPE_LEAVE,
> COROSYNC_EVENT_TYPE_NOTIFY,
> };
>
> +/* multicast message type */
> +enum corosync_message_type {
> + COROSYNC_MSG_TYPE_NOTIFY,
> + COROSYNC_MSG_TYPE_BLOCK,
> + COROSYNC_MSG_TYPE_UNBLOCK,
> +};
> +
> struct corosync_event {
> enum corosync_event_type type;
>
> @@ -42,6 +55,18 @@ struct corosync_event {
> void *msg;
> size_t msg_len;
>
> + int blocked;
> + int callbacked;
> +
> + struct list_head list;
> +};
> +
> +struct corosync_block_msg {
> + void *msg;
> + size_t msg_len;
> + void (*cb)(void *arg);
> +
> + struct work work;
> struct list_head list;
> };
>
> @@ -91,9 +116,71 @@ static void cpg_addr_to_sheepid(const struct cpg_address *cpgs,
> }
> }
>
> +static int send_message(uint64_t type, void *msg, size_t msg_len)
> +{
> + struct iovec iov[2];
> + int ret, iov_cnt = 1;
> +
> + iov[0].iov_base =&type;
> + iov[0].iov_len = sizeof(type);
> + if (msg) {
> + iov[1].iov_base = msg;
> + iov[1].iov_len = msg_len;
> + iov_cnt++;
> + }
> +retry:
> + ret = cpg_mcast_joined(cpg_handle, CPG_TYPE_AGREED, iov, iov_cnt);
> + switch (ret) {
> + case CPG_OK:
> + break;
> + case CPG_ERR_TRY_AGAIN:
> + dprintf("failed to send message. try again\n");
> + sleep(1);
> + goto retry;
> + default:
> + eprintf("failed to send message, %d\n", ret);
> + return -1;
> + }
> + return 0;
> +}
> +
> +static void corosync_block(struct work *work, int idx)
> +{
> + struct corosync_block_msg *bm = container_of(work, typeof(*bm), work);
> +
> + bm->cb(bm->msg);
> +}
> +
> +static void corosync_block_done(struct work *work, int idx)
> +{
> + struct corosync_block_msg *bm = container_of(work, typeof(*bm), work);
> +
> + send_message(COROSYNC_MSG_TYPE_UNBLOCK, bm->msg, bm->msg_len);
> +
> + free(bm->msg);
> + free(bm);
> +}
> +
> +static struct corosync_event *find_block_event(struct sheepid *sender)
> +{
> + struct corosync_event *cevent;
> +
> + list_for_each_entry(cevent,&corosync_event_list, list) {
> + if (!cevent->blocked)
> + continue;
> +
> + if (cevent->type == COROSYNC_EVENT_TYPE_NOTIFY&&
> + sheepid_cmp(&cevent->sender, sender) == 0)
> + return cevent;
> + }
> +
> + return NULL;
> +}
> +
> static void __corosync_dispatch(void)
> {
> struct corosync_event *cevent;
> + struct corosync_block_msg *bm;
>
> while (!list_empty(&corosync_event_list)) {
> cevent = list_first_entry(&corosync_event_list, typeof(*cevent), list);
> @@ -110,6 +197,28 @@ static void __corosync_dispatch(void)
> cevent->nr_members);
> break;
> case COROSYNC_EVENT_TYPE_NOTIFY:
> + if (cevent->blocked) {
> + if (sheepid_cmp(&cevent->sender,&this_sheepid) == 0&&
> + !cevent->callbacked) {
> + /* call a block callback function from a worker thread */
> + if (list_empty(&corosync_block_list))
> + panic("cannot call block callback\n");
> +
> + bm = list_first_entry(&corosync_block_list,
> + typeof(*bm), list);
> + list_del(&bm->list);
> +
> + bm->work.fn = corosync_block;
> + bm->work.done = corosync_block_done;
> + queue_work(corosync_block_wq,&bm->work);
> +
> + cevent->callbacked = 1;
> + }
> +
is cevent->callbacked really needed? How about a static local one?
> + /* block the rest messages until unblock message comes */
> + goto out;
> + }
> +
> corosync_handlers.notify_handler(&cevent->sender,
> cevent->msg,
> cevent->msg_len);
> @@ -119,6 +228,8 @@ static void __corosync_dispatch(void)
> list_del(&cevent->list);
> free(cevent);
> }
> +out:
> + return;
> }
>
> static void cdrv_cpg_deliver(cpg_handle_t handle,
> @@ -127,21 +238,49 @@ static void cdrv_cpg_deliver(cpg_handle_t handle,
> void *msg, size_t msg_len)
> {
> struct corosync_event *cevent;
> + uint64_t type;
> + struct sheepid sender;
>
> - cevent = zalloc(sizeof(*cevent));
> - if (!cevent)
> - panic("oom\n");
> - cevent->msg = zalloc(msg_len);
> - if (!cevent->msg)
> - panic("oom\n");
> + nodeid_to_addr(nodeid, sender.addr);
> + sender.pid = pid;
>
> - cevent->type = COROSYNC_EVENT_TYPE_NOTIFY;
> - nodeid_to_addr(nodeid, cevent->sender.addr);
> - cevent->sender.pid = pid;
> - memcpy(cevent->msg, msg, msg_len);
> - cevent->msg_len = msg_len;
> + memcpy(&type, msg, sizeof(type));
> + msg = (uint8_t *)msg + sizeof(type);
> + msg_len -= sizeof(type);
>
> - list_add_tail(&cevent->list,&corosync_event_list);
> + switch (type) {
> + case COROSYNC_MSG_TYPE_BLOCK:
> + case COROSYNC_MSG_TYPE_NOTIFY:
> + cevent = zalloc(sizeof(*cevent));
> + if (!cevent)
> + panic("oom\n");
> + cevent->msg = zalloc(msg_len);
> + if (!cevent->msg)
> + panic("oom\n");
> +
> + cevent->type = COROSYNC_EVENT_TYPE_NOTIFY;
> + cevent->sender = sender;
> + memcpy(cevent->msg, msg, msg_len);
> + cevent->msg_len = msg_len;
> + if (type == COROSYNC_MSG_TYPE_BLOCK)
> + cevent->blocked = 1;
move cevent->blocked = 1; into case COROSYNC_MSG_TYPE_BLOCK would avoid
if check.
Thanks,
Yuan
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