Re: NFS locking bug -- limited mtime resolution means nfs_lock() does not provide coherency guarantee

From: Andi Kleen (ak@suse.de)
Date: Thu Sep 14 2000 - 04:59:33 EST


On Thu, Sep 14, 2000 at 11:51:20AM +0200, Trond Myklebust wrote:
> The reason I'm sceptical to this and other in-core type solutions is
> that knfsd doesn't keep files open for long: basically it opens a file
> and close it upon processing of each and every request from a
> client. You can therefore easily risk losing the inode between two
> requests while the file is still open on the client.
> If this means that you also lose part of the info in the mtime field,
> then you will trigger a data cache invalidation on the client.

knfsd keeps it only open for a small time, but the page cache references
the inode as long as it has any data pages for the file. As long as you're
not trashing extensively it should stay in memory for a longer time.

-Andi

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