diff mbox

[v3,2/4] libceph: mon_get_version request infrastructure

Message ID 1400777408-7016-3-git-send-email-ilya.dryomov@inktank.com (mailing list archive)
State New, archived
Headers show

Commit Message

Ilya Dryomov May 22, 2014, 4:50 p.m. UTC
Add support for mon_get_version requests to libceph.  This reuses much
of the ceph_mon_generic_request infrastructure, with one exception.
Older OSDs don't set mon_get_version reply hdr->tid even if the
original request had a non-zero tid, which makes it impossible to
lookup ceph_mon_generic_request contexts by tid in get_generic_reply()
for such replies.  As a workaround, we allocate a reply message on the
reply path.  This can probably interfere with revoke, but I don't see
a better way.

Signed-off-by: Ilya Dryomov <ilya.dryomov@inktank.com>
---
 include/linux/ceph/mon_client.h |    9 ++-
 net/ceph/ceph_common.c          |    2 +
 net/ceph/debugfs.c              |    2 +
 net/ceph/mon_client.c           |  123 +++++++++++++++++++++++++++++++++++++--
 4 files changed, 128 insertions(+), 8 deletions(-)

Comments

Sage Weil June 3, 2014, 8:58 p.m. UTC | #1
On Thu, 22 May 2014, Ilya Dryomov wrote:

