Re: File copy system call proposal

From: Albert D. Cahalan (
Date: Mon Dec 10 2001 - 00:44:54 EST

Daniel Phillips writes:

> There's some merit to this idea. As Peter pointed out,
> an in-kernel cp isn' needed: mmap+write does the job.
> The question is, how to avoid the copy_from_user and
> double caching of data?

No, mmap+write does not do the job. SMB file servers have
a remote copy operation. There shouldn't be any need to
pull data over the network only to push it back again!

The user-space copy operation is also highly likely to
lose stuff that the kernel would know about:

extended attributes (IRIX, OS/2, NT)
forks / extra streams (MacOS, NT)
creation time stamp (Microsoft: not ctime or mtime)
author (GNU HURD: person who created the file)
file type (MacOS)
creator app (MacOS)
unique ID (Win2K)
mandatory access control data (Trusted Foo)
non-UNIX permission bits (every other OS)
ACLs (NFSv4, NT, Solaris...)
translator (HURD)
trustees (NetWare)
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to
More majordomo info at
Please read the FAQ at

This archive was generated by hypermail 2b29 : Sat Dec 15 2001 - 21:00:16 EST