Open processing

The type of open that is being done by vn_open is passed in the ts_sysd1 field. This open can be one of the following:

VNOPEN_FILE

A traditional POSIX open() or NFS V4 v_open(). These actions request access rights and optionally can place share reservations on the file. They contend with any other opens that may already be established for this file. The call can fail due to an existing reservation that denies the access requested, or the call can fail if it attempts to deny an access that is already established. Both conflicts cause the call to be rejected with RC=EBUSY. If the PFS does not support Share Reservations, the LFS uses Rsn=JRShrConflict for the former and Rsn=JRAccessConflict for the later.

This call can be blocking or nonblocking, but the LFS does not allow blocking with share reservations requested. That is, if either O_DENYRD or O_DENYWRT are set then O_NONBLOCK must also be set. When the call is blocking it should wait for any conflicting Share Reservations to be removed. When nonblocking, it should be rejected immediately with RC=EBUSY if there is a conflict. The Share reservations established here inhibit any conflicting reading or writing that occur outside of an open context. See Considerations for reading and writing and SetAttr for more information.

VNOPEN_NLM_SHR

This type of open is for a Network Lock Manager Share Reservation. It is not an open in the traditional sense, although there is really no difference to the PFS. SAF/RACF is called for a normal access check . These calls are always nonblocking.

The corresponding vn_close also indicates that it is for a VNOPEN_NLM_SHR, so that the appropriate deny counters can be decremented.

Note that the SMB server also issues v_rdwr outside of an open context. But on the first read or write to a file the LFS issues a vn_open(VNOPEN_FILE ) for it, so once SMB starts reading or writing a file it cannot be denied that access later. That first read or write is rejected if there is already a conflicting Share Reservation that causes the vn_open to be rejected.

NLM opens contend with all other previous opens, but the reservations established do not inhibit subsequent reads and writes from an NFS V3 client. An NFS client does not have an open context and its reads and writes are allowed to violate NLM Share Reservations, but they are rejected if they conflict with a V4 Share Reservation. There are two requirements to correctly enforce Reservations with respect to NFS V3 reads and writes:

The PFS must maintain two pairs of deny counters. These are for (V4_DenyWrt,V4_DenyRd) and (NLM_DenyWrt,NLM_DenyRd).
For a vn_rdwr operation the LFS must pass the type of client that is doing the read or write. This is done in terms of the type of checking that should be performed by the PFS. See Considerations for reading and writing and SetAttr for more information.

VNOPEN_INTERNAL

An internal open issued by the LFS. This is for read and write access, or for read-only access if the file system is Read-only. This operation never denies any accesses. This open should bypass all Share checking, and it does not inhibit later Share Reservations. There may be more than one internal vn_open issued for a file. For each internal vn_open there will be a corresponding internal vn_close. These internal opens are done with system credentials.