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

drivers/block/rbd.c

+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",