Reviewed-by: Josh Durgin <josh.durgin@xxxxxxxxxxx>
On 09/07/2012 02:13 PM, Alex Elder wrote:
Fetch the snapshot context for an rbd format 2 image by calling
the "get_snapcontext" method on its header object.
Signed-off-by: Alex Elder <elder@xxxxxxxxxxx>
---
drivers/block/rbd.c | 85
+++++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 85 insertions(+)
diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c
index d48f025..8ff84fd 100644
--- a/drivers/block/rbd.c
+++ b/drivers/block/rbd.c
@@ -62,6 +62,7 @@
#define RBD_MINORS_PER_MAJOR 256 /* max minors per blkdev */
#define RBD_MAX_SNAP_NAME_LEN 32
+#define RBD_MAX_SNAP_COUNT 510 /* allows max snapc to fit in 4KB */
#define RBD_MAX_OPT_LEN 1024
#define RBD_SNAP_HEAD_NAME "-"
@@ -2234,6 +2235,84 @@ static int rbd_dev_v2_features(struct rbd_device
*rbd_dev)
&rbd_dev->header.features);
}
+static int rbd_dev_v2_snap_context(struct rbd_device *rbd_dev)
+{
+ size_t size;
+ int ret;
+ void *reply_buf;
+ void *p;
+ void *end;
+ u64 seq;
+ u32 snap_count;
+ struct ceph_snap_context *snapc;
+ u32 i;
+
+ /*
+ * We'll need room for the seq value (maximum snapshot id),
+ * snapshot count, and array of that many snapshot ids.
+ * For now we have a fixed upper limit on the number we're
+ * prepared to receive.
+ */
+ size = sizeof (__le64) + sizeof (__le32) +
+ RBD_MAX_SNAP_COUNT * sizeof (__le64);
+ reply_buf = kzalloc(size, GFP_KERNEL);
+ if (!reply_buf)
+ return -ENOMEM;
+
+ ret = rbd_req_sync_exec(rbd_dev, rbd_dev->header_name,
+ "rbd", "get_snapcontext",
+ NULL, 0,
+ reply_buf, size,
+ CEPH_OSD_FLAG_READ, NULL);
+ dout("%s: rbd_req_sync_exec returned %d\n", __func__, ret);
+ if (ret < 0)
+ goto out;
+
+ ret = -ERANGE;
+ p = reply_buf;
+ end = (char *) reply_buf + size;
+ ceph_decode_64_safe(&p, end, seq, out);
+ ceph_decode_32_safe(&p, end, snap_count, out);
+
+ /*
+ * Make sure the reported number of snapshot ids wouldn't go
+ * beyond the end of our buffer. But before checking that,
+ * make sure the computed size of the snapshot context we
+ * allocate is representable in a size_t.
+ */
+ if (snap_count > (SIZE_MAX - sizeof (struct ceph_snap_context))
+ / sizeof (u64)) {
+ ret = -EINVAL;
+ goto out;
+ }
+ if (!ceph_has_room(&p, end, snap_count * sizeof (__le64)))
+ goto out;
+
+ size = sizeof (struct ceph_snap_context) +
+ snap_count * sizeof (snapc->snaps[0]);
+ snapc = kmalloc(size, GFP_KERNEL);
+ if (!snapc) {
+ ret = -ENOMEM;
+ goto out;
+ }
+
+ 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);
+
+ rbd_dev->header.snapc = snapc;
+
+ dout(" snap context seq = %llu, snap_count = %u\n",
+ (unsigned long long) seq, (unsigned int) snap_count);
+
+out:
+ kfree(reply_buf);
+
+ return 0;
+}
+
/*
* Scan the rbd device's current snapshot list and compare it to the
* newly-received snapshot context. Remove any existing snapshots
@@ -2773,6 +2852,12 @@ static int rbd_dev_v2_probe(struct rbd_device
*rbd_dev)
ret = rbd_dev_v2_features(rbd_dev);
if (ret < 0)
goto out_err;
+
+ /* Get the snapshot context */
+
+ ret = rbd_dev_v2_snap_context(rbd_dev);
+ if (ret)
+ goto out_err;
rbd_dev->image_format = 2;
dout("discovered version 2 image, header name is %s\n",
--
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