userns: Implement struct kqid

Add the data type struct kqid which holds the kernel internal form of
the owning identifier of a quota.  struct kqid is a replacement for
the implicit union of uid, gid and project id 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.

Along with the data type struct kqid comes the helper functions
qid_eq, qid_lt, from_kqid, from_kqid_munged, qid_valid, make_kqid,
make_kqid_invalid, make_kqid_uid, make_kqid_gid.

Cc: Jan Kara <jack@suse.cz>
Cc: Dave Chinner <david@fromorbit.com>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>

1 files changed, 125 insertions, 0 deletions

diff --git a/include/linux/quota.h b/include/linux/quota.h
index 524ede8a160a..00ac8d846c14 100644
--- a/include/linux/quota.h
+++ b/include/linux/quota.h
@@ -181,10 +181,135 @@ enum {
 #include <linux/dqblk_v2.h>
 
 #include <linux/atomic.h>
+#include <linux/uidgid.h>
+#include <linux/projid.h>
+
+#undef USRQUOTA
+#undef GRPQUOTA
+enum quota_type {
+        USRQUOTA = 0,           /* element used for user quotas */
+        GRPQUOTA = 1,           /* element used for group quotas */
+        PRJQUOTA = 2,           /* element used for project quotas */
+};
 
 typedef __kernel_uid32_t qid_t; /* Type in which we store ids in memory */
 typedef long long qsize_t;      /* Type in which we store sizes */
 
+struct kqid {                   /* Type in which we store the quota identifier */
+        union {
+                kuid_t uid;
+                kgid_t gid;
+                kprojid_t projid;
+        };
+        enum quota_type type;  /* USRQUOTA (uid) or GRPQUOTA (gid) or PRJQUOTA (projid) */
+};
+
+extern bool qid_eq(struct kqid left, struct kqid right);
+extern bool qid_lt(struct kqid left, struct kqid right);
+extern qid_t from_kqid(struct user_namespace *to, struct kqid qid);
+extern qid_t from_kqid_munged(struct user_namespace *to, struct kqid qid);
+extern bool qid_valid(struct kqid qid);
+
+/**
+ *      make_kqid - Map a user-namespace, type, qid tuple into a kqid.
+ *      @from: User namespace that the qid is in
+ *      @type: The type of quota
+ *      @qid: Quota identifier
+ *
+ *      Maps a user-namespace, type qid tuple into a kernel internal
+ *      kqid, and returns that kqid.
+ *
+ *      When there is no mapping defined for the user-namespace, type,
+ *      qid tuple an invalid kqid is returned.  Callers are expected to
+ *      test for and handle handle invalid kqids being returned.
+ *      Invalid kqids may be tested for using qid_valid().
+ */
+static inline struct kqid make_kqid(struct user_namespace *from,
+                                    enum quota_type type, qid_t qid)
+{
+        struct kqid kqid;
+
+        kqid.type = type;
+        switch (type) {
+        case USRQUOTA:
+                kqid.uid = make_kuid(from, qid);
+                break;
+        case GRPQUOTA:
+                kqid.gid = make_kgid(from, qid);
+                break;
+        case PRJQUOTA:
+                kqid.projid = make_kprojid(from, qid);
+                break;
+        default:
+                BUG();
+        }
+        return kqid;
+}
+
+/**
+ *      make_kqid_invalid - Explicitly make an invalid kqid
+ *      @type: The type of quota identifier
+ *
+ *      Returns an invalid kqid with the specified type.
+ */
+static inline struct kqid make_kqid_invalid(enum quota_type type)
+{
+        struct kqid kqid;
+
+        kqid.type = type;
+        switch (type) {
+        case USRQUOTA:
+                kqid.uid = INVALID_UID;
+                break;
+        case GRPQUOTA:
+                kqid.gid = INVALID_GID;
+                break;
+        case PRJQUOTA:
+                kqid.projid = INVALID_PROJID;
+                break;
+        default:
+                BUG();
+        }
+        return kqid;
+}
+
+/**
+ *      make_kqid_uid - Make a kqid from a kuid
+ *      @uid: The kuid to make the quota identifier from
+ */
+static inline struct kqid make_kqid_uid(kuid_t uid)
+{
+        struct kqid kqid;
+        kqid.type = USRQUOTA;
+        kqid.uid = uid;
+        return kqid;
+}
+
+/**
+ *      make_kqid_gid - Make a kqid from a kgid
+ *      @gid: The kgid to make the quota identifier from
+ */
+static inline struct kqid make_kqid_gid(kgid_t gid)
+{
+        struct kqid kqid;
+        kqid.type = GRPQUOTA;
+        kqid.gid = gid;
+        return kqid;
+}
+
+/**
+ *      make_kqid_projid - Make a kqid from a projid
+ *      @projid: The kprojid to make the quota identifier from
+ */
+static inline struct kqid make_kqid_projid(kprojid_t projid)
+{
+        struct kqid kqid;
+        kqid.type = PRJQUOTA;
+        kqid.projid = projid;
+        return kqid;
+}
+
+
 extern spinlock_t dq_data_lock;
 
 /* Maximal numbers of writes for quota operation (insert/delete/update)