> Add support for mon_get_version requests to libceph.  This reuses much
> of the ceph_mon_generic_request infrastructure, with one exception.
> Older OSDs don't set mon_get_version reply hdr->tid even if the
> original request had a non-zero tid, which makes it impossible to
> lookup ceph_mon_generic_request contexts by tid in get_generic_reply()
> for such replies.  As a workaround, we allocate a reply message on the
> reply path.  This can probably interfere with revoke, but I don't see
> a better way.
> 
> Signed-off-by: Ilya Dryomov <ilya.dryomov@inktank.com>
> ---
>  include/linux/ceph/mon_client.h |    9 ++-
>  net/ceph/ceph_common.c          |    2 +
>  net/ceph/debugfs.c              |    2 +
>  net/ceph/mon_client.c           |  123 +++++++++++++++++++++++++++++++++++++--
>  4 files changed, 128 insertions(+), 8 deletions(-)
> 
> diff --git a/include/linux/ceph/mon_client.h b/include/linux/ceph/mon_client.h
> index a486f390dfbe..585ef9450e9d 100644
> --- a/include/linux/ceph/mon_client.h
> +++ b/include/linux/ceph/mon_client.h
> @@ -40,9 +40,9 @@ struct ceph_mon_request {
>  };
>  
>  /*
> - * ceph_mon_generic_request is being used for the statfs and poolop requests
> - * which are bening done a bit differently because we need to get data back
> - * to the caller
> + * ceph_mon_generic_request is being used for the statfs, poolop and
> + * mon_get_version requests which are being done a bit differently
> + * because we need to get data back to the caller
>   */
>  struct ceph_mon_generic_request {
>  	struct kref kref;
> @@ -108,6 +108,9 @@ extern void ceph_monc_request_next_osdmap(struct ceph_mon_client *monc);
>  extern int ceph_monc_do_statfs(struct ceph_mon_client *monc,
>  			       struct ceph_statfs *buf);
>  
> +extern int ceph_monc_do_get_version(struct ceph_mon_client *monc,
> +				    const char *what, u64 *newest);
> +
>  extern int ceph_monc_open_session(struct ceph_mon_client *monc);
>  
>  extern int ceph_monc_validate_auth(struct ceph_mon_client *monc);
> diff --git a/net/ceph/ceph_common.c b/net/ceph/ceph_common.c
> index 67d7721d237e..1675021d8c12 100644
> --- a/net/ceph/ceph_common.c
> +++ b/net/ceph/ceph_common.c
> @@ -72,6 +72,8 @@ const char *ceph_msg_type_name(int type)
>  	case CEPH_MSG_MON_SUBSCRIBE_ACK: return "mon_subscribe_ack";
>  	case CEPH_MSG_STATFS: return "statfs";
>  	case CEPH_MSG_STATFS_REPLY: return "statfs_reply";
> +	case CEPH_MSG_MON_GET_VERSION: return "mon_get_version";
> +	case CEPH_MSG_MON_GET_VERSION_REPLY: return "mon_get_version_reply";
>  	case CEPH_MSG_MDS_MAP: return "mds_map";
>  	case CEPH_MSG_CLIENT_SESSION: return "client_session";
>  	case CEPH_MSG_CLIENT_RECONNECT: return "client_reconnect";
> diff --git a/net/ceph/debugfs.c b/net/ceph/debugfs.c
> index 8903dcee8d8e..d1a62c69a9f4 100644
> --- a/net/ceph/debugfs.c
> +++ b/net/ceph/debugfs.c
> @@ -129,6 +129,8 @@ static int monc_show(struct seq_file *s, void *p)
>  			seq_printf(s, "%llu statfs\n", req->tid);
>  		else if (op == CEPH_MSG_POOLOP)
>  			seq_printf(s, "%llu poolop\n", req->tid);
> +		else if (op == CEPH_MSG_MON_GET_VERSION)
> +			seq_printf(s, "%llu mon_get_version", req->tid);
>  		else
>  			seq_printf(s, "%llu unknown\n", req->tid);
>  	}
