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SubjectRe: [PATCH] userns: Add basic quota support v2
Jan Kara <jack@suse.cz> writes:

> On Mon 27-08-12 17:12:16, Eric W. Biederman wrote:
>> Add the data type struct qown which holds the owning identifier of a
>> quota. struct qown is a replacement for the implicit union of uid,
>> gid and project stored in an unsigned int and the quota type field
>> that is was used in the quota data structures. Making the data type
>> explicit allows the kuid_t and kgid_t type safety to propogate more
>> thoroughly through the code, revealing more places where uid/gid
>> conversions need be made.
>>
>> Allong with the data type struct qown comes the helper functions
> ^^^^ Along
>
>> qown_eq, qown_lt, from_qown, from_qown_munged, qown_valid, make_qown,
>> make_qown_invalid, make_qown_uid, make_qown_gid.
>>
>> Replace struct dquot dq_id and dq_type with dq_own a struct qown.
>>
>> Update the signature of dqget, quota_send_warning, dquot_get_dqblk,
>> and dquot_set_dqblk to use struct qown.
>>
>> Make minimal changes to ext3, ext4, gfs2, ocfs2, and xfs to deal with
>> the change in quota structures and signatures. The ocfs2 changes are
>> larger than most because of the extensive tracing throughout the ocfs2
>> quota code that prints out dq_id.
>>
>> v2:
>> - Renamed qown_t struct qown
>> - Added the quota type to struct qown.
>> - Removed enum quota_type (In this patch it was just noise)
>> - Added qown_lt, make_qown_invalid, make_qown_uid, make_qown_gid
>> - Taught qown to handle xfs project ids (but only in init_user_ns).
>> Q_XGETQUOTA calls .get_quotblk with project ids.
> Just a couple one minor comments below...
>
>> @@ -130,13 +130,17 @@ static void copy_to_if_dqblk(struct if_dqblk *dst, struct fs_disk_quota *src)
>> static int quota_getquota(struct super_block *sb, int type, qid_t id,
>> void __user *addr)
>> {
>> + struct qown qown;
>> struct fs_disk_quota fdq;
>> struct if_dqblk idq;
>> int ret;
>>
>> if (!sb->s_qcop->get_dqblk)
>> return -ENOSYS;
>> - ret = sb->s_qcop->get_dqblk(sb, type, id, &fdq);
>> + qown = make_qown(current_user_ns(), type, id);
>> + if (qown_valid(qown))
> ^ missing '!'

Good catch thank you.

>> + return -EINVAL;
>> + ret = sb->s_qcop->get_dqblk(sb, qown, &fdq);
>> if (ret)
>> return ret;
>> copy_to_if_dqblk(&idq, &fdq);
> ...
>> +static inline u32 from_qown(struct user_namespace *user_ns, struct qown qown)
>> +{
>> + switch (qown.type) {
>> + case USRQUOTA:
>> + return from_kuid(user_ns, qown.uid);
>> + case GRPQUOTA:
>> + return from_kgid(user_ns, qown.gid);
>> + case XQM_PRJQUOTA:
>> + return (user_ns == &init_user_ns) ? qown.prj : -1;
>> + default:
>> + BUG();
>> + }
>> +}
> I would like a bit more if the function somehow expressed in its name
> that it returns id. id_from_qown() might be a bit too long given how often
> it is used. qown2id() would be OK but it would be inconsistent with how
> names of other functions you've added are formed. So I'm somewhat
> undecided...

The qown vs id distinction bothers me a little bit.

I almost want to name it struct kid, and the functions make_kid,
from_kid etc. Where the emphasis is that we are transforming in and out
of the kernel internal form. I don't really like make_kid because id as
a base name seems to generic and it barely tells you it is. Perhaps
make_kqid. Where we call the quota ids and qid for short?

I am a little uncomfortable calling them kqids because the userspace
code also places format_ids in a plain qid_t. But make_kqid and
from_kqid seems the best alternate set of names I can come up with.

Eric


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