On 2017年12月19日 19:12, Nikolay Borisov wrote:
>
>
> On 19.12.2017 12:45, Qu Wenruo wrote:
>> btrfs_qgroup_inherit structure has two members, num_ref_copies and
>> num_excl_copies, to info btrfs kernel modules to inherit (copy)
>> rfer/excl numbers at snapshot/subvolume creation time.
>>
>> Since qgroup number is already hard to maintain for multi-level qgroup
>> scenario, allowing user to manually manipulate qgroup inherit is quite
>> easy to screw up qgroup numbers.
>>
>> Although btrfs-progs supports such inheritance specification, the
>> options are hidden from user and not documented.
>> So there is no need to allow user to manually specify inheritance in
>> kernel.
>>
>> Reported-by: Nikolay Borisov <nbori...@suse.com>
>> Signed-off-by: Qu Wenruo <w...@suse.com>
>> ---
>> The only concern is, currently we don't have good tool to handle
>> inheritance of multi-level qgroups.
>> The only method to get qgroup numbers correct is to run a quota rescan.
>>
>> So there may be some case where experienced (well, mostly a developer)
>> user can use the hidden btrfs-progs options or manually craft an ioctl
>> to handle multi-level qgroups without costly rescan.
>> ---
>> fs/btrfs/qgroup.c | 56
>> ++++++++++++++--------------------------------
>> include/uapi/linux/btrfs.h | 4 ++--
>> 2 files changed, 19 insertions(+), 41 deletions(-)
>>
>> diff --git a/fs/btrfs/qgroup.c b/fs/btrfs/qgroup.c
>> index 168fd03ca3ac..d8a2413272f9 100644
>> --- a/fs/btrfs/qgroup.c
>> +++ b/fs/btrfs/qgroup.c
>> @@ -2158,9 +2158,24 @@ int btrfs_qgroup_inherit(struct btrfs_trans_handle
>> *trans,
>> }
>>
>> if (inherit) {
>> + /*
>> + * num_excl/rfer_copies indicate how many qgroup pairs needs
>> + * to be manually inherited (copy rfer or excl from src
>> + * qgroup to dst)
>> + *
>> + * Allowing user to manipulate inheritance can easily cause
>> + * problem in multi-level qgroup scenario.
>> + * And the ioctl interface is hidden in btrfs-progs for a long
>> + * time, deprecate them should not be a big problem.
>> + */
>> + if (inherit->__num_excl_copies || inherit->__num_ref_copies) {
>> + ret = -ENOTTY;
>> + btrfs_warn(fs_info,
>> + "manually inherit excl/rfer is no longer supported");
>> + goto out;
>> + }
>> i_qgroups = (u64 *)(inherit + 1);
>> - nums = inherit->num_qgroups + 2 * inherit->num_ref_copies +
>> - 2 * inherit->num_excl_copies;
>> + nums = inherit->num_qgroups;
>> for (i = 0; i < nums; ++i) {
>> srcgroup = find_qgroup_rb(fs_info, *i_qgroups);
>>
>> @@ -2286,43 +2301,6 @@ int btrfs_qgroup_inherit(struct btrfs_trans_handle
>> *trans,
>> ++i_qgroups;
>> }
>>
>> - for (i = 0; i < inherit->num_ref_copies; ++i, i_qgroups += 2) {
>> - struct btrfs_qgroup *src;
>> - struct btrfs_qgroup *dst;
>> -
>> - if (!i_qgroups[0] || !i_qgroups[1])
>> - continue;
>> -
>> - src = find_qgroup_rb(fs_info, i_qgroups[0]);
>> - dst = find_qgroup_rb(fs_info, i_qgroups[1]);
>> -
>> - if (!src || !dst) {
>> - ret = -EINVAL;
>> - goto unlock;
>> - }
>> -
>> - dst->rfer = src->rfer - level_size;
>> - dst->rfer_cmpr = src->rfer_cmpr - level_size;
>> - }
>> - for (i = 0; i < inherit->num_excl_copies; ++i, i_qgroups += 2) {
>> - struct btrfs_qgroup *src;
>> - struct btrfs_qgroup *dst;
>> -
>> - if (!i_qgroups[0] || !i_qgroups[1])
>> - continue;
>> -
>> - src = find_qgroup_rb(fs_info, i_qgroups[0]);
>> - dst = find_qgroup_rb(fs_info, i_qgroups[1]);
>> -
>> - if (!src || !dst) {
>> - ret = -EINVAL;
>> - goto unlock;
>> - }
>> -
>> - dst->excl = src->excl + level_size;
>> - dst->excl_cmpr = src->excl_cmpr + level_size;
>> - }
>> -
>> unlock:
>> spin_unlock(&fs_info->qgroup_lock);
>> out:
>> diff --git a/include/uapi/linux/btrfs.h b/include/uapi/linux/btrfs.h
>> index ce615b75e855..099e088414d6 100644
>> --- a/include/uapi/linux/btrfs.h
>> +++ b/include/uapi/linux/btrfs.h
>> @@ -80,8 +80,8 @@ struct btrfs_qgroup_limit {
>> struct btrfs_qgroup_inherit {
>> __u64 flags;
>> __u64 num_qgroups;
>> - __u64 num_ref_copies;
>> - __u64 num_excl_copies;
>> + __u64 __num_ref_copies; /* DEPRECATED */
>> + __u64 __num_excl_copies; /* DEPRECATED */
>
> I'd prefer we name them something even more generic i.e. :
> pad1, pad2 or unused1, unused2 to really deter any efforts to use them.
> I guess this could shouldn't have been merged in the first place ...Naming like pad1/2 will make the check in btrfs_qgroup_inherit() look quite weird. Although I don't have any better idea, so I'm mostly fine with such rename. Thanks, Qu > >> struct btrfs_qgroup_limit lim; >> __u64 qgroups[0]; >> }; >> > -- > To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in > the body of a message to majord...@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html >
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