rbd: define rbd snap context routines

Encapsulate the creation of a snapshot context for rbd in a new
function rbd_snap_context_create().  Define rbd wrappers for getting
and dropping references to them once they're created.

Signed-off-by: Alex Elder <elder@inktank.com>
Reviewed-by: Josh Durgin <josh.durgin@inktank.com>

diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c
index 2e2e9c35b4e57d8e8974a79b19548ddf4a0da27b..b6775ae1a770600d3b1aae17b2750d6459a8728f 100644 (file)
--- a/drivers/block/rbd.c
+++ b/drivers/block/rbd.c
@@ -671,6 +671,35 @@ static void rbd_client_release(struct kref *kref)
        kfree(rbdc);
 }
 
+/* Caller has to fill in snapc->seq and snapc->snaps[0..snap_count-1] */
+
+static struct ceph_snap_context *rbd_snap_context_create(u32 snap_count)
+{
+       struct ceph_snap_context *snapc;
+       size_t size;
+
+       size = sizeof (struct ceph_snap_context);
+       size += snap_count * sizeof (snapc->snaps[0]);
+       snapc = kzalloc(size, GFP_KERNEL);
+       if (!snapc)
+               return NULL;
+
+       atomic_set(&snapc->nref, 1);
+       snapc->num_snaps = snap_count;
+
+       return snapc;
+}
+
+static inline void rbd_snap_context_get(struct ceph_snap_context *snapc)
+{
+       (void)ceph_get_snap_context(snapc);
+}
+
+static inline void rbd_snap_context_put(struct ceph_snap_context *snapc)
+{
+       ceph_put_snap_context(snapc);
+}
+
 /*
  * Drop reference to ceph client node. If it's not referenced anymore, release
  * it.
@@ -789,18 +818,13 @@ static int rbd_header_from_disk(struct rbd_image_header *header,
        /* Allocate and fill in the snapshot context */
 
        header->image_size = le64_to_cpu(ondisk->image_size);
-       size = sizeof (struct ceph_snap_context);
-       size += snap_count * sizeof (header->snapc->snaps[0]);
-       header->snapc = kzalloc(size, GFP_KERNEL);
+
+       header->snapc = rbd_snap_context_create(snap_count);
        if (!header->snapc)
                goto out_err;
-
-       atomic_set(&header->snapc->nref, 1);
        header->snapc->seq = le64_to_cpu(ondisk->snap_seq);
-       header->snapc->num_snaps = snap_count;
        for (i = 0; i < snap_count; i++)
-               header->snapc->snaps[i] =
-                       le64_to_cpu(ondisk->snaps[i].id);
+               header->snapc->snaps[i] = le64_to_cpu(ondisk->snaps[i].id);
 
        return 0;
 
@@ -870,7 +894,7 @@ static void rbd_header_free(struct rbd_image_header *header)
        header->snap_sizes = NULL;
        kfree(header->snap_names);
        header->snap_names = NULL;
-       ceph_put_snap_context(header->snapc);
+       rbd_snap_context_put(header->snapc);
        header->snapc = NULL;
 }
 
@@ -1720,7 +1744,6 @@ static struct rbd_img_request *rbd_img_request_create(
                                        bool child_request)
 {
        struct rbd_img_request *img_request;
-       struct ceph_snap_context *snapc = NULL;
 
        img_request = kmalloc(sizeof (*img_request), GFP_ATOMIC);
        if (!img_request)
@@ -1728,13 +1751,8 @@ static struct rbd_img_request *rbd_img_request_create(
 
        if (write_request) {
                down_read(&rbd_dev->header_rwsem);
-               snapc = ceph_get_snap_context(rbd_dev->header.snapc);
+               rbd_snap_context_get(rbd_dev->header.snapc);
                up_read(&rbd_dev->header_rwsem);
-               if (WARN_ON(!snapc)) {
-                       kfree(img_request);
-                       return NULL;    /* Shouldn't happen */
-               }
-
        }
 
        img_request->rq = NULL;
@@ -1744,7 +1762,7 @@ static struct rbd_img_request *rbd_img_request_create(
        img_request->flags = 0;
        if (write_request) {
                img_request_write_set(img_request);
-               img_request->snapc = snapc;
+               img_request->snapc = rbd_dev->header.snapc;
        } else {
                img_request->snap_id = rbd_dev->spec->snap_id;
        }
@@ -1785,7 +1803,7 @@ static void rbd_img_request_destroy(struct kref *kref)
        rbd_assert(img_request->obj_request_count == 0);
 
        if (img_request_write_test(img_request))
-               ceph_put_snap_context(img_request->snapc);
+               rbd_snap_context_put(img_request->snapc);
 
        if (img_request_child_test(img_request))
                rbd_obj_request_put(img_request->obj_request);
@@ -3049,7 +3067,7 @@ static int rbd_dev_v1_refresh(struct rbd_device *rbd_dev, u64 *hver)
        kfree(rbd_dev->header.snap_sizes);
        kfree(rbd_dev->header.snap_names);
        /* osd requests may still refer to snapc */
-       ceph_put_snap_context(rbd_dev->header.snapc);
+       rbd_snap_context_put(rbd_dev->header.snapc);
 
        if (hver)
                *hver = h.obj_version;
@@ -3889,19 +3907,14 @@ static int rbd_dev_v2_snap_context(struct rbd_device *rbd_dev, u64 *ver)
        }
        if (!ceph_has_room(&p, end, snap_count * sizeof (__le64)))
                goto out;
+       ret = 0;
 
-       size = sizeof (struct ceph_snap_context) +
-                               snap_count * sizeof (snapc->snaps[0]);
-       snapc = kmalloc(size, GFP_KERNEL);
+       snapc = rbd_snap_context_create(snap_count);
        if (!snapc) {
                ret = -ENOMEM;
                goto out;
        }
-       ret = 0;
-
-       atomic_set(&snapc->nref, 1);
        snapc->seq = seq;
-       snapc->num_snaps = snap_count;
        for (i = 0; i < snap_count; i++)
                snapc->snaps[i] = ceph_decode_64(&p);