Generic MDS_REINT
^^^^^^^^^^^^^^^^^

An 'mdt_rec_reint' structure specifies the generic form for MDS_REINT
requests. Each sub-operation, as defned by the 'rr_opcode' field, has
its own variant of this structure. Each variant has the same size as
the generic 'mdt_rec_reint', but interprets its fields slightly
differently.  Note that in order for swabbing to take place correctly
the sequence of field sizes must the same in every variant as it is in
the generic version (not just the overal size of the sturcture).

----
struct mdt_rec_reint {
	__u32           rr_opcode;
	__u32           rr_cap;
	__u32           rr_fsuid;
	__u32           rr_fsuid_h;
	__u32           rr_fsgid;
	__u32           rr_fsgid_h;
	__u32           rr_suppgid1;
	__u32           rr_suppgid1_h;
	__u32           rr_suppgid2;
	__u32           rr_suppgid2_h;
	struct lu_fid   rr_fid1;
	struct lu_fid   rr_fid2;
	obd_time        rr_mtime;
	obd_time        rr_atime;
	obd_time        rr_ctime;
	__u64           rr_size;
	__u64           rr_blocks;
	__u32           rr_bias;
	__u32           rr_mode;
	__u32           rr_flags;
	__u32           rr_flags_h;
	__u32           rr_umask;
	__u32           rr_padding_4; /* also fix lustre_swab_mdt_rec_reint */
};
----

The 'rr_opcode' field defines one among the several sub-commands for
MDS REINT RPCs. Those opcodes are:

----
typedef enum {
  REINT_SETATTR  = 1,
  REINT_CREATE   = 2,
  REINT_LINK     = 3,
  REINT_UNLINK   = 4,
  REINT_RENAME   = 5,
  REINT_OPEN     = 6,
  REINT_SETXATTR = 7,
} mds_reint_t;
----

Based on that opcode one of the variants of the structure will
actually be used. See <<mds-reint-setattr-rpc>> for one example.

The 'rr_cap' field is not used (and has been dropped in more recent
code updates).

The 'rr_fsuid' field gives the UID of the file system mount point.

The 'rr_fsuid_h' field gives the high bytes of a the file system mount
point UID in an environment where UIDs are 64-bit. The same holds for
the other '_h' fields.

The 'rr_fsgid' field gives the GID of the file system mount point.
For each opcode there is a variant of the 'mdt_rec_reint' that has
identical byte fields, but slightly modified semantics. The following
is for the REINT_SETATTR sub-operation.

The 'rr_suppgid1' and 'rr_suppgid2' fields are supplementary GID
information for kernels that have it.

The 'rr_fid1' and 'rr_fid2' fields specify the file IDs for the
resources being operated upon. If only one resource is being acted
upon then 'rr_fid2' is not used.

The 'rr_mtime' 'rr_atime' and 'rr_ctime' fields give the values of the
time attributes. The 'obd_time' type is also a '__u64'.

The 'rr_size' field gives the value of the size attribute.

The 'rr_blocks' field gives the value of the number-of-blocks
attribute.

The 'rr_bias' field adds additional optional information to the
REINT. The possible values are:

----
enum mds_op_bias {
	MDS_CHECK_SPLIT		= 1 << 0,
	MDS_CROSS_REF		= 1 << 1,
	MDS_VTX_BYPASS		= 1 << 2,
	MDS_PERM_BYPASS		= 1 << 3,
	MDS_SOM			= 1 << 4,
	MDS_QUOTA_IGNORE	= 1 << 5,
	MDS_KEEP_ORPHAN		= 1 << 7,
	MDS_RECOV_OPEN		= 1 << 8,
	MDS_DATA_MODIFIED	= 1 << 9,
	MDS_CREATE_VOLATILE	= 1 << 10,
	MDS_OWNEROVERRIDE	= 1 << 11,
	MDS_HSM_RELEASE		= 1 << 12,
};
----

For example, MDS_DATA_MODIFIED signals to the HSM system that the MDT
should set the corresponding HSM extended attribute. We'll return to
this topic with more details about the individual flags at a later
date.

The 'rr_mode' field gives the value of the mode attribute.

The 'rr_flags' and 'rr_flags_h' fields give the value (and the high
order bytes of the value, respectively, if there are high order bytes)
of the flags attribute.

The 'rr_umask' gives the value of the 'umask' to apply in, for
example, a REINT_CREATE.