> diff --git a/net/ceph/mon_client.c b/net/ceph/mon_client.c
> index 2ac9ef35110b..6b46f1205ceb 100644
> --- a/net/ceph/mon_client.c
> +++ b/net/ceph/mon_client.c
> @@ -477,14 +477,13 @@ static struct ceph_msg *get_generic_reply(struct ceph_connection *con,
>  	return m;
>  }
>  
> -static int do_generic_request(struct ceph_mon_client *monc,
> -			      struct ceph_mon_generic_request *req)
> +static int __do_generic_request(struct ceph_mon_client *monc, u64 tid,
> +				struct ceph_mon_generic_request *req)
>  {
>  	int err;
>  
>  	/* register request */
> -	mutex_lock(&monc->mutex);
> -	req->tid = ++monc->last_tid;
> +	req->tid = tid != 0 ? tid : ++monc->last_tid;
>  	req->request->hdr.tid = cpu_to_le64(req->tid);
>  	__insert_generic_request(monc, req);
>  	monc->num_generic_requests++;
> @@ -496,13 +495,24 @@ static int do_generic_request(struct ceph_mon_client *monc,
>  	mutex_lock(&monc->mutex);
>  	rb_erase(&req->node, &monc->generic_request_tree);
>  	monc->num_generic_requests--;
> -	mutex_unlock(&monc->mutex);
>  
>  	if (!err)
>  		err = req->result;
>  	return err;
>  }
>  
> +static int do_generic_request(struct ceph_mon_client *monc,
> +			      struct ceph_mon_generic_request *req)
> +{
> +	int err;
> +
> +	mutex_lock(&monc->mutex);
> +	err = __do_generic_request(monc, 0, req);
> +	mutex_unlock(&monc->mutex);
> +
> +	return err;
> +}
> +
>  /*
>   * statfs
>   */
> @@ -579,6 +589,96 @@ out:
>  }
>  EXPORT_SYMBOL(ceph_monc_do_statfs);
>  
> +static void handle_get_version_reply(struct ceph_mon_client *monc,
> +				     struct ceph_msg *msg)
> +{
> +	struct ceph_mon_generic_request *req;
> +	u64 tid = le64_to_cpu(msg->hdr.tid);
> +	void *p = msg->front.iov_base;
> +	void *end = p + msg->front_alloc_len;
> +	u64 handle;
> +
> +	dout("%s %p tid %llu\n", __func__, msg, tid);
> +
> +	ceph_decode_need(&p, end, 2*sizeof(u64), bad);
> +	handle = ceph_decode_64(&p);
> +	if (tid != 0 && tid != handle)
> +		goto bad;
> +
> +	mutex_lock(&monc->mutex);
> +	req = __lookup_generic_req(monc, handle);
> +	if (req) {
> +		*(u64 *)req->buf = ceph_decode_64(&p);
> +		req->result = 0;
> +		get_generic_request(req);
> +	}
> +	mutex_unlock(&monc->mutex);
> +	if (req) {
> +		complete_all(&req->completion);
> +		put_generic_request(req);
> +	}
> +
> +	return;
> +bad:
> +	pr_err("corrupt mon_get_version reply\n");
> +	ceph_msg_dump(msg);
> +}
> +
> +/*
> + * Send MMonGetVersion and wait for the reply.
> + *
> + * @what: one of "mdsmap", "osdmap" or "monmap"
> + */
> +int ceph_monc_do_get_version(struct ceph_mon_client *monc, const char *what,
> +			     u64 *newest)
> +{
> +	struct ceph_mon_generic_request *req;
> +	void *p, *end;
> +	u64 tid;
> +	int err;
> +
> +	req = kzalloc(sizeof(*req), GFP_NOFS);
> +	if (!req)
> +		return -ENOMEM;
> +
> +	kref_init(&req->kref);
> +	req->buf = newest;
> +	req->buf_len = sizeof(*newest);
> +	init_completion(&req->completion);
> +
> +	req->request = ceph_msg_new(CEPH_MSG_MON_GET_VERSION,
> +				    sizeof(u64) + sizeof(u32) + strlen(what),
> +				    GFP_NOFS, true);
> +	if (!req->request) {
> +		err = -ENOMEM;
> +		goto out;
> +	}
> +
> +	req->reply = ceph_msg_new(CEPH_MSG_MON_GET_VERSION_REPLY, 1024,
> +				  GFP_NOFS, true);
> +	if (!req->request) {

