Re: Manual page bug: two inaccuracies in nfsd(7)

[NeilBrown <neilb@suse.com>]

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On Fri, Feb 10 2017, Chris Siebenmann wrote:

>  I was recently reading this manual page as part of exploring running
> an NFS server on Ubuntu 16.04 (with Ubuntu's kernel '4.4.0') and found
> two inaccuracies with the current state of the kernel (or at least how
> it looks to me based on both experimentation and code).
>
>  First, there is no /proc/net/rpc/auth.domain directory and cache any
> more. This was removed from the kernel in 2006 (in commit efc36aa5608f),
> so I think it should be safe to remove from current versions of the
> manpage.

I agree.

>
>  Second, the manpage says about the 'flush' files to be found in eg
> /proc/net/rpc/auth.unix.ip:
>
> 	When a number of seconds since epoch (1 Jan 1970) is written to
> 	this file, all entries in the cache that were last updated before
> 	that file become invalidated and will be flushed out. Writing
> 	1 will flush everything. [...]
>
> The bit about 'writing 1 will flush everything' does not appear to be
> accurate.

I was never accurate.  I vaguely remember writing it.  I must have been
confused.

Would you be able to create a patch which fixes these issues, and post
it, with a signed-off-by ?

Thanks,
NeilBrown



>            Experimentally, writing 1 does not work (it flushes nothing),
> and in the current kernel code there is no special handling for a write of
> '1' to the "flush" files in net/sunrpc/cache.c's write_flush() function,
> which I believe is where this is implemented. Based on the implementation,
> the only way to flush everything is to write a time in the future to
> "flush".
>
>  Based on looking at the kernel logs and code diffs, this may have
> changed in commit 778620364ef5, 'sunrpc/cache: make cache flushing more
> reliable', which gitk tells me came between v4.3-rc3 and v4.4-rc1 (it
> was made in October 2015). The commit description definitely talks about
> changing how cache expiry works, and it touches write_flush() et al in
> various ways. This may call for a kernel change to make it work again,
> but even if so I would suggest that the manpage be updated to reflect
> that writing 1 doesn't work in a range of kernel versions (some of which
> will be in the field for years to come, eg Ubuntu 16.04 LTS).
>
> 	- cks
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