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Commit cd892126 authored by Alex Elder's avatar Alex Elder
Browse files

rbd: encapsulate code that gets snapshot info 



Create a function that encapsulates looking up the name, size and
features related to a given snapshot, which is indicated by its
index in an rbd device's snapshot context array of snapshot ids.

This interface will be used to hide differences between the format 1
and format 2 images.

At the moment this (looking up the name anyway) is slightly less
efficient than what's done currently, but we may be able to optimize
this a bit later on by cacheing the last lookup if it proves to be a
problem.

Signed-off-by: default avatarAlex Elder <elder@inktank.com>
Reviewed-by: default avatarJosh Durgin <josh.durgin@inktank.com>
parent 34b13184

drivers/block/rbd.c

+30 −6
Original line number Diff line number Diff line
@@ -2102,6 +2102,25 @@ static struct rbd_snap *__rbd_add_snap_dev(struct rbd_device *rbd_dev, 
	return ERR_PTR(ret);

}



static char *rbd_dev_v1_snap_info(struct rbd_device *rbd_dev, u32 which,

		u64 *snap_size, u64 *snap_features)

{

	char *snap_name;



	rbd_assert(which < rbd_dev->header.snapc->num_snaps);



	*snap_size = rbd_dev->header.snap_sizes[which];

	*snap_features = 0;	/* No features for v1 */



	/* Skip over names until we find the one we are looking for */



	snap_name = rbd_dev->header.snap_names;

	while (which--)

		snap_name += strlen(snap_name) + 1;



	return snap_name;

}



/*

 * Scan the rbd device's current snapshot list and compare it to the

 * newly-received snapshot context.  Remove any existing snapshots
@@ -2118,7 +2137,6 @@ static int rbd_dev_snaps_update(struct rbd_device *rbd_dev) 
{

	struct ceph_snap_context *snapc = rbd_dev->header.snapc;

	const u32 snap_count = snapc->num_snaps;

	char *snap_name = rbd_dev->header.snap_names;

	struct list_head *head = &rbd_dev->snaps;

	struct list_head *links = head->next;

	u32 index = 0;
@@ -2127,6 +2145,9 @@ static int rbd_dev_snaps_update(struct rbd_device *rbd_dev) 
	while (index < snap_count || links != head) {

		u64 snap_id;

		struct rbd_snap *snap;

		char *snap_name;

		u64 snap_size = 0;

		u64 snap_features = 0;



		snap_id = index < snap_count ? snapc->snaps[index]

					     : CEPH_NOSNAP;
@@ -2153,16 +2174,20 @@ static int rbd_dev_snaps_update(struct rbd_device *rbd_dev) 
			continue;

		}



		snap_name = rbd_dev_v1_snap_info(rbd_dev, index,

						&snap_size, &snap_features);

		if (IS_ERR(snap_name))

			return PTR_ERR(snap_name);



		dout("entry %u: snap_id = %llu\n", (unsigned int) snap_count,

			(unsigned long long) snap_id);

		if (!snap || (snap_id != CEPH_NOSNAP && snap->id < snap_id)) {

			struct rbd_image_header	*header = &rbd_dev->header;

			struct rbd_snap *new_snap;



			/* We haven't seen this snapshot before */



			new_snap = __rbd_add_snap_dev(rbd_dev, snap_name,

					snap_id, header->snap_sizes[index], 0);

					snap_id, snap_size, snap_features);

			if (IS_ERR(new_snap)) {

				int err = PTR_ERR(new_snap);
@@ -2183,9 +2208,9 @@ static int rbd_dev_snaps_update(struct rbd_device *rbd_dev) 


			dout("  already present\n");



			rbd_assert(snap->size ==

					rbd_dev->header.snap_sizes[index]);

			rbd_assert(snap->size == snap_size);

			rbd_assert(!strcmp(snap->name, snap_name));

			rbd_assert(snap->features == snap_features);



			/* Done with this list entry; advance */
@@ -2195,7 +2220,6 @@ static int rbd_dev_snaps_update(struct rbd_device *rbd_dev) 
		/* Advance to the next entry in the snapshot context */



		index++;

		snap_name += strlen(snap_name) + 1;

	}

	dout("%s: done\n", __func__);