req->reply

With that change, Reviewed-by:

sage


> +		err = -ENOMEM;
> +		goto out;
> +	}
> +
> +	p = req->request->front.iov_base;
> +	end = p + req->request->front_alloc_len;
> +
> +	/* fill out request */
> +	mutex_lock(&monc->mutex);
> +	tid = ++monc->last_tid;
> +	ceph_encode_64(&p, tid); /* handle */
> +	ceph_encode_string(&p, end, what, strlen(what));
> +
> +	err = __do_generic_request(monc, tid, req);
> +
> +	mutex_unlock(&monc->mutex);
> +out:
> +	kref_put(&req->kref, release_generic_request);
> +	return err;
> +}
> +EXPORT_SYMBOL(ceph_monc_do_get_version);
> +
>  /*
>   * pool ops
>   */
> @@ -981,6 +1081,10 @@ static void dispatch(struct ceph_connection *con, struct ceph_msg *msg)
>  		handle_statfs_reply(monc, msg);
>  		break;
>  
> +	case CEPH_MSG_MON_GET_VERSION_REPLY:
> +		handle_get_version_reply(monc, msg);
> +		break;
> +
>  	case CEPH_MSG_POOLOP_REPLY:
>  		handle_poolop_reply(monc, msg);
>  		break;
> @@ -1029,6 +1133,15 @@ static struct ceph_msg *mon_alloc_msg(struct ceph_connection *con,
>  	case CEPH_MSG_AUTH_REPLY:
>  		m = ceph_msg_get(monc->m_auth_reply);
>  		break;
> +	case CEPH_MSG_MON_GET_VERSION_REPLY:
> +		if (le64_to_cpu(hdr->tid) != 0)
> +			return get_generic_reply(con, hdr, skip);
> +
> +		/*
> +		 * Older OSDs don't set reply tid even if the orignal
> +		 * request had a non-zero tid.  Workaround this weirdness
> +		 * by falling through to the allocate case.
> +		 */
>  	case CEPH_MSG_MON_MAP:
>  	case CEPH_MSG_MDS_MAP:
>  	case CEPH_MSG_OSD_MAP:
> -- 
> 1.7.10.4
> 
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> 
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Ilya Dryomov June 4, 2014, 7:39 a.m. UTC | #2
On Wed, Jun 4, 2014 at 12:58 AM, Sage Weil <sage@inktank.com> wrote:
> On Thu, 22 May 2014, Ilya Dryomov wrote:
>
>> Add support for mon_get_version requests to libceph.  This reuses much
>> of the ceph_mon_generic_request infrastructure, with one exception.
>> Older OSDs don't set mon_get_version reply hdr->tid even if the
>> original request had a non-zero tid, which makes it impossible to
>> lookup ceph_mon_generic_request contexts by tid in get_generic_reply()
>> for such replies.  As a workaround, we allocate a reply message on the
>> reply path.  This can probably interfere with revoke, but I don't see
>> a better way.
>>
>> Signed-off-by: Ilya Dryomov <ilya.dryomov@inktank.com>
>> ---
>>  include/linux/ceph/mon_client.h |    9 ++-
>>  net/ceph/ceph_common.c          |    2 +
>>  net/ceph/debugfs.c              |    2 +
>>  net/ceph/mon_client.c           |  123 +++++++++++++++++++++++++++++++++++++--
>>  4 files changed, 128 insertions(+), 8 deletions(-)
>>
>> diff --git a/include/linux/ceph/mon_client.h b/include/linux/ceph/mon_client.h
>> index a486f390dfbe..585ef9450e9d 100644
>> --- a/include/linux/ceph/mon_client.h
>> +++ b/include/linux/ceph/mon_client.h
>> @@ -40,9 +40,9 @@ struct ceph_mon_request {
>>  };
>>
>>  /*
>> - * ceph_mon_generic_request is being used for the statfs and poolop requests
>> - * which are bening done a bit differently because we need to get data back
>> - * to the caller
>> + * ceph_mon_generic_request is being used for the statfs, poolop and
>> + * mon_get_version requests which are being done a bit differently
>> + * because we need to get data back to the caller
>>   */
>>  struct ceph_mon_generic_request {
>>       struct kref kref;
>> @@ -108,6 +108,9 @@ extern void ceph_monc_request_next_osdmap(struct ceph_mon_client *monc);
>>  extern int ceph_monc_do_statfs(struct ceph_mon_client *monc,
>>                              struct ceph_statfs *buf);
>>
>> +extern int ceph_monc_do_get_version(struct ceph_mon_client *monc,
>> +                                 const char *what, u64 *newest);
>> +
>>  extern int ceph_monc_open_session(struct ceph_mon_client *monc);
>>
>>  extern int ceph_monc_validate_auth(struct ceph_mon_client *monc);
>> diff --git a/net/ceph/ceph_common.c b/net/ceph/ceph_common.c
>> index 67d7721d237e..1675021d8c12 100644
>> --- a/net/ceph/ceph_common.c
>> +++ b/net/ceph/ceph_common.c
>> @@ -72,6 +72,8 @@ const char *ceph_msg_type_name(int type)
>>       case CEPH_MSG_MON_SUBSCRIBE_ACK: return "mon_subscribe_ack";
>>       case CEPH_MSG_STATFS: return "statfs";
>>       case CEPH_MSG_STATFS_REPLY: return "statfs_reply";
>> +     case CEPH_MSG_MON_GET_VERSION: return "mon_get_version";
>> +     case CEPH_MSG_MON_GET_VERSION_REPLY: return "mon_get_version_reply";
>>       case CEPH_MSG_MDS_MAP: return "mds_map";
>>       case CEPH_MSG_CLIENT_SESSION: return "client_session";
