Re: nfsd readahead

[Neil Brown]

On Monday May 31, colin@xxxxxxxxxxxxxxx wrote:
> Hi,
> 
> I was having problems with slow streaming reads over nfs. After much
> investigation, I found that nfsd uses its own cache of readahead
> parameters and that:
> (1) they were not being reused
> (2) they were not being initialized properly

Thanks a lot Colin. (I did get your earlier person email, but it
didn't get to the top of the priority queue until today).

The current code is a bit of a mess isn't it!!!

I have one question about your patch:

> +	file_ra_state_init(&ra->p_ra, file->f_mapping);

I note that the corresponding code in fs/open.c(dentry_open) reads

	file_ra_state_init(&f->f_ra, f->f_mapping->host->i_mapping);

i.e. there is an extra level of indirection.  Is there a reason that
you didn't copy that.

I am seriously thinking of getting rid of the "open_private_file"
stuff, and using dentry_open to open files for nfsd, and just allow it
to init the ra_state, so that nfsd doesn't do it itself.
However that patch touches 13 files, so I want to see it get a bit of
testing first.

Thanks again,
I'll make sure this fix gets through Andrew to Linus,

NeilBrown
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