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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: 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 b1b5402aa9
commit 35d489f946
1 changed files with 85 additions and 0 deletions
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85
drivers/block/rbd.c
View File

@ -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",