>>       case CEPH_MSG_CLIENT_RECONNECT: return "client_reconnect";
>> diff --git a/net/ceph/debugfs.c b/net/ceph/debugfs.c
>> index 8903dcee8d8e..d1a62c69a9f4 100644
>> --- a/net/ceph/debugfs.c
>> +++ b/net/ceph/debugfs.c
>> @@ -129,6 +129,8 @@ static int monc_show(struct seq_file *s, void *p)
>>                       seq_printf(s, "%llu statfs\n", req->tid);
>>               else if (op == CEPH_MSG_POOLOP)
>>                       seq_printf(s, "%llu poolop\n", req->tid);
>> +             else if (op == CEPH_MSG_MON_GET_VERSION)
>> +                     seq_printf(s, "%llu mon_get_version", req->tid);
>>               else
>>                       seq_printf(s, "%llu unknown\n", req->tid);
>>       }
>> diff --git a/net/ceph/mon_client.c b/net/ceph/mon_client.c
>> index 2ac9ef35110b..6b46f1205ceb 100644
>> --- a/net/ceph/mon_client.c
>> +++ b/net/ceph/mon_client.c
>> @@ -477,14 +477,13 @@ static struct ceph_msg *get_generic_reply(struct ceph_connection *con,
>>       return m;
>>  }
>>
>> -static int do_generic_request(struct ceph_mon_client *monc,
>> -                           struct ceph_mon_generic_request *req)
>> +static int __do_generic_request(struct ceph_mon_client *monc, u64 tid,
>> +                             struct ceph_mon_generic_request *req)
>>  {
>>       int err;
>>
>>       /* register request */
>> -     mutex_lock(&monc->mutex);
>> -     req->tid = ++monc->last_tid;
>> +     req->tid = tid != 0 ? tid : ++monc->last_tid;
>>       req->request->hdr.tid = cpu_to_le64(req->tid);
>>       __insert_generic_request(monc, req);
>>       monc->num_generic_requests++;
>> @@ -496,13 +495,24 @@ static int do_generic_request(struct ceph_mon_client *monc,
>>       mutex_lock(&monc->mutex);
>>       rb_erase(&req->node, &monc->generic_request_tree);
>>       monc->num_generic_requests--;
>> -     mutex_unlock(&monc->mutex);
>>
>>       if (!err)
>>               err = req->result;
>>       return err;
>>  }
>>
>> +static int do_generic_request(struct ceph_mon_client *monc,
>> +                           struct ceph_mon_generic_request *req)
>> +{
>> +     int err;
>> +
>> +     mutex_lock(&monc->mutex);
>> +     err = __do_generic_request(monc, 0, req);
>> +     mutex_unlock(&monc->mutex);
>> +
>> +     return err;
>> +}
>> +
>>  /*
>>   * statfs
>>   */
>> @@ -579,6 +589,96 @@ out:
>>  }
>>  EXPORT_SYMBOL(ceph_monc_do_statfs);
>>
>> +static void handle_get_version_reply(struct ceph_mon_client *monc,
>> +                                  struct ceph_msg *msg)
>> +{
>> +     struct ceph_mon_generic_request *req;
>> +     u64 tid = le64_to_cpu(msg->hdr.tid);
>> +     void *p = msg->front.iov_base;
>> +     void *end = p + msg->front_alloc_len;
>> +     u64 handle;
>> +
>> +     dout("%s %p tid %llu\n", __func__, msg, tid);
>> +
>> +     ceph_decode_need(&p, end, 2*sizeof(u64), bad);
>> +     handle = ceph_decode_64(&p);
>> +     if (tid != 0 && tid != handle)
>> +             goto bad;
>> +
>> +     mutex_lock(&monc->mutex);
>> +     req = __lookup_generic_req(monc, handle);
>> +     if (req) {
>> +             *(u64 *)req->buf = ceph_decode_64(&p);
>> +             req->result = 0;
>> +             get_generic_request(req);
>> +     }
>> +     mutex_unlock(&monc->mutex);
>> +     if (req) {
>> +             complete_all(&req->completion);
>> +             put_generic_request(req);
>> +     }
>> +
>> +     return;
>> +bad:
>> +     pr_err("corrupt mon_get_version reply\n");
>> +     ceph_msg_dump(msg);
>> +}
>> +
>> +/*
>> + * Send MMonGetVersion and wait for the reply.
>> + *
>> + * @what: one of "mdsmap", "osdmap" or "monmap"
>> + */
>> +int ceph_monc_do_get_version(struct ceph_mon_client *monc, const char *what,
>> +                          u64 *newest)
>> +{
>> +     struct ceph_mon_generic_request *req;
>> +     void *p, *end;
>> +     u64 tid;
>> +     int err;
>> +
>> +     req = kzalloc(sizeof(*req), GFP_NOFS);
>> +     if (!req)
>> +             return -ENOMEM;
>> +
>> +     kref_init(&req->kref);
>> +     req->buf = newest;
>> +     req->buf_len = sizeof(*newest);
>> +     init_completion(&req->completion);
>> +
>> +     req->request = ceph_msg_new(CEPH_MSG_MON_GET_VERSION,
>> +                                 sizeof(u64) + sizeof(u32) + strlen(what),
>> +                                 GFP_NOFS, true);
>> +     if (!req->request) {
>> +             err = -ENOMEM;
>> +             goto out;
>> +     }
>> +
>> +     req->reply = ceph_msg_new(CEPH_MSG_MON_GET_VERSION_REPLY, 1024,
>> +                               GFP_NOFS, true);
>> +     if (!req->request) {
>
> req->reply
>
> With that change, Reviewed-by:

