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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: Alex Elder <elder@inktank.com>
Reviewed-by: Josh Durgin <josh.durgin@inktank.com>
This commit is contained in:
Alex Elder 2012-07-03 16:01:19 -05:00
parent 34b131849f
commit cd892126c6
1 changed files with 30 additions and 6 deletions
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36
drivers/block/rbd.c
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@ -2102,6 +2102,25 @@ err:
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__);