NFS access of Windows-created files

If a file contains an owning user or group that is a SID, the system attempts to map it to a corresponding UID or GID before returning it to the caller.

In UNIX, authorization data is retrieved by calling stat(2) on a file and examining the owner, group, and mode bits. Over NFSv3, the GETATTR command functions similarly. The system approximates the mode bits and sets them on the file whenever its ACL changes. Mode bit approximations need to be retrieved only to service these calls.

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SID-to-UID and SID-to-GID mappings are cached in both the OneFS ID mapper and the stat cache. If a mapping has recently changed, the file might report inaccurate information until the file is updated or the cache is flushed.