Updated, pushed to testing.

Thanks,

                Ilya
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diff mbox

Patch

diff --git a/include/linux/ceph/mon_client.h b/include/linux/ceph/mon_client.h
index a486f390dfbe..585ef9450e9d 100644
--- a/include/linux/ceph/mon_client.h
+++ b/include/linux/ceph/mon_client.h
@@ -40,9 +40,9 @@  struct ceph_mon_request {
 };
 
 /*
- * ceph_mon_generic_request is being used for the statfs and poolop requests
- * which are bening done a bit differently because we need to get data back
- * to the caller
+ * ceph_mon_generic_request is being used for the statfs, poolop and
+ * mon_get_version requests which are being done a bit differently
+ * because we need to get data back to the caller
  */
 struct ceph_mon_generic_request {
 	struct kref kref;
@@ -108,6 +108,9 @@  extern void ceph_monc_request_next_osdmap(struct ceph_mon_client *monc);
 extern int ceph_monc_do_statfs(struct ceph_mon_client *monc,
 			       struct ceph_statfs *buf);
 
+extern int ceph_monc_do_get_version(struct ceph_mon_client *monc,
+				    const char *what, u64 *newest);
+
 extern int ceph_monc_open_session(struct ceph_mon_client *monc);
 
 extern int ceph_monc_validate_auth(struct ceph_mon_client *monc);
diff --git a/net/ceph/ceph_common.c b/net/ceph/ceph_common.c
index 67d7721d237e..1675021d8c12 100644
--- a/net/ceph/ceph_common.c
+++ b/net/ceph/ceph_common.c
@@ -72,6 +72,8 @@  const char *ceph_msg_type_name(int type)
 	case CEPH_MSG_MON_SUBSCRIBE_ACK: return "mon_subscribe_ack";
 	case CEPH_MSG_STATFS: return "statfs";
 	case CEPH_MSG_STATFS_REPLY: return "statfs_reply";
+	case CEPH_MSG_MON_GET_VERSION: return "mon_get_version";
+	case CEPH_MSG_MON_GET_VERSION_REPLY: return "mon_get_version_reply";
 	case CEPH_MSG_MDS_MAP: return "mds_map";
 	case CEPH_MSG_CLIENT_SESSION: return "client_session";
 	case CEPH_MSG_CLIENT_RECONNECT: return "client_reconnect";
diff --git a/net/ceph/debugfs.c b/net/ceph/debugfs.c
index 8903dcee8d8e..d1a62c69a9f4 100644
--- a/net/ceph/debugfs.c
+++ b/net/ceph/debugfs.c
@@ -129,6 +129,8 @@  static int monc_show(struct seq_file *s, void *p)
 			seq_printf(s, "%llu statfs\n", req->tid);
 		else if (op == CEPH_MSG_POOLOP)
 			seq_printf(s, "%llu poolop\n", req->tid);
+		else if (op == CEPH_MSG_MON_GET_VERSION)
+			seq_printf(s, "%llu mon_get_version", req->tid);
 		else
 			seq_printf(s, "%llu unknown\n", req->tid);
 	}
diff --git a/net/ceph/mon_client.c b/net/ceph/mon_client.c
index 2ac9ef35110b..6b46f1205ceb 100644
--- a/net/ceph/mon_client.c
+++ b/net/ceph/mon_client.c
@@ -477,14 +477,13 @@  static struct ceph_msg *get_generic_reply(struct ceph_connection *con,
 	return m;
 }
 
-static int do_generic_request(struct ceph_mon_client *monc,
-			      struct ceph_mon_generic_request *req)
+static int __do_generic_request(struct ceph_mon_client *monc, u64 tid,
+				struct ceph_mon_generic_request *req)
 {
 	int err;
 
 	/* register request */
-	mutex_lock(&monc->mutex);
-	req->tid = ++monc->last_tid;
+	req->tid = tid != 0 ? tid : ++monc->last_tid;
 	req->request->hdr.tid = cpu_to_le64(req->tid);
 	__insert_generic_request(monc, req);
 	monc->num_generic_requests++;
@@ -496,13 +495,24 @@  static int do_generic_request(struct ceph_mon_client *monc,
 	mutex_lock(&monc->mutex);
 	rb_erase(&req->node, &monc->generic_request_tree);
 	monc->num_generic_requests--;
-	mutex_unlock(&monc->mutex);
 
 	if (!err)
 		err = req->result;
 	return err;
 }
 
+static int do_generic_request(struct ceph_mon_client *monc,
+			      struct ceph_mon_generic_request *req)
+{
+	int err;
+
+	mutex_lock(&monc->mutex);
+	err = __do_generic_request(monc, 0, req);
+	mutex_unlock(&monc->mutex);
+
+	return err;
+}
+
 /*
  * statfs
  */
@@ -579,6 +589,96 @@  out:
 }
 EXPORT_SYMBOL(ceph_monc_do_statfs);
 
