On Fri, 12 Apr 2013 09:42:43 +0800, Wang Shilong wrote:
>> + if (ritem && !is_v0) {
>> + rinfo->cgen = btrfs_root_ctransid(ritem);
>> + rinfo->ogen = btrfs_root_otransid(ritem);
>> + rinfo->sgen = btrfs_root_stransid(ritem);
>> + rinfo->rgen = btrfs_root_rtransid(ritem);
>> + rinfo->ctime = btrfs_stack_timespec_sec(&ritem->ctime);
>> + rinfo->otime = btrfs_stack_timespec_sec(&ritem->otime);
>> + rinfo->stime = btrfs_stack_timespec_sec(&ritem->stime);
>> + rinfo->rtime = btrfs_stack_timespec_sec(&ritem->rtime);
>> + memcpy(rinfo->uuid, ritem->uuid, BTRFS_UUID_SIZE);
>> + memcpy(rinfo->puuid, ritem->parent_uuid, BTRFS_UUID_SIZE);
>> + memcpy(rinfo->ruuid, ritem->received_uuid, BTRFS_UUID_SIZE);
>> + }
>> +
>> + /* TODO: this is copied from the old code, what is it good for? */
>> + if ((!ritem || !btrfs_root_otransid(ritem)) && root_offset)
>> + rinfo->ogen = root_offset;
>
>
> For the older kernel:
> subvolume's original generation is always 0, but
> for snapshot, root_offset equals to its original generation.
> so we set it here.
>
Thanks for this hint! So it's for old style (v0) root_item entries.
My code above is not correct since it accesses a field that is not available
for v0 root items.
I changed it like this:
@@ -502,11 +502,14 @@ static int set_root_info(struct root_info *rinfo, u64 ref_
memcpy(rinfo->uuid, ritem->uuid, BTRFS_UUID_SIZE);
memcpy(rinfo->puuid, ritem->parent_uuid, BTRFS_UUID_SIZE);
memcpy(rinfo->ruuid, ritem->received_uuid, BTRFS_UUID_SIZE);
- }
-
- /* TODO: this is copied from the old code, what is it good for? */
- if ((!ritem || !btrfs_root_otransid(ritem)) && root_offset)
+ } else if (ritem && is_v0 && root_offset) {
+ /*
+ * old style (v0) root items don't contain an otransid field.
+ * But for snapshots, root_offset equals to its original
+ * generation.
+ */
rinfo->ogen = root_offset;
+ }
--
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