5 MDS_STATFS is an RPC that queries data about the underlying file
6 system for a given MDT.
8 It is generated in response to an explicit call for 'statfs'
9 information from the VFS via the 'statfs(2)' function.
12 The MDS_STATFS request message is a so-called "empty" message in that
13 it only has a buffer for the 'ptlrpc_body' with the 'pb_opc' value
16 The reply message conveys 'statfs' data when it succeeds, and an error
19 .MDS_STATFS Generic Packet Structure
23 [width="50%", cols="2a"]
28 ! <<struct-ptlrpc-body,ptlrpc_body>> !
33 ! <<struct-ptlrpc-body,ptlrpc_body>> ! <<struct-obd_statfs,obd_statfs>> !
37 'ptlrpc_body':: RPC descriptor. Only the 'pb_opc' value (MDS_STATFS =
38 41) is directly relevant to the MDS_STATFS request message. The rest
39 of the 'ptlrpc_body' fields handle generic information about the
40 RPC, as discussed in <<struct-ptlrpc-body>>, including generic error
41 conditions. In a normal reply ('pb_type' = PTL_RPC_MSG_REPLY) the
42 'pb_status' field is 0. The one error that can be returned in
43 'pb_status' that is speficially from OST_STATFS' handling is -ENOMEM,
44 which occurs if there is not enough memory to allocate a temporary
45 buffer for the 'statfs' data.
48 File system wide statistics corresponding to 'struct statfs' as well
49 as Lustre-specific information. See <<struct-obd-statfs>> for a