+static void handle_get_version_reply(struct ceph_mon_client *monc,
+				     struct ceph_msg *msg)
+{
+	struct ceph_mon_generic_request *req;
+	u64 tid = le64_to_cpu(msg->hdr.tid);
+	void *p = msg->front.iov_base;
+	void *end = p + msg->front_alloc_len;
+	u64 handle;
+
+	dout("%s %p tid %llu\n", __func__, msg, tid);
+
+	ceph_decode_need(&p, end, 2*sizeof(u64), bad);
+	handle = ceph_decode_64(&p);
+	if (tid != 0 && tid != handle)
+		goto bad;
+
+	mutex_lock(&monc->mutex);
+	req = __lookup_generic_req(monc, handle);
+	if (req) {
+		*(u64 *)req->buf = ceph_decode_64(&p);
+		req->result = 0;
+		get_generic_request(req);
+	}
+	mutex_unlock(&monc->mutex);
+	if (req) {
+		complete_all(&req->completion);
+		put_generic_request(req);
+	}
+
+	return;
+bad:
+	pr_err("corrupt mon_get_version reply\n");
+	ceph_msg_dump(msg);
+}
+
+/*
+ * Send MMonGetVersion and wait for the reply.
+ *
+ * @what: one of "mdsmap", "osdmap" or "monmap"
+ */
+int ceph_monc_do_get_version(struct ceph_mon_client *monc, const char *what,
+			     u64 *newest)
+{
+	struct ceph_mon_generic_request *req;
+	void *p, *end;
+	u64 tid;
+	int err;
+
+	req = kzalloc(sizeof(*req), GFP_NOFS);
+	if (!req)
+		return -ENOMEM;
+
+	kref_init(&req->kref);
+	req->buf = newest;
+	req->buf_len = sizeof(*newest);
+	init_completion(&req->completion);
+
+	req->request = ceph_msg_new(CEPH_MSG_MON_GET_VERSION,
+				    sizeof(u64) + sizeof(u32) + strlen(what),
+				    GFP_NOFS, true);
+	if (!req->request) {
+		err = -ENOMEM;
+		goto out;
+	}
+
+	req->reply = ceph_msg_new(CEPH_MSG_MON_GET_VERSION_REPLY, 1024,
+				  GFP_NOFS, true);
+	if (!req->request) {
+		err = -ENOMEM;
+		goto out;
+	}
+
+	p = req->request->front.iov_base;
+	end = p + req->request->front_alloc_len;
+
+	/* fill out request */
+	mutex_lock(&monc->mutex);
+	tid = ++monc->last_tid;
+	ceph_encode_64(&p, tid); /* handle */
+	ceph_encode_string(&p, end, what, strlen(what));
+
+	err = __do_generic_request(monc, tid, req);
+
+	mutex_unlock(&monc->mutex);
+out:
+	kref_put(&req->kref, release_generic_request);
+	return err;
+}
+EXPORT_SYMBOL(ceph_monc_do_get_version);
+
 /*
  * pool ops
  */
@@ -981,6 +1081,10 @@  static void dispatch(struct ceph_connection *con, struct ceph_msg *msg)
 		handle_statfs_reply(monc, msg);
 		break;
 
+	case CEPH_MSG_MON_GET_VERSION_REPLY:
+		handle_get_version_reply(monc, msg);
+		break;
+
 	case CEPH_MSG_POOLOP_REPLY:
 		handle_poolop_reply(monc, msg);
 		break;
@@ -1029,6 +1133,15 @@  static struct ceph_msg *mon_alloc_msg(struct ceph_connection *con,
 	case CEPH_MSG_AUTH_REPLY:
 		m = ceph_msg_get(monc->m_auth_reply);
 		break;
+	case CEPH_MSG_MON_GET_VERSION_REPLY:
+		if (le64_to_cpu(hdr->tid) != 0)
+			return get_generic_reply(con, hdr, skip);
+
+		/*
+		 * Older OSDs don't set reply tid even if the orignal
+		 * request had a non-zero tid.  Workaround this weirdness
+		 * by falling through to the allocate case.
+		 */
 	case CEPH_MSG_MON_MAP:
 	case CEPH_MSG_MDS_MAP:
 	case CEPH_MSG_OSD_MAP: