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| author | Alex Elder <elder@inktank.com> | 2012-07-27 08:37:15 +0400 |
|---|---|---|
| committer | Alex Elder <elder@inktank.com> | 2012-10-01 23:30:48 +0400 |
| commit | 28cb775de1bd1bcc62c43f767ab81b7b9cfb6678 (patch) | |
| tree | a9ed5f43be03561446be1c08b8221c183ca6ca4c | |
| parent | 6a52325f61760c6a7d7f3ea9736029bc9f63e7f3 (diff) | |
| download | linux-28cb775de1bd1bcc62c43f767ab81b7b9cfb6678.tar.xz | |
rbd: return earlier in rbd_header_from_disk()
The only caller of rbd_header_from_disk() is rbd_read_header().
It passes as allocated_snaps the number of snapshots it will
have received from the server for the snapshot context that
rbd_header_from_disk() is to interpret. The first time through
it provides 0--mainly to extract the number of snapshots from
the snapshot context header--so that it can allocate an
appropriately-sized buffer to receive the entire snapshot
context from the server in a second request.
rbd_header_from_disk() will not fill in the array of snapshot ids
unless the number in the snapshot matches the number the caller
had allocated.
This patch adjusts that logic a little further to be more efficient.
rbd_read_header() doesn't even examine the snapshot context unless
the snapshot count (stored in header->total_snaps) matches the
number of snapshots allocated. So rbd_header_from_disk() doesn't
need to allocate or fill in the snapshot context field at all in
that case.
Signed-off-by: Alex Elder <elder@inktank.com>
Reviewed-by: Josh Durgin <josh.durgin@inktank.com>
| -rw-r--r-- | drivers/block/rbd.c | 15 |
1 files changed, 12 insertions, 3 deletions
diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c index c9de0f8e808e..aff4e8a01ea5 100644 --- a/drivers/block/rbd.c +++ b/drivers/block/rbd.c @@ -540,7 +540,14 @@ static int rbd_header_from_disk(struct rbd_image_header *header, header->comp_type = ondisk->options.comp_type; header->total_snaps = snap_count; - /* Set up the snapshot context */ + /* + * If the number of snapshot ids provided by the caller + * doesn't match the number in the entire context there's + * no point in going further. Caller will try again after + * getting an updated snapshot context from the server. + */ + if (allocated_snaps != snap_count) + return 0; size = sizeof (struct ceph_snap_context); size += snap_count * sizeof (header->snapc->snaps[0]); @@ -552,8 +559,10 @@ static int rbd_header_from_disk(struct rbd_image_header *header, header->snapc->seq = le64_to_cpu(ondisk->snap_seq); header->snapc->num_snaps = snap_count; - if (snap_count && allocated_snaps == snap_count) { - int i; + /* Fill in the snapshot information */ + + if (snap_count) { + u32 i; for (i = 0; i < snap_count; i++) { header->snapc->snaps[i] = |