• Chuck Lever's avatar
    NFS: Add method to retrieve fs_locations during migration recovery · b03d735b
    Chuck Lever authored
    The nfs4_proc_fs_locations() function is invoked during referral
    processing to perform a GETATTR(fs_locations) on an object's parent
    directory in order to discover the target of the referral.  It
    performs a LOOKUP in the compound, so the client needs to know the
    parent's file handle a priori.
    
    Unfortunately this function is not adequate for handling migration
    recovery.  We need to probe fs_locations information on an FSID, but
    there's no parent directory available for many operations that
    can return NFS4ERR_MOVED.
    
    Another subtlety: recovering from NFS4ERR_LEASE_MOVED is a process
    of walking over a list of known FSIDs that reside on the server, and
    probing whether they have migrated.  Once the server has detected
    that the client has probed all migrated file systems, it stops
    returning NFS4ERR_LEASE_MOVED.
    
    A minor version zero server needs to know what client ID is
    requesting fs_locations information so it can clear the flag that
    forces it to continue returning NFS4ERR_LEASE_MOVED.  This flag is
    set per client ID and per FSID.  However, the client ID is not an
    argument of either the PUTFH or GETATTR operations.  Later minor
    versions have client ID information embedded in the compound's
    SEQUENCE operation.
    
    Therefore, by convention, minor version zero clients send a RENEW
    operation in the same compound as the GETATTR(fs_locations), since
    RENEW's one argument is a clientid4.  This allows a minor version
    zero server to identify correctly the client that is probing for a
    migration.
    Signed-off-by: default avatarChuck Lever <chuck.lever@oracle.com>
    Signed-off-by: default avatarTrond Myklebust <Trond.Myklebust@netapp.com>
    b03d735b
nfs4_fs.h 16.7 KB