Re: ext4 features

From: Bill Davidsen
Date: Mon Jul 10 2006 - 18:26:39 EST


Trond Myklebust wrote:

On Sat, 2006-07-08 at 17:04 -0400, Bill Davidsen wrote:


No, I didn't quite mean a manual touch, but a system call to "close and set time to high resolution" for files where time uniformity is important. Consider that in most cases the inodes times are set by the host machine clock, which I close the change reflects the fileserving host idea of time. If there were a call to close a file and set the times like touch, then that could be used, for both local and network files.



Close should never update the time since that would be a violation of
POSIX rules. Normally, an NFS client will never need to update the time:
RPC calls like WRITE, READ and SETATTR will automatically do it for us
whenever necessary.



Let me restate this a third time in another way. What I suggest is a system call, NOT NAMED CLOSE, which does a close and touch. This was all blue sky discussion, new system calls are as valid as nanosecond resolution and syncronization between servers. Since this is a new call it is not specified by POSIX.

And Linus has already suggested that he would accept something similar, when I proposed something like "noatime" mounts, which only updated atime and mtime on open and close, to keep metadata relevant but not have the overhead of constant updates.

Actually, now that I have more free time I may revisit that idea.

--
bill davidsen <davidsen@xxxxxxx>
CTO TMR Associates, Inc
Doing interesting things with small computers since 1979

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