Are exclusive locks implemented in the ONTAP file system using the fcntl or the LockFileEx ?
Applies to
ONTAP 9
Answer
- No,ONTAP file system does not provide exclusive locking at the file system level using
fcntl
orLockFileEx
. - For NFSv3 access, file locking is managed by Network Lock Manager (NLM).
- NLM provides advisory locks only.
- Advisory locks require client applications to check and honor locks.
- Clients may access locked files or regions if the application does not check the lock.
- For NFSv4.x, mandatory locking is supported via the Share Reservation Lock mechanism.
- Share Reservation Lock is enforced at the protocol level.
- When a file is locked with Share Reservation Lock, access from other clients is blocked according to the lock type.
- Details on mandatory locking for NFSv4 are available in How is Mandatory Locking supported for NFSv4 on ONTAP 9.
fcntl
on UNIX/Linux uses POSIX advisory byte-range (record) locking.- On NFSv4.x, the kernel maps
fcntl
locks to NFSv4 LOCK operations. - NFSv4 Share Reservation Lock is different from
fcntl
locks; it is part of the OPEN operation and controls file open modes (share_access
andshare_deny
). - POSIX does not expose share deny semantics via
fcntl
. - Most UNIX/Linux NFSv4 clients use
share_deny-none
by default.
- On NFSv4.x, the kernel maps
- For Windows clients,
LockFileEx
is used for advisory locking over CIFS/SMB.
Lock enforcement depends on application and protocol behavior.
- NFSv3 does not support mandatory locking.
- NFSv4.x supports mandatory locking via Share Reservation Lock, but POSIX APIs (
fcntl
) do not provide a way to request share deny semantics
Additional Information
additionalInformation_text