NFS cookies 2.3.18

Steve Wormley (wormley@io.com)
Sun, 12 Sep 1999 19:49:29 -0500


There is a minor NFS v2 bug(it may also apply to v3) in at least 2.3.17 and
18. In that the kernel assumes:
/* This whole scheme relies on the fact that dirent cookies
* are monotonically increasing.
*

Which is of course, not a good assumption since the RFC defines v2 cookies
as opaque. (v3 cookies are said to be an unsigned 64 bit integer, but still
does not state what, if any assumptions may be made on the value.)
(And at least one program, cfs, just ships it's internal cookie value out,
the kernel then tries to ntohl it and gets a now non-increasing, basically
random value, which breaks the caching and loses hoardes of directory
entries. However since internally cfs uses an increasing value, this is easy
to solve.)
I'm not sure what other NFS implementations may have problems like this, I
suspect it's not a problem for 'normal' implementations, but may crop up
here and there.

-Steve Wormley

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