Re: [PATCH REPOST] rbd: assign watch request more directly

[Josh Durgin]

On 01/04/2013 07:07 AM, Alex Elder wrote:

Both rbd_req_sync_op() and rbd_do_request() have a "linger"
parameter, which is the address of a pointer that should refer to
the osd request structure used to issue a request to an osd.

Only one case ever supplies a non-null "linger" argument: an
CEPH_OSD_OP_WATCH start.  And in that one case it is assigned
&rbd_dev->watch_request.

Within rbd_do_request() (where the assignment ultimately gets made)
we know the rbd_dev and therefore its watch_request field.  We
also know whether the op being sent is CEPH_OSD_OP_WATCH start.

Stop opaquely passing down the "linger" pointer, and instead just
assign the value directly inside rbd_do_request() when it's needed.

This makes it unnecessary for rbd_req_sync_watch() to make
arrangements to hold a value that's not available until a
bit later.  This more clearly separates setting up a watch
request from submitting it.

Signed-off-by: Alex Elder <el...@inktank.com>
---

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

  drivers/block/rbd.c |   20 ++++++++------------
  1 file changed, 8 insertions(+), 12 deletions(-)

diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c
index 21fbf82..02002b1 100644
--- a/drivers/block/rbd.c
+++ b/drivers/block/rbd.c
@@ -1158,7 +1158,6 @@ static int rbd_do_request(struct request *rq,
                          int coll_index,
                          void (*rbd_cb)(struct ceph_osd_request *,
                                         struct ceph_msg *),
-                         struct ceph_osd_request **linger_req,
                          u64 *ver)
  {
        struct ceph_osd_client *osdc;
@@ -1210,9 +1209,9 @@ static int rbd_do_request(struct request *rq,
        ceph_osdc_build_request(osd_req, ofs, len, 1, op,
                                snapc, snapid, &mtime);

-       if (linger_req) {
+       if (op->op == CEPH_OSD_OP_WATCH && op->watch.flag) {
                ceph_osdc_set_request_linger(osdc, osd_req);
-               *linger_req = osd_req;
+               rbd_dev->watch_request = osd_req;
        }

        ret = ceph_osdc_start_request(osdc, osd_req, false);
@@ -1296,7 +1295,6 @@ static int rbd_req_sync_op(struct rbd_device *rbd_dev,
                           const char *object_name,
                           u64 ofs, u64 inbound_size,
                           char *inbound,
-                          struct ceph_osd_request **linger_req,
                           u64 *ver)
  {
        int ret;
@@ -1317,7 +1315,7 @@ static int rbd_req_sync_op(struct rbd_device *rbd_dev,
                          op,
                          NULL, 0,
                          NULL,
-                         linger_req, ver);
+                         ver);
        if (ret < 0)
                goto done;

@@ -1383,7 +1381,7 @@ static int rbd_do_op(struct request *rq,
                             flags,
                             op,
                             coll, coll_index,
-                            rbd_req_cb, 0, NULL);
+                            rbd_req_cb, NULL);
        if (ret < 0)
                rbd_coll_end_req_index(rq, coll, coll_index,
                                        (s32) ret, seg_len);
@@ -1410,7 +1408,7 @@ static int rbd_req_sync_read(struct rbd_device
*rbd_dev,
                return -ENOMEM;

        ret = rbd_req_sync_op(rbd_dev, CEPH_OSD_FLAG_READ,
-                              op, object_name, ofs, len, buf, NULL, ver);
+                              op, object_name, ofs, len, buf, ver);
        rbd_osd_req_op_destroy(op);

        return ret;
@@ -1436,7 +1434,7 @@ static int rbd_req_sync_notify_ack(struct
rbd_device *rbd_dev,
                          CEPH_OSD_FLAG_READ,
                          op,
                          NULL, 0,
-                         rbd_simple_req_cb, 0, NULL);
+                         rbd_simple_req_cb, NULL);

        rbd_osd_req_op_destroy(op);

@@ -1469,7 +1467,6 @@ static void rbd_watch_cb(u64 ver, u64 notify_id,
u8 opcode, void *data)
   */
  static int rbd_req_sync_watch(struct rbd_device *rbd_dev, int start)
  {
-       struct ceph_osd_request **linger_req = NULL;
        struct ceph_osd_req_op *op;
        int ret = 0;

@@ -1481,7 +1478,6 @@ static int rbd_req_sync_watch(struct rbd_device
*rbd_dev, int start)
                                                &rbd_dev->watch_event);
                if (ret < 0)
                        return ret;
-               linger_req = &rbd_dev->watch_request;
        } else {
                rbd_assert(rbd_dev->watch_request != NULL);
        }
@@ -1493,7 +1489,7 @@ static int rbd_req_sync_watch(struct rbd_device
*rbd_dev, int start)
                ret = rbd_req_sync_op(rbd_dev,
                              CEPH_OSD_FLAG_WRITE | CEPH_OSD_FLAG_ONDISK,
                              op, rbd_dev->header_name,
-                             0, 0, NULL, linger_req, NULL);
+                             0, 0, NULL, NULL);

        /* Cancel the event if we're tearing down, or on error */

@@ -1537,7 +1533,7 @@ static int rbd_req_sync_exec(struct rbd_device
*rbd_dev,

        ret = rbd_req_sync_op(rbd_dev, CEPH_OSD_FLAG_READ, op,
                               object_name, 0, inbound_size, inbound,
-                              NULL, ver);
+                              ver);

        rbd_osd_req_op_destroy(op);

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