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Commit 35d489f9 authored by Alex Elder's avatar Alex Elder
Browse files

rbd: get the snapshot context for a v2 image



Fetch the snapshot context for an rbd format 2 image by calling
the "get_snapcontext" method on its header object.

Signed-off-by: default avatarAlex Elder <elder@inktank.com>
Reviewed-by: default avatarJosh Durgin <josh.durgin@inktank.com>
parent b1b5402a
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+85 −0
Original line number Diff line number Diff line
@@ -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	"-"
@@ -2240,6 +2241,84 @@ 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
@@ -2779,6 +2858,12 @@ 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",